Effects of tactile interference stimulation on somatosensory evoked magnetic fields.

Tactile stimulation of the hand interferes with somatosensory evoked brain responses following electrical median nerve stimulation. This effect was studied in eight normal subjects by magnetonecephalography (MEG). When stimulation was applied to the hand ipsilateral to the stimulated nerve, only the third response (3M) was enhanced in five subjects, but other responses were attenuated in all subjects. These interference effects were probably due to interactions in areas 3b and 1. After stimulation of the contralateral hand, only the second response (2M) was enhanced in six subjects. This effect was probably due to the intracerebral interactions mediated through the corpus callosum.