ANATOMY OF MOTOR LEARNING .1. FRONTAL-CORTEX AND ATTENTION TO ACTION

We used positron emission tomography to study new learning and automat ic performance in normal volunteers. Subjects learned sequences of eig ht finger movements by trial and error. In a previous experiment we sh owed that the prefrontal cortex was activated during new learning but not during automatic performance. The aim of the present experiment wa s to see what areas could be reactivated if the subjects performed the prelearned sequence but were required to pay attention to what they w ere doing. Scans were carried out under four conditions. In the first the subjects performed a prelearned sequence of eight key presses; thi s sequence was learned before scanning and was practiced until it had become overlearned, so that the subjects were able to perform it autom atically. In the second condition the subjects learned a new sequence during scanning. In a third condition the subjects performed the prele arned sequence, but they were required to attend to what they were doi ng; they were instructed to think about the next movement. The fourth condition was a baseline condition. As in the earlier study, the dorsa l prefrontal cortex and anterior cingulate area 32 were activated duri ng new learning, but not during automatic performance. The left dorsal prefrontal cortex and the right anterior cingulate cortex were reacti vated when subjects paid attention to the performance of the prelearne d sequence compared with automatic performance of the same task. It is suggested that the critical feature was that the subjects were requir ed to attend to the preparation of their responses. However, the dorsa l prefrontal cortex and the anterior cingulate cortex were activated m ore when the subjects learned a new sequence than they were when subje cts simply paid attention to a prelearned sequence. New learning diffe rs from the attention condition in that the subjects generated moves, monitored the outcomes, and remembered the responses that had been suc cessful. All these are nonroutine operations to which the subjects mus t attend. Further analysis is needed to specify which are the nonrouti ne operations that require the involvement of the dorsal prefrontal an d anterior cingulate cortex.