Physiological and Psychological Study on Reorganization of the Visual Function in the Albino Rat with One Eye Removed at Early Postnatal Days

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Our previous studies have shown that albino rats with one eye enucleated soon after birth (OEB) could relearn a black-white discrimination task faster than rats with one eye enucleated at maturity (OET) when relearning was conducted after the visual cortex lesions contralateral to the remaining eye, whereas both types of rats failed to relearn a pattern discrimination.The present study was then undertaken to examine the question of whether this kind of behavioral reorganization is also demonstrated in a light-dark discrimination of albino rats and in a pattern discrimination of hooded rats, and the following new original findings were established.1. As to a light-dark discrimination in albino rats, both OEBs and OETs could acquire the habit more quickly after the visual cortex lesions contralateral to the remaining eye and after the bilateral visual cortex lesions, and they also be able to relearn after both types of visual cortex lesions. These results indicate that in a light-dark discrimination of albino rats it was not demonstrated the behavioral expression of morphological and physiological changes which are produced by monocular enucleation in the early postnatal days.2. On the other hand, however, in a pattern discrimination of hooded rats, OEBs could acquire and relearn the habit faster than OETs after the visual cortex lesions contralateral to the remaining eye, hence indicating that functional enhancement in the uncrossed visual nervous system produced by early monocular enucleation could actively be involved in a pattern discrimination of hooded rats. Investigations trying to measure the visual acuity of the hooded rat with one eye removed at birth are now under progress in our laboratory in order to clarify the nature of behavioral expression of functional enhancement in the uncrossed visual pathways by early monocular enucleation.