Modulation of ventral premotor and primary motor cortex interactions for accurate visuomotor force control.

Visually guided movements are mediated by visuomotor networks involving multiple cortical areas. While processing in the occipital-parietal-premotor pathway is relatively well understood, the mechanisms by which motor-related frontal and prefrontal regions influence the primary motor cortex (M1), which controls the moving hand during visuomotor tasks, remain unclear. Using dual-site transcranial magnetic stimulation, here we investigated interhemispheric influences from the right M1, dorsal premotor cortex (PMd), ventral premotor cortex (PMv), supplementary motor area (SMA), and dorsolateral prefrontal cortex (DLPFC) on the left M1 during a visuomotor force control task with the right hand, examining how these influences change with enhanced visuomotor performance. Performance (i.e., amount of error) was manipulated by adjusting the visual gain of force feedback. Higher visual gain increases sensitivity to visual feedback, amplifying small force variations and improving error correction, which in turn reduces performance error. Performance enhancement was accompanied by a reduction in the facilitatory influence of the PMv on the contralateral M1. The M1 and DLPFC exerted an inhibitory influence on the contralateral M1 regardless of performance level. The PMd and SMA exerted neither facilitatory nor inhibitory influence on the contralateral M1. These findings suggest distinct modulation patterns of the M1 by different frontal cortical areas and underscore the critical importance of the PMv-M1 interaction in ensuring fine motor precision during visuomotor tasks.