SINGLE RETINAL GANGLION CELLS AND SENSATION
Abstract
Though retinal physiologists have now cataloged more than 20 classes of retinal ganglion cell (RGC) in the primate retina, there is currently considerable uncertainty, and no shortage of controversy, about how the brain uses the signals from each of these specialized retinal circuits for visual perception. This MURI will establish a new experimental paradigm that can reveal how the individual computations performed by the retina impact vision. Recent advances at Rochester now allow the optical recording of the responses of RGCs to visual stimuli, make it possible to classify single RGCs in the living eye of the anesthetized monkey. We will focus our studies on identifying individual RGCs from the three most numerous RGC classes, the midget, small bistratified, and parasol RGCs. These RGCs are often invoked, though in strikingly different ways depending on the model, to explain the perception of red, green, blue, yellow, black, and white. Using optogenetic methods, we are also now able to directly stimulate RGCs with light. To determine the visual percept produced by each class of RGC, we will deliver visual stimuli to the receptive fields of single, previously-classified RGCs simultaneously with optogenetic stimulation of the RGC soma in the awake monkey performing a psychophysical match to sample task. Observed shifts in psychometric functions obtained with red-green, blueyellow, and black-white discriminations will be used to infer the percepts produced by different RGC classes. These psychophysical experiments will require the development of a new adaptive optics (AO) ophthalmoscope that has independent arms for stabilized, AO-corrected stimulus delivery to the receptive fields of single RGCs and for stabilized, AO-corrected the delivery of light focused on the RGC somas for optogenetic stimulation. To minimize aberrations in the instrument to a lower level than has been previously possible, we will incorporate freeform optical elements into our design. This design will enable not only our experiments, it could also improve the optical performance of future AO ophthalmoscopes developed by others. We will also explore whether we can improve the sensitivity of optogenetic stimulation in the primate with the use of M Opsin, which has recently been shown to increase sensitivity 1000-fold in the mouse over previous optogenetic actuators. Any improvement in the primate would not only benefit our experiments by reducing the amount of light required to drive RGCs with optogenetics, it could also benefit efforts to achieve practical brain-computer interfaces in other applications. Finally, in collaboration with David Brainard’s group at the University of Pennsylvania, we will use the RGC receptive field properties and the psychometric functions obtained in our experiments to build a more accurate RGC stage into a computational model of the early stages of visual processing. This model is already used widely in the vision science community, and the refinement our studies will provide, will not only help us understand our own experimental results, they will offer an model that has predictive power for a variety of other psychophysical tasks.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 07, 2023
- Source ID
- FA95502210167
Entities
People
- David R. Williams
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Rochester