BOLD Responses in Multisensory Spatial Cueing

Petra A. Arndt, Department of Psychology, Carl-von-Ossietzky University, Oldenburg, Germany

Abstract
Recent studies showed that sensory-specific brain areas are involved in representing multimodal stimuli sharing semantic or other features. In this fMRI-study we investigate whether this holds for multisensory spatial cueing. In a forced-choice paradigm subjects indicated the position of a previously learned object (gabor stimulus with specific orientation) which is presented together with a distractor. A virtual-acoustics auditory cue given 200ms before visual stimulus onset is located at the target position in 80% and at the distractor position in 20% of the bimodal trials. Unimodal visual, unimodal auditory, bimodal trials and a baseline condition were presented in pseudorandom order. Using sparse imaging technique BOLD-signals were acquired in visual and auditory cortices, parts of the parietal and of the frontal lobe. A random effects analysis (12 participants) revealed activity in the visual cortex under auditory stimulation. This may mirror visual-auditory interaction or the fact that participants expect the target at a specific position. A strong, lateralized activation of the auditory cortex under unimodal visual stimulation suggests an involvement of sensory-specific areas in multisensory cueing. Moreover the contrasts of bimodal vs. visual stimulation and of valid vs. invalid cued trials show activation in the occipito-parietal region involved in multisensory and attentional processes.

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