Physiological normality of the retinal in visually deprived cats.

Cats deprived of visual experience by neonatal suture of the eyelids develop physiological abnormalities in the visual cortex 6,15,16, superior colliculus la and lateral geniculate nucleus (LGN) s. In seeking to determine the site of the physiological impact of visual deprivation it is of obvious interest to know the effect of deprivation on the physiology of the most peripheral visual centre, the retina. The physiological abnormality found in the LGN of visually deprived cats is the partial functional disappearance from the LGN of one subgroup of relay cells, the so-called Y-cells 8. In the normal cat Y-cells in the LGN receive their retinal drive from a functional subgroup of retinal ganglion cells 2,7 also called Y-ceils 4,7, which are distinguished from other ganglion cells by the high conduction velocity of their axons z,5,7,t2 and by several properties of their receptive fields, particularly their large size 2,4,5 and 'non-linear' spatial organizationS, 4. The present experiments were designed to test whether Y-type ganglion cells are present in the visually deprived retina and, if so, whether any abnormality was apparent in their numbers, in their receptive field properties or in the conduction velocities of their axons. The same tests were also applied to ganglion cells of the other two recognized types, X-cells 4,1z and W-cells 12. By all tests the retinal ganglion cells of deprived cats appear to be functionally normal, indicating a more central origin for the physiological abnormalities of visually deprived cats. Experiments were performed on adult cats anaesthetized with ether during surgery and with nitrous oxide (70 % N20-30 % 02) during recording, and paralyzed during recording by continuous intravenous infusion of gallamine triethiodide and dichloride toxiferineL Seven cats were used. Five were monocularly deprived (MD) of visual experience by suture of the eyelids of one eye ~4. Two were binocularly deprived (BD) by suture of the eyelids of both eyes. The suturing was done on the eighth postnatal day, and the eyelids were left sutured until just before recording, 12-18 months later. The cats were mounted in a stereotaxic headholder facing a tangent screen 1 m