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Robert L Seilheimer, Jing Wang, Jasdeep Sabharwal, Cameron S Cowan, Samuel M Wu; Separating ON and OFF Bipolar Cell Contributions to the Retinal Ganglion Cell Receptive Field. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2756.
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© 2017 Association for Research in Vision and Ophthalmology.
The retinal ganglion cell (RGC) receptive field is a fundamental component of spatiotemporal information processing in the visual system, but the synaptic inputs underlying its construction are not well understood. We used single-cell voltage-clamped recordings with white-noise analysis and pharmacological manipulation to analyze the contributions of ON and OFF circuits to the linear excitatory and inhibitory inputs to RGC receptive fields.
Tiger salamander RGCs were voltage-clamped at ECl to measure excitatory currents and at EC to measure inhibitory currents. Cells were classified as ON, OFF, or ON/OFF by their response to whole field light stimulation. Linear spatiotemporal receptive fields were mapped by computing current-weighted averages and current-weighted covariances in response to binary white noise checkerboards in the absence or presence of the metabotropic glutamate receptor agonist L-AP4.
In all cells, the excitatory temporal filter had a characteristic biphasic shape with a faster OFF component and slower ON component. The inhibitory temporal filter had a similar shape, but opposite polarity. In most ON/OFF cells, the ON component of the excitatory temporal filters was significantly decreased by LAP4, while the OFF component was unchanged. Similarly, LAP4 diminished the ON component of the inhibitory filter. In OFF cells, both the ON and OFF components of the excitatory and inhibitory temporal filters retained their shape with LAP4. In ON cells, we see a loss of the ON component of the excitatory temporal filter, however the inhibitory temporal filter was unchanged by LAP4. Preliminary analysis of the second-order temporal filter (current-weighted covariance) in ON/OFF cells reveals the presence of multiple temporal filters, one of which can be altered by LAP4.
By combining white-noise analysis with voltage clamping and LAP4 we were able to dissect the ON and OFF bipolar cell (BC) contributions to various types of RGCs. We found that in ON/OFF cells, both excitatory and inhibitory filters are driven by a combination of ON and OFF BCs. In OFF RGCs, both filters are driven by OFF BCs. In ON cells, the excitatory filter is driven by ON BCs, while the inhibitory filter is driven by OFF BCs.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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