Conservation of preparatory neural events in monkey motor cortex regardless of how movement is initiated.

Antonio H Lara,Andrew J Zimnik,Gamaleldin F Elsayed,Mark M Churchland,John P Cunningham

doi:10.7554/elife.31826

Antonio H Lara, Andrew J Zimnik + Show 3 more

Open Access

https://doi.org/10.7554/elife.31826

Copy DOI

Abstract

A time-consuming preparatory stage is hypothesized to precede voluntary movement. A putative neural substrate of motor preparation occurs when a delay separates instruction and execution cues. When readiness is sustained during the delay, sustained neural activity is observed in motor and premotor areas. Yet whether delay-period activity reflects an essential preparatory stage is controversial. In particular, it has remained ambiguous whether delay-period-like activity appears before non-delayed movements. To overcome that ambiguity, we leveraged a recently developed analysis method that parses population responses into putatively preparatory and movement-related components. We examined cortical responses when reaches were initiated after an imposed delay, at a self-chosen time, or reactively with low latency and no delay. Putatively preparatory events were conserved across all contexts. Our findings support the hypothesis that an appropriate preparatory state is consistently achieved before movement onset. However, our results reveal that this process can consume surprisingly little time.

Highlights

Multiple lines of evidence argue that voluntary movement is preceded by a preparatory stage[1,2,3,4,5,6,7,8,9]
And its electrical disruption erases the RT-savings provided by the delay[17]. These observations are consistent with the presence of a neural process that must occur before voluntary movement can be initiated, yet does not itself cause movement and can be completed in advance when circumstances allow
One can directly observe that the phase and amplitude of movement-related dynamics flow from the state achieved during the delay[19]

Summary

Introduction

Multiple lines of evidence argue that voluntary movement is preceded by a preparatory stage[1,2,3,4,5,6,7,8,9]. The voluntary reaction time (RT, the time between a sensory stimulus and the onset of an evoked movement) is typically longer than expected given afferent and efferent delays, suggesting a timeconsuming preparatory process separating sensation from action. RTs typically become shorter when a delay period separates an instruction from a go cue, presumably because preparation has time to complete before the go cue[2,4,8,10]. And its electrical disruption erases the RT-savings provided by the delay[17]. These observations are consistent with the presence of a neural process that must occur before voluntary movement can be initiated, yet does not itself cause movement and can be completed in advance when circumstances allow

Methods

Results

Conclusion