SEPs in two patients with localized lesions of the postcentral gyrus.
Scalp distributions of median nerve SEPs were studied in normal controls and 2 patients with localized lesions of the postcentral gyrus. In controls, parieto-occipital electrodes registered N20-P27 while frontal electrodes registered P20-N27. Other small components, parieto-occipital P22 and frontal N22, were recognized in about half of the control records. The wave forms at a frontal and a parieto-occipital electrode, both distant from the central region, formed exact mirror images of each other concerning N20-(P22)-P27 and P20-(N22)-N27. Electrodes near the central region contralateral to the stimulation registered cP22-cN30 (central P22 and central N30). When the postcentral gyrus was damaged, N20/P20-P27/N27 and cP22-cN30 were eliminated and the only remaining components were a frontal negative wave (frN) and a contralateral parieto-occipital positive wave (poP). Digital nerve stimulation also evoked poP and frN in both cases. In case 2, poP coincided with P22 of the non-affected side. The following generators were proposed; N20/P20-P27/N27: area 3b, cP22-cN30: areas 1 and 2, poP/early frN (= P22/N22): area 4 at the anterior wall of the central sulcus (due to direct thalamic inputs to motor cortex), late frN: uncertain (SMA?, SII?).
Sonoo
M
M
Department of Neurology, School of Medicine, University of Tokyo, Japan.
Shimpo
T
T
Takeda
K
K
Genba
K
K
Nakano
I
I
Mannen
T
T
D000328:Adult; D001927:Brain Diseases / Q000473:pathology / Q000503:physiopathology*; D004558:Electric Stimulation; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005385:Fingers / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008875:Middle Aged; D011930:Reaction Time; D012535:Scalp / Q000502:physiology