Neurophysiological Evidence for Reduced Use of Prior Sound Patterns to Shape Speech Processing in Autism
Reported perceptual differences in autism may arise from reduced use of prior context to shape incoming sensory input. Speech perception provides a critical test of this account because stable perception requires listeners to integrate variable acoustic signals with contextual expectations. This study examined context-dependent modulation of speech encoding in autistic and non-autistic adults using the frequency-following response (FFR), a neurophysiological measure of phase-locked auditory encoding. Participants heard English intonational pitch contours presented in repetitive and variable contexts while EEG was recorded. Principal component analysis of FFR metrics yielded components indexing neural encoding fidelity and timing. Non-autistic participants showed enhanced encoding fidelity in more predictable contexts, whereas autistic participants showed reduced context-dependent modulation. Neural encoding timing also showed divergent context effects across groups, suggesting altered balance between feedback-based predictive mechanisms and locally driven adaptation processes. Within the autistic group, greater context-related modulation of encoding fidelity was associated with lower ADOS-2 Social Affect severity but poorer speech-in-noise perception, suggesting that the functional impact of contextual modulation depends on input reliability and task demands. These findings indicate that context-dependent modulation of speech encoding is altered in autism and may contribute to individual differences in auditory and social-communicative function. Lay SummaryWhen we listen to speech, the brain often uses sounds it has recently heard to help make sense of new ones, which is especially useful in noisy, everyday settings. In this study, autistic adults brains tended to process speech differently, drawing less on recent sound patterns than non-autistic adults, and this difference was related to their autism domain variability and to understanding speech in background noise. These effects were not simply better or worse but depended on the listening conditions, suggesting that natural differences in how the brain uses recent context may shape some of the ways autistic people listen to speech.