Summary
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.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Competing interest The authors declare no competing interest.
Data and code availability The data and code needed to generate the figures will be made available upon publication.