Those living in cold climates know what a daily struggle walking and staying upright can be: every icy path is a potential hospital bill. Most of the time, the human body manages to keep us vertical. Other times, gravity betrays us, and we are down for the count. But what exactly is going on in our brain to mediate balance, motor dexterity, and, most importantly, keeping upright to prevent embarrassing falls?
Last month, Martyn Goulding and his team at the Salk Institute of Biological Studies reported discovering the neural system that determines our icy path fate. Specifically, these researchers found a cluster of retinoid-related orphan receptor alpha (RORα) neurons in the spinal cord that “function[s] as a ‘mini-brain’ to integrate sensory information and make the necessary adjustments to our muscles so that we don’t slip and fall.” Tracing the nerve fibers in mice with cutting-edge imaging techniques, the researchers found that RORα neurons incorporate information sent from the somatosensory sensors on the soles of the feet to detect subtle changes in pressure and movement. These signals from the light touch transmission pathway eventually reach the brain for further processing. The RORα cluster is also connected to neurons in the ventral spinal cord, suggesting a role in controlling movement as well. Together, the RORα “mini-brain” cluster works to keep us from falling and slipping on those tricky ice paths.
Goulding and his team hypothesize that much of the balancing process is an unconscious procedure. It is thought that the gauging of pressure and movement changes at the feet, and the subsequent processing and feedback from the spinal cord neurons are all happening on autopilot. The example that Steeve Bourane, a postdoctoral researcher in Goulding’s lab, uses is the stiffening of calf muscles: “If you stand on a slippery surface for a long time, you’ll notice your calf muscles get stiff, but you may not have noticed you were using them.” Bourane claims that, as the body is making subtle adjustments to keep balance, the mind is free to address other higher-level tasks – in other words, the autopilot function of balance is adaptive for multifaceted situations that require more than just the tending to balance to overcome.
The discovery of the “mini-brain” balance circuit leads to a whole new wave of research for the neural processes that contribute to movement control and sensing the environment through touch. The research is envisioned to translate to clinical applications, particularly for diseases that affect motor skills and balance. Spinal cord injury patients and the elderly are two demographics that are predicted to benefit most from this novel line of research. These applications may be many years away, however, given that this research focus is just developing. Hopefully, this research will better equip future generations to face the slippery paths of doom that plague cold climates everywhere.
Bourane, S., Grossmann, K. S., Britz, O., Dalet, A., Del Barrio, M. G., Stam, F. J., … & Goulding, M. (2015). Identification of a Spinal Circuit for Light Touch and Fine Motor Control. Cell, 160(3), 503-515.