2012 Volume 10 Pages 39-49
In the present study, the influence of psychological pressure on corticospinal motor tract (CST) excitability was investigated using monophasic transcranial magnetic stimulation (TMS) during a fine finger movement. Nine participants performed a spatiotemporal tracing task using a small laser pointer attached to the right index finger. After seven acquisition trials, they performed two non-pressure trials followed by two pressure trials. A stress was successfully induced; state anxiety, heart rates, and galvanic skin response all increased under pressure. In terms of motor evoked potential (MEP) in the first dorsal interosseous muscle, increases in amplitude and decreases in latency were shown under pressure. Moreover, whereas background electromyography (bEMG) before TMS failed to increase significantly under pressure, the ratio of MEP amplitude to bEMG did increase under pressure. In addition, there was a significant positive correlation between increased CST excitability and decreased performance accuracy from non-pressure to pressure trials. These results suggest that psychological pressure can facilitate the excitatory level of CST during performance of a fine motor skill and that CST excitation under pressure can relate to decreased performance.