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B. Werner, P.B. Cook, C.L. Passaglia; Spatio–Temporal Response Characteristics of Salamander Retinal Ganglion Cells During Contrast Adaptation . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3109.
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© ARVO (1962-2015); The Authors (2016-present)
The spike output of retinal ganglion cells has been shown to adapt to changes in stimulus contrast. The mechanisms underlying the contrast adaptation are not yet understood. Here, we investigated the input currents to retinal ganglion cells in response to temporal and spatial changes in contrast depth.
Perforated patch clamp recordings were obtained from salamander ganglion cells in retinal slices in response to randomly modulated light stimuli. Stimuli consisted of either a spatially uniform spot fluctuating in luminance or an array of bars with each bar independently following a random sequence of luminance values. The range of light intensities (contrast) in this sequence was switched every 42 seconds during stimulus presentation. Responses to the high and the low contrast stimuli were divided into 6 second segments and cross–correlated with the respective light input to characterize the temporal retinal filter at different time delays with respect to the step changes in contrast. For the stimulus consisting of an array of bars the response was correlated with the input sequence of each individual bar to also obtain a spatial profile of the response.
Excitatory current responses correlated with the luminance fluctuation of the central region of the stimulus pattern. The gain of these center responses decreased when contrast was raised and increased when contrast was lowered.. The contrast adaptation took several seconds to complete and seemed faster for low–to–high contrast transitions. The gain of the current noise changed similarly during the process of adaptation so that the signal–to–noise ratio stayed roughly constant.
The input currents to retinal ganglion cells adapt in response to changes in contrast depth of a spatially uniform as well as a spatially patterned stimulus. The patterned stimulus allows one to obtain a spatial profile of the ganglion cell response over the time–course of contrast adaptation.
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