4.2.2  Orbitofrontal underactivation in ASD to angry faces
Adolescents with ASD showed less orbitofrontal activity first in the left orbitofrontal area and then bilaterally compared to controls in response to angry faces. Closely connected to the amygdala, insula and ACC, the orbitofrontal cortex has been implicated in social inhibition and behaviour mediation (Blair et al., 1999; Dias et al., 1996; Elliott et al., 2000; Rolls, 2004; Van Honk et al., 2005). Insensitivity to both punishment and reward and emotion dysregulation has been observed following orbitofrontal damage (Berlin et al., 2004). Furthermore, the orbitofrontal cortex has been implicated in associating stimuli with behavioural outcome, which is integral for outcome predictions for adaptive behaviour (see Rushworth et al., 2007 for a review) as well as inferring others' emotional states (Baron-Cohen et al., 1999). Impairments in representing and associating outcome expectations with aversive stimuli could result in failure to plan and adjust future behaviour. In light of these findings, our observations of orbitofrontal under-activation to angry faces in ASD suggest that atypical integration of information concerning punishment, and difficulty deriving social averseness from angry faces, could contribute to social impairment in ASD. This is consistent with observations that anger processing recruits additional neural areas, supporting the idea that anger requires more resources and contextual information to respond appropriately (Lindner & Rosén, 2006; Pichon et al., 2009). It is interesting to note a lack of orbitofrontal activity differences between adolescents with and without ASD to happy faces, which may be due to reduced need for behavioural adaptation, and mediation following perception of positive emotion. This contrast may explain why adolescents with ASD, with their reduced processing of angry faces, show difficulties in recognizing and interpreting anger.