(A937) Neural Synchronization with Audiovisual Speech Relies on a Sensitive Period

Introduction: Proper sensory at specific time windows are crucial for infant development. Auditory deprivation in the first year disrupts audiovisual speech integration, even after cochlear implantation. Using EEG, we investigated brain synchronization with auditory (A) and audiovisual (AV) speech in cochlear-implanted children (CI).

Methods: 76 children were enrolled, 41 CI children with congenital (CD, N=20) or acquired (AD, N=21) deafness, and 35 hearing controls (HC), aged 4-18 years old. Children listened to ~3 minutes A - AV recordings, followed by 2 comprehension questions to assess accuracy. Neural synchronization with speech envelope and lip movements was analyzed with uni- and multivariate encoding models. We compared envelope tracking (A vs. AV) within groups, assessed reliance on lip movements in AV, and used a classifier to measure accuracy in distinguishing envelope tracking between conditions. Classifier’s results were compared across groups. Global Field Power was computed for AV envelope tracking to examine developmental trajectories.

Results: Only CI children showed enhanced comprehension in AV vs. A condition, especially CD children (pBonf=0.01). Results indicated a main effect of group (HC > CD & AD pBonf < 0.001) and an interaction effect of condition and group (pBonf=0.01). Envelope neural tracking benefited from AV condition only in HC and AD groups (pclust < 0.001), with anticipated neural activity at ∼0 - 100ms. The classifier was more accurate in HC and AD compared to CD group, especially at -100 – 130ms (all pFDR < 0.002). Neural tracking of lip movements was evident only in CI children, with occipital activation at 410–470ms. For both HC and CI children (p < 0.001) emerged a clear developmental pattern in AV envelope tracking.

Conclusions: Auditory deprivation in the first year hampers the development of neural activity related to audiovisual speech integration, indicating a sensitive period where auditory input is critical. This study identified biomarkers of divergent developmental trajectories, helping to tailor future rehabilitative treatments based on the onset of auditory deprivation.