Critical Periods of Maze Acquisition Development in Euthyroid and Hypothyroid Rodents

Abstract

Mice and rats with congenitally-induced hypothyroidism which continued through early adult development were compared with euthyroid animals for acquisition of a simple sensori-motor maze escape response at various periods during development. Whereas euthyroid mice began to demonstrate criterion maze acquisition as early as 16 days of age, and all showed acquisition to criterion by 20 days of age, only a small percentage of hypothyroid mice acquired the maze response between 25 and 30 days of age. Hypothyroid rats, as well as their euthyroid controls, did not show maze acquisition to criterion by 18 days of age; and, whereas the latter had shown the ability to acquire the maze at 50 days of age, hypothyroid animals still showed a decided deficit in maze acquisition at this time.