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Lawrence, Rachael (2022) Examining executive function and its relationship with language outcome in children with and without cochlear implants: a behavioural and functional near-infrared spectroscopy study. PhD thesis, University of Nottingham.

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Abstract

While cochlear implants allow many infants to develop appropriate language skills, the ability of individual children to understand speech varies widely. Established evidence suggests that neurocognitive processes contribute to variable language outcome in paediatric cochlear implant (CI) recipients. The cross-sectional and longitudinal experiments reported in this thesis aimed to investigate the association between executive function (EF) and language performance in normal-hearing (NH) and deaf-implanted children, in addition to the ability of behavioural-EF evoked brain activation and correlates of fronto-temporal cortical connectivity to predict future EF and language outcome.

Parent-reported EF skills were significantly associated with language performance in both NH children and paediatric CI users of preschool age. This relationship was significantly stronger in children with CIs compared with their NH peers. Behavioural EF task-evoked cortical activations, measured using functional near-infrared spectroscopy (fNIRS), were acquired from both cohorts of preschool aged children. Whilst performance on behavioural EF tasks was not associated with language ability, a significant correlation between the amplitude of EF task-evoked activation overlying left prefrontal regions and language performance was observed in NH participants. Interestingly, no association was found between parent-reported EF skills and performance on behavioural EF tasks. Phase Transfer Entropy (PTE) analysis was employed to estimate fNIRS correlates of fronto-temporal directed connectivity. Correlates of both top-down and bottom-up directed connectivity acquired from NH toddlers were able to significantly predict future EF performance, that was in turn associated with language outcome. Furthermore, correlates of bottom-up directed connectivity in NH infants and toddlers were able to directly predict language ability.

The COVID-19 pandemic had an adverse effect on the recruitment of participants to experiments within this thesis. Furthermore, a small sample size for CI users prevented an examination of the association between fNIRS correlates of behavioural EF, cortical connectivity and language outcome in this cohort. However, the current results not only highlight the importance of higher-order top-down processes in language development, but they also support the current theory that such EF mechanisms are potentially more influential in deaf individuals. Furthermore, these findings demonstrate the potential of fNIRS as a brain-imaging tool that is uniquely well-suited for use in cochlear implantation. Future applications of this technology could help explain individual variability in CI outcome and to deliver intervention, such as EF rehabilitation strategies, where required at an earlier stage in a child’s life.

In March 2019, the COVID-19 pandemic induced a mandatory pause in cochlear implantation procedures across the United Kingdom. To minimise the period of auditory deprivation in pre-lingually deaf children, a collaborative project was performed in which novel Personal Protective Equipment (PPE) options were evaluated. The recommendations from this project led to the safe restart of cochlear implantation procedures at the National Health Service (NHS) Hospital Trust affiliated with the primary research site and continue to support the national and international delivery of CI services throughout COVID-19.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Hartley, D.E.H. Wiggins, I.M.
Keywords:	Cochlear implant, Executive function, Language, Children
Subjects:	W Medicine and related subjects (NLM Classification) > WV Otolaryngology
Faculties/Schools:	UK Campuses > Faculty of Medicine and Health Sciences > School of Medicine
Item ID:	69547
Depositing User:	Lawrence, Rachael
Date Deposited:	15 Dec 2022 04:40
Last Modified:	15 Dec 2022 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/69547

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