[Generators of somatosensory evoked potentials following leg nerve stimulation].

Stimulation of the tibial nerve results in complex spinal potentials evoked from the lumbosacral segments of the spinal cord. These potentials suggest the interaction of different generators. Characteristically a triphasic potential can be recorded from L1. It is composed out of an afferent volley in the dorsal roots (R-response) a synaptically strengthened S-response (N21) and a descending reflexly evoked ventral root discharge (A-wave). Above cervical segments of the spinal cord the evoked potentials are probably composed of the afferent volley in the posterior columns (N24), the activity of the nucleus gracilis (N27) and the volley in the medial lemniscus (P30). The primary cortical response P40 is regarded as the specific activity of the somatosensory foot area.