Neural mechanisms of versatile functions in primate anterior cingulate cortex.

The anterior cingulate cortex (ACC) is located on the medial wall of the cerebral hemisphere in humans and non-human primates, and has well developed intracortical and subcortical connections. Recent brain-imaging studies have suggested the possible involvement of the ACC in a variety of cognitive and motor-related functions. To clarify the cellular mechanisms underlying such higher-order functions in the ACC, neuronal activity in distinct areas of the ACC and its adjacent cingulate areas has been examined, through single unit recordings, in monkeys performing specific tasks. Each of the rostral (CMAr), dorsal (CMAd), and ventral (CMAv) cingulate motor areas basically participates in motor-related functions such as preparation and execution of movements. In particular, the CMAr appears to be involved in selection of appropriate motor responses as well as in planning of sequential movements. Furthermore, the CMAr and area 32 may participate in attentional functions which are necessary to select correct actions. These areas have also been implicated in detection of error actions and/or monitoring of action performance. Finally, a number of neurons in the ACC exhibit specific or modulated activity relevant to reward expectation. The primate ACC may play critical roles in performing appropriate actions with attention and in checking the performance to acquire rewards efficiently.