Elevated amygdala response to faces and gaze aversion in autism spectrum disorder.

Autism spectrum disorders (ASD) are often associated with impairments in judgment of facial expressions. This impairment is often accompanied by diminished eye contact and atypical amygdala responses to face stimuli. The current study used a within-subjects design to examine the effects of natural viewing and an experimental eye-gaze manipulation on amygdala responses to faces. Individuals with ASD showed less gaze toward the eye region of faces relative to a control group. Among individuals with ASD, reduced eye gaze was associated with higher threat ratings of neutral faces. Amygdala signal was elevated in the ASD group relative to controls. This elevated response was further potentiated by experimentally manipulating gaze to the eye region. Potentiation by the gaze manipulation was largest for those individuals who exhibited the least amount of naturally occurring gaze toward the eye region and was associated with their subjective threat ratings. Effects were largest for neutral faces, highlighting the importance of examining neutral faces in the pathophysiology of autism and questioning their use as control stimuli with this population. Overall, our findings provide support for the notion that gaze direction modulates affective response to faces in ASD.

Prolonged institutional rearing is associated with atypically large amygdala volume and difficulties in emotion regulation.

Early adversity, for example poor caregiving, can have profound effects on emotional development. Orphanage rearing, even in the best circumstances, lies outside of the bounds of a species-typical caregiving environment. The long-term effects of this early adversity on the neurobiological development associated with socio-emotional behaviors are not well understood. Seventy-eight children, who include those who have experienced orphanage care and a comparison group, were assessed. Magnetic resonance imaging (MRI) was used to measure volumes of whole brain and limbic structures (e.g. amygdala, hippocampus). Emotion regulation was assessed with an emotional go-nogo paradigm, and anxiety and internalizing behaviors were assessed using the Screen for Child Anxiety Related Emotional Disorders, the Child Behavior Checklist, and a structured clinical interview. Late adoption was associated with larger corrected amygdala volumes, poorer emotion regulation, and increased anxiety. Although more than 50% of the children who experienced orphanage rearing met criteria for a psychiatric disorder, with a third having an anxiety disorder, the group differences observed in amygdala volume were not driven by the presence of an anxiety disorder. The findings are consistent with previous reports describing negative effects of prolonged orphanage care on emotional behavior and with animal models that show long-term changes in the amygdala and emotional behavior following early postnatal stress. These changes in limbic circuitry may underlie residual emotional and social problems experienced by children who have been internationally adopted.

Visual exploration strategies and the development of infants' facial emotion discrimination.

We examined the role of visual exploration strategies in infants' discrimination between facial emotion expressions. Twenty-eight 6- to 11-month olds were habituated to alternating models posing the same expression (happy N = 14/fearful N = 14) as eye gaze data were collected with a corneal reflection eye tracker. Gaze behavior analyses indicated that duration of gaze to the eyes and mouth was similar, consistent with what would be expected based on area subtended by those regions, and negatively correlated. This pattern did not differ as a function of age, sex, or habituation condition. There were no posthabituation performance differences as a function of age group (6- to 8-month- versus 9- to 11-month olds). Only infants habituated to happy faces showed longer looking at the novel emotion (fear) when the model was held constant from habituation to test. We found no reliable correlation between this performance and proportion of gaze directed at any one facial region. Consistent with previous work, the group habituated to fear faces showed no reliable posthabituation novelty preference. Individual differences in gaze behavior shed light on this finding. Greater proportion of gaze directed at the eyes correlated positively with preference for the novel emotion (happy). These data suggest that, as in other object classes, visual exploration strategies are an important agent of change in infants' capacity to learn about emotion expressions.