Humans live in a world rich in multisensory information. Often information reaching one sense is completely unrelated to information reaching another sense; that is, they are spatially and temporally incongruent. The goal of the research presented in this thesis was to elucidate the behavioral and neural bases of attention to incongruent audiovisual information. Five issues were addressed: (1) developing an appropriate behavioral paradigm to test bimodal attention, (2) understanding the role of crossmodal suppression in unimodal attention, (3) exploring the interaction of auditory and visual sensory cortex during bimodal selective attention, (4) exploring the role of fronto-parietal networks in bimodal selective attention, and (5) exploring the neural correlates of bimodal divided attention. Two different behavioral paradigms demonstrated that attended information was remembered better than unattended information. Functional magnetic resonance imaging (fMRI) revealed that crossmodal suppression of sensory cortex subserving a non-presented modality occurred consistently during unimodal attention tasks, and increased with attentional demand. During bimodal selective attention, activity was often enhanced in sensory cortex subserving an attended modality and suppressed in sensory cortex subserving an unattended modality, both compared to a bimodal passive baseline. This interaction depended in part on attentional demand and the nature of the stimulus information. No prefrontal regions were consistently activated by bimodal selective attention; however, dorsolateral prefrontal cortex (DLPFC) was recruited during one of the bimodal divided attention paradigms. Furthermore, temporary inactivation of the DLPFC using transcranial magnetic stimulation (TMS) led to decreased bimodal divided attention performance using the same paradigm. However, using a different bimodal divided attention paradigm, DLPFC was not recruited and instead ventrolateral prefrontal cortex (VLPFC) showed task-induced deactivation. This divergence is explained by the unique requirements of the two bimodal divided attention paradigms. Overall, these findings provide improved understanding of how humans process and attend to multisensory information, and raise several questions for further investigation.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.111851 |
| Date | January 2007 |
| Creators | Johnson, Jennifer Adrienne. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Psychology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002612119, proquestno: AAINR32302, Theses scanned by UMI/ProQuest. |
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