The functional diversity of spinal interneurons and locomotor control

Spinal interneuron (IN) circuits ensure coordinated spatiotemporal muscle contractions necessary for complex locomotor behaviors. The identification of molecularly distinct spinal IN populations has enabled detailed and effective investigations into the organization of these circuits. Recent revelations of vast spinal IN diversity, particularly within cardinal spinal IN classes, have given rise to enormous challenges, as well as opportunities, in furthering our understanding of the functional circuit architecture underlying motor control. In the current review, we focus on recent studies revealing distinct spinal IN subpopulations assembled within rhythm-generating and pattern-forming spinal circuits. We briefly summarize how both general and task-specific spinal IN circuit outputs functionally combine, empowering a wide repertoire of locomotor behaviours.