Effects of movement-related cortical activities on pain-related somatosensory evoked potentials following CO2 laser stimulation in normal subjects.

We investigated the change in pain perception produced by the application of movement and vibration to areas adjacent to, and remote from, the painful stimulus. Pain-related somatosensory evoked potentials (pain SEPs) and the pain threshold were evaluated following CO2 laser stimulation in 17 normal subjects. The concurrent application of vibratory stimuli and the voluntary movement of the fingers of the hand to which the pain stimulus was applied significantly reduced and prolonged the pain SEPs and increased the pain threshold, consistent with the gate control theory. Pain SEPs were also significantly attenuated by voluntary (P < 0.001) and passive (P < 0.02) movement of the remote areas such as the foot, but the pain threshold was unaffected. This finding was not produced by vibration or movement imagery of the limbs without active movement. Therefore, interactions between pain perception and movement-related cortical activities must take place in some areas of the brain without relieving pain.