The effects of prenatal cocaine exposure on reversal learning using a simple visual discrimination task in rhesus monkeys.

The purpose of this research was to determine if adult animals that were exposed to cocaine prenatally would be able to adapt to changes in the rules of reinforcement for a simple discrimination task. Treatment groups included 0.0, 1.0, and 3.0 mg cocaine/kg/day and an escalating-dose group that began treatment at 3.0 mg cocaine/kg/day, after which the dose was increased by 0.5 mg cocaine/kg/day every 2 weeks throughout the pregnancy. All animals performed a color and position discrimination task for food reinforcers for approximately 6 years before the present study. For this task, subjects were presented with colored stimuli that determined the correctness of subsequent position choices: left for red or yellow and right for blue or green. At 7 years of age, the rules for obtaining reinforcement were reversed. Animals exposed to all doses of cocaine showed impaired reversal performance. Further, animals exposed to the escalating doses of cocaine continued to show this impairment for over 285 sessions (about 21/2 years). The number of sessions required by subjects to master these contingency changes indicated that, using a task with which they have an extensive history, cocaine-exposed animals have greater difficulty in adapting to important changes in their environment.