A Lack of Neurophysiological Responses to Subliminally Presented Fearful Faces in Adults with High-functioning Autism Spectrum Disorders

Background: Recent studies (Bailey et al., 2005; Critchley et al., 2001; Kamio et al., 2006) have suggested that individuals with autism spectrum disorders (ASD) respond to faces differently from typical developing individuals at an automatic level, even when they can perform face tasks well at a conscious level. Since emotionally significant stimuli are automatically processed outside conscious awareness before being integrated with slower and more elaborative processing, abnormalities of automatic face processing are thought to be essential for the various manifestations of social cognition in individuals with ASD.

Objectives: Our study aimed to examine the neurophysiological basis of subliminal face processing at the V1 level in adults with high-functioning ASD (HFASD) and to compare it with that of healthy adults by measuring the earliest event-related potential (ERP).

Methods: Nine adults with HFASD and 10 healthy control adults performed a low-frequency target detection task in which photographs of faces (fearful, neutral) and objects were presented for 20ms with backward pattern masks either upright or inverted. The latency and peak amplitude of N1 were measured at occipital electrodes (Oz).

Results: In the control group, upright fearful faces evoked greater N1 amplitude at around 100 msec than objects did, but the N1 amplitude for fearful faces was reduced when inverted and did not differ from that for objects. On the other hand, such face-specific responses were not observed in the ASD group.

Conclusions: The findings suggest that individuals with ASD are impaired in the early and automatic processing specific to fearful faces, which was confirmed in individuals with typical development. The explicit social abnormalities observable in individuals with ASD could be explained by such deficits in precognitive face processing.