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キーワード:
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要旨:
Previous research has demonstrated that human observers locate audiovisual signals in space by averaging auditory (A) and visual (V) spatial signals according to their relative sensory reliabilities (=inverse of variance) (Ernst Banks, 2002; Alais Burr, 2004). This form of audiovisual integration is optimal in that it provides the most reliable percept.Yet, the neural systems mediating integration of spatial inputs remain unclear. Multisensory integration of spatial signals has previously been related to higher order association areas such as intraparietal sulcus (IPS) as well as the planum temporale (PT; Bonath et al., 2007). In the current fMRI study, we investigated whether and how early sensory (auditory cortex (A1), PT; visual regions V1-V3) and higher association (IPS) areas represent A and V spatial information. Subjects were presented with synchronous audiovisual signals, at spatially congruent or discrepant locations along the azimuth and at two levels of sensory reliability. Hence, the experimental design factorially manipulated: (1) V location, (2) A location, (3) V reliability. Subjects’ task was to localize the A signal. At the behavioral level, the perceived location of the A input was shifted towards the location of the V input depending on the relative A and V reliabilities. Likewise, at the neural level, the spatial location decoded with linear support vector machines from fMRI signals in brain areas along the A and V processing hierarchies was determined by the relative sensory reliabilities. The spatial location decoded from A1/PT was determined primarily by A spatial information with a stronger influence from V spatial information when the V reliability was high. Conversely, the spatial location decoded from visual areas (V1, V2, V3) and IPS was determined primarily by V spatial information with a stronger A influence when the V information was less reliable. In conclusion, our results suggest that the brain represents audiovisual spatial location in qualitative agreement with reliability-weighted multisensory integration at multiple levels of the cortical processing hierarchy.
