Neural Control of Voluntary Movement Initiation

TLDR

Reaction times to sensory stimuli are long and variable compared to neural transmission times, and the neural mechanisms underlying this variability remain unclear. Single‑cell recordings in the motor cortex of rhesus monkeys were used to test two models, showing that movements begin when neural activity reaches a fixed threshold and that stochastic variability in the growth rate of activity generates the observed reaction‑time distribution. The study demonstrates a direct link between cortical neuron activation and voluntary movement initiation.

Abstract

When humans respond to sensory stimulation, their reaction times tend to be long and variable relative to neural transduction and transmission times. The neural processes responsible for the duration and variability of reaction times are not understood. Single-cell recordings in a motor area of the cerebral cortex in behaving rhesus monkeys ( Macaca mulatta ) were used to evaluate two alternative mathematical models of the processes that underlie reaction times. Movements were initiated if and only if the neural activity reached a specific and constant threshold activation level. Stochastic variability in the rate at which neural activity grew toward that threshold resulted in the distribution of reaction times. This finding elucidates a specific link between motor behavior and activation of neurons in the cerebral cortex.