Vestibular physiology and vestibular evoked myogenic potentials
Older adults often have poorer vestibular, or balance, function and the reasons for this are not well understood. In collaboration with JMU’s Auditory Perception and Physiology Lab, we examine the natural disease state of age-related changes in the human vestibular system, with an emphasis on a sustained stimulation approach to study nonlinear aspects of vestibular reflexes. We use novel electrophysiological methods to identify, for the first time in humans, nonlinearity in cervical and ocular vestibular evoked myogenic potentials (VEMPs) – these responses reflect activation of the otolith balance organs that detect linear acceleration and are important for balance function. Nonlinearities of the vestibular system are crucial to its normal function, but these nonlinearities remain unstudied in humans. Information learned from this research will help to better understand basic aspects of human vestibular function as well as underlying causes of balance difficulties in older adults and may help to develop new clinical tools for the diagnosis and monitoring of vestibular disease.
Vestibular psychophysics
Existing clinical tests assess vestibular function through measures of reflexes such as the VOR, but research suggests reflexes are not always consistent with patient-reported symptoms. That is, patients often report motion-provoked symptoms that are consciously perceived and cortically mediated; yet, clinically we measure brainstem-mediated reflexes and the two do not always align. Most investigations into motion perception have studied perceptual thresholds, and these studies demonstrate frequency-specific findings consistent with vestibular physiology. Anecdotally, our patients rarely experience symptoms from small, slow movements. Rather, vestibular patients report experiencing symptoms because of large, quick head motions. We conduct perceptual studies using suprathreshold stimuli and measures of magnitude estimation. We aim to provide insights into how healthy individuals perceive motion and lay the groundwork for examining these phenomena in patients with vestibular impairments.
Diagnostic vestibular assessments
We conduct research examining current diagnostic assessments used clinically, identifying areas of improvement for diagnostic accuracy as well as the patient-perception of these tests. We also look at the relationship between vestibular tests and functional balance measures (connecting the inner ear to the whole person).