The change of motor cortical excitability between eyes open and closed conditions.

The effect of the eyes closed and eyes open states on transcranial magnetic stimulation (TMS)-induced motor cortex response remains unclear. This study evaluated the difference in TMS-induced motor cortical responses between the eyes open and eyes closed states. Ten healthy right-handed participants participated in three experiments. The stimulation-response curve of motor-evoked potential, short-interval intracortical inhibition, intracortical facilitation, and cortical silent period were determined in both the eyes open and eyes closed states, in random order. The order of performance of the eyes open and eyes closed states was also random. The stimulation-response curve obtained in the eyes open state was steeper than that obtained in the eyes closed state. The resting and active motor thresholds, cortical silent period, short-interval intracortical inhibition, and intracortical facilitation were similar in the eyes open and eyes closed states. These data demonstrate that the eyes closed state may affect the recruitment of cortical circuits and thus diminish the TMS-evoked motor output.