1.1  The spatiotemporal profile of neural activity during affect processing in ASD
There are few studies on the timing of the neural processing of emotional faces in ASD. ERP studies have noted variously a delay, reduced, or lack of activity in children and adults with ASD, relative to controls (Batty et al., 2011; Dawson et al., 2004; McPartland et al., 2004; O'Connor et al., 2005; Wong et al., 2008). A recent ERP study found that adolescents with ASD failed to show emotion-specific responses that were observed in the typically developing group (Wagner et al., 2013). Further, while face scanning was significantly associated with patterns of neural activation during face processing in typically developing adolescents, no such association was found in ASD (Wagner et al., 2013). Significant impairments in emotion recognition in adult, but not child, faces have also been noted in adolescents with ASD (Lerner et al., 2013). The same study also reported a significant association between the latency of the face-sensitive N170 component, localized to the fusiform gyri and inferior temporal areas, and deficits in emotion recognition in adolescents with ASD.
One study that investigated affective processing in adolescents with ASD using magnetoencephalography (MEG), which provides both timing and more accurate spatial information than EEG studies (Hari et al., 2010), showed reduced early emotion-specific gamma-band power, relative to controls, as well as later decreased power across all emotions (Wright et al., 2012). There do not appear to be other studies that have taken advantage of the spatio-temporal precision of MEG to determine the timing and/or brain regional activation differences in developmental ASD populations with emotional faces.