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Erin Zampaglione, Neal Sweeney, Alan Litke, David Feldheim, Alexander Sher; Population-Level Functional Characterization of Direction Selective Mouse Retinal Ganglion Cells. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3245.
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© ARVO (1962-2015); The Authors (2016-present)
Certain retinal ganglions cell (RGC) types, collectively called direction selective cells (DS RGCs), respond to motion in one direction and are suppressed by motion in the opposite direction. This phenomenon is a remarkable emergent property of the retinal neural circuits. The purpose of this study is to characterize these cells’ spatial and temporal response properties at the level of complete populations.
Wildtype mouse retina was isolated and placed on a 512-electrode array to record RGC spiking activity. To measure direction selective responses, full field drifting gratings were shown at a variety of spatial and temporal periods. Additional visual stimuli such as spatio-temporal white noise and full field flashes were presented as well. A single recording yielded action potentials from hundreds of RGCs.<br /> Identified RGCs were classified as either “DS” or “non-DS” based on a normalized difference between the cell’s firing rate in response to its preferred direction versus the opposite one. The DS cells were further characterized and classified by their direction tuning, spatial tuning, temporal tuning, drift speed tuning, white noise stimulus response, and full field flash response.
Approximately 10 to 20% of recorded cells in each preparation displayed clear DS characteristics. We identified up to 7 distinct types based on their directional, spatial, and temporal tuning. We found that the receptive fields of RGCs within some DS type tiled the visual space in a non-random manner. Comparison to analogous rabbit recordings and analysis suggests that these 7 types correspond to the 4 ON/OFF DS cell types, and 3 ON DS cell types, although the spatio-temporal filtering in rabbit DS RGCs is generally sharper than in mouse.
Using the multi-electrode array system, we can simultaneously detect many DS RGCs with a wide variety of functional responses, and classify these cells into distinct types. Our results confirm that the DS RGCs encompass multiple unique cell types, provide additional characterization of each type, and highlight the need to study these cells as a population. The development of this analysis pipeline also provides an opportunity to record from transgenic mouse lines that alter the function of specific genes or cell types potentially involved in DS RGC development and tuning.
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