title: Distribution of scalp somatosensory potentials evoked by stimulation of the tibial nerve in man.
abstract: The scalp distribution of the response to stimulation of the tibial nerve at the medial malleolus was systematically analysed. The somatosensory evoked potential (SEP) was recorded with electrodes placed in a transversal line over the ipsilateral and contralateral postcentral gyri and in a sagittal line over the longitudinal brain fissure. The SEPs recorded over the ipsilateral hemisphere and along the sagittal line were similar to the F response (the response over the foot primary somatosensory region). Over the contralateral hemisphere the waveform of the responses changed obviously from point F to the point C (contralateral hand primary somatosensory region). The C response started with N37, P40 had a longer latency, N50 was not present and the subsequent waves were also considerably different. Mathematical simulation of the responses recorded from the electrodes between points F and C has shown that they represent an electrical algebraic summation of the activity over points F and C. Although the F and C responses may be 2 potentials arising from the opposite sides of a single dipole generator which is located in the medial fissure, it is more probable that the somatosensory evoked potential on tibial nerve stimulation reflects the activity of 2 separate generators.
mesh_terms: D000293:Adolescent; D000328:Adult; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D012535:Scalp / Q000294:innervation*; D013979:Tibial Nerve / Q000502:physiology*