Modality-related scalp responses after electrical stimulation of cutaneous and muscular upper limb afferents in humans.
To elucidate whether the selective electrical stimulation of muscle as well as cutaneous afferents evokes modality-specific responses in somatosensory evoked potentials (SEPs) recorded on the scalp of humans, we compared scalp SEPs to electrical stimuli applied to the median nerve and to the abductor pollicis brevis (APB) motor point. In three subjects, we also recorded SEPs after stimulation of the distal phalanx of the thumb, which selectively involved cutaneous afferents. Motor point and median nerve SEPs showed the same scalp distribution; moreover, very similar dipole models, showing the same dipolar time courses, explained well the SEPs after both types of stimulation. Since the non-natural stimulation of muscle afferents evokes responses also in areas specifically devoted to cutaneous input processing, it is conceivable that, in physiological conditions, muscle afferents are differentially gated in somatosensory cortex. The frontocentral N30 response was absent after purely cutaneous stimulation; by contrast, it was relatively more represented in motor point rather than in mixed nerve SEPs. These data suggest that the N30 response is specifically evoked by proprioceptive inputs.
Department of Neurology, Catholic University, Policlinico A. Gemelli, Largo A. Gemelli 8, 00168 Rome, Italy. drestuccia@rm.unicatt.it
Domenico
D
Restuccia
Massimiliano
M
Valeriani
Angelo
A
Insola
Mauro
M
Lo Monaco
Eugenio
E
Grassi
Carmen
C
Barba
Domenica
D
Le Pera
François
F
Mauguière
D000328:Adult; D000344:Afferent Pathways / Q000502:physiology*; D000779:Anesthetics, Local; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006225:Hand / Q000294:innervation / Q000502:physiology; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008959:Models, Neurological; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D011826:Radial Nerve / Q000187:drug effects / Q000502:physiology; D012016:Reference Values; D012535:Scalp / Q000502:physiology; D012867:Skin / Q000294:innervation*; D013933:Thumb / Q000294:innervation / Q000502:physiology; D014953:Wrist / Q000294:innervation / Q000502:physiology
D000779:Anesthetics, Local