Mechanisms of audiovisual integration in the young and healthy ageing brain

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Jones, Samuel A. ORCID: https://orcid.org/0000-0002-1767-9414 (2019). Mechanisms of audiovisual integration in the young and healthy ageing brain. University of Birmingham. Ph.D.

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Abstract

Throughout our lifespan we are continually exposed to a barrage of multisensory signals. It is only by successfully resolving these signals into a veridical percept that we are able to interact effectively with the world. This crucial process of multisensory integration has previously been shown to change as we age, but the mechanisms underlying these age differences are not well understood. The work described in this thesis applied behavioural testing, psychophysics, computational modelling, and functional MRI to improve our understanding of the relationship between healthy brain ageing and audiovisual integration. Following a review of the existing literature (Chapter 1) and a description of methodology (Chapter 2), I describe a study that utilised Bayesian modelling to describe age differences in responses to a spatial ventriloquist paradigm (Chapter 3). This study revealed that older adults ultimately respond in a similar way to younger adults when presented with audiovisual spatial cues, but reaction time analyses indicated the possibility of different underlying mechanisms. The research outlined in Chapter 4 thus used multivariate analysis of functional MRI data to investigate the cortical networks underpinning audiovisual spatial integration in older adults, finding that these remain largely unchanged throughout the adult lifespan. In Chapter 5 I describe a study that instead applied functional MRI to the investigation of audiovisual speech comprehension and its interactions with age, asynchrony, and background noise. We show that older adults’ speech comprehension is more impaired by the presence of background noise and stimulus asynchrony, but that their perception of the asynchrony itself is intact. We demonstrate neural effects that account for these age differences. Finally, in Chapter 6 I review these various findings and explore their implications in relation to previous and future research.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):