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Limited crossmodal activation in children with hearing loss: An fNIRS study
Poster Session F, Friday, October 2, 2:45 - 4:45 pm, Wangari Maathai
Michaela Svoboda1,2, Natálie Kikoťová1,3, Monika Kučerová1,2, Kateřina Chládková1,2; 1Charles University, Faculty of Arts, 2Institute of Psychology, Czech Academy of Sciences, 3Graduate School of Neural and Behavioral Sciences, University of Tübingen, Tübingen, Germany
Children born deaf or hard of hearing are at risk of language deprivation, irrespective of modality. Although early auditory compensation through hearing aids (HAs) or cochlear implants (CIs) improves access to sound, sensory processing patterns may display altered patterns. One of the phenomena that are still not fully understood is the ability of the young brain to redistribute its functions across parts that remain under-used as a result of sensory deprivation. In case of deafness, brain structures primarily associated with speech processing may become responsive to visually presented stimuli (Finney et al., 2001; Nishimura et al. 1999). This type of adaptation is known as crossmodal plasticity. This reorganization has been hypothesized to negatively affect spoken language acquisition in the past (Lee et al, 2001), although recent evidence challenges this view and shows the earlier concerns as greatly exaggerated (Mushtaq et al., 2020, Zhou et al., 2023). The goal of the present study was to assess auditory cortex activation in Czech preschoolers with hearing loss compensated by HAs and CIs, as well as in normally hearing (NH) children, under auditory and non-auditory conditions. Notably, this age group remains underrepresented in research. We hypothesized that children with HAs and CIs would show stronger auditory cortex responses to visual stimuli than NH peers, whereas NH children would show stronger responses to auditory speech. We additionally explored associations with pure-tone audiometry, hearing age, vocabulary, and sign language exposure. Fourteen children with CIs (mean age = 66.5 months), nine HAs (mean age = 85 months), and 38 with NH (mean age = 63 months) participated in the study. Changes in oxygenated and deoxygenated hemoglobin were recorded using functional near-infrared spectroscopy as indicators of neural activity. Children were exposed to short stories (30–41 s) narrated by a bimodal bilingual female speaker under three conditions: reduced visual cues; muted auditory input; and Czech Sign Language, each presented six times. CI children showed weaker responses to auditory speech over the auditory cortex than NH and HA peers, with no differences detected between the NH and HA groups. Contrary to our prediction, only NH children showed reliable crossmodal activation to both silent speech and sign language. CI children showed a trend toward activation for silent speech left-laterally, although this did not reach statistical significance. Exploratory models revealed no effects of hearing age or vocabulary. Contrary to our hypothesis, poorer PTA was associated with stronger activation. Finally, sign language exposure in CI children predicted greater auditory activation, suggesting a scaffolding effect of early experience with sign language on the development of spoken language. Our results challenge the previously proposed notion that increased cross-modal activation is a typical feature of brains with a history of sensory deprivation. Regarding auditory processing, children with HAs displayed more similarities with NH children than with CI children, which underscores the need to distinguish between these populations in both research and clinical practice. The observed effect of sign language exposure contributes to growing evidence that sign language does not impede spoken language development following hearing restoration.
Topic Areas: Language Development/Acquisition, Signed Language and Gesture