Modulation of turning preferences by learning.

Rats were trained, using water reinforcement, to turn in circles (rotation) during 1 h daily test sessions. Different groups of rats were reinforced for turning either in the same or opposite direction as that elicited previously by D-amphetamine. All rats (n = 14) trained in the 'same' direction readily acquired the task whereas only 13 of 33 rats trained in the 'opposite' direction showed evidence of learning. Two days after cessation of training, the effect of D-amphetamine was greater in rats trained in the 'same' direction and decreased or reversed in rats successfully trained in the 'opposite' direction - these changes were transient, mostly disappearing a week later.