1. Previous studies have shown that rearing with monocular visual deprivation (MD) produces a loss of Y-cells and a reduction in spatial resolution among X-cells in layers A and A1 of the cat's dorsal lateral geniculate nucleus (dLGN). However, there have been no studies of the effects of visual deprivation on the function of the retinogeniculate W-cell pathway, which terminates in the C layers of the dLGN. It also is not known if Y-cells in the C layers are affected by MD in the same way as Y-cells in the A layers. These questions were addressed by the present experiment. 2. Single-cell recordings were made from the C layers of 5 normal adult cats (112 cells) and from the nondeprived (94 cells) and deprived (95 cells) C layers in 10 cats monocularly deprived by lid suture for 3-7 yr. The cells were classified as X, Y, or W on the basis of their receptive-field properties and responses to electrical stimulation of the optic chiasm. In addition, quantitative measures were made of responses to sine-wave gratings of different spatial frequencies. 3. Receptive-field organization, receptive-field center size, spatial and temporal linearity to counterphased sine-wave gratings, and latency to optic chiasm stimulation were similar for C-layer cells in normal cats and in the deprived and nondeprived layers of MD cats. On the basis of these properties, 23% of normal layer-C cells were classified as Y-cells and 72% were classified as W-cells. The Y-cells tended to be located in the magnocellular division of layer C and most (though not all) W-cells were in the parvocellular division. Normal layers C1 and C2 contained almost exclusively W cells. The incidence of Y and W cells was similar to normal in the nondeprived and deprived C-layers of MD cats. 4. In normal cats, W cells typically had the lowest amplitude first-harmonic (F1) response rates to drifting sine-wave gratings. However, many W cells gave quite brisk responses and, overall, there was no significant difference between F1 response amplitudes of Y and W cells. Response amplitudes of Y- and W-cells in the deprived and nondeprived C-layers of MD cats were not significantly different from normal. 5. Normal Y- and W-cells tended to have low optimal spatial frequencies (0.2 c/deg or lower) and spatial resolutions (generally 0.4-1.6 c/deg) to drifting sine-wave gratings.(ABSTRACT TRUNCATED AT 400 WORDS)
Damage to visual cortex (areas 17-19) in kittens or adult cats produces severe retrograde degeneration of neurons in the dorsal lateral geniculate nucleus (LGN). However, some neurons survive in otherwise degenerated portions of the LGN after a visual cortex lesion at any age. Previous studies have shown that there are well-defined differences in potential retinal inputs, soma size, synaptic connections, outputs, and physiological properties of output targets of the surviving LGN cells in cats that received visual cortex damage at different ages. The present experiment investigated the relationships between these differences and the responses of surviving LGN neurons to visual stimulation. Recordings were made from surviving neurons in the degenerated A- and C-layers of the LGN in cats that had received a visual cortex lesion on the day of birth, at 8 weeks of age, or as adults (survival was 11.5-36 months). Normal adult cats were studied for comparison. The visual receptive field was mapped, and tests were carried out to classify each cell as X, Y, or W. In addition, quantitative methods were used to assess response amplitude, strength of receptive-field surround inhibition, spatial-frequency tuning to drifting or counterphased sine-wave gratings, and response to nondominant-eye stimulation for each cell. We found that surviving cells in all LGN layers respond to light, have normal receptive-field organization, and have normal eye dominance following a lesion at any age tested. In addition, gross retinotopic organization of the LGN is normal. However, 2 main abnormalities were observed following a lesion at all 3 ages. First, there is a reduction in the percentage of X cells in the A layers, from 62% in normal LGNs to about 15% in degenerated LGNs. Second, many surviving cells in both the A- and C-layers have abnormally large receptive-field centers. Other differences that were observed between normal A-layer cells and surviving A-layer cells could be attributed to the loss of X cells. These results indicate that cells within a structure that shows severe retrograde degeneration after brain damage can maintain relatively normal function and can take part in potentially important residual neural pathways. Previous studies indicate that these residual pathways can show both anatomical and physiological compensation for the brain damage, and the present findings bear on the consequences and mechanisms of this compensation.
The cat's superior colliculus (SC) receives direct inputs from retinal W-cells (a W-D input) and Y-cells (Y-D input) and an indirect Y-cell input via the lateral geniculate nucleus and visual cortex (Y-I input). In previous studies we have shown that intraocular injection of antibodies raised against large retinal ganglion cells produces a dose-dependent reduction in the Y retinogeniculate pathway. Furthermore, when a sufficiently high antibody concentration is used, there is a substantial loss of the Y pathway and no apparent loss of the W pathway. In the present study, we used the antibodies to investigate the contributions of the Y and W pathways to functional organization within the SC. Binocular injections of low (330 micrograms/100 microliters) or high (1,000 micrograms/100 microliters) antibody concentrations were made. The antibody-mediated effects on SC cells' response properties were compared directly with effects of early binocular deprivation, which have been attributed to a loss of Y-I input. Extracellular single-cell recordings were made from the SC, and cells were classified as receiving Y-D, Y-I, or W-D inputs on the basis of their response latencies to electrical stimulation of the optic chiasm and optic tract. Injections of the low antibody concentration produced no significant effects on inputs to the SC. However, injections of the high antibody concentration resulted in a 70% reduction in SC cells with a Y-D input and an 82% reduction in SC cells with a Y-I input. There was no effect on the percentage of cells with a W-D input. Binocular deprivation produced a 76% reduction in the percentage of cells with Y-I input. Visual response properties of SC cells also were assessed. Injections of the high antibody concentration produced a 55% reduction in cells that respond with a directional preference and a 51% reduction in cells that respond to high-velocity stimuli. Binocular deprivation produced a 78% reduction in the proportion of directional cells and a 25% reduction in cells that respond to the ipsilateral eye. Taken together, the results of this and previous studies using cortical lesions, visual deprivation, and immunoablation suggest that Y-D input is the primary basis for responses to high stimulus velocity, Y-I input is an important basis for directional responses and response through the ipsilateral eye, and W-D input is important for responses to low stimulus velocity.(ABSTRACT TRUNCATED AT 400 WORDS)
Previous studies have shown that antibodies against large retinal ganglion cells (alpha-/Y-cells) reduce the Y-cell retinogeniculate pathway while having little or no effect on the X- or W-cell pathways. The present study investigated the dose-response relationship of these effects. We began by studying effects on the T1 (largely Y-cell-mediated) and T2 (largely X-cell-mediated) waves of the retinal field-potential. Different concentrations of the antibodies were injected intraocularly in adult cats and retinal field-potentials evoked by optic chiasm stimulation were examined. The lowest concentration of immune serum tested (330 micrograms/100 microliter volume) reduced both the T1 and T2 amplitudes. With increasing concentrations, the ratio of T1:T2 amplitudes progressively decreased from 0.71 to only 0.05. The highest concentration of immune serum tested (1000 micrograms/100 microliter volume) virtually eliminated the T1 wave while the T2 wave remained (albeit reduced). Next, we carried out single-cell physiological and morphological studies to verify the effects of the highest antibody concentration and compare them with previous results on effects of the lowest antibody concentration (Kornguth et al., 1982; Spear et al., 1982). In single-cell recordings from the retina, the encounter rates of Y- and X-cells were reduced by 85 and 53%, respectively, after injection of the highest antibody concentration. There was no effect on the encounter rate of retinal W-cells. After injection of the lowest antibody concentration, there was no change in the encounter rates of any of the retinal cell types. Morphological studies revealed an 88-99% loss of alpha-cells in retinae treated with the highest antibody concentration. There also was a substantial (24-57%) loss of medium-size ganglion cells but no loss of small ganglion cells. The loss of alpha-cells was much greater after high-concentration injections than after low-concentration injections. In recordings from the LGN, the proportion of Y-cells was reduced by 87% in laminae receiving input from an eye injected with the highest antibody concentration. Laminae receiving input from an eye injected with the lowest concentration had a 77% reduction in Y-cells. The encounter rate of LGN X-cells was not affected by either concentration. Morphological analysis indicated that the loss of Y-cells in the LGN was not due to changes in cell size. These findings indicate that antibody-mediated effects on retinogeniculate pathways are dose-dependent.(ABSTRACT TRUNCATED AT 400 WORDS)
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