Abstract
Several studies demonstrated that face perception is biased by the prior presentation of another face, a phenomenon termed as face-related after-effect (FAE). FAE is linked to a neural signal-reduction at occipito-temporal areas and it can be observed in the amplitude modulation of the early event-related potential (ERP) components. Recently, macaque single-cell recording studies suggested that manipulating the duration of the adaptor makes the selective adaptation of different visual motion processing steps possible. To date, however, only a few studies tested the effects of adaptor duration on the electrophysiological correlates of human face processing directly. The goal of the current study was to test the effect of adaptor duration on the image-, identity-, and generic category-specific face processing steps. To this end, in a two-alternative forced choice familiarity decision task we used five adaptor durations (ranging from 200–5000 ms) and four adaptor categories: adaptor and test were identical images—Repetition Suppression (RS); adaptor and test were different images of the Same Identity (SameID); adaptor and test images depicted Different Identities (DiffID); the adaptor was a Fourier phase-randomized image (No). Behaviorally, a strong priming effect was observed in both accuracy and response times for RS compared with both DiffID and No. The electrophysiological results suggest that rapid adaptation leads to a category-specific modulation of P100, N170, and N250. In addition, both identity and image-specific processes affected the N250 component during rapid adaptation. On the other hand, prolonged (5000 ms) adaptation enhanced, and extended category-specific adaptation processes over all tested ERP components. Additionally, prolonged adaptation led to the emergence of image-, and identity-specific modulations on the N170 and P2 components as well. In other words, there was a clear dissociation among category, identity-, and image-specific processing steps in the case of longer (3500 and 5000 ms) but not for shorter durations (< 3500 ms), reflected in the gradual reduction of N170 and enhancement of P2 in the No, DiffID, SameID, and RS conditions. Our findings imply that by manipulating adaptation duration one can dissociate the various steps of human face processing, reflected in the ERP response.
Highlights
The ability of the visual system to rapidly adjust to changing environmental conditions is one of its key characteristics (Mesik et al, 2013)
The goal of the present work was to study the behavioral and electrophysiological effects of systematically varying adaptation duration and whether this variation leads to a differentiation between the various stages of face processing, such as the generic category coding vs. processing of identity and image specific information
The behavioral results indicated a better performance and faster decisions for the same identity (SameID) and repetition suppression (RS) conditions when compared with the different identity (DiffID) condition, corresponding to a strong priming effect in these cases (Ellis et al, 1987; Roberts and Bruce, 1989; Johnston and Barry, 2001)
Summary
The ability of the visual system to rapidly adjust to changing environmental conditions is one of its key characteristics (Mesik et al, 2013). At the behavioral level, such face-adaptation-related after-effects are present for various dimensions or aspects of face processing—such as identity (Leopold et al, 2001), distortion (Webster and MacLin, 1999), race, expression, gender (Webster et al, 2004; Kovács et al, 2005, 2006, 2007), attractiveness (Rhodes et al, 2003), or eye-gaze direction (Schweinberger et al, 2007a) It is worth noting, that in some cases, repeated presentations of a given stimulus (or subsequent presentations of two stimuli from the same category) do not lead to perceptual biases (as in the case of adaptation-related after-effects) but rather to behavioral facilitations. Neural adaptation [or its clearest form: the so-called repetition suppression (RS)] paradigms provide a powerful technique to determine the functional properties of face-evoked ERP components and their relation to underlying neural processing modules (Eimer et al, 2011)
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