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Stimulus patterns used in the experiments: Necker cube (A), hidden line eliminated cube (B) and overlapping squares (C).
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We have studied the cerebral activity for the depth perception of the Necker cube by functional magnetic resonance imaging. Three types of line drawing figures were used as stimuli, the Necker cube, hidden line elimination cube and overlapping squares. Subjects were instructed to perceive both orientations of the depth of the Necker cube. They were...
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... This follows from their ability to induce changes in our awareness of different percepts, without changing sensory input. Research has implicated specific dorsal frontal and parietal regions in facilitating these perceptual switches (Inui et al. 2000). These regions are also associated with attentional processing (Vossel et al. 2014), aligning well with our account that highlights the central role of attentional (i.e. ...
Bistable perception follows from observing a static, ambiguous, (visual) stimulus with two possible interpretations. Here, we present an active (Bayesian) inference account of bistable perception and posit that perceptual transitions between different interpretations (i.e. inferences) of the same stimulus ensue from specific eye movements that shift the focus to a different visual feature. Formally, these inferences are a consequence of precision control that determines how confident beliefs are and change the frequency with which one can perceive—and alternate between—two distinct percepts. We hypothesized that there are multiple, but distinct, ways in which precision modulation can interact to give rise to a similar frequency of bistable perception. We validated this using numerical simulations of the Necker cube paradigm and demonstrate the multiple routes that underwrite the frequency of perceptual alternation. Our results provide an (enactive) computational account of the intricate precision balance underwriting bistable perception. Importantly, these precision parameters can be considered the computational homologs of particular neurotransmitters—i.e. acetylcholine, noradrenaline, dopamine—that have been previously implicated in controlling bistable perception, providing a computational link between the neurochemistry and perception.
... This raises questions about the mechanism of periodic perceptual alternation and about the determinants of the switching frequency in individuals. Regarding this issue, human psychophysics and neuroimaging experiments have demonstrated that various cognitive factors such as intention [10][11][12][13] , attention [14][15][16][17][18] or adaptation 7,9,[19][20][21][22] can modulate the perceptual alternation frequency, and parameters of a neural basis, such as the grey matter volume [23][24][25] and average inhibition level 20,[26][27][28][29] , appear to be correlated with the frequency of perceptual alternation. For example, it was observed that asking subjects intentionally to switch or hold their perceptual states can significantly bias their perceptual alternation rate of bistable perception 10,11,13,30 . ...
Bistable perception is characterized by periodic alternation between two different perceptual interpretations, the mechanism of which is poorly understood. Herein, we show that perceptual decisions in bistable perception are strongly correlated with slow rhythmic eye motion, the frequency of which varies across individuals. From eye gaze trajectory measurements during three types of bistable tasks, we found that each subject’s gaze position oscillates slowly(less than 1Hz), and that this frequency matches that of bistable perceptual alternation. Notably, the motion of the eye apparently moves in opposite directions before two opposite perceptual decisions, and this enables the prediction of the timing and direction of perceptual alternation from eye motion. We also found that the correlation between eye movement and a perceptual decision is maintained during variations of the alternation frequency by the intentional switching or retaining of perceived states. This result suggests that periodic bistable perception is phase-locked with rhythmic eye motion.
... Some illusory patterns would be particularly interesting in terms of this issue. For instance, unlike most of the visual illusions already tested in fish, for which low-level mechanisms have also been advanced, ambiguous patterns (such as Necker's cube) are thought to be due to a pure cortical mechanism (Leopold et al. 2002;Britz et al. 2009;Inui et al. 2000). The study of fish exhibiting ambiguous patterns would open up new perspectives on the possibility that the cortex is a sine-qua-non condition for the emergence of this perceptual phenomenon. ...
The study of visual illusions has captured the attention of comparative psychologists since the last century, given the unquestionable advantage of investigating complex perceptual mechanisms with relatively simple visual patterns. To date, the observation of animal behavior in the presence of visual illusions has been largely confined to mammal and bird studies. Recently, there has been increasing interest in investigating fish, too. The attention has been particularly focused on gup-pies, redtail splitfin and bamboo sharks. Overall, the tested species were shown to experience a human-like perception of different illusory phenomena involving size, number, motion, brightness estimation and illusory contours. However, in some cases, no illusory effects, or evidence for a reverse illusion, were also reported. Here, we review the current state of the art in this field. We conclude that a wider investigation of visual illusions in fish is fundamental to form a broader comprehension of perceptual systems of vertebrates. Furthermore, we believe that this type of investigation could help us to address general important issues in perceptual studies, such as the role of ecology in shaping perceptual systems, the existence of interindividual variability in the visual perception of nonhuman species and the role of cortical activity in the emergence of visual illusions.
... Previous studies of the perception of ambiguous gures using EEG trials, event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI) demonstrated that ambiguous image perception activates and deactivated speci c brain areas. 54,55 At rst glance, one expects the perception of visual stimuli to produce the most signi cant neural activity in the occipital lobe, where the primary visual cortex is located. 56 In particular, according to the ERP analysis, occipital neurons exhibit an increase in the generation of β-waves and a decrease of α-waves. ...
Machine learning is a promising approach for electroencephalographic (EEG) trials classification. Its efficiency is largely determined by the feature extraction and selection techniques reducing the dimensionality of input data. Dimensionality reduction is usually implemented via the mathematical approaches (e.g., principal component analysis, linear discriminant analysis, etc.) regardless of the origin of analyzed data. We hypothesize that since EEG features are determined by certain neurophysiological processes, they should have distinctive characteristics in spatiotemporal domain. If so, it is possible to specify the set of EEG principal features based on the prior knowledge about underlying neurophysiological processes. To test this hypothesis, we consider the classification of EEG trials related to the perception of ambiguous visual stimuli. We observe that EEG features, underlying the different ambiguous stimuli interpretations, are defined by the network properties of neuronal activity. Having analyzed functional neural interactions, we specify the brain area in which neural network architecture exhibits differences for different classes of EEG trials. We optimize the feedforward multilayer perceptron and develop a strategy for the training set selection to maximize the classification accuracy, being 85% when all channels are used. The revealed localization of the percept-related features allows about 95% accuracy, when the number of channels is reduced up to 90%. Obtained results can be used for classification of EEG trials associated with more complex cognitive tasks. Taking into account that cognitive activity is subserved by a distributed functional cortical network, its topological properties have to be considered when selecting optimal features for EEG trial classification.
... In the last 10 years, neurophysiological EEG studies have demonstrated momentary fluctuations of brain activity during perception of the Necker cube in right inferior parietal cortex (Britz et al., 2009) and between occipital and frontal areas (Shimaoka et al., 2010). In addition, an fMRI study (Inui et al., 2000) has shown bilateral (symmetrical) activations of premotor and parietal areas associated with NC perception, similar to those that occur during mental image manipulation (Inui et al., 2000). ...
... In the last 10 years, neurophysiological EEG studies have demonstrated momentary fluctuations of brain activity during perception of the Necker cube in right inferior parietal cortex (Britz et al., 2009) and between occipital and frontal areas (Shimaoka et al., 2010). In addition, an fMRI study (Inui et al., 2000) has shown bilateral (symmetrical) activations of premotor and parietal areas associated with NC perception, similar to those that occur during mental image manipulation (Inui et al., 2000). ...
... The lack of significant effects on NC task may be due to different reasons. As previously discussed, it might be possible that our protocol did not target a critical brain region for illusory depth perception, that has been shown to be associated with bilateral activation of premotor and parietal areas (Inui et al., 2000). Perceptual processing of the Necker cube likely recruits more complex networks than those involved in LT (Ricci et al., 2012). ...
Transcranial Magnetic Stimulation (TMS) may affect attentional processing when applied to the right posterior parietal cortex (PPC) of healthy participants in line with neuropsychological and neuroimaging evidence on the neural bases of this cognitive function. Specifically, the application of TMS to right PPC induces a rightward attentional bias on line length estimation in healthy participants (i.e., neglect-like bias), mimicking the rightward bias shown by patients with unilateral spatial neglect after damage of the right PPC. With the present study, we investigated whether right PPC might play a crucial role in attentional processing of illusory depth perception, given the evidence that a rightward bias may be observed in patients with neglect during perception of the Necker Cube (NC). To this end, we investigated the effects of low-frequency rTMS applied to the right or left PPC on attentional disambiguation of the NC in two groups of healthy participants. To control for the effectiveness of TMS on visuospatial attention, rTMS effects were also assessed on a frequently used line length estimation (i.e., the Landmark Task or LT). Both groups also received sham stimulation. RTMS of the right or left PPC did not affect NC perception. On the other hand, rTMS of the right PPC (but not left PPC) induces neglect-like bias on the LT, in line with previous studies. These findings confirm that right PPC is involved in deployment of spatial attention on line length estimation. Interestingly, they suggest that this brain region does not critically contribute to deployment of visuospatial attention during attentional disambiguation of the Necker Cube. Future investigations, targeting different areas of fronto-parietal circuits, are necessary to further explore the neuro-functional bases of attentional contribution to illusory depth perception.
... In comparison to our previously reported data from patients with cocaine dependence (21) and with pathological gambling (20), the present sample of schizophrenic/schizoaffective patients were found to have seemingly better scores on drawing of the tri-dimensional figures in conjunction with a better DROT performance (20). Importantly, scores on the hidden line elimination cube probing stereopsis c.f., Necker cube, necessitating visuospatial ability to shift attention between two equally plausible figural spatial representations (62), correlated with the BMI and the Fagerstrom Test of Nicotine Dependence. While some of the above findings might be accounted by differences in the respective illness' severity, which complicates direct comparisons between the schizophrenic/schizoaffective and addicted groups, the presented data call for further research aimed at understanding the distinctive features of constructional apraxia revealed by copying the hidden line elimination cube vis-à-vis copying other figures in conjunction with the DROT and RMT and their potential role in metabolic and addictive disturbances associated with schizophrenia/schizoaffective disorder. ...
Neurological soft signs (NSSs) are highly prevalent among patients with schizophrenia, but their pathophysiological significance remains unclear. The present study employed perceptual-motor and visuospatial processing tests that have not yet been attempted in this patient population. Patients with schizophrenia or schizoaffective disorder (n = 42) and mentally healthy subjects (n = 10) were administered Copy Figure Test, Detection and Recognition of an Object Test and Road Map Test. As compared to controls, schizophrenic and schizoaffective patients displayed significantly poorer ability to copy three-dimensional figures (namely, Necker- and hidden line elimination cubes) and to orient in space on a road-map test; group differences in copying two-dimensional figures and on objects' recognition against a background noise were not apparent. In the schizophrenia/schizoaffective group, more mistakes on the hidden line elimination cube was associated with greater body mass index and greater severity of nicotine dependence measured via the Fagerstrom Test of Nicotine Dependence. The above findings replicate those of prior reports and extend them to the tasks that do not involve motivational and attentional confounds. Furthermore, the present data support the hypothesis that subtle cerebral cortical abnormalities detected with specific NSSs tests may be related to some aspects of metabolic and motivational function in patients with schizophrenia/schizoaffective disorder.
... The physiological bases for perceptual rivalry and top-down voluntary modulation have been investigated with electrophysi- ology and imaging methods in monkeys ( Leopold and Logothetis, 1996;Xu et al., 2016) and with electroencephalography (Strüber et al., 2001;Kornmeier and Bach, 2004; I ˙ sog ˘lu- Alkac and Strüber, 2006;Mathes et al., 2006;Pitts et al., 2008), magne- toencephalography ( Parkkonen et al., 2008), magnetic resonance imaging (MRI; Lumer et al., 1998;Inui et al., 2000;Sterzer and Kleinschmidt, 2007;Watanabe et al., 2014), and brain stimula- tion ( Ngo et al., 2013;Brascamp et al., 2018) in humans. Sponta- neous perceptual alternation may be mediated by brain regions in visual cortex ( Meng et al., 2005;Frässle et al., 2014;Ishizu and Zeki, 2014) and frontoparietal networks (Cohen, 1959;Ricci and Blundo, 1990;Meenan and Miller, 1994;Bisiach et al., 1999;Miller et al., 2000;Slotnick and Yantis, 2005;Ge et al., 2007;Fagard et al., 2008;Shen et al., 2009;Sterzer et al., 2009;Kanai et al., 2010;Knapen et al., 2011;Wang et al., 2013;Weilnhammer et al., 2013;Megumi et al., 2015). ...
Visual cognition in humans has traditionally been studied with cognitive behavioral methods and brain imaging, but much less with genetic methods. Perceptual rivalry, an important phenomenon in visual cognition, is the spontaneous perceptual alternation that occurs between two distinct interpretations of a physically constant visual stimulus (e.g., binocular rivalry stimuli) or a perceptually ambiguous stimulus (e.g., the Necker cube). The switching rate varies dramatically across individuals and can be voluntarily modulated by observers. Here, we adopted a genomic approach to systematically investigate the genetics underlying binocular rivalry, Necker cube rivalry and voluntary modulation of Necker cube rivalry in young Chinese adults (Homo sapiens, 81% female, 20 1 years old) at multiple levels, including common single nucleotide polymorphism (SNP)-based heritability estimation, SNP-based genome-wide association study (GWAS), gene-based analysis, and pathway analysis. We performed a pilot GWAS in 2441 individuals and replicated it in an independent cohort of 943 individuals. Common SNP-based heritability was estimated to be 25% for spontaneous perceptual rivalry. SNPs rs184765639 and rs75595941 were associated with voluntary modulation, and imaging data suggested genotypic difference of rs184765639 in the surface area of the left caudal-middle frontal cortex. Additionally, converging evidence from multilevel analyses associated genes such as PRMT1 with perceptual switching rate, and MIR1178 with voluntary modulation strength. In summary, this study discovered specific genetic contributions to perceptual rivalry and its voluntary modulation in human beings. These findings may promote our understanding of psychiatric disorders, as perceptual rivalry is a potential psychiatric biomarker.
... Actually, several studies of bistable images using event-related potentials, EEG trials, and fMRI showed that visual perception was accompanied by activation of specific brain areas and deactivation of others. [35][36][37] In particular, a chain of event-related potential components was found during observation of a Necker cube lattice which led to spontaneous perceptual reversals. 37 Our results show that significant changes in the event-related potentials observed in the occipital cortex provide accurate classification of brain states related to the decision-making process. ...
Artificial neural networks (ANNs) are known to be a powerful tool for data analysis. They are used in social science, robotics, and neurophysiology for solving tasks of classification, forecasting, pattern recognition, etc. In neuroscience, ANNs allow the recognition of specific forms of brain activity from multichannel EEG or MEG data. This makes the ANN an efficient computational core for brain-machine systems. However, despite significant achievements of artificial intelligence in recognition and classification of well-reproducible patterns of neural activity, the use of ANNs for recognition and classification of patterns in neural networks still requires additional attention, especially in ambiguous situations. According to this, in this research, we demonstrate the efficiency of application of the ANN for classification of human MEG trials corresponding to the perception of bistable visual stimuli with different degrees of ambiguity. We show that along with classification of brain states associated with multistable image interpretations, in the case of significant ambiguity, the ANN can detect an uncertain state when the observer doubts about the image interpretation. With the obtained results, we describe the possible application of ANNs for detection of bistable brain activity associated with difficulties in the decision-making process.
... Therefore, along with the knowledge of basic features of the brain activity in solving particular tasks, it is of great practical importance to study the influence of the human factors, such as responsibility, motivation, attention, and stress [16,17]. In this context, the neurophysiological research of visual perception focused on the detection of brain activity and interactions between different brain regions [18][19][20][21][22] demonstrated an increased activity in various brain areas, especially in the occipital cortex [18,19,23]. For example, the functional magnetic resonance data [20] indicated a symmetrical activation of the premotor and parietal areas during perception. ...
... In this context, the neurophysiological research of visual perception focused on the detection of brain activity and interactions between different brain regions [18][19][20][21][22] demonstrated an increased activity in various brain areas, especially in the occipital cortex [18,19,23]. For example, the functional magnetic resonance data [20] indicated a symmetrical activation of the premotor and parietal areas during perception. Wang et al. [22] observed that perception of bistable images involved many higher-order frontoparietal and temporal regions. ...
The influence of motivation and alertness on brain activity associated with visual perception was studied experimentally using the Necker cube, which ambiguity was controlled by the contrast of its ribs. The wavelet analysis of recorded multichannel electroencephalograms (EEG) allowed us to distinguish two different scenarios while the brain processed the ambiguous stimulus. The first scenario is characterized by a particular destruction of alpha rhythm (8–12 Hz) with a simultaneous increase in beta-wave activity (20–30 Hz), whereas in the second scenario, the beta rhythm is not well pronounced while the alpha-wave energy remains unchanged. The experiments were carried out with a group of financially motivated subjects and another group of unpaid volunteers. It was found that the first scenario occurred mainly in the motivated group. This can be explained by the increased alertness of the motivated subjects. The prevalence of the first scenario was also observed in a group of subjects to whom images with higher ambiguity were presented. We believe that the revealed scenarios can occur not only during the perception of bistable images, but also in other perceptual tasks requiring decision making. The obtained results may have important applications for monitoring and controlling human alertness in situations which need substantial attention. On the base of the obtained results we built a brain-computer interface to estimate and control the degree of alertness in real time.
... Previous studies of ambiguous figures using EEG trials, eventrelated potentials (ERP) and fMRI showed that perception of bistable images was accompanied by activation of specific brain areas and deactivation of others (Inui et al., 2000;Müller et al., 2005;Kornmeier et al., 2007). In particular, Kornmeier and Bach (2006) found a chain of ERP components during observation of a Necker lattice led to spontaneous perceptual reversals. ...
In order to classify different human brain states related to visual perception of ambiguous images, we use an artificial neural network (ANN) to analyze multichannel EEG. The classifier built on the basis of a multilayer perceptron achieves up to 95% accuracy in classifying EEG patterns corresponding to two different interpretations of the Necker cube. The important feature of our classifier is that trained on one subject it can be used for the classification of EEG traces of other subjects. This result suggests the existence of common features in the EEG structure associated with distinct interpretations of bistable objects. We firmly believe that the significance of our results is not limited to visual perception of the Necker cube images; the proposed experimental approach and developed computational technique based on ANN can also be applied to study and classify different brain states using neurophysiological data recordings. This may give new directions for future research in the field of cognitive and pathological brain activity, and for the development of brain-computer interfaces.
