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Disorders of Visual Recognition
Abstract
Agnosias are disorders of recognition, specific to one sensory channel, that affect either the perceptual analysis of the stimulus or the recognition of its meaning. In the visual modality, objects, faces, and colors can be separately disrupted. Apperceptive object agnosia refers to failure to achieve a structured description of the shape of the object. Associative agnosia refers to inability to attribute a meaning to a correctly perceived stimulus. It must be differentiated from optic aphasia, in which the object is recognized but cannot be named in the visual modality. Associative agnosia and optic aphasia are associated with left occipitotemporal damage, and they differ more quantitatively than qualitatively. The inability to recognize familiar faces (prosopagnosia) can appear in isolation and be, in some cases, associated with a lesion confined to the occipitotemporal region of the right hemisphere. These findings are supportive of the idea that faces have a separate representation in the brain. Disorders of color cognition can affect color categorization, color-name association, and color-object association. They are linked to left hemisphere damage. The ability to recognize objects presented in the visual modality is a hierarchical process in which several cortical areas, corresponding to about 30% of the cortical mantle, participate. Their selective lesion results in a gamut of disorders whose identification provides the experienced neurologist with clues to the locus of damage and contributes to the understanding of the cognitive architecture underpinning recognition. They can result either in the inability to detect any change occurring in the visual field or in the impairment of further stages of the recognition process, from the analysis of the perceptual properties of the stimulus (form, color, motion, depth, etc.) to the achievement of its structural description and, eventually, the attribution of a meaning. In this paper, I focus on the diagnostic and clinical features characterizing the disruption of the last stage of visual information processing; that is, the failure to identify what a stimulus represents despite evidence that its three-dimensional structure has been properly reconstructed. In the literature, this impairment is traditionally referred to as associative agnosia, a psychological construct that attributes the deficit to the inability to associate a well-discriminated percept with its semantic attributes, which are stored in separate cortical areas. In the visual modality, three discrete forms of associative agnosia have been described, affecting objects, faces, and colors. These are treated separately.
... One potential candidate for such an alternative distractor stimulus is faces. Faces are salient stimuli (Jenkins, Lavie, & Driver, 2003;Lavie, Ro, & Russell, 2003), due to their high level of sociobiological importance (De Renzi, 2000). However, it has been suggested that faces may be a 'special' class of distractor in that their processing might not be subject to modulation by perceptual load. ...
... One potential candidate for such a stimulus is faces. Faces are salient stimuli (Jenkins et al., 2003;), due to their high level of sociobiological importance (De Renzi, 2000). As discussed in greater detail in the General Introduction (Section 1.7), faces have been suggested to be a 'special' class of distractor, the processing of which may be mandatory and not be subject to modulation by perceptual load. ...
This thesis examines whether laboratory measures of attention focus in the face of taskirrelevant distraction can predict or reduce real-world experiences of distraction henceforth ‘attention lapses’ (covering both external, and internal sources such as mindwandering), with a specific consideration of educational environments, the adolescence period, and relationships to mood. To establish a novel measure of attention focus in a variety of realworld environments, I conducted real-time sampling of distractibility, mindwandering and mood across a wide range of everyday environments and activities, e.g. reading in the park (Chapter 2). The results established a replicable single construct underlying everyday attention lapses, and also highlighted a negative correlation between attention lapses and mood, with greater levels of mindwandering and distraction from some external sources associated with reduced levels of mood. To assess whether daily-life attention lapses can be predicted from a laboratory attention-task measure, Chapters 3-4 employed a modified attention distractibility task and examined its relationship to distractibility reports in the realworld, specifically educational settings (at secondary school and university) in both adults and adolescents (aged 13-18). The results established that attention lapses in these settings can be predicted from distractor interference effects on task performance (across adults and adolescents) and that while distractibility levels did not differ between adolescents and adults, response variability was significantly higher in adolescence. In addition, perceptual load reduced distractibility in adults but not in adolescents. Chapter 5 subsequently examined whether an interpolated testing intervention was effective in reducing both mindwandering and external distraction during a university lesson. The results demonstrated that interpolated testing reduced mindwandering and increased recall but did not affect distractibility. This thesis thus extends our understanding of the relationship between mindwandering, external 3 distraction and mood in everyday settings, and of methods which might be used both to predict and mitigate such experiences.
... The study included 20 females and 20 males, aged 16.2 ± 2.0 (range [13][14][15][16][17][18][19] years, who experienced migraine with aura. Fifteen (37.5%) patients had visual aura only; 10 (25.0%) patients had visual and somatosensory auras; and 15 (37.5%) patients had visual with/or without somatosensory and with dysphasic aura. ...
... In the other hand, prosopagnosia was reported in only one patient. This could be due to the fact that this function is localized bilaterally [19]. The second most common type of aura in our group of patients was somatosensory phenomena (60%). ...
Complex migraine aura in teenagers can be complicated to diagnose. The aim of this study was to present detailed features of migraine aura in teenage migraineurs.
This cross-sectional study was conducted in the period from 2008 till 2013. A total number of 40 teenage migraineurs (20 females and 20 males) met criteria for this study. The patients were interviewed using a specially designed questionnaire for collecting data about migraine aura features. Main outcome measures were frequency of visual, somatosensory and higher cortical dysfunction (HCD) symptoms in teenage migraineurs population during the aura, and also within each individual.
Visual aura was reported in every attack, followed by somatosensory (60%) and dysphasic (36.4%) aura. Scintillating scotoma and blurry vision were mostly reported and predominant visual symptoms. The most common somatosensory symptom was numbness in hand. HCD were reported by 22 (55%) patients. Slowed speech was mostly reported symptom of HCD, followed by dyslexia, deja vu phenomenon, color dysgnosia, and dyspraxia. In patients with HCD, aura frequency per year (6.18 +/- 3.17 vs. 3.33 +/- 2.03, p = 0.003) and prevalence of somatosensory symptoms (77.3% vs. 38.9%, p = 0.014) were significantly higher than in patients without HCD.
Aura symptoms vary to a great extent in complexity in teenage migraineurs. Consequently, results obtained in this study provide useful information for clinicians when faced with unusual migraine aura.
... Stroke, anoxia, carbon monoxide poisoning are common causes of the disorder; demyelination, tumor, and mercury poisoning are also causes but somewhat less common. 21,22 A particularly well-known patient who fits the visual form agnosia description is DF, a patient who was unable to determine whether a square and rectangle, matched for total flux, were the same shape or not. 23,24 DF also was impaired at segmenting figure from ground, deciding whether shapes were symmetrical or not and, not surprisingly, was profoundly impaired at object recognition. ...
... Demyelination, hemorrhage, and tumor are uncommon causes whereas bilateral lesions involving the inferior temporo-occipital junction and subjacent white matter are the most common anatomic lesions associated with this form of agnosia. 22 Note, however, that this disorder can also occur with unilateral damage to the left or right temporo-occipital region. 32,33 As with apperceptive agnosia, the associative form can be subdivided into two variants. ...
The neuropsychological disorder, known as visual agnosia, refers to the impairment in deriving the meaning of a visually presented stimulus, in spite of the affected individual having intact sensory and low‐level vision, and normal language and semantic function. This type of disorder is intriguing both clinically and scientifically, and vision scientists have studied visual agnosia as a means of shedding light on how the normal visual system functions. Considerable progress has been made in this domain, in parallel with detailed behavioral and neural investigations of the visual system of neurologically intact individuals and of nonhuman primates. Here, we focus specifically on the neuropsychological studies and provide a broad overview of the wide range of impairments that fall under the label ‘visual agnosia’, including those acquired following brain damage in premorbidly normal individuals, those that appear to have been present since birth, and those whose onset is late in life and is associated with neurodegeneration. We also outline the different subtypes of visual agnosia, including those that affect primarily the recognition of faces, words, or objects, and we lay out some of the key questions currently being addressed by researchers in this domain. Copyright © 2010 John Wiley & Sons, Ltd.
This article is categorized under: Psychology > Brain Function and Dysfunction
Neuroscience > Clinical Neuroscience
... [3][4][5] First, a region composed of the fusiform gyrus and its adjacent inferior temporal and occipital gyri with right-hemispheric dominance has been labeled as the fusiform face area, since it is preferentially activated by static facial features in functional neuroimaging studies. 4 Its critical role in face recognition is supported by evidence that damage to this area and brain regions adjacent to it is associated with prosopagnosia, 6 the inability to identify familiar faces. Second, an area of the right lateral occipitotemporal cortex, termed the extrastriate body area, responds preferentially to pictures of the human body, suggesting a specialized system for processing the visual appearance of the human body. ...
... 29 In contrast, prosopagnosic patients with more posterior temporal damage are solely impaired in recognizing familiar faces, but not voices, and can still identify emotional facial expressions. 6 Decoupling of polymodal perceptual representations from their emotional and social contents might explain why lesion studies in animals and humans often associate right-sided or bilateral lesions of the anterior temporal lobes with abnormal social behavior. For example, female monkeys with lesions of the temporal poles, excluding the amygdala, lose their emotional attachment to peer monkeys and even to their own infants. ...
Social cognitive neuroscience is a novel field of interdisciplinary research that examines socio-emotional cognition and behavior by emphasizing the neural substrates of these processes. Insights from this biological perspective have established that socio-emotional processing does not happen in a sequential order but in a recursive and interlinked fashion; that individual brain regions are not associated with one, but multiple, distinct social functions; and that brain regions are organized into dynamically interacting networks. These factors explain why it is difficult to pinpoint the neural substrates of particular social deficits in patients with brain diseases. With that said, there are specific brain regions that are highly specialized for the perception, regulation, and modulation of emotion and behavior. This article will review key aspects of social processing beginning with their underlying neural substrates, including (1) perception of social signals, (2) social and emotional evaluation, and (3) behavioral response generation and selection. Case studies will be used to illustrate the real-life social deficits resulting from distinct patterns of neuroanatomic damage, highlighting the brain regions most critical for adequate social behavior. Continuum Lifelong Learning Neurol 2010;16(4):69-85.
... In colour agnosia, people have intact colour perception, yet have severe difficulties in naming, categorising, and recognising colours and form adequate object-colour associations [7][8][9]. In most cases, colour agnosia is acquired after brain damage, either bilateral or left hemisphere lesions [10], mostly in the occipitotemporal lobe [6]. ...
Colour agnosia is a disorder that impairs colour knowledge (naming, recognition) despite intact colour perception. Previously, we have identified the first and only-known family with hereditary developmental colour agnosia. The aim of the current study was to explore genomic regions and candidate genes that potentially cause this trait in this family. For three family members with developmental colour agnosia and three unaffected family members CGH-array analysis and exome sequencing was performed, and linkage analysis was carried out using DominantMapper, resulting in the identification of 19 cosegregating chromosomal regions. Whole exome sequencing resulted in 11 rare coding variants present in all affected family members with developmental colour agnosia and absent in unaffected members. These variants affected genes that have been implicated in neural processes and functions (CACNA2D4, DDX25, GRINA, MYO15A) or that have an indirect link to brain function, development or disease (MAML2, STAU1, TMED3, RABEPK), and a remaining group lacking brain expression or involved in non-neural traits (DEPDC7, OR1J1, OR8D4). Although this is an explorative study, the small set of candidate genes that could serve as a starting point for unravelling mechanisms of higher level cognitive functions and cortical specialization, and disorders therein such as developmental colour agnosia.
... This is interesting as object recognition has not traditionally been considered to rely on lateralized processes. While there are reports of object agnosia following unilateral lesions to the right or left hemisphere, [80][81][82][83][84] these cases typically also have either prosopagnosia or alexia, depending on the hemisphere. This was also the case in our sample. ...
Knowledge about the consequences of stroke on high-level vision comes primarily from single case studies of patients selected based on their behavioural profiles, typically patients with specific stroke syndromes like pure alexia or prosopagnosia. There are, however, no systematic, detailed, large-scale evaluations of the more typical clinical behavioural and lesion profiles of impairments in high-level vision after posterior cerebral artery stroke. We present behavioural and lesion data from the Back of the Brain project, to date the largest (N = 64) and most detailed examination of patients with cortical posterior cerebral artery strokes selected based on lesion location. The aim of the current study was to relate behavioural performance with faces, objects and written words to lesion data through two complementary analyses: (i) a multivariate multiple regression analysis to establish the relationships between lesion volume, lesion laterality and the presence of a bilateral lesion with performance and (ii) a voxel-based correlational methodology analysis to establish whether there are distinct or separate regions within the posterior cerebral artery territory that underpin the visual processing of words, faces and objects. Behaviourally, most patients showed more general deficits in high-level vision (n = 22) or no deficits at all (n = 21). Category-selective deficits were rare (n = 6) and were only found for words. Overall, total lesion volume was most strongly related to performance across all three domains. While behavioural impairments in all domains were observed following unilateral left and right as well as bilateral lesions, the regions most strongly related to performance mainly confirmed the pattern reported in more selective cases. For words, these included a left hemisphere cluster extending from the occipital pole along the fusiform and lingual gyri; for objects, bilateral clusters which overlapped with the word cluster in the left occipital lobe. Face performance mainly correlated with a right hemisphere cluster within the white matter, partly overlapping with the object cluster. While the findings provide partial support for the relative laterality of posterior brain regions supporting reading and face processing, the results also suggest that both hemispheres are involved in the visual processing of faces, words and objects.
... The lingual and fusiform gyri play important roles in visual processing. A previous study has shown that prosopagnosia is associated with damage to the fusiform and lingual gyri (68). Chao found that damage to the fusiform/lingual gyri correlates with a loss in color perception (69). ...
Background:
The impacts of age and sex on brain structures related to cognitive function may be important for understanding the role of aging in Alzheimer disease for both sexes. We intended to investigate the age and sex differences of cortical morphology in middle-aged and older adults and their relationships with the decline of cognitive function.
Methods:
In this cross-sectional study, we examined the cortical morphology in 204 healthy middle-aged and older adult participants aged 45 to 89 years using structural magnetic resonance imaging (sMRI) data from the Dallas Lifespan Brain Study data set. Brain cortical thickness, surface complexity, and gyrification index were analyzed through a completely automated surface-based morphometric analysis using the CAT12 toolbox. Furthermore, we explored the correlation between cortical morphology differences and test scores for processing speed and working memory.
Results:
There were no significant interactions of age and sex with cortical thickness, fractal dimension, or gyrification index. Rather, we found that both males and females showed age-related decreases in cortical thickness, fractal dimension, and gyrification index. There were significant sex differences in the fractal dimension in middle-aged participants and the gyrification index in older adult participants. In addition, there were significant positive correlations between the cortical thickness of the right superior frontal gyrus and Wechsler Adult Intelligence Scale (WAIS)-III Letter-Number Sequencing test scores in males (r=0.394; P<0.001; 95% CI for r values 0.216-0.577) and females (r=0.344; P<0.001; 95% CI for r values 0.197-0.491), respectively. Furthermore, a significant relationship between the gyrification index of the right supramarginal gyrus (SupraMG) and WAIS-III Digit Symbol test scores was observed in older adult participants (r=0.375; P<0.001; 95% CI for r values 0.203-0.522).
Conclusions:
The results suggest that, compared with males, females have more extensive differences in cortical morphology. The gyrification index of the right SupraMG can be used as an imaging marker of sexual cognitive differences between males and females in older adults. This study helps to further understand sex differences in the aging of the brain and cognition.
... This relationship has been established through both imaging and electrophysiological studies [1][2][3][4]. Data from the local environment are collected by the sensory apparatus and processed in the central nervous system [5,6]. The resulting neural firing patterns across the cerebral cortex are correlated with qualitative perceptual awareness, the formation of memories, and the initiation of contextuallyappropriate behavior [7][8][9][10]. ...
It has historically proven difficult to explain the relationship between neural activity and representative information content. A new approach focuses on the unique properties of cortical neurons, which allow both upstream signals and random electrical noise to affect the likelihood of reaching action potential threshold. Here, each electron is modeled as an electromagnetic point source, interacting in a probabilistic manner with each neuronal membrane. The electron is described as some set of probability amplitudes, distributed across five orthogonal axes: x, y, z, energy state, and time. The membrane potential of each neuron is defined by the probabilistic spatial position and atomic orbital of each local electron, after some time evolution. The mixed sum of all probabilistic component pure states is the physical quantity of information held by the neural network, given by a complex-valued wavefunction. If the probabilistic trajectory of each electron over time t affects the voltage state of multiple computational units, then the system state must be computed as a whole, with the state of each neuron being resolved as every component pure state is resolved. This computational process yields a defined system state at a defined location in time, which immediately becomes the past as a new probability density forms. If the membrane surface of each computational unit is also a charge-detecting polymer substrate that meets the criteria of a holographic recording surface, then this encoding process will generate a holographic projection of representative information content. The constructive and destructive interference of high-dimensional probability amplitudes yields a non-deterministic computational outcome for each neuron. That now-defined system state is paired with a multi-sensory percept, which is exclusively accessed by the encoding structure, with content limited by the range and sensitivity of the sensory apparatus. This model usefully offers a plausible explanation for both perceptual content and non-deterministic computational outcomes emerging from cortical neural network activity.
... This is interesting as object recognition has not traditionally been considered to rely on lateralised processes. While there are reports of object agnosia following unilateral lesions to the right or left hemisphere, [80][81][82][83][84] these cases typically also have either prosopagnosia or alexia, depending on the hemisphere. The majority of visual agnosia cases, however, have bilateral lesions of ventral occipitotemporal cortex, 79 and even in unilateral cases, functional imaging has demonstrated abnormal activation patterns also in the contralesional hemisphere. ...
Knowledge about the consequences of stroke on high level vision comes primarily from single case studies of patients selected based on their behavioural profiles with deficits in the recognition of a specific visual category such as faces or words. There are, however, no systematic, detailed, large-scale evaluations of the more typical clinical behavioural and lesion profiles of impairments in high level vision that may follow posterior cerebral artery (PCA) stroke. These goals were met by the current study through the data collected in the Back of the Brain (BoB) project: to date, the largest (N=64) and most detailed examination of patients with cortical PCA strokes selected based on lesion location rather than behavioural symptoms.
We present here two complementary analyses of the structural neuroimaging data and key indices of behavioural performance with the visual processing words, objects and faces: (1) a multivariate multiple regression analysis to establish the relationships between lesion volume, lesion laterality or the presence of a bilateral lesion with performance on words, objects and faces; and, (2) a voxel-based correlational method (VBCM) analysis to establish whether there are distinct or separate regions within the PCA territory that underpin the visual processing of these categories.
In contrast to the characterization of specific stroke syndromes like pure alexia or prosopagnosia in the literature, most patients in our cohort showed more general deficits in high level vision (n=22) or no deficits at all (n=21). Category-selective deficits were rare (n=6), and were only found for words, which, interestingly could follow left or right hemisphere lesions. The lesion analyses mainly confirmed the pattern reported in more selective cases: word recognition impairments are associated with a left-sided pattern of damage and face recognition deficits with a bilateral albeit right-dominant lesion pattern. Importantly, however, both general and more selective impairment may follow from left or right unilateral as well as bilateral lesions.
While the findings provide partial support for the relative laterality of posterior brain regions supporting reading in the left and, to a lesser extent, face processing in the right hemisphere, the results suggest that both hemispheres are involved in the visual processing of faces, words and objects. This has ramifications for researchers studying the healthy brain and for clinicians working with patients with PCA stroke. Clinicians are recommended to carry out formal assessment of face, word and object recognition as most patients are expected to present with a mixed picture of deficits.
... This point generalises in a way that justifies individuating capacities in more finegrained ways than we typically do. Consider agents who, as a result of brain damage, can recognise objects when held at some orientations but not others, or can recognise what an object is but not what it is used for, or can recognise moving objects but not still objects (De Renzi, 2000). Unless we already know to examine 12 It is worth noting that Fischer (with Tognazzini, 2011) takes blameworthiness to not be decided by reasons-responsiveness alone. ...
The situationist experiments demonstrate that most people’s behaviour is influenced by environmental factors much more than we expect, and that ordinary people can be led to behave very immorally. A number of philosophers have investigated whether these experiments demonstrate that subjects’ responsibility-relevant capacities are impeded. This paper considers how, in practice, we can assess when agents have a reduced capacity to avoid wrongdoing. It critiques some previously offered strategies including appeals to the reasonable person standard, appeals to counterfactuals and understandability of behaviour, and appeals to base rates of wrongdoing. It then proposes we should think a certain factor impeded capacities when this is the best explanation of a change in patterns of responses. With this approach in hand, I then argue that subjects in many of the situationist experiments are (mostly) excused for their actions.
... In colour agnosia, people have intact colour perception, yet have severe difficulties in naming, categorising, and recognising colours and form adequate object-colour associations (Nijboer, van Zandvoort, & de Haan, 2006, 2007a, 2007b. In most cases, colour agnosia is acquired after brain damage, either bilateral or left hemisphere lesions (De Renzi, 2000), mostly in the occipitotemporal lobe (De Vreese, 1991). ...
Colour agnosia is a disorder that impairs colour knowledge (naming, recognition) despite intact colour perception. Previously, we have identified the first and only-known family with hereditary developmental colour agnosia. The aim of the current study was to explore genomic regions and candidate genes that potentially cause this trait in this family. For three family members with developmental colour agnosia and three unaffected family members CGH-array analysis and exome sequencing was performed, and linkage analysis was carried out using DominantMapper, resulting in the identification of 19 cosegregating chromosomal regions. Whole exome sequencing resulted in 11 rare coding variants present in all affected family members with developmental colour agnosia and absent in unaffected members. These variants affected genes that have been implicated in neural processes and functions (CACNA2D4, DDX25, GRINA, MYO15A), that have a indirect link to brain function or development (MAML2, STAU1, TMED3), and a remaining group lacking brain expression or involved in non-neural traits (DEPDC7, OR1J1, OR8D4, RABEPK). Although this is an explorative study, the small set of candidate genes that could serve as a starting point for unravelling mechanisms of higher level cognitive functions and cortical specialization, and disorders therein such as developmental colour agnosia.
... This process is regarded as the associative recognition in the human cognitive system. More specifically, as it is proposed in [3,8] that human object perceptual is a hierarchical process consisting of two stages: (a) a "viewercentered" representation stage, where the features of the object are presented from the viewer's perspective , while the existing features may be incomplete due to occlusion and distance; (b) an "object-centered" representation stage, where the object's features are associated with its class-wise conceptual model stored in the brain. ...
Object detection from 3D point clouds remains a challenging task, though recent studies pushed the envelope with the deep learning techniques. Owing to the severe spatial occlusion and inherent variance of point density with the distance to sensors, appearance of a same object varies a lot in point cloud data. Designing robust feature representation against such appearance changes is hence the key issue in a 3D object detection method. In this paper, we innovatively propose a domain adaptation like approach to enhance the robustness of the feature representation. More specifically, we bridge the gap between the perceptual domain where the feature comes from a real scene and the conceptual domain where the feature is extracted from an augmented scene consisting of non-occlusion point cloud rich of detailed information. This domain adaptation approach mimics the functionality of the human brain when proceeding object perception. Extensive experiments demonstrate that our simple yet effective approach fundamentally boosts the performance of 3D point cloud object detection and achieves the state-of-the-art results.
... This case presents unexpected features. First, a deficit in face familiarity is observed after bilateral or RH lesions [17,18,36]; moreover, patients with left temporo-occipital lesions usually show associative visual agnosia or a more general semantic disorder [17,37,38], while our patient was not agnosic for objects and had normal semantics for famous people. Topographical disorientation and dyschromatopsia were absent. ...
Acquired prosopagnosia is usually a consequence of bilateral or right hemisphere lesions and is often associated with topographical disorientation and dyschromatopsia. Left temporo-occipital lesions sometimes result in a face recognition disorder but in a context of visual object agnosia with spared familiarity feelings for faces, usually in left-handers. We describe a patient with a left temporo-occipital hemorrhagic lesion unexpectedly resulting in a deficit of face familiarity, which could represent a mild form of associative prosopagnosia. Our patient failed to feel familiarity feelings even with very well-known famous faces but had neither visual object agnosia nor defects with semantics or naming of celebrities. This was confirmed even when the patient was re-tested a year later. We speculate that a graded lateralization of face processing could be at the basis of occasional cases of prosopagnosia.
... This process is regarded as the associative recognition in the human cognitive system. More specifically, as it is proposed in [3,8] that human object perceptual is a hierarchical process consisting of two stages: (a) a "viewercentered" representation stage, where the features of the object are presented from the viewer's perspective , while the existing features may be incomplete due to occlusion and distance; (b) an "object-centered" representation stage, where the object's features are associated with its class-wise conceptual model stored in the brain. ...
Object detection from 3D point clouds remains a challenging task, though recent studies pushed the envelope with the deep learning techniques. Owing to the severe spatial occlusion and inherent variance of point density with the distance to sensors, appearance of a same object varies a lot in point cloud data. Designing robust feature representation against such appearance changes is hence the key issue in a 3D object detection method. In this paper, we innovatively propose a domain adaptation like approach to enhance the robustness of the feature representation. More specifically, we bridge the gap between the perceptual domain where the feature comes from a real scene and the conceptual domain where the feature is extracted from an augmented scene consisting of non-occlusion point cloud rich of detailed information. This domain adaptation approach mimics the functionality of the human brain when proceeding object perception. Extensive experiments demonstrate that our simple yet effective approach fundamentally boosts the performance of 3D point cloud object detection and achieves the state-of-the-art results.
... An example of the associationist approach to neuropsychological deficits is Déjerine's description of the pathological mechanisms bringing about "pure alexia", as shown in Fig. 10 (see Bub et al., 1993;Henderson, 2009). A similar mechanism had been suggested by Carl Freund (1889), to account for the selective inability to name (not to identify) objects in the visual modality (optische Aphasie, optic aphasia, see De Renzi, 2000;Riddoch, 1999, for reviews). The associationist approach to the component deficits of language is illustrated in Fig. 11 by the "Bell's" schema of the French neurologist Jean-Martin Charcot (1885;Clarac and Boller, 2009). ...
Reports of clinical observations of impairments of human mental functions that can be traced back to brain damage or dysfunction date to centuries ago. However, the naissance of neuropsychology as a scientific discipline is much more recent, dating to the 19th century. A most relevant observation was Paul Broca's report that damage to a frontal premotor region in the left hemisphere causes a deficit of spoken language (aphasia). Starting from this finding, other disorders brought about by brain damage were described, with impairments of perception and object recognition (agnosia), behavioral control, decision making, reasoning and intelligence, movement planning (apraxia), spatial orientation and attention, and memory (amnesia). The early study of individual patients with outstanding clinically apparent deficits (“single cases”) was followed by the investigation of groups of patients, using standardized psychometric tests, and statistical procedures of data analysis. In the second half of the 20th century neuropsychology became an independent scientific discipline, and, starting from the early 1960s, with its own scientific journals (Neuropsychologia, Cortex). In humans the correlation between behavioral deficits on the one hand and the localization of the responsible cerebral lesion on the other hand was initially based on post mortem autoptic findings. Beginning in the late 1930s also cortical brain stimulation of patients during awake surgery provided information about the localisation of cerebral functions. Starting from the late 1970s a variety of non-invasive methods for visualizing in vivo the brain became available for many patients. Neuropsychology, with the investigation of the disorders of higher mental functions caused by brain damage, has contributed both to the understanding of the neural and functional architecture of the mind, and to the diagnosis and rehabilitation of the disorders of its multiple component processes.
... Warrington (1975) offered that this problem lies in impaired access to generic engrams (memory traces) that describe categories of objects made up of a multitude of similar elements. Essentially, damage to a modality-specific meaning pro- cess (semantic system) is proposed, either in terms of defective access to or a degradation of semantic memory store for visual seman- tic representations themselves (De Renzi, 2000). Whether perception is entirely normal in associative agnosia (and just dissociated from semantics) remains somewhat con- troversial, and it is unclear whether any patient with truly normal perception and this form of agnosia exists. ...
Humans have the remarkable ability to encode and remember thousands of familiar objects in great detail, and yet the psychological and neural mechanisms that contribute to this facility remain elusive. This review considers the recent progress made on this topic, with consideration given to the data gleaned from a host of relevant methodologies. The results of psychophysical and neuroimaging investigations are considered alongside findings that examine object recognition in individuals with deficits in this domain. We also consider the emergence of object recognition skills through behavioral and imaging studies with children. Theoretical accounts and new techniques, including representational (dis)similarity analysis and deep convolution networks, are also considered. As is often the case in such reviews, more questions are raised than answers provided, and the comprehensive understanding of the mechanisms giving rise to visual object recognition remains an alluring challenge to cognitive science.
... Achromatopsy is also associated with occipito-temporal lesions, mainly on the right side. In the majority of cases it has a favorable outcome, except when the lesion is more posteriorly located, the case in our patient 4 . ...
The association of visual agnosia and prosopagnosia with cerebral metastasis is very rare. The presence of symmetric and bilateral cerebral metastases of melanoma is also uncommon. We report the case of a 34 year-old man who was admitted to hospital with seizures and a three-month history of headache, with blurred vision during the past month. A previous history of melanoma resection was obtained. CT of the skull showed bilateral heterogeneous hypodense lesions in the occipito-temporal regions, with a ring pattern of contrast enhancement. Surgical resection of both metastatic lesions was performed after which the patient developed visual agnosia and prosopagnosia. On follow-up, he showed partial recovery of visual agnosia, while prosopagnosia was still evident. The relevance of this case is the rare presentation of metastatic malignant melanoma affecting homologous occipito-temporal areas associated with prosopagnosia and associative visual agnosia.
... En la investigación sobre percepción en sujetos atípicos, como ocurre en el caso de los pacientes agnósicos, el reconocimiento de objetos se ve influenciado por el modo de presentación de los mismos. Los pacientes agnósicos tienen un mayor éxito para reconocer objetos reales en comparación con fotografías o dibujos [4,5], esto seguramente debido a que los objetos reales proporcionan información tridimensional que resulta clave para ayudar en su identificación [6,7]. ...
... One might argue that this is not surprising as the neuronal damage underlying such problems can be extensive. Associative visual agnosias are usually associated with damage to the anterior left temporal lobe (De Renzi, 2000;Goldberg, 1990;Greene, 2005). This damage, as it is often caused by strokes or head injuries, would not be associated with cell loss restricted to one cortical column. ...
We do not dispute the possibility of the existence in the brain of “grandmother cells”, which are very finely tuned neurons that fire only in the presence of specific objects or categories. However, we question the causal efficacy of such neurons at the functional or behaviour level. We claim that, even though very familiar items, such as “my grandmother”, may well have associated grandmother neurons, these neurons have very little, or no impact on the actual recognition of my grandmother. A study by Thomas, Van Hulle, and Vogels [(2002). Encoding of categories by noncategory-specific neurons in the inferior temporal cortex. Journal of Cognitive Neuroscience, 13, 190–200. doi:10.1162/089892901564252] found finely tuned, category-specific neurons in the inferior temporal cortex of monkeys, but also found that when these neurons were removed from their analysis, this had no effect on categorisation performance. Further, we have found no reported cases of the loss of recognition of single, highly familiar objects, which also argues for a lack of causal efficacy of grandmother-cell neurons.
... En la investigación sobre percepción en sujetos atípicos, como ocurre en el caso de los pacientes agnósicos, el reconocimiento de objetos se ve influenciado por el modo de presentación de los mismos. Los pacientes agnósicos tienen un mayor éxito para reconocer objetos reales en comparación con fotografías o dibujos [4,5], esto seguramente debido a que los objetos reales proporcionan información tridimensional que resulta clave para ayudar en su identificación [6,7]. ...
Objetivo:
Diseñar una configuración experimental para conocer el grado en que las modalidades de presentación de estímulos afectan el reconocimiento visual de objetos.
Materiales y Métodos:
Se diseñó un sistema de bajo costo para mostrar estímulos en tres modalidades: imágenes, videos y objetos reales. Fueron seleccionados 80 objetos, controlando las variables de manipulabilidad, edad de adquisición, familiaridad, complejidad visual y frecuencia léxica. Se realizó una prueba piloto utilizando el sistema con cinco personas sanas y se midieron los tiempos de reacción en la nominación de los objetos.
Resultados:
Las diferencias en los tiempos de reacción entre las modalidades observadas apoyan la influencia de la modalidad de presentación en el reconocimiento de objetos.
Conclusiones:
Las propiedades de volumen de los objetos permitirían la exploración de características que las fotografías no tendrían; razón por la cual, los tiempos de reacción para los objetos reales y los videos fueron menores. Son valiosos los aportes que ofrecen una alternativa de bajo costo para la visualización y el reconocimiento de objetos.
... orientation, luminance, contrast, color perception). These can be present after occipito-temporal brain injury (De Renzi, 2000). ...
Music is a special and unique part of human nature. Not only actively playing (making music in a group or alone) but also passive listening to music involves a richness of processes to make music the ideal tool to investigate how the human brain works. Acquired amusia denotes the impaired perception of melodies, rhythms, and the associated disability to enjoy music which can occur after a stroke. Many amusia patients also show deficits in visual perception, language, memory, and attention. Hence, the question arises whether amusia actually describes an independent clinical picture or is better described by a general perceptual deficit for auditory, as well as visual, and speech-related material. Additionally, the question in what way impaired abilities in attention and working memory influence the performance in the music perception task remains to be investigated. Behavioral investigations, lesion analysis, and functional magnetic resonance imaging were performed to assess the anatomical and functional correlates of these deficits. A better and more detailed understanding of amusia and connected cognitive deficits is not only relevant in terms of fundamental neuroscience but also from a clinical point of view: symptoms of amusia are rare, mostly undiscovered, and the underlying mechanisms are hitherto insufficiently understood.
... Durante las últimas décadas se ha publicado una diversidad de libros y artículos que han avanzado considerablemente nuestra comprensión de los trastornos perceptuales asociados con patologías cerebrales; es importante mencionar al menos Bauer (2012), De Renzi (1982, 2000, Farah (1992Farah ( , 2004, Riddoch & Humphreys (2003), Tonkonogy & Puente (2009) y Vignolo (2003. Más aun, se han descrito nuevas formas de agnosias, como es la agnosia para voces familiares conocida como fonagnosia (Van Lancker & Canter, 1982;Van Lancker, Cummings, Kreiman, & Dobkin, 1988), la dificultad para reconocer sabores familiares denominada como agnosia gustativa (Small, Bernasconi, Bernasconi, Sziklas, & Jones-Gotman, 2005) y los trastornos en el reconocimiento de olores o agnosia olfativa (Mendez & Ghajarnia, 2001). ...
... Agnosia is defined as a neurologic disorder through which the patient loses the ability to recognize persons, objects, shapes or sounds depending on the sense involved whereas the sense might not be defective and there might not be any memory loss (1). Chronologically, agnosia was first described by Carl Wernicke (1874) and Kussmaul (1877) who tried to respectively explain receptive aphasia and word deafness via agnosia (2). ...
... Agnosia is another problem that may be seen in patients with posterior circulation insufficiency. Agnosias are disorders of recognition, and objects, faces, and colors cannot be separately distinguished (28). Visual agnosia can be as high as 8.5% in isolated infarctions in the superficial region of the PCA (29). ...
Neurodegenerative disorders are characterized by decreased regional cerebral blood flow. Supporting this concept, both
cognitive training exercises and physical activity promote blood flow increase and correlate with healthy cognitive aging. The terminal
branches of the posterior circulation supply blood to areas of the brain, such as the thalamus, hippocampus, occipital lobe, and
cerebellum, involved with important intellectual functions, particularly recent memory, visual-spatial functioning, and visuomotor
adaptations. Amnesia and visual agnosia may be a complication of not only posterior circulation infarctions but also vertebrobasilar
insufficiency (VBI) without accompanying structural infarcts. The cognitive impairment may be a manifestation of transient attacks and
may persist beyond resolution of symptoms related to ischemia. Early recognition of cognitive deficits in the VBI patient is important
because several recent reports show stent placements or medical treatment may improve cognition.
... Object recognition has been described as a hierarchical process (Ungerleider & Haxby, 1994), where posterior regions of the ventral stream process low-level features of an object (Grill-Spector et al., 1999), and more anterior regions integrate those basic features into a more abstract representation necessary for the object to acquire a meaning (semantic processing) (Ungerleider & Mishkin, 1982). The right and left hemispheres are thought to be differentially involved in these stages e right brain-damaged patients were found to be impaired on perceptual processing (apperceptive agnosia), whereas left brain-damaged patients were found to be impaired in semantic processing (associative agnosia) (De Renzi, 2000;De Renzi, Scotti, & Spinnler, 1969;Warrington & Taylor, 1978). Regions of left posterior temporal cortex, including the fusiform gyrus, the ITG and the MTG, were found to be activated during conceptual processing of both pictures and words in several neuroimaging studies (Bookheimer, 2002;Thompson-Schill, 2003;Vandenberghe, Price, Wise, Josephs, & Frackowiak, 1996;Xu, Gannon, Emmorey, Smith, & Braun, 2009). ...
... Although optic aphasia is often associated with agnosia, 6,7 it differs in the capacity to copy shapes -a compromised ability in aperceptive agnosia 3,8,9 -and in recognition of the presented object through other sensorial means 10 -also compromised in associative agnosia. 3,8,9,11 Four important aspects must be considered to differentiate among these disorders: 1 -Patients with optical aphasia are able to demonstrate by gestures or mimes that, although they are unable to name a certain object, they recognize it. 2 -There are mistakes while naming the objects, however, these are semantically related to the presented object; 3 -There is insensitivity concerning the quality of visually presented stimulus such as drawings or tri-dimensional objects; 4 -There is no compromise in daily life activities. ...
Optic aphasia is characterized by a deficit in naming objects presented visually, as a result of left occipito-temporal lesion. It differs from other neuropsychological disorders due to the nature of the deficits and impairment of cognitive function. A 52 year-old patient, admitted after an episode of sub-acute infarction in the territory of the left posterior cerebral artery involving the temporo-occipital region, was submitted to neuropsychological evaluation as part of a diagnostic investigation and presented specific characteristics of this disorder, as well as impairment to episodic memory. The relevance of the present case is justified not only due to the rarity of the disorder, but also because it highlights the importance of differential diagnosis in the treatment of patients. Déficits cognitivos associados à afasia óptica: contribuição neuropsicológica para o diagnóstico diferencial. Resumo – Afasia óptica consiste num déficit de nomear objetos apresentados visualmente como resultado de lesão occipito-temporal esquerda. Difere de outras desordens neuropsicológicas devido à natureza do déficit e comprometimento de funções cognitivas. Um paciente de 52 anos, internado após episódio de infarto subagudo em território de artéria cerebral posterior esquerda com acometimento da região têmporo-occipital, foi subme-tido à avaliação neuropsicológica como parte de investigação diagnóstica e apresentou características específicas desta desordem, bem como comprometimento de memória episódica. A relevância deste estudo é justificada não somente pela raridade com que a afasia óptica se apresenta, mas porque evidencia a importância do diagnóstico diferencial no tratamento dispensado aos pacientes. Palavras-chave: afasia óptica, avaliação neuropsicológica, diagnóstico diferencial.
... Especially during aura, different types of agnosia can occur, linked to specific cortical areas in the lateral occipital complex related to visual recognition (Malach et al., 1995). Prosopagnosia is associated with dysfunction in at least two neighboring visual areas, in the inferior occipital cortex, and in the lateral posterior fusiform gyrus (De Renzi, 2000;Haxby et al., 2000). The relative paucity of prosopagnosia in migraine may be related to the fact that this function is bilaterally represented. ...
Abstract Migraine is the most common neurologic condition. One-third of migraineurs experience transient neurologic symptoms, the so-called aura. There is strong evidence that spreading depression (SD) is the electrophysiologic substrate of migraine aura. SD is an intense pan-depolarization wave that slowly propagates in gray matter by way of contiguity and transiently disrupts neuronal function. When induced subcortically, striatal SD causes hemiparesis, hippocampal SD can trigger seizures and impact cognition, and bilateral thalamic SD can diminish consciousness. Recent data show that transgenic mice expressing familial hemiplegic migraine (FHM) type 1 mutations in voltage-gated Ca2+ channels (Cav2.1) develop mutation-specific aura-like signs after a cortical SD similar to patients with the respective mutation. These signs are associated with facilitated subcortical SD propagation. As in FHM, mice with the R192Q mutation develop pure hemiplegia associated with cortical SDs propagating into caudoputamen. S218L mice display additional signs such as seizures and coma when SD propagates into hippocampus and thalamus. In hyperexcitable FHM brains, SD may propagate between cortex and subcortical structures via permissive gray matter bridges, or originate de novo in subcortical structures, to explain unusual and severe aura signs and symptoms. Reciprocal spread and reverberating waves can explain protracted attacks.
... Patients with aperceptive agnosia have difficulties to see an object as a whole or in a meaningful way and cannot match, copy, discriminate or categorize drawings, pictures or objects. The typical patient with associative agnosia is unable to name an object or the image of an object that is shown to him/her, and makes semantic errors [35]. Nonetheless, if the verbal definition is presented to the patient with aperceptive or associative agnosia (e.g., a cutting implement consisting of two blades joined by a swivel pin that allows the cutting edges to be opened and closed, for the object "scissors"), s/he will often be able to name it. ...
Assistive technologies represent a potential solution to allow people with Alzheimer's disease (AD) to remain in their home for as long as possible. They involve the use of technological devices called prompts, which aim to provide adapted cognitive assistance when needed. However, a literature review of the field revealed a predominant use of verbal prompts with little knowledge of their real effectiveness. In order to help adapting assistive technologies to the particular cognitive profile of people with AD, this paper proposes comprehensive guidelines. First, we identify the main deficits of AD that influence the effectiveness of prompts. Second, we detail which prompting strategy to use accordingly. Third, we propose an experimental protocol based on a well-known test, and new prompting software, which allows for the validation of the proposed guidelines. Finally, we present the preliminary results of a first experiment conducted in our laboratory with participants ranging from mild to moderate AD. This paper is a revised and expanded version of a paper entitled Smart Homes for People with Alzheimer's Disease: Adapting Prompting Strategies to the Patient's Cognitive Profile presented at the 5th International Conference on Pervasive Technologies Related to Assistive Environments (PETRA 2012).
... In the latter I typically observe its features and can name them—e.g., " there's a red after-image, " " that's a veridical percept that shows me that there is a red rose out there, " etc. Neurological lesions show that the phenomenology and the epistemology of this system are processed by different brain mechanisms. In associative agnosia the patient can see perfectly well but cannot recognize what she is seeing (De Renzi, 2000). In blindsight the patient can see nothing but can recognize ( " guess " correctly) what the object 'out there' is, including its color. ...
This paper reviews four current theories of brain-consciousness relations—classical Cartesian Dualism, the Identity Theory, Eliminative Materialism, and a new form of Substance Dualism that includes a modified form of the Cartesian theory. This entails a critical examination of our basic concepts of what consciousness is, of the nature of the body image, and the relation of phenomenal space to physical space. This investigation reaches the same result as that attained recently by the physicist Bernard Carr (2008)—that what is needed is a paradigm shift in our basic concepts of the geometry of the Universe. In order to understand phenomenal consciousness we need to replace the present four-dimensional model with a higher-dimensional structure, in which a phenomenal space (with its contents) and physical space (with its contents) are different cross-sections (branes) of a higher-dimensional space (the bulk).
Keywords: brain—consciousness—mechanisms—substance dualism—brane theory
Data gathered in the field of the experimental social psychology have shown that it is more difficult to recognize a person through his/her voice than through his/her face and that false alarms (FA) are produced more in voice than in face recognition. Furthermore, some neuropsychological investigations have suggested that in patients with damage to the right anterior temporal lobe (ATL) the number of FA could be higher for voice than for face recognition.
In the present study we assessed FA during recognition of famous people from faces and voices in patients with unilateral ATL tumours and in normal participants tested after anodal transcranial direct current stimulation (tCDS), over the left or right ATL. The number of FA was significantly higher in patients with right than in those with left temporal tumours on both face and voice familiarity. Furthermore, lesion side did not differentially affect patient's sensitivity or response criterion when recognizing famous faces, but influenced both these measures on a voice recognition task. In fact, in this condition patients with right temporal tumours showed a lower sensitivity index and a lower response criterion than those with left-sided lesions. In normal subjects, the greater right sided involvement in voice than in face processing was confirmed by the observation that right ATL anodal stimulation significantly increased voice but only marginally influenced face sensitivity. This asymmetry between face and voice processing in the right hemisphere could be due to the greater complexity of voice processing and to the difficulty of forming stable and well-structured representations, allowing to evaluate if a presented voice matches or not with an already known voice.
Unilateral spatial neglect is a neuropsychological syndrome, more frequent after damage to the right cerebral hemisphere, featuring an impaired ability to orient toward the contralateral left side of space and the body, and the inability to detect and report events from that side, of which patients are not aware. In addition to these defective manifestations, patients may show gratuitous behaviors, which include additional productions, unrelated to the task's demand, such as drawings and repeated marks (perseveration) in exploratory target cancellation tasks. Neglect is a multi-component deficit, whose diverse manifestations share a divide between the attended ipsilateral and the neglected contralateral sides of space. Different pathological mechanisms contribute to neglect, including perceptual and premotor impairments, that may be specific to sensory modality, sector of space, and mental images. Neglect may manifest in different coordinate frames with reference to the body and body parts, and objects (egocentric and allocentric neglect). Spatial neglect is a severely disabling disorder, which interferes with functional recovery from stroke. The neural correlates of neglect include cerebral cortical regions surrounding the sylvian fissure: the posterior inferior-parietal cortex, the temporo-parietal junction, the posterior-superior temporal and the frontal premotor cortices, subcortical gray nuclei and white matter fiber tracts connecting these regions. Neglect is independent of, and cannot be traced back to, sensory and motor deficits, and may be interpreted as a derangement of multiple networks, primarily based in the right hemisphere, supporting spatial attention and representation of space and objects in it.
Aim
This study evaluates the spectrum of visual impairment in stroke survivors.
Methods
The Impact of Visual Impairment after Stroke (IVIS) study is a multi-centre, acute stroke unit, prospective epidemiology study. Comprehensive visual examination was offered to all stroke survivors.
Results
1500 stroke admissions were recruited. 1204 stroke survivors had visual assessment. Reduced central vision was documented in 529, visual field loss in 308, ocular motility abnormalities in 533 stroke survivors, visual perception deficits in 59 stroke survivors and visual inattention in 315 stroke survivors. About half, regardless of visual impairment type, were visually asymptomatic. Recovery, whether full or partial, was best for central vision, ocular motility abnormalities and visual perception deficits (about 70% improvement) occurring over a mean follow-up period of 2–3 months.
Conclusions
Incidence of impaired central vision, visual field loss, ocular motility disorders and visual inattention was 29.4%, 24.8%, 39.3% and 26.2% respectively. Visual impairment was more likely to occur in more severe stroke and older stroke survivors. Asymptomatic cases raise concerns for acute stroke units where robust specialist vision screening is not routine. Those with partial/no recovery require specialist follow-up and management whilst the wide range of abnormalities highlight the need for specialist visual assessment acutely.
•
Implications for rehabilitation
• Visual impairment is a common consequence of stroke.
• Incidence of visual impairment is about 60%.
• Significant numbers of stroke survivors are visually asymptomatic, highlighting the need for standardised vision assessments.
• Many stroke survivors have persistent long-term visual impairment, necessitating referral and access to specialist eye care services.
La agnosia visual es una deficiencia visual adquirida que se caracteriza por la dificultad para reconocer estímulos sin podérselo atribuir a pérdida de la visión, dificultades en el lenguaje o deterioro mental general. El tratamiento se ha enfocado principalmente en el entrenamiento de estrategias compensatorias y menos común en la rehabilitación neuropsicológica. El objetivo del presente artículo es mostrar la mejoría clínica significativa alcanzada por dos pacientes con agnosia visual aperceptiva que fueron sometidos a un programa de rehabilitación neuropsicológica, modelo PAINT.
In the present chapter, I shall argue that neuropsychological data provide some evidence that inferential and referential competences are functionally isolable, i.e., that they can operate independently of one another. In extreme cases, one competence can be completely damaged without this resulting in an impairment of the other, and vice versa (double dissociation). One side of the dissociation, i.e., selective damage to referential abilities, is well attested in the relevant neuropsychological literature. It is common, for instance, in visual agnosia, an impairment of the capacity to recognise visually presented objects which is crucially unrelated to deficit in elementary vision, language, memory, and general cognitive decline. Critically, the patients’ performances in inferential tasks (e.g., definition naming, word-word matching) are usually perfectly preserved. The second side of the dissociation, i.e., the selective impairment of inferential competence, is rarer but also attested. Deficits in inferential performances can be found in a variety of syndromes, such as semantic dementia, semantic aphasia, and Alzheimer’s Disease. None of the syndromes presented above is selective for inferential competence. Nevertheless, as we shall see, selective damage to inferential competence has been observed several times, and the number of cases has grown considerably in recent years.
In this chapter, based on the previously discussed experimental data, and on a wider review of the relevant neurosemantic literature, I provide a more detailed discussion of the specific neural regions which underpin, respectively, inferential competence and referential competence.
This paper summarizes the multidisciplinary pediatric assessment methods of 3 European centers for identifying and assessing cerebral visual impairment in childhood. It describes a comprehensive neurodevelopmental assessment evaluation in which visual aspects play an important part. Developmental trajectories and the heterogeneity of the clinical picture are emphasized. Multidisciplinary ophthalmology and neurodisability/neurology teamwork together with the parent and teachers, to reach an integrated and individualized perspective for the individual child, are described. This comprehensive assessment is the starting point for habilitation programs and interventions, that can support and meet the child's needs and help them reach their optimal potential. Future developments in classification of the cerebral visual impairment conditions, building on the child's individual assessment profile, will further enhance the direction of clinical, educational, and research progress.
What is a higher cortical function? As one examines the abilities of a human, one is struck by our ability to use tools and create wonderful buildings or works of art. But our ability to communicate by speaking and writing and reading we believe is the best example of a higher cortical function. These centers that are responsible for language are primarily in the dominant hemisphere. The motor type of aphasia (Broca’s area) originates from the inferior frontal gyrus, while the sensory type of aphasia originates in the superior temporal gyrus (Wernicke’s area).
Background:
There are many disorders of higher visual processing that result from damage to specific areas of the cerebral cortex that have a specific role in processing certain aspects (modalities) of vision. These can be grouped into those that affect the ventral, or "what?", pathway (e.g., object agnosia, cerebral achromatopsia, prosopagnosia, topographagnosia, and pure alexia), and those that affect the dorsal, or "where?", pathway (e.g., akinetopsia, simultanagnosia, and optic ataxia).
Evidence acquisition:
This article reviews pertinent literature, concentrating on recent developments in basic science research and studies of individual patients.
Results:
An overview of the current understanding of higher cerebral visual processing is followed by a discussion of the various disorders listed above.
Conclusions:
There has been considerable progress in the understanding of how the extrastriate visual cortex is organized, specifically in relation to functionally specialized visual areas. This permits a better understanding of the individual visual agnosias resulting from damage to these areas.
Die Störung der primären Wahrnehmung wird hier dargestellt — vorwiegend der visuellen und akustischen. Sie ist einerseits wichtig wegen psychopathologischer Symptome, die bei fortgeschrittenen Demenzsyndromen vorliegen können, andererseits sind die Mechanismen der Wahrnehmung wichtig zum Verständnis von komplexen Wahrnehmungsstörungen wie den Halluzinationen. Auf dem Weg eines Stimulus durch das Gehirn betrachten wir den ersten Schritt, die Wahrnehmung. Sie ist in der Agnosie gestört — ein seltenes neuropsychologisches Syndrom, das beispielsweise bei degenerativen Hirnerkrankungen beobachtet wird. Da Störungen der primären Wahrnehmung in der Psychopathologie nur eine geringe Bedeutung haben, werden die Störungen nur knapp dargestellt. Die komplexen Wahrnehmungstäuschungen, die viel häufigeren Halluzinationen, werden in ▸ Kap. 12 geschildert.
Wernicke proposed that knowledge of the outside world was conceptualized and that the necessary information that makes up these concepts is stored in many different and interconnected areas of the brain. He clearly made a distinction between knowledge of a word itself (i.e. the sound or pronunciation of it) and knowledge of its meaning or ‘concept’. Since the era of the diagram makers (see also Chap. 4), there has been a discussion of how concepts are anatomically represented in the brain. Several of the earlier researchers truly considered a ‘centre’ for conceptual knowledge, similar to the anatomical centres for motor or speech functions. Some, for example, Mills, even believed that this concept centre was identical to the naming centre [1]. Most others, like Wernicke or Lichtheim, considered the concept centre more of a theoretical construct with a largely heuristic purpose, at least not something with a strict anatomical definition. To them, the true meaning of words and sentences emerged as the result of the complex interplay (association) between many different areas.
In philosophical semantics, a distinction has been proposed between inferential and referential lexical semantic competence. The former accounts for the relationship of words to the world, the latter for the relationship of words among themselves. Recent neuroscience research suggests that the distinction might be actually neutrally implemented. That is, that inferential and referential abilities might be underpinned by two functionally independent cognitive architectures, with partly different neural realizations. This hypothesis is consistent brain patient data, supporting the notion of a functional double dissociation between inferential and referential abilities, and with neuroscience data, suggesting that inferential and referential abilities are underpinned by at least partly different regions of the human brain. The principal aim of this article is to provide the first comprehensive and critical review of the empirical evidence in favour of such hypothesis.
It is well to warn the student beginning the study of language function prior to the development of modern Neuroimaging this had been an area of much confusion, with much disagreement and multiple hypotheses. This discussion will be limited to the more practical problems of anatomical localization.
In the preceding sections, we have alluded to various areas in the dominant hemisphere concerned with speech and language. The reader may well have been confused by the introduction of such terms as aphasia, apraxia, agnosia and dyslexia. It is well to warn the student beginning the study of language function that prior to the development of modern neuroimaging this had been an area of much confusion, with much disagreement and multiple hypotheses. This discussion will be limited to the more practical problems of anatomical localization.
Visuospatial information is generally thought to be processed only by the right hemisphere. A rapid review of the literature shows that such is not the case. Investigations carried out using the mental rotation paradigm, that we consider a paragon of visuospatial processing, reveal that the right hemisphere does play an essential part in the task, although the cooperation of left hemisphere is probably also necessary. The right hemisphere specialisation for visuospatial processing thus appears to be less marked than it is for language.
The first two editions of Stroke Syndromes were widely welcomed as authoritative reference works in the assessment and diagnosis of stroke. This revised and updated third edition remains the definitive guide to patterns and syndromes in stroke. A comprehensive survey of all types of neurological, neurophysiological and other clinical dysfunction due to stroke. The book contains descriptions of clinical problems encountered in stroke patients and their differential diagnosis, enhancing pattern recognition and enabling clinicians to differentiate between possible locations on the basis of symptoms and signs. The companion volume Uncommon Causes of Stroke completes this highly authoritative reference work which clinicians in neurology will find essential to the understanding and diagnosis of stroke.
Attention and planning can be altered by stroke, which can influence motor performance. Although the influence of these factors on recovery from stroke has been explored for the upper extremity, their impact on balance and gait are unknown. This perspectives article presents evidence that altered motor and visuospatial attention influences motor planning of voluntary goal-directed movements post-stroke, potentially impacting balance and gait. Additionally, specific strategies for rehabilitation of balance and gait post-stroke in the presence of these factors are discussed. Visuospatial attention selects relevant sensory information and supports the preparation of responses to this information. Motor attentional impairments may produce difficulty with selecting appropriate motor feedback, potentially contributing to falls. An original theoretical model is presented for a network of brain regions supporting motor and visuospatial attention, and motor planning of voluntary movements. Stroke may influence this functional network both locally and distally interfering with input and/or output of the anatomical or functional regions involved impacting voluntary movements. Though there is limited research directly examining leg function, evidence suggests alterations in motor and visuospatial attention influences motor planning and has a direct impact on performance of gait and balance. This model requires testing comparing healthy adults to individuals with stroke.
© 2015 American Physical Therapy Association.
Seth develops a convincing and detailed internalist alternative to the sensorimotor-contingency theory of perceptual phenomenology. However, there are remaining conceptual problems due to a semantic ambiguity in the notion of "presence" and the idea of "subjective veridicality." The current model should be integrated with the earlier idea that experiential "realness" and "mind-independence" are determined by the unavailability of earlier processing stages to attention. Counterfactual richness and attentional unavailability may both be indicators of the overall processing level currently achieved, a functional property that normally correlates with epistemic reliability. Perceptual presence as well as phenomenal transparency express epistemic reliability on the level of conscious processing.
In his Discussion Paper, Seth makes the case for counterfactual richness of predictive processing models in explaining perceptual presence and its absence in synesthetic concurrent percepts. Here, we question the relevance of counterfactual richness for these and related phenomena, and we argue that alternative theories of perception that incorporate top-down/bottom-up facilitatory interactions are at no relative disadvantage in addressing them. This work was authored as part of the Contributor's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no
IntroductionAura occurs in 20-30% of patients with migraine. Some descriptions of aura go far beyond the most frequent visual and sensory symptoms, suggesting the involvement of different cortical areas. The aim of this prospective study was to evaluate the frequency and types of disorders of higher cortical functions (HCF) that occur during visual and/or sensory aura.Methods
We interviewed 60 patients with visual and/or sensory aura about HCF disorders of praxia, gnosia, memory, and speech, during aura. Patients were divided into two groups, with and without HCF disorders, and were compared in terms of demographic data and aura characteristics.ResultsFrom all 60 patients, 65% reported at least one HCF disorder during aura. The patients with HCF disorders had longer-lasting auras (28.51 ± 16.39 vs. 19.76 ± 11.23, p = 0.016). The most common HCF disorders were motor dysphasia (82.05%) and dysnomia (30.74%). Motor dysphasia was more often reported by patients with visual as well as sensory aura (p = 0.002). The number of HCF disorders correlated with the aura duration (p = 0.003).Conclusion
According to our results, HCF disorders during aura occur more often than previously thought. The aura duration has some influence on the HCF disorders.
The notion of a neuron that responds selectively to the image of a particular complex object has been controversial ever since Gross and his colleagues reported neurons in the temporal cortex of monkeys that were selective for the sight of a monkey's hand (Gross, Rocha-Miranda, & Bender, 1972). Since that time, evidence has mounted for neurons in the temporal lobe that respond selectively to faces. The present paper presents a critical analysis of the evidence for face neurons and discusses the implications of these neurons for models of object recognition. The paper also presents some possible reasons for the evolution of face neurons and suggests some analogies with the development of language in humans.
The perception of faces is sometimes regarded as a specialized task involving discrete brain regions. In an attempt to identi$ face-specific cortex, we used functional magnetic resonance imaging (fMRI) to measure activation evoked by faces presented in a continuously changing montage of common objects or in a similar montage of nonobjects. Bilateral regions of the posterior fusiform gyrus were activated by faces viewed among nonobjects, but when viewed among objects, faces activated only a focal right fusiform region. To determine whether this focal activation would occur for another category of familiar stimuli, subjects viewed flowers presented among nonobjects and objects. While flowers among nonobjects evoked bilateral fusiform activation, flowers among objects evoked no activation. These results demonstrate that both faces and flowers activate large and partially overlapping regions of inferior extrastriate cortex. A smaller region, located primarily in the right lateral fusiform gyrus, is activated specifically by faces.
Previous experimenters have found that 4-day-old neonates look longer at their mother's face than at a stranger's face. We have replicated this finding under conditions where the infants are only provided with visual information on identity, with all the usual stimuli associated with the presence of the mother's face absent. The structure responsible for this cannot be equated with Conspec, the innate structure underlying face preference in neonates (Johnson & Morton, 1991). In a second experiment, we show that infants do not discriminate mother from stranger when both women are wearing head scarves. This indicates that, unlike older infants (de Schonen, Gil de Diaz, & Mathivet, 1986; de Schonen & Mathivet, 1990), neonates acquire a representation of their mother's face in which the hair line and outer contour have an integral part. This suggests that the system responsible for the neonates' performance is not the same as the one at work in older infants.
Three prosopagnosic patients were given four face tests, two perceptual (an unknown face identification test and an age estimation test) and two also implying memory (a familiarity check test and a famous face recognition test). The patients' performance was assessed with reference to the score distribution of the normal population. A patient was found to fail both perceptual and mnestic tests, without any noticeable difference between them. Also the second patient had poor scores on both kinds of tests, but his impairment was significantly greater on the perceptual ones. The third patient, on the contrary, showed no perceptual deficit and only failed the mnestic tests. His inability to recognize the individuality of an item among members of the same category was strictly confined to faces and never present for other classes of stimuli (cars, coins, personal belongings). This finding is supportive of the thesis that in a few patients the deficit underlying prosopagnosia is face specific.
We describe a patient with a deficit in imagery ability, following a left posterior cerebral artery infarction and possible anoxic episode. This deficit was inferred from the patient's performance on several tasks, including one in which normal adults are known to rely on imagery and two that tested imagery nonverbally, allowing us to examine the possibility of a language-imagery disconnection. In addition, we queried the patient on some cognitive capacities related to visual imagery: dreaming, geographical knowledge, and introspection regarding visual and auditory imagery. Hypotheses concerning the critical lesion site and underlying cognitive mechanism of image generation deficits are discussed in relation to this and other recent cases of impaired imagery ability with intact recognition ability, and the relevance of this deficit to the "imagery debate" is discussed.
AG, a pure case of optic anomia (object naming impaired; action naming good) is described. We consider the fit of experimental data from AG to different theoretical accounts of optic aphasia. Overall, we find no evidence for impairments intrinsic to semantic representations, but we note a number of problems that we interpret as indicating a slight, and specific, weakness in semantic access from vision. We also note a mild problem in generating names to a cue (verbal fluency). The main aim of the report was to provide a full description of tests of visual, semantic, and speech output skills in this patient in relation to the processing of visually presented objects and scenes, within a sequential information processing account which enables some theoretical implications to be drawn, albeit not conclusively.
Visual stimulus naming was studied in a 66-year-old male patient with optic aphasia subsequent to left occipito-temporal infarction. While having difficulty in naming objects perceived visually, he was able to name objects by viewing gestures illustrating their use, and to name actions shown in pictures. These results suggest that naming performance depends on the kind of stimulus that is visually presented (object vs. action). The present findings lend support to congnitive models which postulate the existence of visual and functional semantic systems.
Following a cerebral vascular accident, a patient showed a classical disconnection syndrome: left-hand tactile anomia, apraxia and dysgraphia and right-hand constructional apraxia. What made the case unusual was the presence of hand asymmetry in the performance of some matching-to-sample tasks carried out in foveal vision. The left hand committed significantly more errors than the right hand when it was not possible to identify on a perceptual basis the stimulus that was to be matched, because it was removed (memory condition) or was indicated verbally (verbo-visual matching), or had the same name but not the same physical appearance as the match (capital and lower-case letter matching). No hand difference emerged when the stimulus remained in full view throughout the matching task (perceptual condition). The hand effect, however, was limited to colours and letters. Objects, geometrical shapes and unfamiliar faces were matched with equal proficiency by both hands under every condition of presentation. Left-hand errors also significantly outnumbered right-hand errors in sorting colours according to hue and colouring drawings. MRI showed an infarct in the left cingulate white matter that ran parallel to the trunk of the corpus callosum, and an infarct of the splenium. However, the latter did not prevent the transmission of colour and letter information between the two hemispheres, as shown by the performance on perceptual equivalence tasks and by the correct right-hand responses to stimuli projected to the left visual field. We propose that this pattern of deficit is contingent upon the specific role that the left hemisphere plays in categorizing a given colour patch as belonging to a definite colour region (red, blue, etc.) and in grapheme recognition. Without the assistance of the left side the right hemisphere lacks the benefit provided by meaning identification. In our patient the left brain did receive information from the right brain and was able to process it, but was prevented by the paracallosal lesion from transmitting what it knew to the right motor area. No hand effect emerged for objects and geometrical shapes, because their semantic memory is bilaterally represented.
The purpose of this research was to compare several tests requiring the recognition of unknown faces for their power to discriminate among different groups of patients with unilateral cerebral lesions. These groups were: 1) right brain-damaged patients without visual field defects (N = 31); 2) right brain-damaged patients with visual field defects (N = 19); 3) left brain-damaged patients without visual field defects (N = 50); 4) left brain-damaged patients with visual field defects (N = 14).
We report detailed analyses of the performance of a patient, DHY, who as a consequence of strokes in the left occipital lobe and the periventricular white matter in the region of the spleniuni, showed severely impaired naming of visual stimuli despite spared recognition of visual stimuli and spared naming in other modalities. This pattern of performance-labeled "optic aphasia"-has been previously interpreted as support for the hypothesis that there are independent semantic systems, either a visual and a verbal semantic store (Beauvois, 1982; Lhermitte & Beauvois, 1973) or a right hemisphere and a left hemisphere semantic system (Coslett & Saffran, 1989, l092), which are "disconnected" in these patients. We provide evidence that DHY shows precisely the types of performance across a variety of verbal and visual tasks that have been used to support these claims of separate semantic systems: (1) good performance in naming to definition and naming objects presented for tactile exploration (which has been interpreted as evidence of spared verbal or left hemisphere semantic processing), and (2) good performance on various "semantic" tasks that do not require naming (which has been interpreted as access to spared visual or right hemisphere semantic processing). Nevertheless, when nonverbal semantic tasks were modified such that they required access to more detailed semantic information for accurate performance, DHY was Par less accurate, indicating that she did not access complete semantic information about objects in the visual modality. We argue that these data undermine the claim that cases of optic aphasia can be explained only by proposing multiple semantic systems. We propose an alternative account for this pattern of performance, within a model of visual object naming that specifies a single, modality-independent semantic system. We show that the performance of DHY and other "optic aphasic" patients can be explained by proposing a deficit in accessing a complete, modality-independent, lexical-semantic representation from an intact stored, structural description of the object. We discuss the implications of these conclusions for claims about the neuroanatomical correlates of semantic and visual object processing.
The existence of optic aphasia has been taken as strong evidence for a fractionation of knowledge representations into modality-specific systems (visual, tactile, etc.) in addition to verbal semantics. However, the multiplication of knowledge bases and the existence of unimodal aphasias has often come under severe attack. In this paper, the central issues concerning optic aphasia will be reassessed by looking more closely at modern reports and by interpreting them within a framework that allows for a fractionation of object knowledge. An overview of the literature showed that patients with a disorder of visual naming may be divided according to whether or not stimulus quality affects performance. A further analysis of these two groups was undertaken with respect to the retrieval of knowledge concerning colours of objects. It allowed us to reclassify optic aphasia as an impairment of a «direct» route for visual naming. The «direct» route is from the object's structural description to the phonological output lexicon without access to functional or associative object knowledge.
In this paper, we discuss the case of a patient, AB, who presented a pattern of performance corresponding to that usually known as optic aphasia. In particular, her visual object naming was severely impaired, while tactile naming and naming to definition were significantly better. In addition to the classical visual anomia, the patient also showed a deficit in tasks requiring categorization and access to associative knowledge. We interpret the results of our patient in line with the explanation proposed by Coslett and Saffran i.e. a disconnection between right hemisphere and left hemisphere semantic knowledge. Damage to the left occipital region requires the initial processing of visual information to be carried out in the right hemisphere only, and a lesion of the splenium of the corpus callosum interrupts the flow of information from the right to the left hemisphere. However, the pattern of symptoms observed in our patient can only be fully explained by combining this framework with a model which distinguishes visual from verbal semantics. While the right hemisphere has a complete visual semantic organization, it has only a basic and concrete associative semantic representation. AB's difficulties in categorizing and in accessing associative knowledge as the result of a visuo-verbal disconnection were also interpreted in this light. Furthermore, we suggest that the variable patterns of optic aphasia and the different behaviour of associative visual agnosic patients may be explained by interindividual differences in the levels of verbal and visual semantics in the right hemisphere.
"62 PATIENTS WITH UNILATERAL CORTICAL LESIONS WERE GIVEN 2 TESTS OF FACIAL RECOGNITION, WHICH REQUIRED RECOGNITION OF WELL-KNOWN FACES AND RECOGNITION FROM IMMEDIATE MEMORY OF PREVIOUSLY UNKNOWN FACES. THE RIGHT HEMISPHERE GROUP WAS IMPAIRED RELATIVE TO THE LEFT HEMISPHERE GROUP ON BOTH TESTS. IN NEITHER GROUP WAS THERE A SIGNIFICANT CORRELATION BETWEEN THE SCORES ON THE 2 TASKS, INDICATING THAT THE TASKS WERE TESTS OF SEPARATE AND DISTINCT FUNCTIONS. THE RESULTS ARE DISCUSSED IN TERMS OF THE CLINICAL SYNDROME, PROSOPAGNOSIA. IT IS SUGGESTED THAT PROSOPAGNOSIA MAY BE A CONSTITUENT OF AN AMNESIC SYNDROME." (PsycINFO Database Record (c) 2012 APA, all rights reserved)
we wish to query the utility of the apperceptive-associative agnosic classification
propose a classification which reflects the complexity of the component processes involved in visual object recognition and the manner in which such processes may selectively break down
deficits in visual object processing within a framework of normal vision
consider the classical distinction between apperceptive and associative agnosia
suggest that apperceptive and associative agnosia are syndromes which tend to obscure rather than clarify the nature of a patient's problems, and the relations between these problems and normal vision
deficits need to be classified according to the process(es) which are disrupted
classification and lesion sites / impaired shape processing / impaired transformation processes / integration processes / loss of stereoscopic vision / access to form knowledge / semantic knowledge (PsycINFO Database Record (c) 2012 APA, all rights reserved)
A series of visual identification tests was presented to 51 subjets with unilateral cortical lesions (25 left-sided, 26 right-sided) and to 30 controls. The test material included photographs and designs of human faces, meaningless line patterns, shadow patterns, and photographs of different objects in the same category (e.g. cups). The results confirm those of previous studies showing the predominant role of right hemispheric lesions in deficits of recognition of the human face. In addition, they demonstrate this same predominance whether the faces were presented as photographs or as simple designs. No correlation was found between the results of the tests of facial recognition, taken as a group, and those of the tests of identification of similar objects, of meaningless patterns, and of shadow patterns representing a complex perceptive task, also taken as a group. Based on these results, a hypothesis of the existence of an autonomous defect of human facial recognition is discussed.
Three experiments are described which investigated the ability of neonates to discriminate between the face of their mother and that of a strange adult female and to show face recognition. The first experiment indicated a reliable preference for the mother's face even where a control for olfactory information was used. No evidence for any effect of sex or breast vs. bottle feeding was found. A second experiment used the same procedure but substituted a visual mask for the olfactory one previously adopted. Under these conditions no evidence of preference was found. Finally, a third experiment considered the possibility that mothers were actively recruiting their own infant's attention and found that adult observers were unable reliably to distinguish mothers from strangers on the basis of any differential behaviour by mother and stranger. The conclusion is drawn that neonates can recognize their mother on the basis of visual clues alone and that these cues relate to memory for featural attributes of the mother's face rather than to attention-recruiting behaviour on her part.
Populations of visual neurones have been discovered in one area of the temporal association cortex that respond to different aspects of facial information. The responses of these cells have many of the properties hypothesized for ‘gnostic units’ and provide insight into the final stages of visual processing leading to recognition of an object as a face and more specifically the identity of the face.
Visual object recognition was investigated in a group of eighty-one patients with right- or left-hemisphere lesions. Two tasks were used, one maximizing perceptual categorization by physical identity, the other maximizing semantic categorization by functional identity. The right-hemisphere group showed impairment on the perceptual categorization task and the left-hemisphere group were impaired on the semantic categorization task. The findings are discussed in terms of categorical stages of object recognition. A tentative model of their cerebral organization is suggested.
The case is presented of a patient who showed visual naming disturbances caused by a left occipital infarction. His performance on tests of visual naming, of recognition not requiring a verbal response, and of verbal-visual matching demonstrated a wide range of qualitatively different errors, including complete inability to recognize the object, access to partial semantic knowledge, and mere name finding difficulty. On the basis of the present case and of a review of the recent literature, the clinical distinction between visual associative agnosia and optic aphasia and the relation of these disorders with the anatomical site of lesion are discussed.
Prosopagnosia is a neurologically based deficit characterized by the inability to recognize faces of known individuals in the absence of severe intellectual, perceptual, and memory impairments. The nature of the underlying disturbance was investigated in three patients in an attempt to identify the structural and functional levels at which the processing of faces breaks down, the relation between prosopagnosia and associated deficits, and the specificity of the prosopagnosic disturbance. The breakdown of face processing resulted from unilateral damage in different cerebral structures of the right hemisphere in the three patients, and it involved different functional levels of face processing, but all three patients displayed perceptual impairments of unequal severity. In one patient (R.M.), the deficit encompassed all perceptual operations on faces, including matching identical views of the same faces, but it did not extend to all categories of objects characterized by a close similarity among their instances; the second patient (P.M.) exhibited a less severe perceptual impairment but was unable to derive the configurational properties from a facial representation and to extract its physiognomic invariants; the third patient (P.C.) had not lost the capacity to differentiate faces on the basis of their configurations but could not associate a facial representation with its pertinent memories. Associated deficits were present in each patient but differed depending on the anatomofunctional locus of the breakdown, although all patients were impaired at recognizing noncanonical views of objects that they readily recognized when shown from a conventional viewpoint. However, performance dissociation within patients and double dissociation between patients suggest that these associated deficits are not necessary concomitants of prosopagnosia.
Studies of brain-damaged patients have revealed the existence of a selective impairment of face processing, prosopagnosia, resulting from lesions at different loci in the occipital and temporal lobes. The results of such studies have led to the identification of several cortical areas underlying the processing of faces, but it remains unclear what functional aspects of face processing are served by these areas and whether they are uniquely devoted to the processing of faces. The present study addresses these questions in a positron emission tomography (PET) study of regional cerebral blood flow in normal adults, using the 15 oxygen water bolus technique. The subjects participated in six tasks (with gratings, faces and objects), and the resulting level of cerebral activation was mapped on images of the subjects' cerebral structures obtained through magnetic resonance and was compared between tasks using the subtraction method. Compared with a fixation condition, regional cerebral blood flow (rCBF) changes were found in the striate and extrastriate cortex when subjects had to decide on the orientation of sine-wave gratings. A face-gender categorization resulted in activation changes in the right extrastriate cortex, and a face-identity condition produced additional activation of the fusiform gyrus and anterior temporal cortex of both hemispheres, and of the right parahippocampal gyrus and adjacent areas. Cerebral activation during an object-recognition task occurred essentially in the left occipito-temporal cortex and did not involve the right hemisphere regions specifically activated during the face-identity task. The results provide the first empirical evidence from normal subjects regarding the crucial role of the ventro-medial region of the right hemisphere in face recognition, and they offer new information about the dissociation between face and object processing.
Optic aphasia is a rare, visual modality-specific naming disorder. We describe a patient who developed this disorder subsequent to a left occipital lobe infarction. Like another case that we described previously, this patient performed normally on a variety of tasks assessing the recognition of objects he could not name. Additionally, although he never read aloud a single word, his performance on lexical decision and word comprehension tasks was far better than chance. We suggest that his performance was mediated by a right hemisphere semantic system.
We report the case of a 71-year-old woman with partial cortical blindness attributable to cortical degeneration. Her visual acuity and colour perception were satisfactory but she was almost totally unable to recognize objects or people by sight. Investigations revealed a hitherto unreported dissociation between relatively well preserved shape discrimination and gravely impaired figure-ground discrimination. Thus, she was able to discriminate between a square and an oblong matched for total surface but she was unable to detect a simple shape against a pattern background. In a series of experiments it was shown that she could identify single printed capital letters of the alphabet relatively satisfactorily. She had no difficulty in identifying single, simple geometric shapes. By contrast, she was unable to discriminate configurations of two or three overlapping or concentric, simple, shapes. Strikingly she appeared to be "blind" to subjective contours and she was unable to perceive visual illusions normally. These deficits are interpreted to reflect a failure to achieve primitive organization of visual information rather than higher level perceptual impairments. The results are discussed in the context of physiological and computational models of early visual information processing.
We report a quantitative investigation of three patients who presented with a profound prosopagnosia. They were tested on a series of tests of face perception, face recognition, and paired associate learning using faces. A patient with marked perceptual difficulties but no difficulty whatever in recognizing faces was tested as a control. The control patient's performance was as bad or worse on the tests of perception of faces, and it is concluded that impaired performance on tests of face perception does not contribute to difficulties in recognizing familiar faces. The major difference between the three prosopagnosic patients was the evidence of covert recognition in two of these cases but not in the third. We use this evidence to argue that the perceptual/mnestic distinction is an inappropriate classification and would suggest instead that the two types may be described in terms either of a disconnection of the face recognition units or of damage to the units themselves.
The purpose of this study was to explore whether patients with left posterior cerebral artery (PCA) lesions have defective mental visual imagery and to differentiate whether such a deficit stems from a loss of knowledge about the visual appearance of objects or from an inability to create mental visual images out of preserved visual knowledge. Normal controls and patients with either left or right PCA lesions were asked to verify low- and high-imagery sentences and then to verify pictorial representations of the predicates of high-imagery sentences. High-imagery questions concerned either the shape or the color of objects. In addition, perceptual discrimination of shape and color was assessed. Patients with right PCA lesions were impaired on the perceptual discrimination tasks. Left PCA patients did not significantly differ from controls on low-imagery sentences but scored significantly lower on shape and color questions. Their impairment was distinctly more severe with the pictorial than with the verbal versions of shape and color questions. In comparison to patients with occipital left PCA lesions, patients with temporo-occipital left PCA lesions were selectively impaired on verbal and visual color questions. It is concluded that patients with left PCA lesions lack knowledge about shape and color of objects, but that their ability to convert visual knowledge into mental images is preserved.
A right-hemisphere advantage in a mother's face recognition task in infants aged between 4 and 10 months was found to exist by de Schonen, Gil de Diaz, and Mathivet. The present study was designed to test (a) whether the right-hemisphere advantage would still prevail if the task requirements were different from those in the previous study, and (b) whether any information was communicated from one hemisphere to the other. 18-42-week-old infants were presented with an operant conditioning situation where they had to discriminate between their mother's and a stranger's face within one visual hemifield. Transfer of learning from one visual hemifield to the other was also measured. The results confirm the existence of a right-hemisphere advantage in discriminating between face stimuli. This advantage was weaker in the female than in the male population. No hemispheric transfer of learning was observed to occur.
This review is an enquiry into why the early clinical evidence for a colour centre in the cerebral cortex of man was so successfully dismissed for the best part of a century. The imperfection of this evidence cannot be the reason, for the same evidence that was rejected earlier is accepted today. Instead, it was because the prevalent concepts of vision as a function, and of the role of the cerebral cortex in it, dominated facts and prevented acceptance of evidence showing a specialization for colour in the visual cortex. It was only after those concepts were overthrown by the demonstration of functional specialization in the visual cortex of the primate that the evidence for a colour centre in the human brain became acceptable. Today, our new knowledge of the colour areas and pathways in the primate brain allows us to give a more complete account of the pathophysiology of cerebral achromatopsia in man.
Optic aphasia is characterized by the ability to name from description and palpation but an inability to name visually-presented objects. Although originally attributed to a disconnection of visual information from object names, optic aphasia is often considered to be a mild form of visual agnosia. We describe a patient with optic aphasia who could access semantic information relevant to objects he could not name and comprehend written words he could not read. These data suggest that, at least in certain cases, this visual modality-specific naming impairment may not be attributable to impaired visual recognition. We suggest that this patient's preserved object recognition and reading comprehension was mediated by a semantic system supported by the right hemisphere.
It has been postulated that for prosopagnosia to occur, bilateral lesions of the central visual system are usually necessary. All but 1 of the 10 previously documented cases that came to autopsy showed this pattern. However, the long survival period after the onset of prosopagnosia in most of these patients limits the value of the autopsy findings for clinicopathological correlation. A patient is presented who died 10 days after she had developed prosopagnosia, topographagnosia and an agnosia for real objects seen from noncanonical views. These clinical symptoms corresponded directly to the autopsy finding of a recent large occipitotemporal ischaemic infarct in the territory of the right posterior cerebral artery. An additional right frontal infarct and a cortical microinfarct in a deep left lateral parieto-occipital sulcus were both old lesions and had passed unnoticed clinically. This first report of a direct clinicopathological correlation between a fresh right posterior lesion and prosopagnosia demonstrates that bilateral involvement of the visual system is not a prerequisite for prosopagnosia.
We investigated the neuropsychological correlates of left posterior cerebral artery (LPCA) infarcts with a quantitative systematic approach and found a pattern of impairment extending well beyond the classical syndrome of alexia without agraphia. Sixteen consecutive patients with CT scan evidence of an infarct confined to the territory of LPCA were given a battery of tests assessing the following abilities. (1) Reading and writing; (2) naming and pointing to colours; (3) naming the same 30 objects on visual (objects and coloured photographs), tactile and verbal presentation; and (4) verbal memory. These tests were administered to large control samples and the performance of LPCA patients was considered pathological if it fell below the score of the last or second to last control patient.
Seventy five per cent of PCA patients had alexia without agraphia. Although a lesion of the CT scal slice where the pineal is represented appeared to be crucially associated with alexia, the severity of the disorder increased when contiguous upper or lower slices were also involved. Not only colour anomia, but also object and especially photograph anomia could almost always be shown in alexies and were highly correlated with the degree of the reading impairment. The naming deficit was also present when items were presented in the tactile and verbal modality, in spite of the integrity of the oral language areas. Every right-handed patient, alexic as well as nonalexic, was impaired on at least two of the three verbal memory tests and most on all of them. The findings are discussed in terms of the anatomofunctional mechanisms subserving verbal memory and the transmission of visual information to the speech areas.
The aim of this paper is to develop a theoretical model and a set of terms for understanding and discussing how we recognize familiar faces, and the relationship between recognition and other aspects of face processing. It is suggested that there are seven distinct types of information that we derive from seen faces; these are labelled pictorial, structural, visually derived semantic, identity‐specific semantic, name, expression and facial speech codes. A functional model is proposed in which structural encoding processes provide descriptions suitable for the analysis of facial speech, for analysis of expression and for face recognition units. Recognition of familiar faces involves a match between the products of structural encoding and previously stored structural codes describing the appearance of familiar faces, held in face recognition units. Identity‐specific semantic codes are then accessed from person identity nodes, and subsequently name codes are retrieved. It is also proposed that the cognitive system plays an active role in deciding whether or not the initial match is sufficiently close to indicate true recognition or merely a ‘resemblance’; several factors are seen as influencing such decisions.
This functional model is used to draw together data from diverse sources including laboratory experiments, studies of everyday errors, and studies of patients with different types of cerebral injury. It is also used to clarify similarities and differences between processes responsible for object, word and face recognition.
The left and right hemispheres of three complete commissurotomy subjects were tested for the ability to comprehend abstract concepts. A technique was used which allows prolonged viewing of stimulus material restricted to a single visual hemi-field. Twenty-three trials involving a sample inspection figure and a three-choice answer array were presented to each hemi-field with instructions to point to the one picture in the choice array related to the sample. As none of the possible choices matched the sample stimulus on any concrete level, correct responses required an abstract mental association. Both the verbal and non-verbal hemispheres performed the task at a high level of proficiency in all subjects. It was further noted that both commissurotomy and normal subjects experienced difficulty in articulating the involved abstract relationship when asked to do so under a free vision condition. The results demonstrate that the right hemisphere, lacking a highly developed language system, can nevertheless support sophisticated cognitive processing at an abstract level, and further suggest that the associative process is not necessarily language-mediated in either hemisphere.
Visual recognition of pictorial material was investigated in a group of 74 patients with localised cerebral lesions. Four tasks of visual perception, figure/ ground, fragmented drawings, enlarged drawings, and photographs of objects from an unconventional view, were administered. An unimpaired performance of the right posterior group on the figure/ground task contrasted with a marked deficit on the unconventional view objects task. It was demonstrated that there is a favoured view for efficiency of object recognition. The findings provide evidence that gestalt formation is intact whereas perceptual classification is impaired in patients with right posterior lesions. The implications of this interpretation of the data for theories of object recognition are discussed.
A test requiring the identification of unfamiliar faces was developed and given to groups of patients with lesions of the left or the right hemisphere as well as to a large group of control patients. Performance level in the control group showed a slight decline with age but was not related to education or sex. The mean performance levels of both brain-damaged groups were significantly inferior to that of the control group. In addition, however, the mean performance level of the patients with right hemisphere lesions was significantly inferior to that of the patients with left hemisphere lesions and grossly defective performances were made mainly by patients with right hemisphere lesions. Performance level was not related to the presence of visual field defect, the presence of aphasia, type of lesion or intrahemispheric locus of lesion. A number of considerations suggested that the observed interhemispheric difference in performance was not related to a possible difference in the extent of lesion in the two groups.
The neuropsychologic, neuroanatomic, and neurophysiologic correlates of achromatopsia were studied in two patients. Prosopagnosia accompanied the color perception defect in the bilateral case but not in the unilateral one. No other neuropsychologic disturbance was present in either case. The lesions compromised the ventromedial sector of the occipital lobe in both cases. Cerebral evoked responses produced by pattern shift stimulation were normal for black and white but abnormal for red and green, when stimulation was given in the achromatopsic field.
Critical analysis of postmortem and CT scan data indicates that prosopagnosia is associated with bilateral lesions of the central visual system. Those lesions are located in the mesial occipitotemporal region and are functionally symmetric. The prime factor in the appearance of prosopagnosia is the requirement to evoke the specific context of a given visual stimulus. The "ambiguity" of the stimulus (the frequency with which different members of a group are visually similar) is an adjuvant factor. But prosopagnosia is not specific to human faces. The phenomenon appears in relation to any visually "ambiguous" stimulus whose recognition depends on contextual memory evocation.
Two cases (G.G. and A.V.) are described of cognitive impairment resulting from herpes simplex infection. Both cases demonstrated anomic disorders and impairments in drawing but only in G.G.'s drawings was there a reliable selective impairment for items from natural categories. Both cases, however, showed an impairment for the retrieval of knowledge concerning the colours of objects. The impairment has, in the past, been ascribed to interference from colour anomia; this was not so for the present cases. For G.G. and A.V., impairments in object-colour retrieval were related to errors in picture naming. More errors were associated with items that induced circumlocutions than to those that were correctly named. The impairment was also present for some items that were named correctly. The patients' impairments are discussed within a model in which object-colour knowledge is functionally situated between an object's shape description and its output phonology but on a separate route from other associated object knowledge.
The early position that prosopagnosia is predominantly associated with right hemisphere (RH) injury was challenged by the finding that in practically all cases that come to autopsy pathological data point to bilateral damage. Yet the rejection of the RH hypothesis may have been too hasty. We report three prosopagnosic patients in whom MRI and CT documented a lesion confined to the right occipito-temporal areas and PET confirmed that hypometabolism involved the RH only. A review of the literature brought out 27 cases with neuroimaging evidence that prosopagnosia was associated with RH damage plus four cases with surgical evidence. It remains, however, that the inability to recognize familiar faces is a rare disorder, not manifested by the majority of patients with right temporo-occipital injury. We submit that right-handers differ in the degree of their RH specialization in processing faces and that in only a minority of them is it so marked that it cannot be compensated for by the healthy left hemisphere.
Following a trauma that mainly involved the right hemisphere, a 21-year-old girl showed a profound impairment in visual object recognition, without language and intellectual deficit. Her elementary sensory functions were preserved and she performed in the normal range on visual matching tasks, on taks requiring to detect small differences between similar complex shapes and in copying drawings, without any evidence of a line by line approach. Her deficit emerged with tests that, though not implying identification of meaning, demanded to disentangle a form from a confused background and to achieve a highly structured description of the stimulus. In addition to this high-level perceptual processing disorder, there was a deficit in recovering from the visual store the shape of an object, also when the performance did not involve perceptual discrimination, e.g., in drawing from memory or telling the physical difference between two named stimuli. Knowledge of the semantic and contextual attributes of objects was intact. The case is taken as evidence that the borders of apperceptive agnosia may be ampler than usually thought and its distinction from associative agnosia less rigid, with some patients laying in-between the two syndromes.
We report the case of a 21-year-old man who sustained brain damage due to anoxia. His visual acuity was normal and his colour perception was adequate if not completely normal. However, his shape discrimination was so impaired that he had great difficulty distinguishing a square from an oblong or a large square from a smaller square. At the same time, other aspects of his shape perception were remarkably intact. His performance on a shape detection task was good. He had no difficulty on tests of figure-ground (boundary) segmentation and his perception of subjective and illusory contours appeared to be normal. S.M.K.'s performance on a number of tasks is compared with that of a patient (F.G.P.) previously reported who showed the opposite pattern of deficit (Kartsounis and Warrington, Neuropsychologia 29, 969-980, 1991). This evidence of a double dissociation between two components of shape perception is discussed in the context of a neurophysiological model of the organization of the visual system.
We report a patient who, following the partial removal of a tentorial meningioma, suffered a hematoma in the left occipital lobe, which was resected. He showed severe anomia for visually presented stimuli, while naming was normal when they were presented in the tactile, auditory and verbal modality. His performance on visuo-perceptual tests, not requiring meaning identification, provided evidence that he was able to access the stored representations of stimuli. When recognition was assessed with non-verbal tasks, a mixed pattern of findings emerged and the patient showed features of both associative agnosia and optic aphasia. He was severely impaired in producing pantomimes in response to pictures, but only marginally impaired in sorting figures from the same superordinate category into fine-grained subcategories. He performed within the normal range on an associative task, in which the distractors bore no semantic relation to the target, but made many errors when the distractors and the target were semantically related. We propose that the interpretation advanced by Coslett and Saffran (Brain, 1989) for optic aphasia also holds for associative agnosia and argue that both syndromes reflect the impaired access of structured representations to left hemisphere semantics, but differ in terms of the degree of compensation provided by the semantic resources of the right hemisphere. Since the anatomical basis of the two syndromes may be very similar, we submit that what makes the difference is the semantic potential of the patient's right hemisphere.