Spatio‐temporal interactions in cat retinal ganglion cells showing linear spatial summation.

Abstract

3. These Q cells appear to form a homogeneous group which is probably a subset of the tonic W cells (Stone & Fukuda, 1974) or sluggish centre-surround cells (Cleland & Levick, 1974).4. The over-all spatio-temporal frequency characteristics of cells showing linear spatial summation are not separable in space and time. The form of the spatial frequency responsivity function of these cells depends upon the temporal frequency at which it is measured while the temporal phase of their response measured at any constant temporal frequency depends upon the spatial frequency of the stimulus.5. The behaviour of X and Q cells is quite well explained by an extension of the model in which signals from centre and surround mechanisms with radially Gaussian weighting functions are summed to provide the drive to the retinal ganglion cell. While the general form of the temporal frequency response characteristics of these ganglion cells are probably provided by the characteristics of elements common to the centre and surround pathways, the spatio-temporal interactions can be explained by assuming that the surround signal is delayed relative to the centre signal by a few milliseconds.

Selective Ablation of a Class of Amacrine Cells Alters Spatial Processing in the Retina

“…For this minimization, we followed the standard approach described by Enroth-Cugell et al (1983), with one addition: the major and minor radii of the center were allowed to be different because we found that many cells had asymmetric centers. R (k) was then computed as:…”

“…To determine how the NPY cells affect the center and surround, we fit the spatial tuning curves from NPY cell-ablated retinas and controls to the predictions of a standard receptive field model, a difference-of-Gaussians model (Rodieck, 1965;Enroth-Cugell and Robson, 1966;Enroth-Cugell et al, 1983;Shapley and Lennie, 1985), and examined which parameters of the center and surround were different between the two groups. Six parameters were evaluated: the size of the center and surround, the strength of the center and surround, the asymmetry of the center, and the relative phase between the center and surround.…”

Temporal-chromatic interactions in LGN P-cells

“…In addition to the phase shift caused by temporal filtering, center and surround can have transport delays that are temporal frequency-independent. The surround delay is constrained to be larger than the center delay, as characterized in cat ganglion cells (Derrington & Lennie, 1982;Enroth-Cugell et al, 1983;Frishman et al, 1987) and those of macaque (Lee et al, 1989a;Yeh et al, 1995).…”

Spatiotemporal integration of light by the cat X-cell center under photopic and scotopic conditions

“…All measurements were based on responses with fundamental component amplitudes in the range of 5-10 impulses s −1 . This is a range in which X-cell responses scale linearly with contrast (Enroth-Cugell et al, 1983;Troy & Enroth-Cugell, 1993). Responsivity is defined as the amplitude of the fundamental component divided by the contrast that evoked the response.…”

“…From a number of studies, we know that the radius of the center of the X-cell receptive field is invariant with temporal frequency in the range 0.5 to 30 Hz at high photopic illuminance (Enroth-Cugell et al, 1983;Dawis et al, 1984;1993). At higher temporal frequencies, however, the X-cell center expands (Frishman et al, 1987;1993).…”