Auditory Event-Related Spectral Perturbations in Children with and without ASD
Sensory atypicalities are well established in ASD and represent core diagnostic criteria (APA, 2013). Although the neurobiological underpinnings of these features are not well defined, there is consensus that they show bidirectional influences on perceptual systems throughout development.
Previous studies have explored the associations between EEG activity and sensory response patterns in ASD. The electrophysiological signatures of sensory processes are observed in both the alpha (8-12Hz) and gamma (30-60Hz) bands. Gamma activity has been reported during a variety of early sensory responses and facilitates sensory processing (Skinner et al., 2000; Singer & Gray, 1995). Increased gamma power in ASD was associated with lower P50 suppression, suggesting ineffective inhibitory control (Orekhova et al., 2008). Alpha activity had been implicated in sensory gating (Klimesh et al., 2007). In High-Risk infants, reversed alpha asymmetry was associated with increased sensory seeking (Damiano-Goodwin et al., 2018).
(1) Examine between group (ASD vs. TYP) differences in EEG event related spectral perturbations (ESRP) during an auditory mismatch negativity paradigm; (2) Explore associations between parent-reported sensory response patterns and ESRP activity in children with ASD.
We present findings from 31 children (16 ASD) ages 5-11. A larger sample (N = 60) is anticipated by Spring 2019. Parents completed the Sensory Experiences Questionnaire (Baranek, 2006). Participants watched a silent video while standard and novel sounds (7%) played in the background. EEG was recorded via a 12-channel Electro Cap at 500Hz with Neuroscan and band-pass filtered (0.15Hz – 70HZ) online. Offline EEG processing used EEGLAB (Delorme & Makeig, 2004). ESRP from -200-500ms around novel sounds at electrode Cz was measured, based on previous research (Donkers et al., 2013). We explored the association between SEQ patterns and ESRP in the gamma range and examined other spectral bands.
Low gamma activity was enhanced from baseline (150-300ms) in ASD compared to controls. Theta activity (4-8Hz) was reduced (0-400ms) in ASD compared to TD controls (Figure 1). There were no associations between ERSP and SEQ patterns, though peak theta and peak low gamma were negatively correlated (r = -.63, p = .03).
Our preliminary findings suggest that processing of auditory stimuli differ between children with and without ASD. Children with ASD had elevated gamma-related responses, suggesting enhanced sensory processing and gating. Children without ASD showed more evaluative processing (Donkers et al., 2015) with greater theta activity post stimulus. Theta is commonly studied in relation to working memory processing and enhanced theta in TD controls may reflect greater cognitive evaluation to the novel stimulus across the course of the MMN task. Further work is required to characterize the neurophysiological signatures of sensory processing in ASD and relate them to sensory processing atypicalities. Further analysis of gamma and theta power, including the timing of peaks (Isler et al., 2010) could inform about the biological underpinning of sensory atypicalities in ASD.
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