1. We examined the activity of neurons in the globus pallidus (GP) while monkeys (n = 2) performed sequential pointing movements under two task conditions: visually guided (TRACK task) and remembered (REM task). 2. Almost two-thirds of the task-related neurons in GP (155/236) were considered task dependent because they displayed exclusive or enhanced (greater than ±50%) changes in activity for one of the two task conditions. 3. More than 65% of the task dependent neurons were termed REM neurons because they either displayed changes in activity thai occurred only during the REM task or displayed changes that were more pronounced (greater than ±50%) during the REM task than during the TRACK task. 4. Nearly half of the REM neurons in GP displayed changes in activity that were limited to a single phase of the REM task (i.e., phase specific). Phase-specific neurons varied in the extent to which their activity depended on the particular sequence of movements performed. Some displayed a change in activity for all of the eight different movement sequences. Others displayed a change in activity during only one of the eight different sequences (i.e., phase and sequence specific). 5. We speculate that an ensemble of GP neurons with phase specific responses could be used to encode the detailed spatiotemporal characteristics of a sequential movement. In this way, GP neurons would provide part of the neural substrate that solves the 'serial order of motor behavior problem'.
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