Properties of a spinal somatosensory evoked potential recorded in man.

Somatosensory evoked potentials were recorded from the skin overlying the cervical and lumbar spinal cord of man after stimulation of median and tibial nerves respectively. The early negative component (N11) of the cervical potential and the negative lumbar potential (N14) were studied. The spatial properties of N11 and N14 indicate a spinal cord origin. Evidence partly from threshold studies, shows that the low threshold cutaneous afferent fibres were responsible for activating the generators of the potentials. A conditioning test stimulation procedure supports a postsynaptic generator. It is concluded that N11 and N14 have properties similar to the cord dorsum potentials recorded in animals and probably have the same generator, the neurones of the dorsal horn.