The disruptive effects of methamphetamine on delayed-matching-to-sample performance reflect proactive interference and are reduced by SCH23390

• We characterize the pattern of memory disruption produced by methamphetamine.
• Disruptions to delayed matching-to-sample performance reflected proactive interference.
• Methamphetamine produces similar memory disruptions to MDMA.
• Methamphetamine's effect on memory was reduced by the D1 antagonist SCH23390.

Different drugs produce different patterns of impairment on delayed matching-to-sample tasks. For example, (+/−)3,4-methylenedioxymethamphetamine (MDMA) produces an increase in proactive interference. That is, subjects are less accurate when they are required to make a response different to the one they made on the immediately previous trial. The current study assessed whether methamphetamine also produces this particular pattern of disruption in delayed matching-to-sample performance in rats. Methamphetamine primarily reduced accuracy on trials where the correct response differed from the one made on the previous trial. Thus methamphetamine, like MDMA and other stimulant-based drugs of abuse, increased proactive interference. This impairment was reduced by prior administration of the dopamine D1 antagonist SCH23390. These results further extend a general conclusion that a range of stimulant-based drugs may disrupt working memory function indirectly via a tendency to repeat previously made responses and that this disruption is related to D1 receptor activity.