Diversity of set-related neuronal activity in the dorsal premotor cortex of monkeys during a path-planning task

Actions involve multiple levels. The dorsal premotor area (PMd) of the primate cerebral cortex is involved in the preparation of actions based on perceptual information. In this study, we recorded neuronal activity from the PMd of monkeys while they performed a path-finding task. In the task, the animals were required to move a cursor step by step to a goal in a maze-like display, and the arm movement and the direction of the cursor operation were dissociated. We observed neurons involved in the preparation of a single arm movement and neurons involved in the preparation of a single cursor operation. Cursor operation-related neurons were also obtained from the lateral prefrontal cortex (lPFC), but the PMd neurons showed more preparatory properties during the execution period than the lPFC neurons. Furthermore, we found neurons involved in the preparation of a specific sequence of cursor movements. The PMd included not only all types of single-shot preparatory neurons but also preparatory neurons for a variety of complex sequences for arm movements and cursor manipulation. These results suggest that the PMd contains diverse neurons involved in different levels of action preparation. Such diversity is one of the critical neural bases for robust goal-directed behavior in complex environments.