Changes in Corticospinal Circuits During Premovement Facilitation in Physiological Conditions

Changes in corticospinal excitability have been well documented the preparatory period before movement, however, their mechanisms and physiological role not entirely elucidated. We aimed to investigate functional changes of excitatory circuits during a reaction time (RT) motor task (thumb abduction) healthy subjects (HS). 26 HS received single pulse transcranial magnetic stimulation (TMS) over primary cortex (M1). After visual go signal, we calculated RT delivered TMS at three intervals (50, 100, 150 ms) within movement onset, recording evoked potentials (MEP) from abductor pollicis brevis (APB) task-irrelevant digiti minimi (ADM). found that increased MEP APB amplitude when 150, 50 ms demonstrating occurrence premovement facilitation (PMF). increase was greater shorter interval (MEP ) restricted (no significant effects were detected ADM). also reported time-dependent side-dependent effect on (greater dominant side). In conclusion, here report side-dependent, selective facilitatory is onset (PMF), supporting basis PMF target muscle protocol.