4.2.1  Atypical cingulate activation: delayed functional specialization of threat-relevant affective processing in ASD
Adolescents with ASD showed reduced left ACC and late right posterior cingulate (PCC) activation to angry faces and early right ACC and PCC underactivation to happy faces. The cingulate gyrus is functionally and cytoarchitecturally heterogeneous, with the anterior and posterior regions reciprocally connected with different regions of the brain (see Vogt et al., 1992 for a review). Classically, the cingulate gyrus is divided into the ACC and PCC, with the former linked to executive functioning, including affective processing, and the latter associated with evaluative processes (Vogt et al., 1992).
In ASD structural, functional and cyto-architectural idiosyncrasies of the ACC have been reported (e.g., Haznedar et al., 1997; Simms et al., 2009). In typically developing children, a shift from only the amygdala to the amygdala and ACC activity during threat-relevant affect processing has been shown, with children utilizing the earlier-developing subcortical structures involving the amygdala and adolescents employing the later maturing functionally specialized cortical route that includes the ACC (Hung et al., 2012). Our data showing consistently reduced ACC activation in ASD is congruent with the notion of immature processing of angry faces in adolescents with ASD, relative to their typically developing peers.
Interestingly, decreased right PCC activation in ASD was noted only to happy faces. As a canonical ‘evaluative’ region, the PCC is implicated in monitoring and assessing the external environment (Vogt et al., 1992). In typically developing children increased PCC activity to both happy and fearful faces relative to a non-emotional cognitive task has been noted (Habel et al., 2005). Reduced activation in the PCC in adolescents with ASD suggests its inadequate recruitment and, is in line with overall limbic underactivation in ASD.