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1. Spatial summation within cat retinal receptive fields was studied by recording from optic-tract fibres the responses of ganglion cells to grating patterns whose luminance perpendicular to the bars varied sinusoidally about the mean level. 2. Summation over the receptive fields of some cells (X-cells) was found to be approximately linear, while for other(More)
The contrast sensitivity to gratings drifting at 2.0 Hz has been measured for X and Y type retinal ganglion cells, and these data have been used to characterize the sizes and peak sensitivities of centers and surrounds. The assumption of Gaussian sensitivity distributions is adequate for both types of cells, but allows a better description of X than of Y(More)
Visual stimulation outside the classical receptive field can have pronounced effects on cat retinal ganglion cells. We characterized the effects of such stimulation by varying the contrast, spatial frequency, temporal frequency, and spatial extent of remote drifting sinusoidal gratings. We found that the mean firing rate of some X-cells and most Y-cells(More)
1. The discharges of ganglion cells in the cat's retina were recorded under conditions intended to isolate the cone system.2. Stiles' two-colour threshold technique permitted the photopic system to be studied when at its highest sensitivity. The absolute sensitivity of a ganglion cell, expressed in equivalent photons of lambda(max) at the cornea per impulse(More)
Spatiotemporal frequency responses were measured at different levels of light adaptation for cat X and Y retinal ganglion cells. Stationary sinusoidal luminance gratings whose contrast was modulated sinusoidally in time or drifting gratings were used as stimuli. Under photopic illumination, when the spatial frequency was held constant at or above its(More)
It has been suggested for a number of years that ganglion cells inform the rest of the brain about contrast in the retinal image. The purpose of the work undertaken here was to demonstrate this fact explicitly. Extracellular recordings were made from X- and Y-cell axons of the optic tracts of anesthetized cats. Responses of these cells to gratings that were(More)
The spatio-temporal characteristics of cat retinal ganglion cells showing linear summation have been studied by measuring both magnitude and phase of the responses of these cells to drifting or sinusoidally contrast-modulated sinusoidal grating patterns. It has been demonstrated not only that X cells behave approximately linearly when responding with(More)
1. Grating patterns were used to obtain a quantitative description of cells in the visual cortex of the cat whose response amplitude depended critically upon the orientation of the moving grating.2. In all such cells the impulse frequency was found to decrease linearly with angle on either side of an optimum angle (the preferred angle) until the response(More)
1. Evidence was obtained that the impulse/quantum (I/Q) ratio of the central response mechanism of retinal ganglion cells in the cat is controlled by the steady effective retinal flux of the background.2. One experiment revealed that the I/Q ratio was decreased as the area of an adapting spot, of constant illumination, was increased. The curve relating the(More)