VISUAL DEPRIVATION DOES NOT AFFECT THE ORIENTATION AND DIRECTION SENSITIVITY OF RELAY CELLS IN THE LATERAL GENICULATE-NUCLEUS OF THE CAT

Visual deprivation in early life profoundly affects the characteristic sensitivity of visual cortical cells to stimulus orientation and dire ction. Recently, relay cells in the lateral geniculate nucleus (LGNd) have been shown to exhibit significant degrees of orientation and dire ction sensitivity. The effects of visual deprivation upon these proper ties of subcortical cells are unknown. In this study cats were reared from birth to 6-12 months of age in total darkness; the orientation an d direction sensitivities of area 17 (striate cortex) and LGNd cells w ere compared. All cells were studied using identical quantitative tech niques and statistical tests designed to analyze distributions of angl es. The results confirm previous work and indicate that the orientatio n and direction sensitivities of cells in area 17 are profoundly reduc ed by dark rearing. In marked contrast, these properties of LGNd relay cells are unaffected. The result is that, unlike in the normal cat, i n dark-reared cats the orientation and direction sensitivities of cell s in the LGNd and visual cortex do not differ. It is concluded that (1 ) the orientation and direction sensitivities of cortical cells contri bute little, if at all, to the sensitivities of LGNd cells since LGNd cells exhibit normal sensitivities even though the cortical cells proj ecting to them exhibit greatly reduced sensitivities and (2) during no rmal development intracortical mechanisms appear to expand upon and/or modify the weak orientation and direction sensitivities of their inpu ts. These intracortical mechanisms depend upon normal visual experienc e since in dark-reared cats, but not normal ones, the orientation and direction sensitivities of cells in the LGNd and visual cortex do not differ quantitatively or qualitatively.