Our current objective is to determine whether pallidal neurons discharge differently during movements that are a part of a learned spatial sequence. We have recorded the activity of more than 250 neurons in the external and internal pallidal segments of five monkeys that learned to move to multiple sequences of two or three peripheral targets under several conditions. These movements could be to targets that became visible at the time of the trigger, either in random order or in a fixed sequence, or they could be made to remembered target locations. The remembered target locations were presented under two conditions either each was precued, with a delay from precue to trigger, or the entire sequence had to be remembered (ALL8). Whereas the fixed, repeated sequence task might elicit implict learning, the remembered task requires that the animal explicitly learn the sequence. A large fraction of the pallidal cells studied show a significant difference between the mea n dischar ge rate before the GO signal (HOLD) in the random or fixed task, compared with the precued or remembered task. Another significant group of pallidal cells shows a change in perimovement discharge during the ALL8 task, compared with the random or fixed tasks. We are now completing analysis to determine whether these different types of responses occurred in cells in different locations of the globus pallidus. A manuscript on sequence learning and pallidal discharge is in preparation. FUNDING NIH grants RR00166 and NS15017.
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