Ocular dominance of cortical cells in cats dark-reared into maturity after short postnatal monocular deprivation

Abstract

We studied the preservation of the early monocular deprivation effect by rearing kittens in complete darkness for long periods (9.5 to 20 months) after a monocular deprivation period of 4 weeks that was initiated at the age of 1 month (MDDR cats). For comparison, four groups of kittens were used: monocularly deprived as those described above and then reared in normal light conditions (MDN), monocularly deprived at the age of 1 month (MD), and dark-reared (DR) or normally light-reared (NOR) from birth. Recordings from the visual cortex of MDDR and MDN cats showed that there was a clear preference for cells driven only by the experienced eye compared with the deprived eye. This preference was found whether, subsequent to the monocular deprivation period, these cats were dark- or light-reared ( P < 0.005 for MDDR and MDN compared with NOR cats). The difference between the MDDR, MDN, and MD groups of cats was reflected in the proportions of binocularly driven cells; the largest number of binocularly driven cells was found in the MDDR cats. There was no bias toward either eye in the ocular dominance distribution of cortical cells in cats that were reared in total darkness (DR) or in the light under normal conditions (NOR). We thus conclude that the long-term dark period during development did not erase the effect of early monocular deprivation on the cat visual cortex provided that the latter lasted 4 weeks prior to the dark period.