Abstract
Fast periodic visual stimulation (FPVS) is a powerful method for investigating the brain activity underlying human face processing. Previous studies have shown that FPVS provides a reliable index of the face inversion effect (FIE) (Liu-Shuang et al., 2013) and individual differences in face recognition ability (Xu et al., 2014). In the current study, the FPVS method was used to compare the discrimination of upright and inverted faces of 6 adults with Autism Spectrum Disorder (ASD) and 6 age-matched typically developed (TD) control participants. A repeated face stimulus (A) was presented at a frequency of 6Hz (F) for a 60-second block with a different oddball face (B, C, D) interspersed at every 5th cycle of presentation (F/5=1.2Hz) (i.e., AAAABAAAACAAAAD....). Faces within each 60-second block were presented either in their upright or inverted orientations. It is hypothesized that the 6Hz response reflects sensitivity to stimuli belonging to the generic face category whereas the 1.2Hz oddball response indicates sensitivity to a particular individuated face. The results showed that the repeated face stimuli produced an enhanced EEG signal at the fundamental 6Hz frequency and its harmonics (12Hz, 18Hz, etc.) with the largest activation found at medial-occipital electrode sites. Both the ASD and TD groups showed the FIE in which upright faces elicited a greater EEG amplitude than inverted faces. At the 1.2Hz frequency and its harmonics (2.4Hz, 3.6Hz, etc.) , participants in the TD group showed the FIE where a greater signal was generated by the upright oddball face than the inverted oddball face. In contrast, participants in the ASD group exhibited the same EEG response to the upright and inverted oddball face. The lack of the FIE to the individuated oddball face in the ASD group is consistent with the behavioral findings indicating that adults with ASD have difficulty discriminating individual faces.
Meeting abstract presented at VSS 2015