Evidence that binocular competition affects the postnatal development of Y-cells in the cat's lateral geniculate nucleus

Abstract

Cats reared from birth with the lids of one eye sutured develop abnormalities of their geniculo-cortical systems: geniculate neurons in layers that are deprived of visual input grow less than those receiving visual inputs from the normal eye4,1°; the percentage of recordable geniculate cells that are Y-cells is greatly reduced in the deprived layers9; cortical neurons lose most of their input from the deprived eyeS, 11-13 and when the cats are using the deprived eye they show limited visually guided behavior 2,7. However, these abnormalities occur primarily in the binocular segments of the geniculo-striate system, within which the central, binocularly viewed portion of the visual field is mapped. In the monocular segment the neurons are relatively unaffected. Thus, the geniculate neurons are of normal size a, the proportion of Y-cells is normal 9, cortical cells in area 17 can be driven from the deprived eye and some display normal receptive field properties8, ~3. Finally, these cats can respond appro- priately to objects moving in the monocular segment of the visual field of the deprived eye 7. These differences in the effects of monocular deprivation upon the monocular and binocular segments of the visual pathways are most easily explained by a develop- mental mechanism involving binocular competition that occurs during development between neurons innervated by one eye and neurons innervated by the other. Monoc- ular suture upsets this balance; neurons in the deprived geniculate laminae develop abnormally because they are at some disadvantage relative to the non-deprived neurons, and as a result the deprived cells fail to develop a significant number of functional cortical connections. In the monocular segment, by definition, there can be no binocular competition, and thus the deprived neurons in the monocular seg- ment develop without many of the abnormalities found in the binocular segment. Since the monocular segment receives from the peripheral visual field and the binoc- ular segment from the more central parts of the visual field, it has been necessary to show that the differences between the monocular and the binocular segments are not merely differences between the central and the peripheral parts of the visual pathways. This has been done by rearing cats that have one eye closed and a limited, fairly central lesion placed in the retina of the other eye. In these cats the deprived visual