Possible Neural Mechanisms Underlying Sensory Over-Responsivity in Individuals with ASD

Purpose of Review Sensory over-responsivity (SOR) is an excessively unpleasant response to or avoidance of sensory stimuli, e.g., sound and light, which is prevalent among individuals with autism spectrum disorder (ASD). Despite its negative impacts on personal and social lives, knowledge about the occurrence of and mechanisms underlying SOR is inadequate. This review of studies on SOR in ASD summarizes the evidence on the close relationship of SOR with prenatal and genetic factors and presents information on neural mechanisms underlying SOR. Recent Findings Emerging studies have reported that SOR symptoms are related to abnormal structural connectivity in the brain, particularly decreased inter-hemispheric connectivity in subcortical regions (the thalamus and basal ganglia) and increased intra-hemispheric connectivity in the basal ganglia, especially in the right cerebral hemisphere, and with an enlarged amygdala. In the resting state, functional connectivity between the pulvinar and primary sensory regions, the basal ganglia, the limbic system (the amygdala and hippocampus), the temporal cortex, the prefrontal cortex, and sensorimotor regions is enhanced, while structural and functional connectivity between the thalamus and cortex is diminished. Summary These findings indicate that the functional abnormalities associated with SOR are probably due to reduced top-down regulation, which inhibits the reorientation of attention from external stimuli, thereby causing difficulty in filtering out and/or integrating sensory information and then lowering inhibition in generating excessive responses to the incoming sensory stimuli.