Perseverative behaviour after amphetamine; dissociation of response tendency from reward association.

Low doses of amphetamine were found to alter the ability of marmosets to take account of changes in reward values of object stimuli in a visual discrimination task. Under amphetamine, animals changed their motor responses and stimulus choice in order to preserve the acquired reward value or meaning of certain stimuli. These results suggest that the perseverative effect of amphetamine on behaviour is due to impaired cognitive flexibility rather than to an enhancement of motor habit.