Topic 1.3 - Neural mechanisms of cross-modal plasticity in Hearing Impairment (animal model, ESR 3)

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The topic Neural mechanisms of cross-modal plasticity in Hearing Impairment (animal model) will be hosted at the Medizinische Hochschule Hannover, under the supervision of Andrej Kral.

In the congenitally deaf cat (animal model of congenital deafness), we want to investigate neuronal substrates of cross-modal reorganisation, providing one part of the mechanisms for compensation of hearing loss. Such compensation may depend on the individual and his/her compensation strategy. The reliance on non-auditory information likely contributes to interindividual outcome variation in hearing therapy and the resulting communication skills. We could demonstrate that crossmodal reorganisation is area specific, follows supramodal functions and involves only minority of the neuronal resources of the reorganised area. We want to determine the interindividual variability of the extent of the cross-modal reorganisation. This may underlie the interindividual variability in outcomes of communication training. In contrast to adult onset of deafness, early onset of deafness negatively impacts on bimodal (audio-visual) cooperation. We will investigate higher-order auditory, somatosensory and visual areas and focus on the auditory influence on multimodal association areas, where loss of auditory input is likely to prevent the faculty of multimodal integration. Using modern multi-electrode arrays, we can record up to 256 neurons at the same time. This will allow us to characterise an individual animal and for the first time so as to focus on interindividual variability also in animal models. Finally, we will investigate the effective connectivity (phase-based and rate-based) between these areas in hearing and deaf animals.

Based on our previous results on the dorsal auditory cortex, we assume that in other cortical areas we will find cross-modal reorganisation along with neurons still responsive to auditory (CI) stimulation. Additionally, we anticipate finding markedly reduced auditory influences in somatosensory visual and multimodal areas. These will demonstrate in reduced number of auditory-responsive neurons, reduced auditory-evoked firing rates and significantly reduced coupling between auditory and non-auditory areas. The coupling changes will be cortical-layer-specific. Finally, using temporally-challenging visual stimuli we expect to find timing deficits in non-auditory areas of deaf cats that would support a reference function of the auditory system for development of timing precision.

Part of this project will take place at the Centre Hospitalier Brugmann. It will enable the ESR to capitalise on the Brussels expertise in EEG to allow comparing outcomes in humans and animals and develop understanding for EEG correlates of invasive neurophysiological measures observed in animal experiments.

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