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Viewing patterns made by monkeys to conspecific and human faces during a Visual Paired Comparison Task (VPC). Images were manipulated by inversion (A, B), low-pass filtering (C, D), and high-pass filtering (E, F).
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... problems with the design of the study are present, raising concerns about the overall conclusions. First, the authors make the erroneous claim that inverting faces produces a qualitative shift from configural to parts-based processing [8]. Moreover, while blurring faces effectively removes high-spatial frequency information, there is little evidence that this coincides with impaired parts-based processing and recent evidence in rhesus monkeys suggests the contrary [7, Figure 1]. Second, the monkey's face expertise was evaluated using only conspecific and human faces. Based on subjects' social housing and captive rearing history, at least some expertise would be expected for both species' faces. A more complete assessment of expertise requires the inclusion of both nonexpert face and nonface categories. Third, following from previous work, it is presumption that fixations on the eyes are diagnostic of configural processing in monkeys [9]. The justification for this is unclear but it appears based on the logic that a) humans process faces configurally and attend to the eyes more than any other feature, b) inverting faces impairs configural processing and reduces attention to the eyes, therefore, c) if rhesus monkeys attend to the eyes, they must be processing faces configurally. This logic is seriously flawed and must be addressed if the authors are to use eye fixations as their sole dependent measure, particularly given previous negative findings in macaques [7, described above], and humans [10]. Finally, if attending more to the eye region of upright and/or blurred faces compared to inverted faces supports configural processing, what results could support the alternative hypothesis, parts-based processing? Perhaps subjects would rely on a single face part (excluding the eyes because they are linked to configural processing)? It does not appear that the experimental design can sufficiently and independently address these alternative hypotheses with the dependent measure ...
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Which processes in the human brain lead to the categorical perception of speech sounds? Investigation of this question is hampered by the fact that categorical speech perception is normally confounded by acoustic differences in the stimulus. By using ambiguous sounds, however, it is possible to dissociate acoustic from perceptual stimulus represent...
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... But the additional involvement of fronto-parietal regions is consistent with claims that the dorsal stream, sensorimotor system plays a role as well (D'Ausilio et al., 2009;Pulvermuller & Fadiga, 2010). However, it has been argued extensively that dorsal stream involvement in speech perception is driven by task demands associated with discrimination paradigms (working memory, conscious attention to phonemic level information) rather than computational systems needed to recognize speech sounds (Bishop et al., 1990;Hickok, 2009Hickok, , 2014Hickok & Poeppel, 2007;Rogalsky et al., 2011;Venezia et al., 2012). The present study used a discrimination paradigm and so involvement of the dorsal speech stream is expected in analyses that do not covary out the effects of task. ...
Auditory and visual speech information are often strongly integrated resulting in perceptual enhancements for audiovisual (AV) speech over audio alone and sometimes yielding compelling illusory fusion percepts when AV cues are mismatched, the McGurk-MacDonald effect. Previous research has identified three candidate regions thought to be critical for AV speech integration: the posterior superior temporal sulcus (STS), early auditory cortex, and the posterior inferior frontal gyrus. We assess the causal involvement of these regions (and others) in the first large-scale (N = 100) lesion-based study of AV speech integration. Two primary findings emerged. First, behavioral performance and lesion maps for AV enhancement and illusory fusion measures indicate that classic metrics of AV speech integration are not necessarily measuring the same process. Second, lesions involving superior temporal auditory, lateral occipital visual, and multisensory zones in the STS are the most disruptive to AV speech integration. Further, when AV speech integration fails, the nature of the failure-auditory vs visual capture-can be predicted from the location of the lesions. These findings show that AV speech processing is supported by unimodal auditory and visual cortices as well as multimodal regions such as the STS at their boundary. Motor related frontal regions do not appear to play a role in AV speech integration.
... In the speech domain, a number of researchers have considered these motor activations as being necessary for speech processing and understanding (Iacoboni, 2008), in line with the suggestions of Liberman et al. (1967) that speech is perceived by mapping sounds into articulatory gestures. However, the exact functional role of this motor activity is still debated (Scott et al., 2009), with some studies arguing that sensorimotor information is not required in most contexts of speech perception (Hickok, 2009). To investigate this question, the use of TMS as an interference technique offers a unique opportunity. ...
Recent evidence has reported that the motor system has a role in speech or emotional vocalization discrimination. In the present study we investigated the involvement of the larynx motor representation in singing perception. Twenty-one non-musicians listened to short tones sung by a human voice or played by a machine and performed a categorization task. Thereafter continuous theta-burst transcranial magnetic stimulation was applied over the right larynx premotor area or on the vertex and the test administered again. Overall, reaction times (RTs) were shorter after stimulation over both sites. Nonetheless and most importantly, RTs became longer for sung than for "machine" sounds after stimulation on the larynx area. This effect suggests that the right premotor region is functionally involved in singing perception and that sound humanness modulates motor resonance.
... But an alternative view proposes that motor activation can occur, but that it is not necessary. The involvement has been characterized as modulatory (Hickok, 2009; Lotto et al., 2009; but see Wilson, 2009) or as being specific to certain situations and materials (Toni et al., 2008). In any case, evidence showing a link between specific properties of speech sounds being perceived and the articulators needed to produce them suggest that there is a link between representations. ...
The interactive-alignment account of dialogue proposes that interlocutors achieve conversational success by aligning their understanding of the situation under discussion. Such alignment occurs because they prime each other at different levels of representation (e.g., phonology, syntax, semantics), and this is possible because these representations are shared across production and comprehension. In this paper, we briefly review the behavioral evidence, and then consider how findings from cognitive neuroscience might lend support to this account, on the assumption that alignment of neural activity corresponds to alignment of mental states. We first review work supporting representational parity between production and comprehension, and suggest that neural activity associated with phonological, lexical, and syntactic aspects of production and comprehension are closely related. We next consider evidence for the neural bases of the activation and use of situation models during production and comprehension, and how these demonstrate the activation of non-linguistic conceptual representations associated with language use. We then review evidence for alignment of neural mechanisms that are specific to the act of communication. Finally, we suggest some avenues of further research that need to be explored to test crucial predictions of the interactive alignment account.
... In the current study we examine how these individual differences manifest in speech processing, with a particular focus on the role of the motor system in speech perception. Although studies of speech perception generally reveal some involvement of premotor and motor regions (Devlin & Aydelott, 2009) there remains disagreement about whether this activity is an obligatory part of speech processing (D'Ausilio et al., 2009;Meister, Wilson, Deblieck, & Wu, 2007;Wilson, Saygin, & Sereno, 2004), or might instead reflect other associated processes (Hickok, 2010;Hickok et al., 2008;Scott & Wise, 2004;Scott, Mcgettigan, & Eisner, 2009). We hypothesised that inter-individual variability in cognitive ability may be one factor that contributes to the seemingly inconsistent pattern of results present in the literature. ...
... Despite these provocative findings, however, the degree to which premotor and motor processing is a necessary component of speech perception is still unclear, and recent reviews of the literature have called for caution when interpreting the above results (Hickok, 2008(Hickok, , 2009Hickok and Poeppel, 2007;Lotto, Hickok, & Holt, 2009;Scott et al., 2009). One reason for caution is that the above findings are not always replicated; for example, in a repetitive TMS study of premotor regions, Sato, Tremblay, and Gracco (2009) reported slower phoneme discrimination only (requiring phonemic segmentation) but no effect on phoneme identification or syllable discrimination (Sato et al., 2009). ...
... The only frontal region exhibiting elevated activity during speech perception was the left inferior frontal gyrus (pars orbitalis). The failure to observe significant neural activation in premotor and motor cortices during speech perception compared to matched non-speech perception is in line with suggestions from Scott et al. (2009) andLotto, Holt, andHickok (2009) that the presence of premotor and motor activation in fMRI studies of speech perception might be a consequence of inappropriate baseline conditions, and the failure to adopt an appropriate level of control for false positives. ...
... A more moderate view that has been promoted by some authors is that the motor system may at most provide a modulatory influence on perceptual processes carried out in auditory cortical fields under adverse listening conditions, such as when the acoustic signal is degraded (Hickok, 2009b(Hickok, , 2010Wilson, 2009). According to this proposal, motor information provides a top-down influence on perceptual processes, perhaps in the form of forward models (Hickok & Saberi, in press;Rauschecker & Scott, 2009;Poeppel et al., 2008;Hickok & Poeppel, 2007;van Wassenhove, Grant, & Poeppel, 2005). ...
Many models of spoken word recognition posit that the acoustic stream is parsed into phoneme level units, which in turn activate larger representations [McClelland, J. L., & Elman, J. L. The TRACE model of speech perception. Cognitive Psychology, 18, 1-86, 1986], whereas others suggest that larger units of analysis are activated without the need for segmental mediation [Greenberg, S. A multitier theoretical framework for understanding spoken language. In S. Greenberg & W. A. Ainsworth (Eds.), Listening to speech: An auditory perspective (pp. 411-433). Mahwah, NJ: Erlbaum, 2005; Klatt, D. H. Speech perception: A model of acoustic-phonetic analysis and lexical access. Journal of Phonetics, 7, 279-312, 1979; Massaro, D. W. Preperceptual images, processing time, and perceptual units in auditory perception. Psychological Review, 79, 124-145, 1972]. Identifying segmental effects in the brain's response to speech may speak to this question. For example, if such effects were localized to relatively early processing stages in auditory cortex, this would support a model of speech recognition in which segmental units are explicitly parsed out. In contrast, segmental processes that occur outside auditory cortex may indicate that alternative models should be considered. The current fMRI experiment manipulated the phonotactic frequency (PF) of words that were auditorily presented in short lists while participants performed a pseudoword detection task. PF is thought to modulate networks in which phoneme level units are represented. The present experiment identified activity in the left inferior frontal gyrus that was positively correlated with PF. No effects of PF were found in temporal lobe regions. We propose that the observed phonotactic effects during speech listening reflect the strength of the association between acoustic speech patterns and articulatory speech codes involving phoneme level units. On the basis of existing lesion evidence, we interpret the function of this auditory-motor association as playing a role primarily in production. These findings are consistent with the view that phoneme level units are not necessarily accessed during speech recognition.
... It is well-known that patients with Broca's aphasia often have very large lesions involving the left motor speech system and can have very severe speech production deficits (Naeser et al., 1989), yet are quite capable of processing speech sounds as evidenced by their preserved word-level comprehension (Damasio, 1992;Goodglass, 1993;Goodglass & Kaplan, 1983;Hillis, 2007). Thus, to a first approximation, the existence of Broca's aphasia, in which there is a dissociation between speech production (impaired) and speech comprehension (preserved), constitutes evidence against the motor theory of speech perception (Hickok, 2009b(Hickok, , 2009cLotto, Hickok, & Holt, 2009). Previous studies, however, presented group-based data and do not report detailed lesion information, relying instead on clinical diagnosis of Broca's aphasia to infer lesion location. ...
The discovery of mirror neurons in macaque has led to a resurrection of motor theories of speech perception. Although the majority of lesion and functional imaging studies have associated perception with the temporal lobes, it has also been proposed that the 'human mirror system', which prominently includes Broca's area, is the neurophysiological substrate of speech perception. Although numerous studies have demonstrated a tight link between sensory and motor speech processes, few have directly assessed the critical prediction of mirror neuron theories of speech perception, namely that damage to the human mirror system should cause severe deficits in speech perception. The present study measured speech perception abilities of patients with lesions involving motor regions in the left posterior frontal lobe and/or inferior parietal lobule (i.e., the proposed human 'mirror system'). Performance was at or near ceiling in patients with fronto-parietal lesions. It is only when the lesion encroaches on auditory regions in the temporal lobe that perceptual deficits are evident. This suggests that 'mirror system' damage does not disrupt speech perception, but rather that auditory systems are the primary substrate for speech perception.
... For example, even if we assume that the manipulation affected perception and not bias, stimulation of lip (or tongue) cortex may prime the acoustic correlates of these sounds in auditory cortex via sensory-motor associations (e.g., forward models), which may facilitate perception in auditory areas. This explanation holds that motor systems can modulate acoustic perception of speech in a top down fashion, much like lexical context can (Hickok, 2009b). ...
The discovery of mirror neurons in the macaque monkey has ignited intense interest in motor theories of cognition, including speech and language. Here we examine two such claims, that the perception of speech sounds critically depends on motor representations of speech gestures (the motor theory of speech perception) and that the representation of action-related semantic knowledge critically depends on motor representations involved in performing actions. We conclude that there is strong evidence against the claim that speech perception critically depends on the motor system and that there is no conclusive evidence in support of the view that the motor system supports action semantics. We propose instead that motor-related activity during perceptual processes stem from spreading activation in sensory-motor networks that are critical for speech and language production.
Emerging neurophysiologic evidence indicates that motor systems are activated during the perception of speech, but whether this activity reflects basic processes underlying speech perception remains a matter of considerable debate. Our contribution to this debate is to report direct behavioral evidence that specific articulatory commands are activated automatically and involuntarily during speech perception. We used electropalatography to measure whether motor information activated from spoken distractors would yield specific distortions on the articulation of printed target syllables. Participants produced target syllables beginning with /k/ or /s/ while listening to the same syllables or to incongruent rhyming syllables beginning with /t/. Tongue-palate contact for target productions was measured during the articulatory closure of /k/ and during the frication of /s/. Results revealed "traces" of the incongruent distractors on target productions, with the incongruent /t/-initial distractors inducing greater alveolar contact in the articulation of /k/ and /s/ than the congruent distractors. Two further experiments established that (i) the nature of this interference effect is dependent specifically on the articulatory properties of the spoken distractors; and (ii) this interference effect is unique to spoken distractors and does not arise when distractors are presented in printed form. Results are discussed in terms of a broader emerging framework concerning the relationship between perception and action, whereby the perception of action entails activation of the motor system.
