The sensorimotor transformation of cross-modal spatial information in the anterior intraparietal sulcus as revealed by functional MRI

The parietal cortex in monkeys and humans has been shown to play an important role in the transformation of sensory information to motor commands. However, it is still unclear whether in humans, these areas are divided functionally into subregions based on different combinations of sensory and motor modalities. To identify subregions in the parietal cortex involved in the sensorimotor information transformation between different modalities, functional MRI was used to examine brain areas activated during tasks requiring different sensorimotor transformations-i.e., various combinations of eye (saccade) or finger movements triggered by visual or somatosensory cues. We then compared the activations between cross-modal conditions (eye movements triggered by somatosensory cues and finger movements triggered by visual cues) and intramodal (eye movements triggered by visual cues and finger movements triggered by somatosensory cues) conditions. Although the parietal cortex was involved in all tasks regardless of sensorimotor combinations, the only region activated to a greater degree in the cross-modal conditions compared to the intramodal conditions was the anterior portion of the intraparietal sulcus (a-IPS). The results suggest that the a-IPS plays an important role in the sensorimotor transformation of cross-modal spatial information.