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The Development of Excitation-Inhibition Balance relates to Speech Processing: Evidence from EEG

Poster B71 in Poster Session B, Tuesday, October 24, 3:30 - 5:15 pm CEST, Espace Vieux-Port

Katharina Menn1, Hannah Plueckebaum2, Lars Meyer1,3; 1Research Group Language Cycles, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 2Center for Cognitive Science, University of Kaiserslautern-Landau, Germany, 3Clinic for Phoniatrics and Pedaudiology, University Hospital Münster, Germany

Sensory processing relies on the collective interactions of billions of neurons, which communicate by sending either excitatory or inhibitory signals (Wu et al., 2011). In healthy brains, excitation and inhibition are in check (E/I balance; Rubenstein & Merzenich, 2003), meaning that cortical excitation in response to a stimulus is followed by proportional inhibition, allowing for the effective encoding and interpretation of sensory information (Oswald et al., 2006). Here, we test the relevance of E/I balance for auditory processing of speech. To include a maximal range of E/I balance, we analyze electroencephalography (EEG) data from both healthy children and a group of children with autism, for which prior work, including our own (Plueckebaum et al., in revision), has observed E/I imbalance (Sohal & Rubenstein, 2019). We examined the relationship between E/I balance and auditory processing of naturalistic speech for a final sample of 64 non-autistic children matched by age, sex, and nonverbal-IQ to 58 autistic children between 6 and 17 years of age. We employed a recently introduced functional measure of E/I balance based on the amplitude and temporal autocorrelation of alpha oscillations in resting-state EEG recordings (Bruining et al., 2020). Auditory speech processing was quantified through EEG encoding models (temporal response functions, TRFs; Crosse et al., 2016) using the speech spectrogram as predictor. In addition to the neural measures, individual differences in general autism symptoms were assessed for all children using the Autism Spectrum Screening Questionnaire (ASSQ). We observed significant prediction accuracies to the spectral TRF model for non-autistic and autistic groups (both p < .001), which we employed as indicators of speech processing. We also found a significant relationship between the developmental trajectory of E/I balance and speech processing (p = .048). Specifically, we observed that better neural processing of speech was related to balanced E/I across childhood. In contrast, lower spectral processing responses were linked to an increase in relative excitation and thus E/I imbalance in older children. Critically, we find that the relationship between speech processing and E/I balance was significantly moderated by individual differences in general autism symptoms (p = .03). Children with more pronounced autism symptoms displayed a stronger relationship between E/I imbalances and speech processing than children with less pronounced symptoms. Our results provide evidence for a relationship between E/I balance and auditory–sensory speech processing, highlighting the potential vulnerability of speech processing in autistic children to an E/I imbalance compared to their non-autistic counterparts. Our results support the proposal that E/I balance is crucial for the spectro–temporal response tuning of the auditory cortex and highlight the importance of understanding E/I balance in the neurobiology of language.

Topic Areas: Speech Perception, Disorders: Developmental

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