Reduced Auditory Steady State Responses in Autism Spectrum Disorder

Abstract

AbstractBackgroundAuditory steady state responses (ASSRs) are elicited by clicktrains or amplitude-modulated tones, which entrain auditory cortex at their specific modulation rate. Previous research has reported reductions in ASSRs at 40Hz for autism spectrum disorder (ASD) participants and first-degree relatives of people diagnosed with ASD [1,2].MethodsUsing a 1.5s-long auditory clicktrain stimulus, designed to elicit an ASSR at 40Hz, this study attempted to replicate and extend these findings. Magnetencephalography (MEG) data were collected from 18 adolescent ASD participants and 18 typically developing controls.ResultsThe ASSR localised to bilateral primary auditory regions. Regions of interest were thus defined in left and right primary auditory cortex (A1). While the transient gamma-band response (tGBR) from 0-0.1s following presentation of the clicktrain stimulus was not different between groups, for either left or right A1, the ASD group had reduced oscillatory power at 40Hz from 0.5 to 1.5s post-stimulus onset, for both left and right A1. Additionally, the ASD group had reduced inter-trial coherence (phase consistency over trials) at 40Hz from 0.64-0.82s for right A1 and 1.04-1.22s for left A1.LimitationsIn this study, we did not conduct a clinical autism assessment (e.g. the ADOS), and therefore it remains unclear whether ASSR power and/or ITC are associated with the clinical symptoms of ASD.ConclusionOverall, our results support a specific reduction in ASSR oscillatory power and inter-trial coherence in ASD, rather than a generalised deficit in gamma-band responses. We argue that this could reflect a developmentally relevant reduction in non-linear neural processing.