in pharmacokinetics, anatomy of the prefrontal cortex, social behavior, and life span. Other advantages to studying relapse in non-human primates include the ability of the animal to reinstate self-administration, and to learn complex behaviors in order to obtain the drug. Animal studies have shown that a reduction in negative withdrawal symptoms is not necessary to maintain drug taking in laboratory animals; the key to these studies is operant conditioning and reinforcement. Protocols Self-administration To self-administer the drug of interest the animal is implanted with an intravenous catheter and seated in a primate chair equipped with a response lever. The animal is seated in a ventilated chamber and trained on a schedule of drug self-administration. In many studies the self-administration task begins with presentation of a stimulus light (located near the response panel) that may change colors or turn off upon completion of the operant task. The change in visual stimulus is accompanied by an injection of the given drug through the implanted catheter. This schedule is maintained until the animals learn the task. Extinction Extinction in non-human primates is analogous, with some limitations, to abstinence in humans. In order to extinguish drug-seeking behavior the drug is substituted with a saline solution. When the animal performs the task it has been trained to perform it is no longer reinforced with an injection of the drug. The visual stimulus associated with the drug and completion of the task is also removed. The extinction sessions are continued until the animal ceases the drug-seeking behavior by pressing the lever. Reinstatement After the animal’s drug-seeking behavior is extinguished, a stimulus is presented to promote the reinstatement of that same drug-seeking behavior (i.e., relapse). For example, if the animal receives an injection of the drug in question it will likely begin working on the operant task for which it was previously reinforced. The stimulus may be the drug itself, the visual stimulus that was initially paired with the drug intake, or a stressor such as an acoustic startle or foot shock. However, the stimulus used to trigger reinstatement can influence the psychological processes involved. Neuroimaging Neuroimaging has contributed to the identification of the neural components involved in drug reinstatement as well as drug-taking determinants such as the pharmokinetics, neurochemistry, and dose of the drug. The neuroimaging techniques used in non-human primates include positron emission tomography (PET), which uses radiolabeled ligand tracers to measure neurochemistry in vivo