Figure 3. Spontaneous motor bursts are initiated at different segmental levels.

A, single slow time-base recording from the right lumbar ventral root. B, expanded view of three cycles (1, 2 and 3) indicated in A and monitored on 16 ventral roots. In B1 the activity was initiated at the thoracic level, in B2 at the lumbar level and in B3 at the coccygeal level. C, plot of the number of spontaneous cycles generated at various spinal levels and diagram of the spinal cord indicating the zones (in grey) in which burst cycles were preferentially initiated.