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Heiko Schmid, Alex A. Thomas, Maureen A. McCall; Estimates Of Ganglion Cell Receptive Field Organization Differ With Stimulus Configuration. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4566.
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© ARVO (1962-2015); The Authors (2016-present)
Receptive fields (RF) of retinal ganglion cells (RGCs) have excitatory centers and antagonistic surrounds, which can be defined using either stationary spots or drifting sinewave gratings. Area response functions (ARFs) use stationary spot stimuli, while spatial frequency response functions (SFRFs), use drifting sinewave gratings. We compared these techniques in evaluating RF organization of mouse RGCs to determine if they produce similar results.
Extracellular responses were recorded from WT mouse RGC axons in vivo. Spot diameters range from 5-52o of visual angle. Bright (100cd/m2) or dark (3cd/m2) spots are presented on a 20cd/m2 background (67% contrast) to stimulate ON or OFF RGCs, respectively. RF center diameter was defined as the spot size that evoked the largest response. The presence of a surround was defined as a significant response decrease as spot diameters increased from optimal. Sinewave grating (60% contrast; 37cd/m2 mean luminance) spatial frequency ranged from 0.01-0.26c/d. We used a Fast Fourier Transform to parse out the response portion synced to grating drift rate (the fundamental component or F0). RF diameter was estimated from the spatial frequency that produced the largest F0 response. The presence of a surround was defined as a significantly reduced response at lower spatial frequencies. We compared RF organization predicted from ARFs and SFRFs of 27 RGCs.
Estimates of RF center size corresponded; RGCs with lower optimal spatial frequency had larger RF diameters. No relationship in the estimates of surround presence was found. Using ARF criteria, 70% of RGCs had a surround, whereas only 18% had surrounds using the SFRF. Of 19 RGCs with surrounds in ARFs, only five also had surrounds in their SFRF. This difference is not due to display constraints, a half cycle of a 0.1c/d grating subtends 46o of visual angle, similar to our larger spot diameters.
In an intact mouse preparation, drifting gratings are useful for defining and examining RF center properties, but stationary spots should be used to evaluate the RF surround. The difference could be related to center/surround temporal interactions, which would differ for stationary and moving stimuli.
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