James O. Phillips - US grants

This application seeks support for a basic research symposium designed to stimulate a thorough discussion of areas of controversy in the field of vestibular physiology and related movement control. Over the course of 2 and 1/2 days, there will be six workshops concerning active research areas. We will bring together scientists interested in psychophysics, systems level neuroscience, and cellular and molecular mechanisms to facilitate discussions that incorporate a broad perspective. This format will provide basic information to the field at large, help resolve issues by direct confrontation of scientists with disparate views and inform younger investigators about the important issues in the field that they are entering. Indeed, the principal objective of this grant is to generate funds so that junior investigators and women and minority participants who are making exciting contributions to the field but who have limited travel funds may attend the meeting. An airing of the issues raised in this symposium will ultimately guide the clinical application of our knowledge in persons with balance and orientation problems, as well as a variety of motion-induced visual disorders.

This project will provide research and development of methods for electrically stimulating the vestibular nerve following loss of function from the vestibular end organs. The objective of this research is to develop methods of electrically stimulating the vestibular nerve, which can provide patient benefit during transient attacks of irregular activity leading to dizziness and/or act as a component of a balance prosthesis. This contract is directed towards animal studies with close ties to clinical applications in human patients in the near future.

Implantable vestibular prosthetic devices, based on cochlear implants, are an emerging technology currently in limited clinical trials. These devices have significant technical constraints and may have limited ability to restore reflexive eye movements with head motion, and appear promising for improving function in some patients with bilateral vestibular deficits. To date, all available devices only stimulate semicircular canal afferents to restore sensitivity to angular acceleration. The other half of the vestibular system, that responding to linear acceleration, is not addressed by these prostheses. Our hypothesis is that restoration of semicircular canal function can improve a patients? sense of balance by working with residual otolith function. If true, our findings may help select the candidates for vestibular implantation who would be most likely to benefit from this technology. Our methodology is to examine eye movements and perform single unit recordings from macaques with vestibular implants during combined linear acceleration and prosthetic semicircular canal stimulation. Our project has two specific aims. In the first, we will examine if prosthetic canal stimulation, like natural canal stimulation, can enable discrimination between linear acceleration from gravity from acceleration due to translation. The ability to discriminate tilt from translation is a fundamental role of the semicircular canal system and critical to spatial orientation. This first aim will use the differences in eye movements elicited during tilt and translation to discern whether prosthetic canal signals can facilitate discrimination of reorientation due to gravity from translation. In the second aim, we will record single unit vestibular nucleus neuronal activity to compare the interactions of prosthetic semicircular canal signals with natural otolith signals to interactions of natural semicircular canal and otolith signals. These experiments will be the first looking at how prosthetic vestibular signals and natural signals interact in the brain. These experiments should provide insight into how the brain process signals from currently used vestibular prostheses and may lead to improvements in approaches to treatment of vestibular problems.