Earlier finish of motor planning in the premotor cortex predicts faster motor command in the primary motor cortex: Human intracranial EEG evidence

Abstract

The human motor system operates under hierarchical control during finger movements. The non-primary motor cortex (premotor cortex, PM, and supplementary motor area, SMA) organizes motor planning, while the primary motor cortex (M1) is responsible for motor execution. We utilized the high temporal and spatial resolution of intracranial EEG (iEEG) to investigate how the temporal dynamics of high-gamma oscillations in these hierarchically organized motor sub-regions, during both pre-movement planning and motor execution, correlated with reaction times (RTs) in a cued finger movement task. Our results showed that high-gamma power in PM, SMA, and M1 activated sequentially. More importantly, the sustained high-gamma activation in the non-primary motor cortex and the peak latency of high-gamma power in M1 significantly predicted RTs. Specifically, the faster the activation of the non-primary motor cortex returned to baseline, the faster the motor command in M1, resulting in shorter RTs. Furthermore, pairwise phase coherence between motor areas revealed that more sustained connectivity correlated with longer RTs. These findings illustrate the relationship between the temporal profiles of high-gamma activity in human motor areas and response performance.