Scientists discover how brain processes balance

Over 70 million of people in North America suffer vestibular loss. For these patients, performing basic daily living activities becomes difficult since even small head movements are accompanied by dizziness and the risk of falling.

A sensory system in the inner ear (the vestibular system) is responsible for helping us keep balance by providing a stable visual field during movement. Researchers have already developed a basic understanding of how the brain constructs perceptions of ourselves in motion, but until now, no one has understood the crucial step by which the neurons in the brain select the information needed to keep us in balance.

The way that the brain takes in and decodes information sent by neurons in the inner ear is complex. The peripheral vestibular sensory neurons in the inner ear take in the time varying acceleration and velocity stimuli caused by movement by sending nerve impulses.

Scientists previously believed that the brain decoded this information linearly and tactually attempted to reconstruct the time course of velocity and acceleration stimuli. But by combining electrophysiological and computational approaches, Kathleen Cullen and Maurice Chacron, two professors in McGill University’s Department of Physiology, have been able to show that neurons in the vestibular nuclei in the brain instead decode incoming information nonlinearly as they respond preferentially to unexpected, sudden changes in stimuli. They also discovered that the selective transmission of vestibular information they were able to document for the first time occurs as early as the first synapse in the brain.

“We were able to show that the brain has developed this very sophisticated computational strategy to represent sudden changes in movement in order to generate quick accurate responses and maintain balance,” explained Professor Cullen. “I keep describing it as elegant, because that’s really how it strikes me.”