Auditory Brainstem Development in Autism: From Childhood Hypo-Responsivity to Adult Hyper-Reactivity
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Background
Autism spectrum disorder (ASD) is characterized by sensory disruptions, including auditory processing differences, which can significantly impact social, emotional, and cognitive development. This study investigates auditory brainstem development in Autistic children and adults using auditory brainstem responses (ABRs) and acoustic startle responses (ASRs), two key measures of auditory processing. We hypothesize that early hypo-responsivity in children, measured with ABRs, may lead to compensatory neural adaptations, resulting in hyper-reactivity in adulthood, measured by ASRs.
Methods
The study included 40 Autistic children, 57 non-Autistic children, 20 Autistic adults, and 21 non-Autistic adults. Participants underwent peripheral hearing screening, ABR testing at slow and fast click-rates, and ASR measurements. ABR wave and ASR latencies and amplitudes were analyzed. Statistical analyses included mixed-model ANOVAs and Spearman’s correlations to examine group differences and associations with age.
Results
Autistic children exhibited increased ABR wave latencies and reduced amplitudes, indicating slower neurotransmission and reduced neural responsivity in the ascending auditory pathway. In contrast, Autistic adults showed normalized ABR latencies but increased ASR magnitude, suggesting hyper-reactivity to auditory stimuli. Age-related correlations revealed that ABR latencies increased with age in non-Autistic participants, while ASR magnitude was negatively correlated with age in non-Autistic participants. The associations were significantly different between groups.
Conclusion
The findings support the hypothesis that Autistic children experience auditory brainstem hypo-responsivity, which may normalize in adulthood but lead to maladaptive hyper-reactivity. These results highlight the role of early auditory disruptions in shaping long-term sensory processing and reactivity in Autism, emphasizing the need for further research into the neural mechanisms underlying these differences.
