The eye captures light but the brain is where vision is experienced. The capacity of retinal prostheses to restore some vision in blind individuals has been demonstrated at the retinal level, but it is unknown how the brain will be receptive to the new neural message after a prolonged period of visual deprivation resulting from retinal degenerative diseases. Neural remodeling that occurs in retinal degenerative diseases can have an impact on the usefulness of retinal prostheses in visual restoration. Mammalian retinal degenerations, initiated by gene defects in rods, cones or the retinal pigmented epithelium, often trigger loss of the photoreceptors; thus, effectively leaving the neural retina without sensory input. The neural retina responds to this challenge by remodeling, first by subtle changes in neuronal structure and later by large-scale reorganization. This type of retinal remodeling can alter normal light transmission pathway in the retina and result in activation of different ganglion cell groups between light and electrical stimulation. In this proposal, the PI proposes to use transcorneal electrical stimulation (TcES) to probe the neural connection between the retina and the visual cortex via direct stimulation of the retinal ganglion cells from a current passing through the cornea. By using positron emission tomography (PET) and 18F-fluorodeoxyglucose (FDG) to compare brain activation between light stimulation and electrical stimulation of the retina in patients with RP, we will be increase our understanding how retinal remodeling is reflected in the visual cortex. The study can then help us gain insight into cortical reorganization resulting from the retinal degenerative process.
