MacMillan catalyst

Abstract

We studied the ocular dominance distribution in visual cortex of kittenswhich had been monocularly exposed to moving-pattern stimuli underanesthesia and paralysis. 1. We did not obtain any discernible changesin ocular dominance, confirming the previous reports that anesthesia andparalysis prevent ocular dominance plasticity from occurring. 2. Theplasticity, however, was restored under the acute experimental conditionby a cortical infusion of 1-noradrenaline (1-NA). In the 1-NA-infusedvisual cortex, the ocular dominance distribution was clearly shifted tothe open eye after monocular exposure for about 20-24 h. 3. We alsostudied how quickly and to what extent the changes were induced when theduration of the combined treatment was varied. The results were: (i)the earliest change was observed in approximately 12 h withdisappearance of binocular cells, (ii) the treatment was most effectiveafter 20-24 h in inducing the shift of ocular dominance, and (iii) thetreatment longer than 24 h (up to 45 h) did not necessarily enhance theshift, though the state of reduced binocularity was sustainedthroughout. 4. The effects of the cortical 1-NA infusion combined withmonocular exposure became less with increasing the age of experimentalanimals, suggesting the presence of the ``susceptible period{''} in theacute experiments. 5. The effects seemed to become smaller toward theend of a given recording session, suggesting that the restoredplasticity wanes with time. The present results further support theidea that the direct activation of the NA system enhances corticalplasticity, in principle, independent of general conditions ofexperimental animals.