Parallel planning through an optimal neural subspace in motor cortex

Abstract

Preparatory activity in motor cortex may facilitate movement execution by representing movement parameters (representational theory) or by initializing movement-related dynamics to an optimal state (dynamical system theory). Here, we confronted these two theories using neural data from non-human primates. We analyzed the structure of preparatory activity in a task where animals needed to plan two movements simultaneously. Contrary to what the representational theory predicted, we did not find evidence for the concurrent representation of the two movements. Instead, our data revealed that parallel planning was achieved by adjusting preparatory activity to an intermediate state that served as an optimal initial condition to generate both movements. This optimization quantitatively explained fluctuations in the animals' behavior, and directly supported the dynamical system theory. Together, these results uncover a simple mechanism for planning multiple movements in parallel, and shed light on an enduring debate about the nature of preparatory activity in motor cortex.

Behavioral measurements of motor readiness in mice

“…For example, if a different instruction is given after activity reaches an initial condition, the activity can hop over to a different initial condition in activity space (Bracewell et al, 1996; Ames et al, 2014), presumably reflecting a change of motor plan. In this framework, since unique locations in activity space correspond to readiness for specific future actions, the finding that mice can simultaneously plan multiple actions open intriguing questions about how such activity state could be supported by preparatory activity (Figure 7) (Meirhaeghe et al, 2022). Future studies using population neural recordings during simultaneous motor planning is needed to shed light on this question.…”

“…for specific future actions, the finding that mice can simultaneously plan multiple actions open intriguing questions about how such activity state could be supported by preparatory activity (Figure 7) (Meirhaeghe et al, 2022). Future studies using population neural recordings during simultaneous motor planning is needed to shed light on this question.…”