Clarke's Column Neurons as the Focus of a Corticospinal Corollary Circuit

Proprioceptive sensory signals inform the CNS of the consequences of motor acts, but effective motor planning involves internal neural systems capable of anticipating actual sensory feedback. Just where and how predictive systems exert their influence remains poorly understood. We have explored the possibility that spinocerebellar neurons that convey proprioceptive sensory information also integrate information from cortical command systems. Analysis of the circuitry and physiology of identified dorsal spinocerebellar tract neurons located in Clarke's column mouse spinal cord reveals distinct populations of Clarke's column neurons that receive direct excitatory and/or indirect inhibitory inputs from descending corticospinal axons. The convergence of these descending inhibitory and excitatory inputs to Clarke's column neurons establishes local spinal circuits with the capacity to mark or modulate incoming proprioceptive input. Together, our genetic, anatomical, and physiological studies provide evidence that Clarke's column spinocerebellar neurons nucleate local spinal corollary circuits of relevance to motor planning and evaluation.