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Mapping of the preferred direction in the motor cortex

Georgopoulos, Apostolos P., Merchant, Hugo, Naselaris, Thomas, Amirikian, Bagrat
Proceedings of the National Academy of Sciences of the United States of America 2007 v.104 no.26 pp. 11068-11072
cells, cerebral cortex, cortex, monkeys
Directional tuning is a basic functional property of cell activity in the motor cortex. Previous work has indicated that cells with similar preferred directions are organized in columns perpendicular to the cortical surface. Here we show that these columns are organized in an orderly fashion in the tangential dimension on the cortical surface. Based on a large number of microelectrode penetrations and systematic exploration of the proximal arm area of the motor cortex while monkeys made free reaching 3D movements, it was estimated that (i) directional minicolumns are [almost equal to]30 μm in width, (ii) minicolumns with similar preferred directions tend to occur in doublets or triplets, and (iii) such minicolumns tend to repeat every [almost equal to]240 μm (estimated width of a column), with intermediate preferred directions represented in a gradient. These findings provide evidence for an orderly mapping of the preferred direction in the motor cortex.