RP214 - Speech-in-Noise Processing in Adults with Autism Spectrum Disorder

Abstract:
Individuals diagnosed with autism spectrum disorder (ASD) often have difficulty perceiving speech-in-noise (SIN), but the behavioral and neural mechanisms underlying variability in SIN performance remain unclear. This research project assessed how behavioral and cortical measures of attention and inhibition related to SIN performance in persons with ASD and in a group of neurotypical listeners. Results showed significant differences between listener groups in SIN performance. In addition, differences in sustained auditory attention, acceptance of noise, and neural measures of inhibition were also found. Overall, results highlight auditory processing differences in individuals with ASD that likely contribute to SIN performance.

Summary:
Rationale
Many individuals diagnosed with autism spectrum disorder (ASD) have normal pure-tone hearing sensitivity but experience poor speech-in-noise (SIN) perception and difficulty filtering out background noise. SIN perception and the ability to filter background noise are critical skills that correlate highly with academic performance and will impact everyday conversations at school, in the workplace, and in social situations. Recent work suggests differences in cortical gating, a measure of neural inhibition, may underlie SIN deficits in neurotypical listeners (Campbell et al. 2020). It is untested if differences in neural inhibition underlie SIN deficits in persons with ASD. The present study used a brain-behavior protocol to determine whether cortical gating predicted SIN performance in adults with ASD. Results were compared to a group of neurotypical listeners. Behavioral measures of auditory attention, acceptance of noise, and self-reported listening surveys were also collected. We hypothesized persons with ASD who exhibited poorer cortical gating would exhibit larger SIN deficits.

Methods
A two-group, cross-sectional design was employed. Thirty-two adult listeners with normal hearing participated in the study, and twelve of the listeners had a confirmed diagnosis of autism spectrum disorder (ASD). Speech-in-noise perception was measured using the QuickSIN. Behavioral measures also included the Connor’s Continuous Auditory Test of Attention, Acceptable Noise Level, and self-reported listening surveys (Speech, Spatial, and Qualities Questionnaire). An auditory sensory gating paradigm was used to elicit auditory event-related potential (ERP) responses. For the ERP measures, the stimuli consisted of a pair of 1000 Hz tones with a 500 ms interstimulus interval. The ERP response waveforms to each stimulus in the pair were analyzed separately. A sensory gating ratio was computed by comparing the neural response elicited by stimulus 1 and 2 in the pair. Enhanced sensory gating, or greater cortical inhibition, would be associated with smaller ERP responses to the second stimulus compared to the first. Brain-behavior correlates were assessed using linear mixed-effects regressions.

Results
SIN performance was significantly poorer in adults with ASD compared to neurotypical listeners. Significant differences in auditory sensory gating were also observed across groups. Overall, significantly less cortical gating was observed in listeners with ASD relative to the neurotypical group and differences were most pronounced in the attend condition. Measures of auditory attention were significant predictors of SIN performance across groups; however, differences in sensory gating did not explain significant variability in SIN performance across groups.

Conclusions
Differences in auditory attention may explain variability in SIN performance. Thus, interventions targeting underlying attention deficits could potentially improve SIN outcomes in persons with ASD. While differences in cortical gating were observed across groups, differences in neural inhibition did not predict SIN outcomes in persons with ASD.