Frances Meredith, Ph.D.
Meet the Researcher
Frances Meredith, Ph.D. received her Ph.D. in Neuroscience from the University of Colorado, Anschutz Medical Campus, in 2012.
She is now in her third postdoctoral year in Dr. Katherine Rennie’s laboratory in the Department of Otolaryngology at the University of Colorado.
Dr. Meredith's grant is funded by William Randolph Hearst Foundation through their William Randolph Hearst Endowed Otologic Fellowship.
The Research
University of Colorado Denver
The role of K+ conductances in coding vestibular afferent responses
Approximately 615,000 people in the United States suffer from Meniere’s disease, a disorder of the inner ear that causes episodic vertigo, tinnitus and progressive hearing loss. The underlying etiology of the disease is not known but may include defects in ion channels and alterations in inner ear fluid potassium (K+) ion concentration. Specialized hair cells inside the ear detect head movement in the vestibular system and sound signals in the cochlea. A rich variety of channels is found on the membranes of hair cells as well as on the afferent nerve endings that form connections (synapses) with hair cells. Many of these channels selectively allow the passage of K+ ions and are thought to be important for maintaining the appropriate balance of K+ ions in inner ear fluids. I study an unusual type of nerve ending called a calyx, found at the ends of afferent nerves that form synapses with type I hair cells of the vestibular system. These nerves send electrical signals to the brain about head movements. My goal is to use immunocytochemistry and electrophysiology to identity K+ channels on the calyx membrane and to explore their role in regulating electrical activity and K+ levels in inner ear fluid. I will identify potential routes for K+ entry that could influence calyx properties. I will investigate whether altered ionic concentrations in inner ear fluid change the buffering capacity of K+ channels and whether this affects the signals that travel along the afferent vestibular nerve to the brain. Meniere’s disease is a disorder of the entire membranous labyrinth of the inner ear and thus affects both the vestibular sensory organs and the cochlea. Similar K+ ion channels are expressed in vestibular and auditory afferent neurons. Studying ion channels present in both auditory and vestibular systems will reveal properties common to both systems and will increase our understanding of the importance of ion channels in Meniere’s disease.
Research Area: Ménière’s Disease
Long-term goal: The long-term goals of my research are to find out whether expression of ion channels varies in calyces innervating different regions of the vestibular sensory epithelium and to explore the roles that ion channels play in shaping electrical signals carried to the brain. It is important to understand the basic functioning of ion channels: knowledge of their role in sensory coding and knowing how their expression varies regionally may contribute to the design of effective technologies, e.g. cochlear and vestibular implants, to mitigate the effects of inner ear disorders. In addition, linking ion channel deficits to pathology of the inner ear may enable us to treat vestibular and auditory symptoms using ion channel modulators.