Ch. Enroth-Cugell

Receptive field properties of X and Y cells in the cat retina derived from contrast sensitivity measurements

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 cells. The size and peak sensitivity can be specified more precisely, in general, for the center than for the surround. The data also show that for both types of cells (1) center radius increases with eccentricity, but is two to three times larger than Y cells than for X cells at a given eccentricity, (2) spatial resolution is an excellent predictor of center size, (3) the larger the center or surround, the lower its small spot sensitivity at a specific mean lumminance and (4) the surround is nearly as strong as the center for large or diffuse stimuli. X cell surrounds are relatively weaker in the middle of the receptive field than Y cell surrounds, but X cell surrounds are larger relative to their centers.

Light distribution in the cat's retinal image

Abstract The illuminance distribution in the retinal image of a luminous line was measured using a fiber optic probe inserted into the otherwise intact eye of the anesthetized cat. This method allowed the line-spread function of the eye to be determined over a very large range of distances from the center of the image. While the line-spread function fell to half-height within a few minutes of arc for all pupil sizes (1.25′ for the optimum pupil diameter of 1 mm), the tail of the function declined inversely as the three-halves power of the distance and had not reached zero at 20°.

Responses to sinusoidal gratings of two types of very nonlinear retinal ganglion cells of cat

Perhaps 35% of all of the ganglion cells of the cat do not have classical center-surround organized receptive fields. This paper describes, quantitatively, the responses of two such cell types to stimulation with sinusoidal luminance gratings, whose spatial frequency, mean luminance, contrast, and temporal frequency were varied independently. The patterns were well-focused on the retina of the anesthetized and paralyzed cat. In one type of cell, the maintained discharge was depressed or completely suppressed when a contrast pattern was imaged onto the receptive field (suppressed-by-contrast cell). In the other type of cell, the introduction of a pattern elicited a burst of spikes (impressed-by-contrast cell). When stimulated with drifting gratings, the cells mean rate of discharge was reduced (suppressed-by-contrast cell) or elevated (impressed-by-contrast cell) over a limited band of spatial frequencies. There was no significant modulated component of response. The reduction in mean rate of suppressed-by-contrast cells caused by drifting gratings had a monotonic dependence on contrast, a relatively low-pass temporal-frequency characteristic and was greater under photopic than mesopic illuminance. If grating of spatial frequency, that when drifted evoked a response from these cells, were instead held stationary and contrast-reversed, the mean rate of a suppressed-by-contrast cell was also reduced and that of an impressed-by-contrast cell increased. But, for contrast-reversed gratings, the discharge contained substantial modulation at even harmonic frequencies, the largest being the second harmonic. The amplitude of this second harmonic did not depend on the spatial phase of the grating, and its dependence on spatial frequency, at least for suppressed-by-contrast cells, was similar to that of the reduction in mean rate of discharge. Our results suggest that the receptive fields of suppressed-by-contrast and impressed-by-contrast cells can be modeled with the general form of the nonlinear subunit components of Hochstein and Shapleys (1976) Y cell model.

Receptive-field properties of Q retinal ganglion cells of the cat.

The goal of this work was to provide a detailed quantitative description of the receptive-field properties of one of the types of rarely encountered retinal ganglion cells of cat; the cell named the Q-cell by Enroth-Cugell et al. (1983). Quantitative comparisons are made between the discharge statistics and between the spatial receptive properties of Q-cells and the most common of cat retinal ganglion cells, the X-cells. The center-surround receptive field of the Q-cell is modeled here quantitatively and the typical Q-cell is described. The temporal properties of the Q-cell receptive field were also investigated and the dynamics of the center mechanism of the Q-cell modeled quantitatively. In addition, the response vs. contrast relationship for a Q-cell at optimal spatial and temporal frequencies is shown, and Q-cells are also demonstrated to have nonlinear spatial summation somewhat like that exhibited by Y-cells, although much higher contrasts are required to reveal this nonlinear behavior. Finally, the relationship between Q-cells and Barlow and Levicks (1969) luminance units was investigated and it was found that most Q-cells could not be luminance units.

The cat's pupillary light response under urethane anesthesia.

Pupillary area was measured in urethane-anesthetized cats as a function of retinal illuminance. When appropriate corrections are made for differences in experimental procedures, it was found that the pupillary response of the urethane-anesthetized cats eyes to light was basically unchanged from that of the alert behaving cat. This preparation may therefore be a very satisfactory one in which to study the pupillary response pathway in a higher mammal.