The Effect of Intravenous Anesthetics on Fear Learning and Memory

Study Overview
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Brief Summary
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People often develop fearful responses to things, but have no conscious control over the fear. This is a basic form of unconscious memory, called fear conditioning. Intravenous anesthetic drugs have remarkable effects on conscious memory, but it is unknown whether they have similar effects on these unconscious fear memories. To address this question, the investigators will study 114 healthy adult volunteer subjects. The subject is given a very low dose of an anesthetic drug intravenously (i.e. through the bloodstream). The dose is so low that the subject might not even be able tell if they are getting the drug. While they are receiving the drug, the subject will perform a series of memory tests and a fear conditioning experiment, which are set up like a very simple computer game. To create the fear response, subjects will occasionally receive a mildly uncomfortable shock to their arm. The subject is able to determine the highest level of shock that they will receive. The investigators are doing this study because the investigators wish to know exactly how the drugs affect the way people process fear and emotion. This knowledge might one day be used in the treatment of some psychiatric disorders.

Detailed Description
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People often develop fearful responses to things, but have no conscious control over the fear (e.g. phobias). This is a basic form of unconscious memory, called fear conditioning. Intravenous anesthetic drugs have remarkable effects on conscious memory, but it is unknown whether they have similar effects on these unconscious fear memories. To address this question, the investigators will study 114 healthy adult volunteer subjects. The subject is given a very low dose of an anesthetic drug intravenously (i.e. through the bloodstream). The dose is so low that the subject might not even be able tell if they are getting the drug. While they are receiving the drug, the subject will perform a series of memory tests and a fear conditioning experiment, which are set up like a very simple computer game. To create the fear response, subjects will occasionally receive a mildly uncomfortable shock to their arm. The subject is able to determine the highest level of shock that they will receive. The investigators are doing this study because the investigators wish to know exactly how the drugs affect the way people process fear and emotion. This knowledge might one day be used in the treatment of some psychiatric disorders.

Official Title
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The Effect of Intravenous Anesthetics on Fear Learning and Memory

Conditions
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Phobias

Intervention / Treatment
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* Drug: Placebos
* Drug: Propofol 0.45mcg/mL
* Drug: Propofol 0.90mcg/mL
* Drug: Thiopental 1.5mcg/mL
* Drug: Thiopental 3mcg/mL


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: age between 18 and 50 minimum of high school education fluent in English normal vocabulary Exclusion Criteria: any significant medical or psychiatric comorbidity (e.g. asthma, diabetes, hypertension, depression, high anxiety)--subjects must be in excellent health such that they would be classified as American Society of Anesthesiologists Physical Status Class I deficit in vision or hearing that would impede the study allergies to any of the study drugs, to soybeans, or to eggs a history of head trauma a family history of major psychiatric illness body mass index > 30 kg/m2 a recent history of recreational drug use prior exposure to the study materials pregnancy a personal or family history of any porphyria failure to exhibit a skin conductance response to deep inspiration the ability to read Chinese characters assessment by the investigators that the subject may be unable to cooperate or comply with the study requirements.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Placebo Comparator: Placebos<br>Saline Infusion | Drug: Placebos<br>* IV Saline infusion for 2 hours.<br>|
| Active Comparator: Propofol 0.45mcg/mL<br>Anesthetic Drug Infusion | Drug: Propofol 0.45mcg/mL<br>* IV Propofol infusion for 2 hours.<br>* Other names: Propofol;|
| Active Comparator: Propofol 0.90mcg/mL<br>Anesthetic Drug Infusion | Drug: Propofol 0.90mcg/mL<br>* IV Propofol infusion for 2 hours.<br>* Other names: Propofol;|
| Active Comparator: Thiopental 1.5mcg/mL<br>Anesthetic Drug Infusion | Drug: Thiopental 1.5mcg/mL<br>* IV Thiopental 1.5mcg/mL infusion for 2 hours<br>* Other names: Thiopental;|
| Active Comparator: Thiopental 3mcg/mL<br>Anesthetic Drug Infusion | Drug: Thiopental 3mcg/mL<br>* IV Thiopental 3mcg/mL infusion for 2 hours<br>* Other names: Thiopental;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| GSR Trial 1 | Galvanic skin repose (GSR) to the first habituation trial (yes/no). Coding: Yes (0) and No (1) | First Trial, for up to 1 day | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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anesthetic drugs, associative memory, fear