Coordinated Activation of Rhythmogenic Networks in the Spinal Cord

The hindlimb locomotor CPGs of the rodents are distributed along the thoraco-lumbar segments of the spinal cord. We found that an additional rhythmogenic network resides in the sacrocaudal segments of the spinal cord. This network controls the axial and tail musculature of rodents. It is tightly coupled to the locomotor pattern generators to ensure body stabilization during movements. The rostrocaudal coupling between the locomotor and body-stabilizing networks is mediated by propriospinal/descending neurons, the axons of which travel through the lateral (VLF, LF and DLF) and ventral (VF) white matter funiculi. Caudo-rostral coupling between the two networks was found during noradrenergic activation of the sacral segments. This coupling accounts for an increase in the excitability of rostral lumbar motoneurons and the resultant increased probability for their recruitment