Effects of Stress Hormones on Emotion and Cognition

Overview

The purpose of this study is to examine how hormonal changes that occur during stressful situations affect thought and emotions. Results from this study may lead to treatments that can alleviate the psychological effects of trauma. Levels of cortisol and norepinephrine increase in response to stress; these hormones also influence thought processes. This study will give hydrocortisone and/or yohimbine (a stimulator of central norepinephrine) to healthy adults in order to model the stress response and to better understand the way people process information during traumatic events. This study comprises two experiments in which the stress response is pharmacologically modeled. Participants in the study will have two study visits. During Visit 1, participants will undergo a psychiatric assessment, complete neuropsychological tasks, and have their IQ measured. During Visit 2, participants will be given hydrocortisone and/or yohimbine. Blood will be collected before and during this. Participants will then perform two experiments. In one experiment, participants will hear a story with emotional and non-emotional segments; in a second experiment, participants will view both emotional and non-emotional stimuli.

Memories for traumatic events are fundamentally different from typical memories. Individuals who witness or are involved in an extremely stressful event, such as a robbery or a violent act, retain highly accurate memories for the information directly related to the trauma (e.g., a gun or verbal threat), while surrounding details are poorly remembered. This so-called weapon focus phenomenon has been found in both naturalistic and laboratory studies with humans. However, difficulties with the control of naturalistic studies and approximating trauma in the lab limit the validity of these findings. Neurophysiologically, cortisol and norepinephrine are principal mediators of the stress response, and both influence memory function. In particular, cortisol improves memory at low levels but impairs memory at higher doses. Similarly, some evidence indicates that norepinephrine also enhances memory in low doses and either impairs or does not influence memory at high doses. Much of the experimental work in this area has been conducted with animals. Studies have recently begun to extend these paradigms to humans. To better understand memory processing during trauma, hydrocortisone and/or yohimbine (a stimulator of central norepinephrine) will be administered to healthy adults in two experiments in order to pharmacologically model the stress response. Following infusion, participants will hear a story with emotional and nonemotional segments in one experiment (N = 80) and emotional as well as nonemotional stimuli (faces and scenes) in another experiment (N = 80). It is predicted that relative to the placebo, hydrocortisone will impair memory for both emotional and nonemotional information, yohimbine will improve memory for both types of information, and the combination of hydrocortisone and yohimbine will enhance memory for emotional aspects and impair memory for the nonemotional segments of the story. Results from this study will permit a better understanding of how emotionally charged memories are encoded and will potentially lead to treatments to mitigate the psychological effects of traumatic exposure.