Quantitative studies of cell size in the cat's dorsal lateral geniculate nucleus following visual deprivation.

Abstract

The effects of visual deprivation upon dorsal lateral geniculate (DLG) cell size were compared for seven kittens reared with monocular lid-suture (MD), seven with binocular lid-suture (BD), and six with one eye lid-sutured and the other eye enucleated soon after birth (MD-E). Six additional kittens were reared normally for comparison. For each kitten the cross-sectional areas of 300 cells were measured in one or both nuclei. Measurements were taken from the binocular segment of laminae A and A1 and the monocular segment of lamina A. In agreement with previous studies, cells in the binocular segment of the deprived laminae of MD cats were smaller (33-34%) than those in the non-deprived laminae. Comparisons with normal animals indicated that this difference was due to an increase (10-15%) in size of cells in the non-deprived laminae as well as a decrease (23-25%) in size of cells in the deprived laminae. Cells in the monocular segment also were affected by deprivation in MD cats, and this effect increased with the age (and duration of the deprivation) of the animal. However, it was always smaller than the decrease in cell size in the binocular portion of the DLG. In BD kittens, DLG cells were smaller (7-12%) than normal in all portions of the nucleus, including both the binocular and monocular segments. Direct comparisons between the deprived laminae of MD and BD kittens indicated that the decrease in cell size was greater for MD kittens in the binocular segment, but tended to be greater for BD kittens in the monocular segment. In MD-E kittens, DLG cells in the deprived laminae were smaller (11-17%) than normal in all portions of the nucleus, including both the binocular and monocular segments. Thus, the effects of deprivation were similar to those in BD kittens, even though inputs from the deprived eye had been placed at a competitive advantage in MD-E kittens. These results indicate that two factors may affect cell size in the DLG of visually deprived cats: deprivation per se and abnormal binocular competition. Finally, separate analyses for the ten largest and the ten smallest cells in each lamina of each cat were carried out in an attempt to determine if the changes in cell size were limited to the largest cells. In every case, differences observed for the total sample of cells were paralleled by differences from normal of both the largest cells present and the smallest cells present in the deprived laminae. Since at least two alternative interpretations can account for this finding, the question of whether the large cells are selectively affected by visual deprivation remains unanswered in the cat.