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A. J. Barrow, F. Gao, S. M. Wu; Spatio-temporal Properties of the Rod and Cone Network. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1050.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the spatio-temporal properties of the rod and cone receptive field and the contributions of individual ionic currents to the network response.
Voltage responses were recorded from salamander rods and cones using current clamp, while cells were stimulated with either a bar of light, an m-sequence modulated checkerboard, or center spot with surround annulus. Rod-Rod and rod-cone coupling measurements were performed with the double patch configuration. Simulation of currents in the rod network was performed using a Runge-Kutta finite difference method in MATLAB.
Simulation of the rod network shows that voltage gated potassium channels responsible for the resting potential are the largest contributors to signal filtering in neighboring rods. Numerical solution of a passive network, assuming 4 neighboring rods shows that the measured resistance between neighboring rods is very close to the effective coupling resistance between two rods. Stimulating cones using m-sequence modulated center-surround stimuli shows mutual inhibition when a center stimulus followed a surround stimulus, and when a surround is followed by a center stimulus. However the magnitude of this inhibition is asymmetric, with center stimuli following surround stimuli showing more inhibition than surround stimuli Center stimuli hyperpolarized the cone, and surround stimuli alone caused no response.
Measurements of coupling resistance between neighboring rods is a close estimate of the actual resistance between two rods. Although Ih is a large contributor to the to the voltage response of single cells, other potassium channels play a more important role in lateral propagation of signals in the rod network. In cones, mutual inhibition from center-surround inhibition is asymmetric with respect to time.
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