The effects of selective response preparation on corticospinal excitability

OBJECTIVE: Both motor imagery and selective motor cues enhance performance. Motor cortex is activated during motor imagery. We wanted to learn if sele ctive motor cueing also activates motor cortex. METHODS: We gave normal rig ht-handed subjects information about which hand to use to respond to an imp erative stimulus (selective intention) or where in space an imperative stim ulus would occur (selective attention). To minimize anticipatory responses, warning stimulus validity was 80%. During this choice reaction time task, we recorded magnetic motor evoked potentials. Imperative stimuli and transc ranial magnetic stimulation were presented randomly to assess the effect of warning cues on reaction times and corticospinal excitability. RESULTS: Se lective intentional and attentional warning cues reduced reaction times, bu t neither stimulus altered motor evoked potentials. CONCLUSIONS: These resu lts suggest that unlike motor imagery, selective intention to respond to an imperative stimulus and shifting spatial attention to an imperative stimul us do not alter corticospinal excitability.