Asymmetric neural responses for facial expressions and anti-expressions

We examined whether neural responses to these complementary stimulus pairs were equivalent or asymmetric, and also tested for norm-based coding by comparing whether stronger responses are elicited by expressions and anti-expressions than neutral faces. Observers viewed 20 s sequences of 6 Hz alternations of neutral faces and expressions, neutral faces and anti-expressions, and expressions and anti-expressions. Responses were analyzed in the frequency domain. Significant responses at half the frequency of the presentation rate (3 Hz), indicating asymmetries in responses, were observed for all conditions. Inversion of the images reduced the size of this signal, indicating these asymmetries are not solely due to differences in the low-level properties of the images. While our results do not preclude a norm-based code for expressions, similar to identity, this representation (as measured by the FPVS EEG responses) may also include components sensitive to which configural distortions form meaningful expressions.

Source: Neuropsychologia - September 5, 2018 Category: Neurology Source Type: research