Motion got you feeling queasy? It may be all in your head... or your ears

Jan. 25, 2021

New research from the University of Rochester Medical Center has detailed a part of the nervous system by which the brain can modify our sense of balance. The current study expands our understanding of how balance stimuli are received by the brain while also offering insights into potential drug targets in the ear, which may be leveraged for treating motion sickness and balance disorders.

Joseph Holt, Ph.D. standing in front of tan background wearing a blue button up shirt. He is smiling wearing a grey goatee with brown hair.“In my opinion, these data are one of the first steps in beginning to unravel the functional significance of the efferent vestibular system,” Joseph C. Holt, Ph.D., senior author of the study published in the journal Scientific Reports said. The efferent vestibular system (EVS) begins as a small collection of neurons that travel from the brainstem out to the ear where our sense of balance begins. While there is still little known about the function of the EVS, URMC researchers are uncovering more about the role these neurons may play in processing motion stimuli and maintaining our balance.

Holt and his team recorded an increase in the activity of vestibular afferent neurons in mice during stimulation of the EVS system. The excitatory effects of EVS stimulation were diminished by the application of scopolamine, a drug widely used to treat motion sickness in humans, demonstrating for the first time that EVS mechanisms in the ear are also targeted by this drug.This animation illustrates some of the various synaptic mechanisms governing the responses of mammalian vestibular afferents to efferent stimulation.

Previously, it was believed that scopolamine only targeted similar receptors in the brain. Holt said that the receptors within the inner ear will also need to be considered when thinking about contributors to motion sickness. “The responses that we've recorded in mice are comparable to responses in primates, and a variety of other balance models, so we feel confident in that what we've seen in mice is directly applicable to other species including humans.”

Additional URMC co-authors on the study include Glenn T. Schneider, M.D., Choongheon Lee, Ph.D., Anjali Sinha, M.S. and Paivi M. Jordan, Ph.D. The research was supported with funding from the NIH National Institutes of Deafness and other Communication Disorders (NIDCD).