4th Annual Meeting of the International Multisensory Research Forum
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Emiliano Macaluso

Spatiotemporal contributions to audiovisual speech perception: A PET study
Poster

Emiliano Macaluso
Institute of Cognitive Neuroscience, University College London, London, UK

Nathalie George
Laboratoire de Neurosciences Cognitives et Imagerie Cerebrale, LENA - CNRS UPR 640, Paris, France

Jon Driver
Institute of Cognitive Neuroscience, University College London, London, UK

Ray Dolan
Wellcome Department of Imaging Neuroscience, Institute of Neurology, London, UK

Charles Spence
Department of Experimental Psychology, University of Oxford, Oxford, UK

     Abstract ID Number: 134
     Full text: Not available
     Last modified: May 20, 2003

Abstract
Positron Emission Tomography (PET) was used to study spatio-temporal contributions to audiovisual speech processing. In agreement with previous research, we found that synchronous, as compared to asynchronous, audiovisual stimulation yielded increased activity in both multimodal associative areas (superior temporal sulcus), and in unimodal visual areas. The critical manipulation of stimulus position (auditory and visual stimuli presented from either the same location versus from opposite sides) showed that: 1) ventral occipital areas and the superior temporal sulcus were unaffected by the relative location of the stimuli; 2) lateral and dorsal occipital areas were selectively engaged when bimodal stimulation was synchronous and came from the same location; and 3) the right inferior parietal lobule was activated for synchronous stimulation when the auditory and visual stimuli were presented from different locations. The latter activation may represent the neural correlate of the 'ventriloquism' effect, since this condition is typically associated with an illusory shift of perceived auditory position toward the visual location. We conclude that different occipital regions are involved in different aspects of audiovisual stimulus processing. In particular, while ventral areas appear to be more involved in stimulus discrimination and identification, more dorsal areas appear to be associated specifically with multisensory spatial interactions.


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