title: SEPs to finger joint input lack the N20-P20 response that is evoked by tactile inputs: contrast between cortical generators in areas 3b and 2 in humans.
abstract: A method using a DC servo motor is described to produce brisk angular movements at finger interphalangeal joints in humans. Small passive flexions of 2 degrees elicited sizable somatosensory evoked potentials (SEPs) starting with a contralateral positive P34 parietal response thought to reflect activation of a radial equivalent dipole generator in area 2 which receives joint inputs. By contrast, electric stimulation of tactile (non-joint) inputs from the distal phalanx evoked the usual contralateral negative N20 reflecting a tangential equivalent dipole generator in area 3b. Finger joint inputs also evoked a precentral positivity equivalent to the P22 of motor area 4, and a large frontal negativity equivalent to N30. It is suggested that natural stimulation allows human SEP components to be differentiated in conjunction with distinct cortical somatotopic projections.
authors.affiliation: Brain Research Unit, University of Brussels, Faculty of Medicine, Belgium.
authors.forename: J E
authors.initials: JE
authors.lastname: Desmedt
authors.forename: I
authors.initials: I
authors.lastname: Ozaki
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D004558:Electric Stimulation; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D005384:Finger Joint / Q000502:physiology*; D005385:Fingers / Q000502:physiology; D006801:Humans; D008297:Male; D010812:Physical Stimulation / Q000295:instrumentation / Q000379:methods; D011930:Reaction Time; D012879:Skin Physiological Phenomena; D014110:Touch