title: The effect of contrast polarity reversal on face detection: evidence of perceptual asymmetry from sweep VEP.
abstract: Contrast polarity inversion (i.e., turning dark regions light and vice versa) impairs face perception. We investigated the perceptual asymmetry between positive and negative polarity faces (matched for overall luminance) using a sweep VEP approach in the context of face detection (Journal of Vision 12 (2012) 1-18). Phase-scrambled face stimuli alternated at a rate of 3 Hz (6 images/s). The phase coherence of every other stimulus was parametrically increased so that a face gradually emerged over a 20-s stimulation sequence, leading to a 3 Hz response reflecting face detection. Contrary to the 6 Hz response, reflecting low-level visual processing, this 3 Hz response was larger and emerged earlier over right occipito-temporal channels for positive than negative polarity faces. Moreover, the 3 Hz response emerged abruptly to positive polarity faces, whereas it increased linearly for negative polarity faces. In another condition, alternating between a positive and a negative polarity face also elicited a strong 3 Hz response, indicating an asymmetrical representation of positive and negative polarity faces even at supra-threshold levels (i.e., when both stimuli were perceived as faces). Overall, these findings demonstrate distinct perceptual representations of positive and negative polarity faces, independently of low-level cues, and suggest qualitatively different detection processes (template-based matching for positive polarity faces vs. linear accumulation of evidence for negative polarity faces).
authors.affiliation: Psychological Sciences Research Institute (IPSY) and Institute of Neuroscience (IoNS), University of Louvain, Belgium, 10 Place du Cardinal Mercier, 1348 Louvain-la-Neuve, Belgium. Electronic address: joan.liu@uclouvain.be.
authors.forename: Joan
authors.initials: J
authors.lastname: Liu-Shuang
authors.affiliation: School of Psychology and Neuroscience, University of St-Andrews, Westburn Lane, St Andrews, Fife KY16 9JP, United Kingdom.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Ales
authors.affiliation: Psychological Sciences Research Institute (IPSY) and Institute of Neuroscience (IoNS), University of Louvain, Belgium, 10 Place du Cardinal Mercier, 1348 Louvain-la-Neuve, Belgium.
authors.forename: Bruno
authors.initials: B
authors.lastname: Rossion
authors.affiliation: Stanford Vision and NeuroDevelopment Lab, Department of Psychology, Stanford University, Jordan Hall, Building 420, Stanford, CA 94305-2130, USA.
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Norcia
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology*; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005145:Face; D000066499:Facial Recognition / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009949:Orientation / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D012684:Sensory Thresholds / Q000502:physiology; D055815:Young Adult
keywords: Contrast reversal; EEG; Face perception; Phase coherence scrambling; SSVEP; Sweep VEP