The Effect of Intravenous Anesthetics on Fear Learning and Memory

Not Applicable

Completed

Interventions: Drug: Propofol 0.90mcg/mL
Drug: Thiopental 1.5mcg/mL
Drug: Thiopental 3mcg/mL
Drug: Propofol 0.45mcg/mL
Drug: Placebos

Brief Summary: 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: 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.

Recruitment & Eligibility

Inclusion Criteria

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.

Arm && Interventions