Using Clustering to Examine Inter-individual Variability in Topography of Auditory Event-Related Potentials in Autism and Typical Development

Abstract

Although prior studies have compared sensory event-related potential (ERP) responses between groups of autistic and typically-developing participants, it is unclear how heterogeneity contributes to the results of these studies. The present study used examined individual differences in these responses. 130 autistic children and 81 typically-developing children, aged between 2 and 5 years, listened to tones at four identity levels while 61-channel electroencephalography was recorded. Hierarchical clustering was used to group participants based on rescaled ERP topographies between 51 and 350 ms. The hierarchical clustering analysis revealed substantial heterogeneity. Some of the seven clusters defined in this analysis were characterized by prolonged fronto-central positivities and/or weak or absent N2 negativities. However, many other participants fell into clusters in which N2 responses were present at varying latencies. Atypical response morphologies such as absent N2 responses and/or prolonged positive-going responses found in some autistic participants may account for prior research findings of attenuated N2 amplitudes in autism. However, there was also considerable overlap between groups, with participants of both groups appearing in all clusters. These results emphasize the utility of using clustering to explore individual differences in brain responses, which can expand on and clarify the results of analyses of group mean differences.

Autism Spectrum Disorder and auditory sensory alterations: a systematic review on the integrity of cognitive and neuronal functions related to auditory processing

“…The ASD group shows a reduced performance in both auditory and audiovisual modalities for whole-word recognition tasks with high SNRs (Stevenson et al 2017 ), when compared with TD peers. High-functioning ASD adults show a speech comprehension rate of nearly 100% in the absence of noise, similar to IQ-matched controls (Piatti et al 2021 ; Dwyer et al 2021 ). However, under noise conditions, the ASD group presents worse speech comprehension and neural over-responsiveness (Piatti et al 2021 ; Dwyer et al 2021 ).…”

“…High-functioning ASD adults show a speech comprehension rate of nearly 100% in the absence of noise, similar to IQ-matched controls (Piatti et al 2021 ; Dwyer et al 2021 ). However, under noise conditions, the ASD group presents worse speech comprehension and neural over-responsiveness (Piatti et al 2021 ; Dwyer et al 2021 ). Such results suggest that noise may increase the threshold needed to extract meaningful information from sensory inputs, affecting speech comprehension.…”

“…It was possible to verify a pattern of linear increases in response strength accompanied by a disproportionately strong response to 70 dB stimuli for ASD young children, correlated with auditory distractibility (Dwyer et al 2020 ). In a similar study, some clusters of ASD individuals presented weak or absent N2 by 60 dB and increased strength with higher intensities (70 or 80 dB) (Dwyer et al 2021 ). However, there was an overlap between ASD and TD participants in several clusters (Dwyer et al 2020 , 2021 ), suggesting that sensory impairments in ASD might be largely accounted for the wide interindividual variability that exists within the spectrum.…”

“…In a similar study, some clusters of ASD individuals presented weak or absent N2 by 60 dB and increased strength with higher intensities (70 or 80 dB) (Dwyer et al 2021 ). However, there was an overlap between ASD and TD participants in several clusters (Dwyer et al 2020 , 2021 ), suggesting that sensory impairments in ASD might be largely accounted for the wide interindividual variability that exists within the spectrum.…”

The Autism Phenome Project: Toward Identifying Clinically Meaningful Subgroups of Autism

“…In the APP, autistic participants exhibit—at the group mean level—diminished amplitudes of the N2, a negative-going cortical response to auditory stimuli over frontocentral channels ∼200–350 ms post-stimulus, at Time 1 ( Dwyer et al, 2021a ), consistent with prior studies ( Williams et al, 2021 ). However, examination of inter-individual differences in ERP morphologies suggests this pattern is driven by a subset of participants with atypical positive-going ERP responses over the spatiotemporal window associated with the N2 ( Dwyer et al, 2021c ). Although the behavioral implications of this ERP positivity are unclear, this finding illustrates how group averages can distort and occlude patterns at the individual and subgroup levels.…”