Participation of the primate presupplementary motor area in sequencing multiple saccades

The aim of this study was to investigate whether, and how, the presupplementary motor area (pre-SMA) is involved in the organization of oculomotor sequence. We trained two monkeys to perform three center-out saccades in six different orders. Each sequence consisted of a block of eight trials, initially with visual instruction ( 4 trials) and then from memory ( 4 trials). During memory-guided performance of sequential saccades, similar to75% of task-related neuronal activity was selective for, or influenced by, the numerical position of saccades within each sequence ( rank order). Neurons tuned for the direction of saccades were in the minority. We also found that 22% of sampled neurons increased their activity preferentially at a transitional period when monkeys were in the process of renewal of required saccade sequences. These data indicate that the pre-SMA is involved in the organization of oculomotor sequence, particularly in representing rank-order information and in updating sequence information. Together with previous reports on the participation of the pre-SMA in sequencing of multiple arm movements, we propose here that this area may contribute to cognitive aspects of sequential behavioral control, in an effector-independent manner.