Investigating the perception of face identity in adults on the autism spectrum using behavioural and electrophysiological measures

In the present study, we investigated face processing in individuals with self-reported Autism Spectrum Disorder (ASD, n = 16) and typically developing control participants (n = 16) using behavioural and electrophysiological measures. As a measure of their face memory, we administered the Cambridge Face Memory Test to participants in the ASD group. The results showed that the scores of the ASD participants were reliably below the age- and gender-matched norms of neurotypical individuals. To measure brain responses to faces, we used the fast periodic visual stimulation method, presenting photographs of a same-identity face (i.e., base face) at a constant frequency of 6 Hz (F) interleaved with different-identity faces (i.e., the oddball faces) presented at 1.2 Hz. The 6 Hz presentation of the base face and 1.2 Hz presentation of the oddball face elicited periodic brain responses corresponding to face detection and face individuation processes, respectively. Participants viewed four blocks of upright faces and four blocks of inverted faces. The results showed an enhanced EEG response to upright base faces at 6 Hz frequency and its harmonics compared to inverted faces, and the response was most focal over medial occipital channels. An enhanced response was found to upright oddball faces at 1.2 Hz and its harmonics compared to the inverted faces, and the response was centred over occipito-temporal channels in the right hemisphere. Critically, no differences or interactions were found between the ASD and typically developing groups in the responses to either the 6 Hz base faces or the 1.2 oddball faces. These results suggest that in individuals with ASD, the earlier stage of face perception, as measured by the fast periodic visual stimulation paradigm, can be dissociated from the later memory stage of face processing, as assessed by the Cambridge Face Memory Test.