Abstract: The brain growth spurt was expressed as velocity curve of the incre-ase of brain weight in 0-20 day-old Wistar pups, the curve peak wasaround the 10 day-old stage. The experiment on development of appetitivediscrimination learning of Y maze in 12-20 day-old pups was carried outand a large enhancement of learning le level in the 16 day-old pups (afterdays of "brain growth spurt") was observed. The result indicates thatthe appetitive discrimination learning of Y maze is closely related tothe brain growth in preweanling rats. The experiment showed that the level of learning behavior of Ymaze for the pups of rotational type which could be induced by Amphe-tamine was better than that for the pups of non-rotational type whichcould not be induced by Amphetamine. Moreover, the best level of learningbehavior was for the pups of the right rotational type in keeping withthe direction of food reward (right arm) and the appearance was gettinggradually more obvious with the days. It suggests that the learning ofleft-right discrimination has close relation to the function asymmetryof the two hemispheres in preweanling rats.

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