Neural Responsivity to Tactile and Auditory Sensory Stimuli in Youth with and without ASD

Background: Children with ASD often exhibit sensory over-responsivity (SOR), which may cause them to react negatively to sensory stimuli such as noisy environments or scratchy clothing (Liss et al., 2006).  Rates of SOR are over five times higher in children with ASD than in typically developing (TD) children (e.g., Baranek et al., 2006; Ben-Sasson et al., 2007) and SOR is associated with increased functional impairment in children with ASD (e.g., Liss et al., 2006; Pfeiffer et al., 2005).  Results from a prior study from our lab examining fMRI responses to visual and auditory stimuli suggest that hyperactivation in the limbic system, primary sensory cortices, and prefrontal cortex is associated with higher SOR symptoms (Green et al, in press). The present study extends our early findings by examining fMRI responses to tactile and auditory stimuli in youth with and without ASD.

Objectives: 1) To examine differences in brain responses to auditory and tactile stimuli in youth with and without ASD; 2) To examine the relationship between parent- and child-reported SOR symptoms and brain responses to sensory stimuli; and 3) To examine functional connectivity during exposure to sensory stimuli.

Methods: Participants were 16 children and adolescents with ASD and 16 TD matched controls, between 8-17 years.  During fMRI, participants were presented with mildly aversive auditory stimuli (noisy traffic sounds) and tactile stimuli (scratchy sweater rubbed from wrist to elbow).  The block design paradigm included 4, 15-sec trials of each stimulus type: the auditory stimulus, tactile stimulus, or both. Participants’ parents rated their symptoms of SOR with the Short Sensory Profile (Dunn, 1999). Scores on the relevant subscales (auditory and tactile sensitivity) were standardized and combined to create a sensory composite score. Parents also rated their children’s anxiety symptoms using the SCARED.

Results: FSL was used to run subject-level and then group-level analyses. Within- and between-group analyses were thresholded at Z>2.3 (p<.01). The ASD group showed greater activation in amygdala, hippocampus, thalamus, striatum, orbital frontal cortex, and somatosensory cortex. A regression model was used to predict fMRI response within both groups from SOR scores, controlling for anxiety. The same areas were significantly related to SOR score in both groups. Additional analyses examine functional connectivity with the amygdala as a seed region.

Conclusions: In one of the first fMRI studies of tactile stimulation with children with ASD, we confirm prior findings that SOR is related to hyperactivation of the limbic system and primary sensory cortices. Functional connectivity between amygdala and striatum, orbital frontal cortex, and somatosensory cortex is also discussed.