Abstract
Monocular deprivation (MD) during an early postnatal period causes a loss of visual cortical response to the deprived eye (Ocular dominance (OD) shift). When MD is combined with inactivation of the visual cortex by muscimol infusion, cortical neurons lose their response to the open eye (reverse OD shift). Although these two forms of OD plasticity differ in direction, it is largely unknown whether their other characteristics are also different. Such information would be useful to clarify mechanisms underlying these two plasticity. The normal OD shift proceeds rapidly and the physiological effect of MD saturates after 48 hours in kittens. Therefore, we examined how rapidly the reverse OD shift proceeds and whether the shift could be induced in adults, to compare the dynamics and age-dependency of two forms of OD plasticity. We have inhibited the visual cortical neurons by infusing muscimol in four-week old kittens and adults. After 3-6 days of MD, OD of cortical neurons was evaluated by single-unit recording. The reverse OD shift was observed after 6-day MD as reported previously. After 3-day MD, however, the reverse OD shift was not observed and the OD distribution remained similar to that of normal animals. In adults, OD distribution in the inhibited cortex remained unchanged even after 7-day MD. These results suggest that the reverse OD shift might reflect a mechanism of developmental plasticity that has a slower time course than the normal OD shift. [J Physiol Sci. 2006;56 Suppl:S177]
