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Identification of a spinal circuit for light touch and fine motor control.

Bourane S, Grossmann KS, Britz O, Dalet A, Del Barrio MG, Stam FJ, Garcia-Campmany L, Koch S, Goulding M

Sensory circuits in the dorsal spinal cord integrate and transmit multiple cutaneous sensory modalities including the sense of light touch. Here, we identify a population of excitatory interneurons (INs) in the dorsal horn that are important for transmitting innocuous light touch sensation. These neurons express the ROR alpha (ROR) nuclear orphan receptor and are selectively innervated by cutaneous low threshold mechanoreceptors (LTMs). Targeted removal of ROR INs in the dorsal spinal cord leads to a marked reduction in behavioral responsiveness to light touch without affecting responses to noxious and itch stimuli. ROR IN-deficient mice also display a selective deficit in corrective foot movements. This phenotype, together with our demonstration that the ROR INs are innervated by corticospinal and vestibulospinal projection neurons, argues that the ROR INs direct corrective reflex movements by integrating touch information with descending motor commands from the cortex and cerebellum.