Impairing and enhancing effects of psychosocial stress on episodic memory and eyewitness report

Abstract

Research conducted over the past two decades has contributed a wealth of new knowledge to the field's understanding of stress effects on memory. It has been widely demonstrated that stress can either facilitate or impair memory, depending on 1) the phase of memory processing influenced by stress hormones and 2) the valence or arousing nature of the encoded information. It has also been reported that, when stress levels are significantly elevated at encoding, emotional memory is preserved (or enhanced) while memory for non-emotional information is impaired. These effects have been discussed at the neurobiological level with respect to the stress hormone, cortisol, and the impairing and facilitating modulatory effects it has on regions of the brain involved in emotional learning and memory. Whether diurnal shifts in basal levels of cortisol modulate these effects remains unknown. Additionally, it remains unknown whether enhancing and impairing effects of stress on memory result in memory traces that are more or less open to alteration by subsequent experiences, such as observed in the so-called "misinformation" effect.The current dissertation aimed to investigate the effects of stress on encoding of thematically negatively arousing and non-emotional events, composed of negatively arousing and neutral stimuli. Our goal in using more complex materials, in lieu of stimuli (e.g. word lists, images) traditionally used in studies of emotion and memory, was to examine the effects of stress on encoding of information more representative of a real-world event. Within this framework we examined 1) the effects of basal cortisol levels on stress modulation of memory encoding, and 2) the integration of subsequent misinformation on memory for negatively arousing versus non-arousing events encoded under stress. The research included in this dissertation aims to further the field's current understanding of the effects of stress on memory processes. Findings are relevant to the literature on traumatic memory, eyewitness testimony, and the effects of moderate to severe emotion on long-term episodic memory.