Magnetic cortical responses evoked by tactile stimulation of the middle finger in man.

Topographic distribution of cerebral magnetic responses to air-puff stimulation of the hairy skin of the middle finger was studied in healthy humans. The magnetic response was biphasic, with peak amplitudes at 57 +/- 16 ms and 108 +/- 34 ms. The field distributions for both deflections were interpreted in terms of equivalent current dipole sources at SI; the sources were different for the two deflections, although spatially close to each other. The electric evoked response was more complex in waveform, possibly reflecting activation of additional radial or deep current sources.