Reduced Beta and Gamma Band Activity to Auditory Stimuli in Children with Autism Spectrum Disorders.

Background: Abnormal sensory reactivity is a key feature in the DSM-5 and is related to the most functional impairment in individuals with autism spectrum disorders (ASD). Auditory processing is the most commonly affected sensory domain. Atypical auditory processing is hypothesized to play a role in social, communicative, and cognitive deficits in ASD. However, there is little research examining the basis of auditory processing dysfunction in ASD.

Objectives: To examine brain oscillations during a sensory gating paradigm in children with ASD using electroencephalography (EEG). Based on previous research, we hypothesized that children with ASD will have reduced beta and gamma band activity to the click sounds compared to typically-developing (TD) controls.

Methods: Participants included 21 children with ASD (M= 8.6 years, SD= 2.14), and 20 age-matched TD children. EEG data were collected during a modified sensory gating paradigm consisting of 100 paired-click stimuli while the participant watched a silent movie. The base-line corrected time-frequency characteristics measured included a) evoked power, representing signal intensity, and b) phase-locking factor, depicting synchronization of signals across trials. The following regions of interest (ROI) were identified 1) Beta: 13–18 Hz from 60-90 ms and 2) Early gamma: 30–50 Hz from 20–60 ms and 3) Late gamma: 30–50 Hz from 60–90 ms. Data from each ROI were analyzed using a 2 (Clicks) by 2 (Group) ANOVA procedure. Caregivers of all participants filled out the Sensory Profile questionnaire.

Results: Evoked power and phase synchronization plots show that children with ASD appear to have less evoked power and reduced synchronization than the TD group to the clicks. (Figures 1 and 2). The ANOVA evaluating evoked beta power indicated a significant group effect, F_(1,39)= 25.1, p < .0005, η²_p = .39, with reduced beta evoked power in both clicks in the ASD group compared to controls. Similarly, the ANOVA examining beta phase synchronization indicated significantly reduced beta phase synchrony to both clicks in the ASD group compared to controls, F_(1,39) = 27.3, p < .0005, η²_p = .41. There were no group or interaction effects in early or late gamma-band evoked power. However, early gamma phase synchronization was significantly reduced in the ASD group compared to controls for both clicks, F_(1,39) = 10.5, p = .002, η²_p = .21. There were no significant group differences in late gamma synchrony. Across all participants, greater sensory processing issues as measured by the Sensory Profile total score was associated with lower click 1 evoked beta power (r=.44, p= .004), lower beta phase synchronization (r=.49, p= .001) and lower gamma synchrony (r=.45, p= .003).

Conclusions: Results shows that children with ASD have reduced evoked power and phase synchronization of beta activity and reduced early gamma phase synchrony during auditory processing compared to controls, specifically in orienting and filtering auditory stimuli. Moreover, neural oscillations of click 1 strongly correlate with sensory processing in everyday activities suggesting that the sensory processing deficits observed in children with ASD may arise from atypical neurophysiological functioning specifically when orienting to an auditory stimulus.