Variability and discrimination reversal learning in the open field following septal lesions in rats.

Response variability on a 10 position horizontal response task and a position-habit discrimination followed by 2 reversals was examined in groups of rats with septal damage and operated control rats in the open field. As revealed by the number of positions with responses and the one position with the most responses, the rats with septal damage were reliably less variable in responding than the controls. In addition, the rats with septal damage made a reliably greater number of responses during extinction of the response. In the second experiment, groups of animals were tested for discrimination learning in a 2 part experiment using both a free-ranging and restricted open field. In both parts of the experiment, the rats with septal lesions learned the discrimination and both reversals faster than the controls. Animals tested in the restricted field learned the discrimination slightly faster than those tested in the free-ranging field. The superior discrimination learning for the rats with septal lesions was discussed as a lesion-induced increase in the incentive value of positive reward, producing shorter observed response latencies, resulting in a shorter delay of reinforcement.