Responses in left inferior frontal gyrus are altered for speech-in-noise processing, but not for clear speech in autism.

Researchers used brain scans to study how autistic adults process speech in noisy versus quiet conditions. They found that autistic people's brains showed less activity in a key speech area (left frontal region) when listening to speech with background noise, compared to non-autistic people. However, both groups had similar brain responses when listening to clear speech without noise. This may help explain why autistic people often struggle to understand conversations in noisy places like restaurants or classrooms.

This neuroimaging study examined brain responses during speech recognition in noisy versus quiet conditions in 17 autistic adults and 17 matched controls. Using fMRI, researchers found that autistic individuals showed reduced activation in the left inferior frontal gyrus when processing speech in noise compared to clear speech, while controls showed higher activation. Both groups had similar responses in other speech-processing regions (right insula, left inferior parietal lobule) and showed comparable brain activity for clear speech processing. The study also replicated previous findings of impaired voice identity recognition in autism.

These results suggest specific neural dysfunction in noisy speech processing may underlie real-world communication difficulties in crowded environments.

Results suggest interventions should specifically target speech-in-noise processing skills and environmental modifications to reduce background noise. Findings support accommodations like preferential seating, noise-reducing headphones, or FM systems in educational and workplace settings. May inform development of targeted auditory training programs.

Small sample size (17 per group) limits generalizability. Study focused on adults only, so findings may not apply to children. Cross-sectional design cannot establish causality. Limited to auditory-only speech recognition task, which may not reflect real-world multimodal communication scenarios.

Autistic individuals often have difficulties with recognizing what another person is saying in noisy conditions such as in a crowded classroom or a restaurant. The underlying neural mechanisms of this speech perception difficulty are unclear. In typically developed individuals, three cerebral cortex regions are particularly related to speech-in-noise perception: the left inferior frontal gyrus (IFG), the right insula, and the left inferior parietal lobule (IPL). Here, we tested whether responses in these cerebral cortex regions are altered in speech-in-noise perception in autism.

Seventeen autistic adults and 17 typically developed controls (matched pairwise on age, sex, and IQ) performed an auditory-only speech recognition task during functional magnetic resonance imaging (fMRI). Speech was presented either with noise (noise condition) or without noise (no noise condition, i.e., clear speech). In the left IFG, blood-oxygenation-level-dependent (BOLD) responses were higher in the control compared to the autism group for recognizing speech-in-noise compared to clear speech. For this contrast, both groups had similar response magnitudes in the right insula and left IPL.

Additionally, we replicated previous findings that BOLD responses in speech-related and auditory brain regions (including bilateral superior temporal sulcus and Heschl's gyrus) for clear speech were similar in both groups and that voice identity recognition was impaired for clear and noisy speech in autism. Our findings show that in autism, the processing of speech is particularly reduced under noisy conditions in the left IFG-a dysfunction that might be important in explaining restricted speech comprehension in noisy environments.