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Naturalistic speech encoding in children with dyslexia: the influence of bilingualism and talker familiarity
Poster Session C, Thursday, October 1, 10:45 am - 12:45 pm, Wangari Maathai
This poster is part of the Sandbox Series.
Gaël Cordero1, Kaja R. Benz1, Tobias Reichenbach2, Marie Lallier1,3; 1Basque Center on Cognition, Brain and Language, Donostia/San Sebastián, Spain, 2Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany, 3Ikerbasque – Basque Foundation for Science, Bilbao, Spain
Speech perception requires resolving the lack of invariance inherent in the acoustic realization of phonemes across speakers, a process that is facilitated by talker familiarity. Difficulties in accounting for speaker-specific variability may disrupt acoustic-phonetic mapping, potentially impacting the development of robust phonological processing skills. Developmental dyslexia is typically characterized by a phonological impairment and has been linked to speaker‑specific information processing abnormalities including atypical encoding of pitch‑related cues and broader deficits in speaker‑specific processing, such as impaired speaker recognition, poor speech‑in‑noise comprehension, and aberrant acoustic‑phonetic mapping. In contrast, early bilingual experience may enhance speaker‑specific information processing: bilinguals show strengthened pitch encoding in both clear and noisy conditions and outperform monolinguals in speaker recognition. Bilingualism may therefore act as a protective factor for the speaker‑specific processes affected in dyslexia, with potential benefits for phonological and reading skills. However, existing work has relied largely on behavioural methods, leaving the neurobiological basis of these effects unclear; the few neuroimaging studies have used isolated stimuli, limiting ecological validity; and none has examined how dyslexia and bilingualism interact. The present study is designed to address these gaps. Sixty Basque–Spanish bilingual children, thirty with a dyslexia diagnosis, will complete a MEG paradigm using naturalistic speech. Speech will be presented in a two-by-two design crossing listening condition (clear vs. speech‑in‑babble) and speaker identity (familiar and unfamiliar). Participants will additionally complete a battery of tasks indexing phonological and reading skills and speaker‑specific information processing. Bilingual exposure will be quantified through a questionnaire that the primary caretakers of participants will be asked to respond. For each of the four MEG conditions, we will compute the cortical contribution to the Frequency‑Following Response (FFR), which indexes the brain’s phase‑locked encoding of features such as the fundamental frequency and its harmonics. The FFR can be modulated by attention, experience, and task demands, providing a window into both sensory and higher‑order contributions to speech encoding. We will combine condition-wise FFR analyses with mixed-effects modelling to assess how bilingualism and dyslexia jointly modulate speech encoding. Across groups, we anticipate greater amplitude of the cortical FFRs in clear relative to speech‑in‑babble conditions, with a parallel enhancement for familiar compared to unfamiliar voices. Individuals with dyslexia are expected to show attenuated FFRs across conditions relative to controls, yet we hypothesize that high bilingualism may compensate these effects. Finally, we predict that variability in the strength of the FFRs will track individual differences in speaker‑specific processing and phonological and reading skills. This study will allow us to integrate currently disparate findings on how dyslexia and bilingualism influence speech encoding and processing. Evidence consistent with our hypothesis would highlight bilingualism as a factor worth considering in discussions about potential interventions for dyslexia. Furthermore, evidence that dyslexia involves difficulty leveraging speaker‑specific information, with consequences for phonological and reading development, would prompt a re‑examination of the origins of this developmental disorder. At the conference, we will present pilot data and preliminary analyses illustrating the feasibility of our approach and discuss emerging patterns in the data.
Topic Areas: Disorders: Developmental, Speech Perception