Tyler Godat Thesis Defense on January 26, 2023
9:00 a.m., 310 Gavett Hall
Functional Imaging and Classification of Retinal Ganglion Cells in the Living Primate Eye
Advisor: David Williams
The primate fovea is perhaps the most important location for vision in the retina, being specialized for high resolution spatial and chromatic vision, but it has been traditionally difficult to study in ex vivo electrophysiology and especially in vivo. The crucial visual properties conferred by the fovea are mediated by neurons called retinal ganglion cells, which exist in twenty or more distinct types that all tile the retina and are present from the far periphery up to the inner edge of the foveal slope. Microelectrode recordings of foveal retinal ganglion cells have been challenging due to their reduced size and the fragility of tissue survival in excised retina. Some of these difficulties in observing individual cells have been overcome in the in vivo retina by combining high resolution fluorescence adaptive optics ophthalmoscopy with calcium imaging to optically record functional responses in the living primate eye. The work in this thesis attempts to advance knowledge of functional properties of retinal ganglion cells at the primate fovea by studying their responses to various stimuli in the living primate (macaca fascicularis) eye. This includes measurements of retinal ganglion cells’ chromatic tuning and cone weightings, made possible by silent substitution style uniform chromatic flicker stimuli, and measurements of cells’ spatial transfer functions, made possible by monochromatic drifting gratings of various spatial frequencies. In particular, the most common type of retinal ganglion cell, the midget, is studied extensively to generate a broader understanding of the specialization and importance of the primate fovea. This work thus provides a closer look at the in situ spatial, chromatic, and temporal properties of these retinal ganglion cells than ever before possible. A novel stimulation delivery arm as part of a dual adaptive optics ophthalmoscope is also developed as part of this work to improve the resolution and breadth of stimuli used to interrogate the functional properties of retinal ganglion cells. These imaging and stimulation techniques provide a suite of tools for assessing and characterizing the functional properties of retinal ganglion cells in vivo which will inform the next generation of vision restoration strategies such as optogenetics and retinal prostheses.
