Neurons in dorsal premotor cortex represent the switching of intended hand path in a delayed reaching task

Dorsal premotor cortex (PMd) is considered to play a crucial role in motor preparation, yet how the variation of neuronal activity affects the generation of different circumstances dependent movements remains unclear. Here we trained two monkeys to perform a delayed reaching task instructed by two sets of cues, one for indicating the target locations and another for indicating a conditionally presented virtual obstacle in the reaching path, which required the monkey to make a bypassing instead of straight reaching. We recorded the activity of PMd neurons and investigated how they responded to the switching of intended hand path induced by obstacle bypassing. Comparing the neuronal activity between hand bypassing trials and straight reaching trials, we found 30% of the total 687 set-related neurons showed different overall discharging level, and another 24% showed different onset time during the delay period. We also found 16% of the neurons were modulated only by target location and 14% were modulated by both target location and path switching. Our results demonstrate PMd neurons not only represent the planning of reaching to different target locations, as many previous studies have shown, but also represent the switching of intended reaching path induced by hand bypassing, suggesting how PMd neurons coordinate for such circumstances dependent motor planning.