Propriospinal neurons as relay pathways from brain to spinal cord

Spinal interneurons (SpINs) facilitate local, intersegmental, and long-distance neuronal connections and are crucial for coordinated motor and sensory activity within the spinal cord. Spinal cord injuries (SCIs) damage direct descending pathways but spare many SpINs. However, traumatic injury and inflammation can cause maladaptive plasticity and excitability in SpINs, which may be detrimental to spinal relay circuits. Recent studies in human patients and SCI animal models have revealed several strategies for modulating SpIN function to promote functional recovery. Here we summarize recent progress in our understanding of SpIN function in intact and spinal cord lesioned mammals and describe the cellular mechanisms of SpIN adaptations and their contribution to adaptive and maladaptive plasticity in post-SCI relay circuits.