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Session: Neurophysiology: Biological Neural Networks
Session starts: Thursday 24 January, 10:40
Presentation starts: 10:40
Room: Lamoraalzaal

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Yan Zhao (Northwestern University)
Hui Chen (Northwestern University)
Xiaorong Liu (Northwestern University)
John Troy (Northwestern University)

Abstract:
The receptive field (RF) organization of retinal ganglion cells (RGCs) determines how they preferentially respond to visual stimuli. In the mouse retina, an increasingly popular model for vision research, most RFs are thought to be composed of an excitatory center and a concentric antagonistic surround [1]. However, a thorough systematic characterization of these RF organizations in the mouse is lacking. To advance our understanding about its structure and function, we developed a method to characterize both the center and surround mechanism of many RFs simultaneously at the level of spike output. We performed in vitro multielectrode array (MEA) recordings on whole-mount retina preparations, using spatiotemporal Gaussian white-noise (GWN) checkerboard stimuli to map numerous RFs via spike-triggered average analysis [2]. Typically in the mouse, GWN is not effective at eliciting spikes attributed to the surround mechanism, due to a low probability of simultaneously stimulating multiple sub-areas of the annular surround. To tease out the surround mechanism from that of the center, we used several different checker dimensions ranging from 50μm in diameter to fullfield stimulation to elicit different contributions from the center and surround. Since RGCs exhibit spatial tuning, stimulation of RGCs with different stimulus sizes resulted in an area response function, in which the RGC spike rate varies as a function of the stimulus size. By modelling the area response function as the integral of a difference of Gaussians [3], the spatial properties of center and surround are extracted from the parameters of the 2-dimensional Gaussians. Consistent with previous reports, 89.8% (N=557) of the RGCs had center-surround organization, with diameters of 253.0+8.6μm and 1008.3+31.9μm (mean+SEM), for the center and surround respectively. ON cells exhibited the largest center diameters (320.5+12.5μm), followed by ON-OFF cells (281.3+14.5μm) and OFF cells (263+11.2μm). Interestingly, the classification of 43.0% of RGCs, as determined by the response dominance index, changed as the stimulus size increased. The area-response GWN method for MEA recordings has numerous applications including physiological classification of mouse RGCs, developmental studies of the maturing retina, a better understanding of contrast sensitivity and adaptation, and the study of retinal degeneration in models of eye diseases.