Individual differences in audiovisual integration and timing

Sight and sound are processed in different parts of the brain and at different times, creating discrepancies between the relative arrival time of auditory and visual information at primary and multisensory cortices. Despite this, a commonly accepted view is that the brain strives for and achieves temporal unity across different sensory modalities. Using individual differences in subjective synchrony and audiovisual temporal processing, this thesis examines whether audiovisual synchronisation across different audiovisual processes is ever actually achieved and whether the timing of multisensory events is supported by unified or disparate mechanisms. Chapter 2 examines whether estimates of subjective synchrony across audiovisual integration and explicit temporal judgements are consistent within and between individuals. This chapter finds remarkable disunity in subjective audiovisual timing within individuals, characterised by negatively correlated estimates of perceptual asynchrony across tasks, which challenge existing accounts of how the nervous system maintains temporal coherence. Instead, a new theory of temporal renormalisation is proposed, whereby the relative timing of audiovisual signals within different mechanisms is perceived relative to the average timing across mechanisms. Chapter 3 reveals that individual differences in audiovisual synchronisation across different tasks are reflected in the structural variability of distinct brain clusters, suggesting that audiovisual relative timing is processed by multiple task-specific temporal mechanisms, whose performance is supported by distinct neural substrates. Chapter 4 explores the possibility that these perceptual mechanisms might contribute to reading ability, which is audiovisual in nature. Aspects of audiovisual temporal processing are found to be impaired in dyslexia and linearly related to reading ability. Altogether this thesis provides novel contributions to the understanding of the underlying mechanisms of audiovisual temporal processing as well as of its relationship to higher cognitive functions.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

City University London

Year dc:date.issued

2014

Author dc:creator

• Ipser, A.

• BF Psychology