Reduced Inferior Frontal Cortex Response to Explicit Emotion Judgment in Autism

Background:  The ability to accurately identify others’ emotions is a critical skill for successful social interaction. Many individuals with autism spectrum disorders (ASD) struggle with everyday social interactions, largely due to difficulty reading others’ emotions from faces (Harms et al., 2010) and from their body postures (Hadjikhani et al., 2009). Watching an agent in action can trigger emotional contagion which may be mediated by the inferior frontal cortex (IFC). Inferring emotions from actions and from their contexts (explicit vs. implicit) has been relatively under-examined in ASD. This study used dynamic action scenarios to examine the neural mechanisms, especially the role of the IFC, in mediating this process in ASD. 

Objectives:  The primary objective of this functional MRI study was to investigate the nature of brain responses associated with explicit and implicit perception of emotional information in high-functioning adults with ASD.

Methods:  fMRI data were collected from 5 high-functioning adults with ASD and 5 typically developing control participants (data collection still in progress). Participants watched a series of short videos (9 seconds each) of characters involved in emotional action scenarios. Participants were told to judge the emotion expressed by the character (happy, sad, angry, or afraid) or identify an object in each video. In the control condition, participants watched neutral videos of characters and made a perceptual judgment. The stimuli were presented in an event-related design, and the data were acquired using a Siemens 3T Allegra scanner. Data analysis was performed with SPM8 (Statistical Parametric Mapping) software.

Results:  Preliminary results of this study are: 1) Behavioral data showed that both groups performed significantly above chance on all video types (p < .05), and there were no significant group differences in accuracy. However, the ASD group had slower reaction times than the control participants for emotion and object videos; 2) There was robust bilateral extrastriate body area (EBA) activation (x = -46, y = -68, z = 0; x = 46, y = -66, z = 0) in both ASD and typical control participants for both emotion and object tasks, especially for the emotion task; and 3) There was a significantly decreased response in the right inferior frontal cortex (IFC) in the ASD participants, relative to typical controls, while judging emotions from the characters in the videos (p < .005, uncorrected; cluster threshold = 100 voxels).

Conclusions:  Robust EBA activation seen in both groups across conditions suggests intact general perceptual brain responses to explicit and implicit emotional action observation in ASD. However, the IFC response exclusive to explicit emotion judgment in the typical group was absent in the ASD group. This points to a potential difference in the cognitive strategy between both groups: while explicit emotional information recruits high level frontal areas in typical individuals, this same information, although adequately perceived, may not be processed at this level by those with ASD.