Presentation Title

The effect of methamphetamine pre-exposure on habit formation in male rats

Abstract

Operant conditioning is a type of learning where behaviors become more or less likely to reoccur after being rewarded or punished. Habits are motor responses performed automatically in response to a particular stimulus, which can be very adaptive because it frees up cognitive workspace for other tasks. Habits form after repeated pairings of the operantly-conditioned behavior with a desirable outcome, and eventually, the behavior will occur even when the outcome is no longer rewarding. The parallel here to addiction is not coincidental, as substance abuse is thought to change the brain networks involved with habit. However, the neural circuitry underlying the transition in behavior from goal-directed to environment-elicited is not completely understood. Significant sexual dimorphism has been found in the number of reward exposures needed during operant training for an animal to begin to respond habitually rather than in a goal-directed manner. Exposure to methamphetamine prior to operant training does not advance the transition in female rats, as the literature has indicated for male rats pre-exposed to psychostimulants. This study investigated the effect of pre-exposure of methamphetamine on Long Evans male rats with 120 stimulus-response exposures on a variable-interval thirty-second schedule, which is a level of reinforcement subthreshold to habit in male rats. Following pairing of the sugar-pellet reward with taste-aversive lithium chloride, the rate of responding (nose-poke behavior) for both the methamphetamine pre-treated and control groups showed that both were sensitive to reward devaluation. This implies that the methamphetamine pretreatment did not accelerate habit formation at this level of training. While this is the same result as the previous study with female rats, it does indicate a divergence from previous studies that found that pre-exposure with psychostimulants accelerates habit formation in male rats.

Primary Faculty Mentor Name

Dr. Donna Toufexis

Graduate Student Mentors

Hannah Schoenberg

Status

Undergraduate

Student College

College of Arts and Sciences

Program/Major

Neuroscience

Primary Research Category

Biological Sciences

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The effect of methamphetamine pre-exposure on habit formation in male rats

Operant conditioning is a type of learning where behaviors become more or less likely to reoccur after being rewarded or punished. Habits are motor responses performed automatically in response to a particular stimulus, which can be very adaptive because it frees up cognitive workspace for other tasks. Habits form after repeated pairings of the operantly-conditioned behavior with a desirable outcome, and eventually, the behavior will occur even when the outcome is no longer rewarding. The parallel here to addiction is not coincidental, as substance abuse is thought to change the brain networks involved with habit. However, the neural circuitry underlying the transition in behavior from goal-directed to environment-elicited is not completely understood. Significant sexual dimorphism has been found in the number of reward exposures needed during operant training for an animal to begin to respond habitually rather than in a goal-directed manner. Exposure to methamphetamine prior to operant training does not advance the transition in female rats, as the literature has indicated for male rats pre-exposed to psychostimulants. This study investigated the effect of pre-exposure of methamphetamine on Long Evans male rats with 120 stimulus-response exposures on a variable-interval thirty-second schedule, which is a level of reinforcement subthreshold to habit in male rats. Following pairing of the sugar-pellet reward with taste-aversive lithium chloride, the rate of responding (nose-poke behavior) for both the methamphetamine pre-treated and control groups showed that both were sensitive to reward devaluation. This implies that the methamphetamine pretreatment did not accelerate habit formation at this level of training. While this is the same result as the previous study with female rats, it does indicate a divergence from previous studies that found that pre-exposure with psychostimulants accelerates habit formation in male rats.