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Abstract

The macaque ventral intraparietal area (VIP), located in the fundus of the intraparietal sulcus (IPS), is considered a polymodal association area that responds to visual, tactile, vestibular and auditory stimuli. VIP receives projections from multiple visual areas and from auditory regions in the posterior superior temporal (pST) cortex. In humans, several studies have reported activation of the pST and IPS to sound source motion confirming the existence of a dorsal processing stream for spatial aspects of sound in humans. In order to bridge the gap between single-unit recordings in monkeys and neuroimaging studies in humans, we used high-resolution fMRI in monkeys to further investigate these results. First, we created a virtual acoustic space environment using binaural sound recording techniques with miniature microphones inserted into a macaque head cast. We validated the acoustics of the technique and by measuring saccadic eye movements during playback to sound sources we were able to confirm a behavioral response to different locations. We then performed fMRI to identify cortical areas sensitive to sound motion in azimuth of the left and right hemifields. Preliminary results showed that all moving sounds activated areas MT, MST and the IPS. Contrasting left and right sound-motion conditions against center yielded greater activation in contralateral VIP. These results suggest that interaural information induced by lateralized sounds is processed along a dorsal cortical processing stream comprising VIP in the respective contralateral hemisphere.