Cerebral Cortex Advance Access published online on July 20, 2009
Cerebral Cortex, doi:10.1093/cercor/bhp147
Context-Dependent Place-Selective Responses of the Neurons in the Medial Parietal Region of Macaque Monkeys
1 Division of Applied System Neuroscience, Advanced Medical Research Center, Nihon University Graduate School of Medical Science, Itabashi, Tokyo 173-8610, Japan, 2 Japan Society for the Promotion of Science (JSPS), Chiyoda, Tokyo 102-8471, Japan, 3 Laboratory for Anatomy and Physiology, Tokyo Seiei College, Katsushika, Tokyo 124-8530, Japan, 4 Department of Physiology and Biochemistry, Chiba University School of Nursing, Chuo, Chiba 260-8672, Japan, 5 ARISH, Nihon University, Chiyoda, Tokyo 102-0073, Japan
Address correspondence to Nobuya Sato, PhD, Division of Applied System Neuroscience Nihon University Graduate School of Medical Science, 30-1 Ohyaguchi-Kamicho, Itabashi, Tokyo 173-8610, Japan. Email: nsato{at}med.nihon-u.ac.jp.
To investigate the role of the medial parietal region (MPR), comprising area 7m and the retrosplenial and posterior cingulate cortices, in spatial navigation, we analyzed the spatial aspect of the responses of the MPR neurons in monkeys while they actively performed a navigation task in a virtual environment. One-third of the analyzed MPR neurons were activated depending on the location of the monkeys in the environment, that is, showed place-selective responses. Some neurons showed varying responses based on the starting point (SP) or destination. We further investigated the responses of the place-selective neurons when the monkeys were shown animations of the entire navigation route, including the preferred field, and a segment of the route, including an area around the preferred field, and a still image of the preferred field. We observed that the responses of some place-selective neurons reduced when the monkeys viewed the preferred field in the segmented animation or in the still image compared with when they viewed the entire animation. These results suggested that the knowledge about the SP or destination, that is, context, is necessary to activate place-selective neurons. The effect of such contextual information suggests that the MPR plays decisive roles in spatial processing such as navigation.
Key Words: medial parietal cortex • navigation • posterior cingulate cortex • retrosplenial cortex • virtual environment