Effects of dark adaptation on spatial and temporal properties of receptive fields in cat lateral geniculate nucleus.

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Abstract
The effect of dark adaptation on the spatial organization of receptive fields of single cells in the lateral geniculate nucleus [LGN] of the cat was studied. In many LGN cells, the ability of the receptive field surround to suppress the response of the center was diminished following dark adaptation. The degree of reduction of the surround antagonistic strength varied from cell to cell and was independent of the various classifications of visual neurons (X/Y, on/off, layer, A/layer, A1 and central/peripheral). Most cells also showed an increase in the apparent size of the excitatory center upon dark adaptation. On the average, the width of the most effective bar stimulus located at the center of the receptive field increased > 2-fold. The effect of dark adaptation on the temporal properties of LGN receptive fields was studied. In many cells, dark adaptation changed the temporal modulation transfer function: it flattened the amplitude function and changed the phase relationship between the center response and the surround response. Retinal ganglion cells showed qualitatively similar behavior to that of LGN neurons. The data do not support the notion that retinal ganglion cell centers converge on LGN cells to form their surround mechanism.