NEURAL CONTROL OF VOLUNTARY MOVEMENT INITIATION

When humans respond to sensory stimulation, their reaction times tend to be long and variable relative to neural transduction and transmissi on times. The neural processes responsible for the duration and variab ility 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 ii the neural activity reached a specific and constant thr eshold activation level. Stochastic variability in the rate at which n eural activity grew toward that threshold resulted in the distribution of reaction times. This finding elucidates a specific link between mo tor behavior and activation of neurons in the cerebral cortex.