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

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.

Gender bending: auditory cues affect visual judgements of gender in biological motion displays

“…With that in mind, there are important diVerences between the methods used here and those used by others. For example, the eVects reported here were elicited by adaptation periods almost three times longer than those used by others (Kovacs et al 2006;Schweinberger et al 2008). Similarly, the stimuli used here were abstract representations of gender categories (female walkers, male walkers, and so on), rather than speciWc examples from within categories.…”

“…Those issues are important because, while gender aftereVects have been reported by others, there are data to suggest that the eVects are category speciWc (e.g. Kovacs et al 2006) and do not generalise across modalities (Schweinberger et al 2008). It is tempting to interpret those results as suggesting that gender is encoded only within modalities (visual, auditory, and so on) and even within categories within a modality.…”

Neural repetition suppression to identity is abolished by other-race faces

“…As expected, Western and Eastern observers showed an ORE, as assessed in a separate face recognition task. Previous electrophysiological adaptation studies compared the ERPs to target faces, ignoring the response to adaptor faces (46)(47)(48)(49). In our experiment, this conventional approach failed to reveal any significant difference across conditions.…”

“…Therefore, the amount of RS is related to the capacity of a neural population to discriminate stimuli and could be compared with a novelty detection mechanism (31), decreasing neural responses' redundancy and increasing coding efficiency (31,36,(43)(44)(45). Interestingly, the face-sensitive N170 component shows preferential RS to faces but not to other visual categories (46), as well as to face identity (47)(48)(49). Thus, RS represents a powerful tool to elucidate the time-course and the nature of the neural representations leading to the all look alike effect.…”

Position specificity of adaptation-related face aftereffects

“…Regarding faces and the FAE, Melcher [67] used a variant of the gender adaptation experiment with the stimuli of Kovács et al [12]. In his study, subjects had a three-alternative forced choice recognition task of male faces morphed together with female faces.…”