Face-specificity is robust across diverse stimuli and individual people, even when interstimulus variance is zero
School of Psychology, Cognition Institute, University of Plymouth, Plymouth, UK Psychophysiology
(Impact Factor: 3.18).
01/2013; 50(3). DOI: 10.1111/psyp.12013
The N170 is a brain electrical potential proposed to index the earliest time of categorical perception of faces in occipitotemporal visual areas implicated in face cognition, being more negative for faces than nonface objects between 120 and 200 ms. The interstimulus variance (ISV) account instead explained N170 face-specificity as an artifact due to objects varying more visually than faces. Ganis, Smith, and Schendan (2012) tested this account directly, finding that N170 face-specificity remains even when ISV is eliminated. Here, N170 peak amplitude and face-specificity is quantified for individual stimuli and participants, revealing that the right hemisphere N170 is especially sensitive to stimulus variability. Further, ISV contributes 0 to 37% to N170 face-specificity. These findings provide evidence for optimizing face processing science. The paradigm can apply to any research in which ISV may be uncontrolled (e.g., category comparisons).
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ABSTRACT: In cognitive science, there is an ongoing debate about the architecture of the mind: does it consist of a number of mental “organs” each managing a different function in isolation, or is it more of general processor, adaptable to a wide range of tasks? One corner of this debate has centered on face processing. This is because face-perception is crucial to normal human functioning and some evidence shows that faces may be processed by the brain in a privileged way compared to other types of stimuli. For example, in EEG brain recordings, the N170 is a characteristic signal that occurs after a participant is exposed to an image of a face, but it is much less pronounced when other stimuli are shown. More than 15 years of research on the “N170 face effect” have yielded the standard view that the N170 is at the very least face-sensitive, and possibly even face-specific, that is, indexing modular processes tied exclusively to facial geometries. The specificity claim is clearly stronger, and hence subject to significant controversy; while the more conservative “sensitivity” claim had been regarded (until recently) as effectively settled. Nevertheless, Thierry and colleagues, in a contentious 2007 article, sought to undermine even this ‘conservative’ consensus: they argued that the apparent face-responsiveness of the N170 in prior research was due to systematic flaws in experimental design. Fiery debate has followed. In this review, we put the debate in its historical and philosophical context, and try to spell out some of the theoretical and logical assumptions that underlie the claims of the competing camps. We then show that the best available evidence counts, at least partially, against the Thierry et al. construal of the N170. Accordingly, it would be premature to abandon the “conservative” account of the N170, according to which it is—minimally—responsive to faces. We conclude by returning to the more controversial claim about face-specificity, and try to clarify what such a view would entail from a theoretical standpoint.
Neuropsychological Trends 04/2013; 13(1):7-26. DOI:10.7358/neur-2013-013-earp · 0.15 Impact Factor
Available from: link.springer.com
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ABSTRACT: The study of neurophysiological approaches together with rare and common risk factors for Autism Spectrum Disorder (ASD) allows elucidating the specific underlying neurobiology of ASD. Whereas most neurophysiologically based research in ASD to date has focussed on case-control differences based on the DSM- or ICD-based categorical ASD diagnosis, more recent studies have aimed at studying genetically and/or neurophysiologically defined homogeneous ASD subgroups for specific neuronal biomarkers. This review addresses the neurophysiological investigation of ASD by evoked and event-related potentials, by EEG/MEG connectivity measures such as coherence, and transcranial magnetic stimulation. As an example of classical neurophysiological studies in ASD, we report event-related potential studies which have illustrated which brain areas and processing stages are affected in the visual perception of socially relevant stimuli. However, a paradigm shift has taken place in recent years focussing on how these findings can be tracked down to basic neuronal functions such as deficits in cortico-cortical connectivity and the interaction between brain areas. Disconnectivity, for example, can again be related to genetically induced shifts in the excitation/inhibition balance. Genetic causes of ASD may be grouped by their effects on the brain's system level to identify ASD subgroups which respond differentially to therapeutic interventions.
Journal of Neural Transmission 07/2014; 121(9). DOI:10.1007/s00702-014-1265-4 · 2.40 Impact Factor
Available from: Haline E Schendan
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ABSTRACT: People categorize objects more slowly when visual input is highly impoverished instead of optimal. While bottom-up models may explain a decision with optimal input, perceptual hypothesis testing (PHT) theories implicate top-down processes with impoverished input. Brain mechanisms and the time course of PHT are largely unknown. This event-related potential study used a neuroimaging paradigm that implicated prefrontal cortex in top-down modulation of occipitotemporal cortex. Subjects categorized more impoverished and less impoverished real and pseudo objects. PHT theories predict larger impoverishment effects for real than pseudo objects because top-down processes modulate knowledge only for real objects, but different PHT variants predict different timing. Consistent with parietal-prefrontal PHT variants, around 250 ms, the earliest impoverished real object interaction started on an N3 complex, which reflects interactive cortical activity for object cognition. N3 impoverishment effects localized to both prefrontal and occipitotemporal cortex for real objects only. The N3 also showed knowledge effects by 230 ms that localized to occipitotemporal cortex. Later effects reflected (a) word meaning in temporal cortex during the N400, (b) internal evaluation of prior decision and memory processes and secondary higher-order memory involving anterotemporal parts of a default mode network during posterior positivity (P600), and (c) response related activity in posterior cingulate during an anterior slow wave (SW) after 700 ms. Finally, response activity in supplementary motor area during a posterior SW after 900 ms showed impoverishment effects that correlated with RTs. Convergent evidence from studies of vision, memory, and mental imagery which reflects purely top-down inputs, indicates that the N3 reflects the critical top-down processes of PHT. A hybrid multiple-state interactive, PHT and decision theory best explains the visual constancy of object cognition.
Frontiers in Psychology 09/2015; 6. DOI:10.3389/fpsyg.2015.01289 · 2.80 Impact Factor
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