Functional and Behavioral Changes Induced by Retinal Electrical Stimulation in Experimental Animal Models of Retinal Degeneration

Description

The number of people of all ages around the world with visual impairment is estimated to be 285 million, of whom 39 million are all blind. The cause of global blindness includes Age-related Macular Degeneration (AMD) where around 2 million are affected (WHO 2010). Retinitis Pigmentosa (RP) is another group of eye disorders that cause progressive vision loss, and is estimated to affect 1 in 3,500 people in the United States and Europe. In recent decades, bionic vision system is being developed for use as a substitute for natural vision in blind patients with AMD/RP, where electrical pulses are applied to the retina or the cerebral cortex to restore partial vision to the implant recipients. Bionic vision devices using the retinal approach have proved to provide some improvements to their vision-related life. The long-term use of these devices using both retinal approach and non-retinal approach will inevitably induce modulation to the brain circuitry that is sparsely studied.Electrical stimulation of retina could induce modulatory effect in different parts of the brain, including both visual and non-visual regions. We have investigated the effect of electrical stimulation of retina on the spatial interactions of neurons in the visual cortex with support allocated from the General Research fund for 2011/12 (CityU123412). It is essential to study the modulatory effect, that is not addressed previously, of cortical activity in both visual and nonvisual regions induced by electrical excitation of retinal tissue from using the bionic vision devices for a prolonged period of time.In this project, we propose a novel study on the after-effect of a prolonged stimulation of the retina using a transcorneal electrical stimulation (TES) approach. Our first preliminary results show that one set of TES parameters activates both the visual and the non-visual brain regions. Our second preliminary results on behavioral test demonstrate depressive-like behaviors in rodent with retinal degeneration but not in rodent with normal vision. To further investigate the functional and behavioral changes after a prolonged stimulation, we propose to characterize the cortical electrophysiology in details by investigating changes in latency, amplitude, distribution and power of electrical evoked potentials and oscillations in both visual and non-visual regions using a wide range of stimulus parameters and conduct a battery of behavioral tests.This study could contribute to understand the processing and information transmission between different brain regions under retinal stimulation, both in healthy and visual deficit population, as well as decipher the effect of a prolonged stimulation of the retina from a brain-wide perspective and its behavioral consequences. The proposed research would lead to an important insight to choose optimal electrical parameters for a prolonged use of the bionic vision system, leading to the contribution of the development of the next generation visual implant.