Visual tracking and neuron activity in the post-arcuate area in monkeys.

1. A visual tracking task from a predetermined zone to another predetermined zone with use of a hand was trained in 3 macaque monkeys. They rotated the handle at the wrist joint by flexing or extending. A total of 88 neurons in the posterior bank of the arcuate sulcus, contralateral to the hand used, was related to the task. These neurons were designated as (post-arcuate-) FB neurons, following von Bonin and Bailey's terminology. 2. The FB neurons were classified into 4 types according to their discharge patterns during the task; (1) non-reciprocally, visually coupled neurons (6 neurons); (2) non-reciprocally movement-coupled neurons (41 neurons); (3) reciprocally movement-coupled neurons (17 flexion type and 8 extension type); and (4) finally, non reciprocally movement-coupled depression type neurons (15 neurons). These activations started before the movement onset, as detected in the displacement trace, and were not correlated to the EOG. 3. A possible functional significance of these neurons was discussed. A suggestion was made that in the FB area, after receiving the visual cue information, a function for the later movement direction and tis initiation are produced and sent to the motor apparatus within the brain so that effective tracking task can be performed.