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Abstract:
We used event-related fMRI to investigate the brain areas
involved in the integration of spatially coincident visual and
tactile stimuli. LED's and piezo-electric vibrators were placed
together on the toes and visual and tactile stimuli were presented
either individually, together on the same side of space or together
but on opposite sides of space. Participants' were instructed to
detect and respond to (via a button press) the modality indicated
on a projector screen in front of them. Reaction times indicated
speeded target detection for bimodal inputs on the same vs.
opposite sides of space (p <.05). These gains and decrements in
behaviour were mirrored by enhanced and depressed activation in
primary visual and tactile sensory areas to spatially congruent and
incongruent bimodal inputs respectively. Application of
electrophysiological criteria to the BOLD response suggested that
these effects were mediated by a network of association areas
including the intra-parietal sulcus, insula, superior temporal
gyrus, ventrolateral posterior nucleus of the thalamus and the
medial aspect of the frontal lobe (area 6).
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