Eye coding mechanisms in early human face event-related potentials

Rousselet, G. A. , Ince, R. A.A. , van Rijsbergen, N. J. and Schyns, P. G. (2014) Eye coding mechanisms in early human face event-related potentials. Journal of Vision, 14(13), Art. 7. (doi: 10.1167/14.13.7) (PMID:25385898)

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In humans, the N170 event-related potential (ERP) is an integrated measure of cortical activity that varies in amplitude and latency across trials. Researchers often conjecture that N170 variations reflect cortical mechanisms of stimulus coding for recognition. Here, to settle the conjecture and understand cortical information processing mechanisms, we unraveled the coding function of N170 latency and amplitude variations in possibly the simplest socially important natural visual task: face detection. On each experimental trial, 16 observers saw face and noise pictures sparsely sampled with small Gaussian apertures. Reverse-correlation methods coupled with information theory revealed that the presence of the eye specifically covaries with behavioral and neural measurements: the left eye strongly modulates reaction times and lateral electrodes represent mainly the presence of the contralateral eye during the rising part of the N170, with maximum sensitivity before the N170 peak. Furthermore, single-trial N170 latencies code more about the presence of the contralateral eye than N170 amplitudes and early latencies are associated with faster reaction times. The absence of these effects in control images that did not contain a face refutes alternative accounts based on retinal biases or allocation of attention to the eye location on the face. We conclude that the rising part of the N170, roughly 120–170 ms post-stimulus, is a critical time-window in human face processing mechanisms, reflecting predominantly, in a face detection task, the encoding of a single feature: the contralateral eye.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Van Rijsbergen, Dr Nicola and Rousselet, Dr Guillaume and Schyns, Professor Philippe and Ince, Dr Robin
Authors: Rousselet, G. A., Ince, R. A.A., van Rijsbergen, N. J., and Schyns, P. G.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
College of Science and Engineering > School of Psychology
Journal Name:Journal of Vision
Publisher:Association for Research in Vision and Ophthalmology (ARVO)
Copyright Holders:Copyright © 2014 ARVO
First Published:First published Journal of Vision 14(13): Art 7
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
591881Understanding age-related changes in processing facial emotionPhilippe SchynsBiotechnology and Biological Sciences Research Council (BBSRC)BB/J018929/1INP - CENTRE FOR COGNITIVE NEUROIMAGING
546511Effects of age, luminance and pupil size on retinal and cortical processing speedGuillaume RousseletLeverhulme Trust (LEVERHULME)F/00 179/BDINP - CENTRE FOR COGNITIVE NEUROIMAGING