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Mushtaq, F. (2020) Development of a functional near-infrared spectroscopy based objective measure of paediatric cochlear implant outcome. PhD thesis, University of Nottingham.

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Abstract

A cochlear implant (CI) is a surgically implanted prosthetic device that is used to partially restore the sensation of hearing in deaf individuals. In the United Kingdom, CIs are the therapy of choice for profoundly deaf children. In the case of congenital deafness, CIs are often fitted within the first year of life in order to facilitate spoken language acquisition. However, although most children develop good speech skills, outcomes remain varied.

It is important to identify paediatric CI listeners with poor speech perception as early as possible to limit the detrimental consequences of poor access to sound on speech and language development during a critical period for auditory development, particularly in CI users implanted as infants. Whilst behavioural speech assessments cannot be completed reliably until children reach pre-school age, it may be possible for clinicians to recognise poor CI performers from their brain responses to speech.

In this project, we aimed to identify cortical measures of speech perception in 6-12 year old normal hearing (NH) children and profoundly deaf CI listeners that could be used to distinguish between good and poor speech recognition. Specifically, we examined whether the left lateralisation of normal speech processing, the ability to distinguish between different levels of speech intelligibly (varied in terms of spectral content or amplitude modulation depth), and the cross-modal activation of auditory brain regions by visual stimuli were related to hearing status and behavioural speech perception scores. We used functional near-infrared spectroscopy (fNIRS), an optical neuroimaging technique that is safe for repeated use with CI users of all ages, throughout the research.

We successfully recorded cortical responses in frontal and temporal brain regions elicited by auditory and visual stimuli in NH children and CI users. We found that fNIRS responses were not left lateralised in paediatric NH individuals. NH children and CI users with good speech perception both elicited statistically significantly stronger responses to modulated and intelligible speech than unmodulated and unintelligible auditory signals. However, good CI users demonstrated statistically significantly greater activation to visual speech than NH listeners, indicating that these two groups process auditory, but not visual, input in a similar way.

These promising findings demonstrate the potential for developing fNIRS into an objective measure to evaluate speech perception in paediatric CI users. This research forms an important and valuable step towards not only learning about which stimulus combinations offer the greatest functional contrast between good and poor CI performers, but also identifying cortical mechanisms that may influence CI outcome.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Hartley, D. E. H. Wiggins, I. M. Kitterick, P. T. Anderson, C. A.
Keywords:	Cochlear implants, Hearing loss, Speech perception, Auditory processing, fNIRS, Functional brain imaging
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:	60447
Depositing User:	Mushtaq, Faizah
Date Deposited:	20 Oct 2023 08:23
Last Modified:	20 Oct 2023 08:23
URI:	https://eprints.nottingham.ac.uk/id/eprint/60447

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