Electrophysiological Correlates of Visual Adaptation to Faces and Body Parts in Humans

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Abstract
The existence of facial aftereffects suggests that shape-selective mechanisms at the higher stages of visual object coding — similarly to the early processing of low-level visual features — are adaptively recalibrated. Our goal was to uncover the ERP correlates of shape-selective adaptation and to test whether it is also involved in the visual processing of human body parts. We found that prolonged adaptation to female hands — similarly to adaptation to female faces — biased the judgements about the subsequently presented hand test stimuli: they were perceived more masculine than in the control conditions. We also showed that these hand aftereffects are size and orientation invariant. However, no aftereffects were found when the adaptor and test stimuli belonged to different categories (i.e. face adaptor and hand test, or vice versa), suggesting that the underlying adaptation mechanisms are category-specific. In accordance with the behavioral results, both adaptation to faces and hands resulted in a strong and category-specific modulation — reduced amplitude and increased latency — of the N170 component of ERP responses. Our findings suggest that shape-selective adaptation is a general mechanism of visual object processing and its neural effects are primarily reflected in the N170 component of the ERP responses.