Conditioned place preference

Conditioned place preference (CPP) is a form of Pavlovian conditioning used to measure the motivational effects of objects or experiences. By measuring the amount of time an animal spends in an area that has been associated with a stimulus, researchers can infer the animal's liking for the stimulus. This paradigm can also be used to measure conditioned place aversion with an identical procedure involving aversive stimuli instead. Both procedures usually involve mice or rats as subjects. This procedure can be used to measure extinction and reinstatement of the conditioned stimulus. Certain drugs are used in this paradigm to measure their reinforcing properties. Two different methods are used to choose the compartments to be conditioned, and these are biased vs. unbiased. The biased method allows the animal to explore the apparatus, and the compartment they least prefer is the one that the drug is administered in and the one they most prefer is the one where the vehicle is injected. This method allows the animal to choose the compartment they get the drug and vehicle in. In comparison, the unbiased method does not allow the animal to choose what compartment they get the drug and vehicle in and instead the researcher chooses the compartments. Conditioned place preference (CPP) is a form of Pavlovian conditioning used to measure the motivational effects of objects or experiences. By measuring the amount of time an animal spends in an area that has been associated with a stimulus, researchers can infer the animal's liking for the stimulus. This paradigm can also be used to measure conditioned place aversion with an identical procedure involving aversive stimuli instead. Both procedures usually involve mice or rats as subjects. This procedure can be used to measure extinction and reinstatement of the conditioned stimulus. Certain drugs are used in this paradigm to measure their reinforcing properties. Two different methods are used to choose the compartments to be conditioned, and these are biased vs. unbiased. The biased method allows the animal to explore the apparatus, and the compartment they least prefer is the one that the drug is administered in and the one they most prefer is the one where the vehicle is injected. This method allows the animal to choose the compartment they get the drug and vehicle in. In comparison, the unbiased method does not allow the animal to choose what compartment they get the drug and vehicle in and instead the researcher chooses the compartments. Humans have also been shown to develop conditioned place preferences; for example, individuals taking therapeutic doses of amphetamine develop a CPP for where they consumed the drug. As in Pavlovian conditioning, an initially neutral stimulus, in this case environmental cues, is repeatedly paired with an unconditioned stimulus that naturally produces a response prior to conditioning (the unconditioned response). Over time and pairings the neutral stimulus will come to elicit responses similar to the unconditioned response. In conditioned place preference the unconditioned stimulus could be any number of things including food pellets, water, sweet fluid, novel toys, social interaction, drug intoxication, drug withdrawal, foot shock, illness, wheel running or copulation. The initially neutral environmental cues become associated with the motivational properties of the unconditioned stimulus leading to either approach or avoidance of the environment. Often in practice there is a control and treatment group used to strengthen the ability to make causal claims from the results. The treatment group is administered the unconditioned stimulus while the control group is given saline or nothing to control for all elements of the procedure. The conditioned place preference protocol makes use of an apparatus that contains two or more compartments or areas. These two compartments are designed so that the animal can discriminate between them. Differently patterned walls or floors or different types of floor texture may be used to ensure the animal can discriminate between the compartments. Conditioned place preference involves three phases: habituation, conditioning and preference testing. In the habituation procedure the animal is given a chance to explore the apparatus. This is done to reduce the effects of novelty and usually consists of one five-minute trial. In the preference testing phase the animal is allowed barrier free access to all compartments of the apparatus. Time spent in each compartment is measured either by the experimenter or by motion detecting software; often the mean seconds per minute spent in each compartment is calculated. Statistical testing is used to determine whether the time difference is large enough, in comparison to the control group, to conclude that conditioned place preference or aversion has occurred. Strength of conditioning is inferred by the magnitude of the difference or in the amount of time taken for the response to show extinction. In the conditioning phase the unconditioned stimulus (e.g. morphine) is administered to the animal (usually a mouse or rat) in the treatment group. In this phase of the procedure the animal is only allowed access to one compartment of the apparatus. This compartment will become associated with the motivational effects of the unconditioned stimulus. The environment will come to elicit approach or avoidance-withdrawal depending on the nature of the unconditioned stimulus. The conditioning procedure usually consists of eight or more five-minute sessions. In the standard conditioned place preference procedure, when the unconditioned stimulus is rewarding, rodents will be more likely to approach the compartment that contains cues associated with it. Alternatively, when the unconditioned stimulus is aversive, rodents will be more likely to escape and avoid the compartment that contains cues associated with it. Timing of presentation of the unconditioned stimulus can determine whether place preference or aversion will be conditioned. For example, in trials testing drugs of abuse, if the animal experiences the initial pleasurable effects of the drug while in the conditioning context, the result will likely be conditioned place preference. However, if the animal is given the drug and then the experimenter implements a sufficient delay so that the animal is experiencing the negative after effects of the drug, conditioned place aversion is more likely to occur. The timing of these events can be manipulated by the experimenter in order to condition place preference or avoidance.