Neurophysiological Processing of Rise Time in Children with Autism Spectrum Disorder

Background: Amplitude rise time is a critical acoustic cue for speech perception, yet its neurophysiological processing remains uninvestigated in autism spectrum disorder characterized by communication deficits, sensory abnormalities and often speech delay. This study examined whether children with autism spectrum disorder differ from typically developing peers in auditory event-related potential components across a continuum of rise times. Methods: Electroencephalography was recorded during passive presentation of pure tones with five rise time values (15, 30, 60, 120, 240 ms) in 42 children (21 with autism spectrum disorder, 21 typically developing, aged 4–10 years). Linear mixed models were used to analyze latencies and amplitudes of P1 and N2 components. Results: Children with autism spectrum disorder showed a less systematic pattern of neural modulation across rise times compared to typically developing peers. P1 amplitude was reduced at 15 and 60 ms (trend at 30 ms), with no significant group differences at longer rise times. N2 latency showed an atypical decrease at 60 ms compared to 30 ms, contrasting with the systematic increase observed in typically developing children. P1N2 amplitude reached a minimum at 60 ms in autism spectrum disorder, whereas typically developing children showed a gradual decrease across rise times. Conclusions: These findings provide the first evidence of atypical neurophysiological processing of rise time in children with autism spectrum disorder, with the most pronounced differences in the range of rapid acoustic onsets. Group differences were not detected at longer rise times, suggesting a selective rather than global deficit in temporal envelope processing.