1.4  Adolescence
In typically developing individuals, recognition of emotional face expressions follows a protracted developmental trajectory that extends into late adolescence (e.g., Batty & Taylor, 2006; Kolb et al., 1992). Asynchronous development of emotion recognition is well established (De Sonneville et al., 2002; Pichon et al., 2009) and neuroimaging findings have demonstrated the shifting involvement of different neural networks over the course of development (Hung et al., 2012; Killgore & Yurgelun-Todd, 2007; Monk et al., 2003; Thomas et al., 2001). At around 11 years of age emotional processing abilities undergo marked improvement, which would implicate greater demands on neural processes involved in emotional processing in early adolescence (Tonks et al., 2007).
There are few studies on emotional face processing in adolescents with ASD, representing a serious gap in the literature, as adolescence is a period of vulnerability, volatility and increased stress (Spear, 2000) during which the prevalence of negative emotions peaks and shows greater variability (Compas et al., 1995; Hare et al., 2008). Behavioural studies investigating emotional face processing in adolescents with ASD have shown affective processing comparable to controls (Grossman et al., 2000; Rieffe et al., 2007). Adolescents with ASD in these studies showed deficits in decoding emotions from static and dynamic facial affect overall, and, although they have been shown to identify specific emotions (Rump et al., 2009) such as happiness and sadness readily, they have difficulties with more complex emotions such as embarrassment (Capps et al., 1992) and identifying emotions when shown videos (Koning & Magill-Evans, 2001). Individuals with Asperger Syndrome but not high-functioning autism have shown intact emotion perception (Mazefsky & Oswald, 2007).
Adults with ASD continue to experience difficulties when presented with brief or subtle emotions, and may never reach the same level of competency in emotional processing as typically developing adults (Begeer et al., 2006; Rieffe et al., 2007). The impairment in emotional processing in adults with ASD is consistent with the notion that individuals with ASD require compensatory strategies to achieve average performance. Although competency with emotional recognition in ASD improves with age, this skill often plateaus at a performance level below that of typically developing peers, or is associated with atypical brain activations to achieve comparable performance levels. These results underscore the need to examine the adolescent period of emotional processing in ASD to obtain a clearer understanding of the emotional development in this population.
Thus, the present study explored the neural substrates of implicit emotional face processing in adolescents with ASD using MEG, providing both temporal and spatial measures of brain processes, focusing on the neural areas implicated in emotional processing. We hypothesized that adolescents with ASD would show (1) shorter response latencies to emotional faces as they are not distracted by the emotions and (2) reduced and delayed patterns of neural activation in the frontal, limbic and temporal areas, key constituents of the social brain.