Role for supplementary motor area cells in planning several movements ahead.

To achieve a volitional goal, we need to execute multiple movements in a specific temporal order. After repetitive performance of a particular sequence of movements, we are able to memorize and execute the whole sequence without external guidance. Where and how in the brain do we store information necessary for the orderly performance of multiple movements? We have found a group of cells in the cerebral cortex of monkeys whose activity is exclusively related to a sequence of multiple movements performed in a particular order. Such cellular activity exists in the supplementary motor area, but not in the primary motor cortex. We propose that these cells contribute a signal about the order of forthcoming multiple movements, and are useful for planning and coding of several movements ahead.