Cerebellar Control on Prefrontal-Motor Connectivity During Movement Inhibition

Converging evidence suggests a crucial role of right inferior frontal gyrus (r-IFG) and right pre-supplementary motor area (r-preSMA) in movement inhibition control. The present work was aimed to investigate how the effective connectivity between these prefrontal areas and the primary motor cortex could change depending on the activity of the cerebellar cortex. Paired transcranial magnetic stimulation (TMS) was delivered in healthy subjects over the r-IFG/left primary motor area (l-M1) and over r-preSMA/l-M1 before (100 ms after the fixation cross onset) and 50, 75, 100, 125, and 150 ms after the presentation of a Go/NoGo visual cue establishing the specific time course and the causal interactions of these regions in relation to l-M1 as measured by motor evoked potentials (MEPs). The same paired-pulse protocol was applied following sham or real cerebellar continuous theta burst stimulation (cTBS). Following sham cTBS, for NoGo trials only, MEPs collected showed the expected pattern of activation for both r-IFG-l-M1 and r-preSMA-l-M1 connectivity, characterized by peaks of increased and decreased MEP amplitude regularly repeated every 50 ms. Following cerebellar cTBS, this pattern of activation related to NoGo trials was modified selectively for the r-IFG-M1 but not for r-preSMA-M1 connection. A common monitoring action of r-IFG and r-preSMA in inhibitory control was confirmed. The effects of cerebellar cTBS showed a specific interaction between cerebellum and r-IFG activity during the inhibitory process.