title: Somatosensory evoked potentials via lumbosacral pathways: a comment on naturalistic stimulation.
abstract: Somatosensory evoked potentials (SEPs) were averaged from several scalp derivations in 3 subjects (1 M, 2 F) for transcutaneous electrical stimulation of toes and perineum. These lumbosacral SEPs were amplitude-focal at vertex for 40-300 msec components. Peak latencies in the 40-120 msec time segment were significantly later for perineal stimulation of equivalent subjective magnitude, contrary to expectation from relative afferent pathway lengths. One subject (M) showed a monotonic latency retardation of an intermediate component (SP50-SN75) for equivalent stimuli at lips, fingers, toes, genitalia, and perianum. Vertex potentials (SN140-SP200) did not show this temporal sequence. Though interpretation of such data is currently ambiguous, systematic application of comparative evoked potential/magnetic field techniques could yield data useful to clinical neurologists.
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory; D005260:Female; D005385:Fingers / Q000502:physiology; D006801:Humans; D008046:Lip / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000502:physiology; D010502:Perineum / Q000502:physiology; D014034:Toes / Q000502:physiology