The Effects of Expectation on Natural and Drug -Induced Rewards
Condition: Drug Abuse
MeSH terms: Substance-Related Disorders
Study type: Observational

Summary: 
      Background:

        -  Environmental cues frequently induce expectancies in individuals that may strongly
           influence the actual experience associated with the cue. This has both positive and
           negative consequences for behavior and decision making. For instance, when an addicted
           individual experiences cues associated with imminent drug taking, an expectancy of the
           coming experience is also formed and very likely has an effect on the subsequent
           experience of the drug.

        -  Researchers are interested in studying how the brain responds to these kinds of
           environmental cues and expectancies in order to learn more about addiction and craving
           in substance-abusing individuals.

      Objectives:

        -  To compare the response to rewards (both drug-related and non-drug-related) in cocaine
           users and non-using individuals.

        -  To study the effect of expectation on reward-related (both drug-induced and
           non-drug-induced) responses and brain activity in cocaine users and non-using
           individuals.

      Eligibility:

      -Individuals between 18 and 45 years of age who are regular cocaine users but otherwise
      healthy, or healthy individuals who are not cocaine users.

      Design:

        -  This study involves two experiments. Participants will be assigned to one or both
           experiments.

        -  Participants must not use any drugs for at least 3 days before the visit, may not
           consume alcohol for 24 hours before the visit, and may not consume caffeinated beverages
           for 12 hours before the visit. On the day of the visit, participants will provide both
           urine and breath samples to test for drug/alcohol use.

        -  Experiment 1: In the MRI scanner, participants will respond to questions and images on a
           screen, and will receive small amounts of flavored liquid (chocolate or cherry) through
           a tube in the mouth.

        -  Experiment 2: In the MRI scanner, participants will respond to questions and images on a
           screen, and will receive injections of liquid (saline solution or a drug that provides a
           high similar to cocaine) through an intravenous line. Participants in this experiment
           will return for follow-up visits and provide urine samples for further study.

        -  The specific assignment (to Experiment 1 or Experiment 2 or both experiments) will
           determine the number of study days and follow-up visits required.
    

Detailed description: 
      Objective: Environmental cues frequently induce expectancies in the course of normal daily
      life. When an individual smells and sees the coffee before tasting it, an expectancy of the
      coming experience is formed that influences the actual experience of consuming the coffee.
      Similarly, when an addicted individual experiences cues associated with imminent drug taking,
      an expectancy of the coming experience is also formed. This protocol will examine neural
      responses to cues predictive of a stimulus (neutral or rewarding) and to the subsequent
      receipt of the predicted stimulus.

      Study Population: Study participants will include 18-50 year old, male and non-pregnant
      female otherwise healthy cocaine dependent individuals and control individuals who have a
      history of some stimulant use but no history of abuse or dependence on any other drug other
      than nicotine.

      Design: The study will employ fMRI to elucidate the neural underpinnings of reward
      processing. The rewarding stimuli to be studied will be taste stimuli (small squirt of juice
      or chocolate) and a drug stimulus (intravenous methylphenidate (IV MPH)). For taste stimuli,
      cues will vary in sensory modality (visual vs. olfactory) and in novelty (well-known vs.
      novel). Novel and well-known cue stimuli will be included on each experimental day so the
      development of expectancy can be studied as the cue-taste pairing is learned and compared to
      the well-known cue-taste pairing. The MPH/saline injections will receive a written cue.

      Outcome Measures: BOLD fMRI signal to reward stimuli will be compared in the various cuing
      conditions.
    

Time perspective: Other
Keywords: fMRI; Methylphenidate; Taste; Olfaction; Addiction