Among many other jobs, the nervous system uses streams of information gathered from multiple senses to guide movement. The eyes detect obstacles. Balance gauges in the ears keep the head level. And sensors in the muscles and joints monitor limb position. Much of the resulting flood of information is preprocessed by sensory circuits before it reaches the brain. Visual signals, for instance, are processed by neurons and light sensors at the back of the eye before being transmitted to the visual centers in the brain. It seemed likely that touch signals were similarly processed by neural circuits in the spinal cord, but such circuits had not been identified—until recently. Neurobiologists at Salk Institute (La Jolla, CA) have now mapped the neural circuitry of the spinal cord that processes the sense of light touch by integrating motor commands from the brain with sensory signals from the limbs in mice.

The research group, headed by Martyn Goulding, traced the nerve fibers that carry signals from the touch sensors in the feet to their connections in the spinal cord in mice. These sensory fibers connected with a group of neurons expressing a receptor called RORα, which in turn connected with neurons in the motor region of brain. To investigate the role of RORα neurons in touch and movement, the scientists selectively disabled these neurons in the spinal cords of mice. Mice lacking functional RORα neurons were substantially less sensitive to light touch but were able to walk and stand normally on flat ground. When placed on a narrow, elevated beam, however, the mice had difficulty walking (Cell 160, 503–515; 2015). The scientists attributed this difficulty to an impairment of the ability to sense when a foot was slipping and respond with postural adjustment and correction of the foot position.

This study is part of a branch of research that aspires to explain how the nervous system processes and integrates sensory information to generate movement. “How the brain creates a sensory percept and turns it into an action is one of the central questions in neuroscience,” stated Goulding in a press release. “Our work is offering a really robust view of neural pathways and processes that underlie the control of movement and how the body senses its environment.” A better understanding of these pathways could improve therapies for injuries and diseases that affect movement and balance.