Cortisol Effects on Emotional Memory: Independent of Stress Effects
PublisherThe University of Arizona.
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AbstractThe primary aim of this dissertation is to clarify how stressful experiences impact the formation of emotional memory. The first portion reviews historical evidence that numerous emotional memory phenomena, as well as conceptualizations thereof, span multiple cultural traditions and extend to ancient art and literature. Emotional memory phenomena involving stress-induced amnesia, such as psychogenic amnesia and recovered memories of trauma, is found to be less ubiquitous. The review of historical conceptualizations of emotional memory is followed by a review of modern research and theory, much of which is informed by animal models and cognitive neuroscience. These reviews provide a variety of testable hypotheses that are addressed by the three original experiments reported here. The first involved inducing stress in human subjects before they encoded emotional or neutral material, then assessing long-term memory and its relationship with salivary cortisol concentrations. The second involved administering different doses of cortisol to human subjects immediately before they encoded emotional or neutral material, then assessing long-term memory and its relationship with salivary cortisol concentrations. The third involved inducing stress in human subjects while presenting a combined memory encoding and fear conditioning task. Long-term episodic and fear memory were tested and compared with salivary cortisol concentrations. The experimental results indicated that mildly emotional stimuli formed stronger memories than indifferent stimuli, but that emotionally stressful experiences partially impeded the formation of memories about the experience, even while facilitating emotional learning (fear conditioning) during the experience. The results also indicated that the stress hormone cortisol was likely not responsible for the stress-induced memory alterations, disaffirming some popular theories and animal models. Rather, cortisol appeared to produce independent effects that dose-dependently promoted the storage of particular aspects of memory. The neurobiological underpinnings of these results and how the findings fit with historical and modern conceptualizations of emotional memory is discussed.