Topic 1.1 - Binaural restoration in children with SSD (ESR 1)

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Topic 1.1, Binaural restoration in children with SSD, will be hosted at the KU Leuven (Belgium) and supervised by Astrid van Wieringen and Jan Wouters.

The goal of this research project is to investigate the cortical reorganisation of children with single sided deafness (SSD) following intervention with a CI (SSD-CI), compared to a group of children with SSD but not fitted with a CI (SSD-noCI) and a group of children with normal hearing (NH). SSD significantly affects cortical symmetry, as it results in an increased dominant representation of the normal ear compared to the deaf ear. However, research shows that early intervention in children with SSD can restore the hemispheric representations of bilateral auditory input in the auditory cortex. In Leuven currently 15 infants with SSD have received a CI and their behavioural performance (language, cognition) is compared to those with SSD without a CI and NH children. Using EEG-based objective measures, we will investigate the binaural restoration at the subcortical and cortical level of the auditory pathway in children who are four years and older. It is expected that hemispheric asymmetry differs for those who process sounds on only one side compared to those with bilateral input, and that binaural integration will be (partially) restored for those with a CI.

The early-stage researcher (ESR) will create a binaural interaction measure in children (based on one validated in adults). We will investigate the latency and morphology of the P1 component of auditory evoked potentials, which are known to be biomarkers for the development of the cortical pathways. We will also develop a two-ear paradigm, in which a modulated and an unmodulated stimulus are presented simultaneously. The modulated stimulus evokes sustained responses, from which a measure of binaural integration can be derived (cf Gransier et al 2017, for adults). Prior to investigating in children with congenital SSD, this measure will be validated in 10 children with NH to achieve reference values. Subsequently, changes in neural activity in response to left, right and bilateral input will be investigated in a pilot study with adults with SSD and a CI to optimise the protocol. It is expected that these adults will not demonstrate similar changes in cortical plasticity as children who receive their CI at a very young age. After validation, the binaural protocol will be applied to around five children from each of the three groups (SSD-CI, SSD-noCI, NH), i.e. to those who are four years and older. Transient (P1) and sustained responses (binaural integration) can be obtained within a limited measurement time of 25 minutes. It is expected that children in the SSD-noCI group will present deviant cortical latencies, as reflected in the P1, as well as absence of binaural interaction, compared to children in the SSD-CI and NH groups.

Part of the project will take place at the Centre Hospitalier Brugmann and at HörSys. With the first secondment, the ESR will acquire knowledge and skills on state-of-the art techniques used in the clinic. In addition, the novel stimulation strategies developed by the ESR in Leuven can also be evaluated by cochlear implantees at this hospital, thereby strengthening collaboration across the Belgian Dutch- and French-speaking communities. With the second secondment, the ESR will be able to link the behavioural data obtained in humans to the modelling work done at HörSys.

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