Imaging Technique Provides Real-Time View of Retinal Stimulation
At the Biomimetic MicroElectronic Systems Engineering Research Center (BMES ERC), researchers developed a novel imaging technique that allows real-time observation of cells in animal retinas as they respond to electrical stimulation. An image produced from this accomplishment was featured on the cover of the Journal of Neurophysiology.
BMES is a National Science Foundation-funded ERC, headquartered at the University of Southern California.
Currently available retinal implants allow for the restoration of some vision in certain blind individuals, but they have a low level of resolution. This work will aid in designing algorithms that make future implants more powerful, thus helping wearers perceive the world around them more richly.
To achieve their breakthrough, researchers used a technique called viral vectoring to make a certain type of cell in the eye glow under electrical stimulation. The technique relied on genetically encoded calcium indicators (GECIs)—fluorescent proteins which report cellular activity through changes in brightness. To produce GECIs in the targeted retinal ganglion cells (RGCs), researchers designed a viral vector that contained the DNA encoding for GECIs. Injecting the virus into the eye of an animal model caused the majority of RGCs to be infected by the virus. Within two weeks, cellular machinery of the infected RGCs converted their DNA into GECI proteins.
The experiments represent the first time that electrically elicited RGC activity was directly observed in a blind retina. Once the RGCs expressed GECIs – that is, showed that the GECIs were present – electrical stimulus was applied. Simultaneously, a highly sensitive camera captured the stimulated retinal ganglion glowing in response.