Carmelo Bellardita: "Propriospinal interneurons funnel sensory inputs into abnormal patterns of muscle activity after spinal cord injury"

Abstract: Spinal cord injury (SCI) often results in muscle paralysis and spasticity, the origin for which is related to permanent alterations of the spinal circuits caudal to the injury site. A poor repertoire of functional movements and the appearance of abnormal muscle activity characterize this state. To date, no spinal circuit has been identified underlying this abnormal activity. Here, we used mouse genetics together with in vivo optogenetics and electrophysiology to show that propriospinal V2a (Chx10+) neurons can generate functional multi-joint movements in physiological states, driving a closed-loop feedforward excitatory system in the spinal cord. However, after SCI, V2a neurons generate sustained spinal network activity and funnel this activity into abnormal patterns of muscle activation. This study identifies a distinct microcircuit in which V2a neurons represent the core element of a spinal sensory-motor integration system whose altered activity results in dysfunctional movements after SCI.