Flashbulb memories represent a unique phenomenon linking research on cognition with research on emotion, yet most studies on this phenomenon have characterized collective events that are negative and unexpected in nature. In contrast, the 2016 American election of Donald Trump was a public, culturally-shared event, eliciting extreme emotional responses that were positive for some individuals but negative for others, as well as varying levels of surprise. We longitudinally evaluated autobiographical memories for Election Night 2016 in a large online sample of Clinton supporters, Trump supporters, and third-party/non-voters over a 12-month period, in terms of both objective memory metrics (information quantity and memory consistency) and subjective memory metrics (including memory confidence, metacognition, and sensory experience). Emotional responses to the election outcome varied widely, with Clinton supporters reporting highly negative responses, Trump supporters reporting highly positive responses, and third-party/non-voters reporting mildly negative responses. Emotional intensity was enhanced in surprised versus non-surprised individuals. Relative to third-party/non-voters, Clinton and Trump supporters reported greater memory vividness, event importance, and sensory experience. Additionally, limited valence effects on subjective memory were observed (including higher memory confidence in Trump supporters and higher memory rehearsal in Clinton supporters). These differences in subjective experience were observed despite similar levels of information quantity and consistency as a function of valence. This characterization of memories for surprising positive events suggests they share many of the paradoxical qualities of memories for negative events often discussed as "flashbulb memories", but also points to potential differences in memory phenomenology for personal versus collectively-experienced events.

Stress can powerfully influence episodic memory, often enhancing memory encoding for emotionally salient information. These stress-induced memory enhancements stand at odds with demonstrations that stress and the stress-related hormone cortisol can negatively affect the hippocampus, a brain region important for episodic memory encoding. To resolve this apparent conflict and determine whether and how the hippocampus supports memory encoding under cortisol, we combined behavioral assays of associative memory, high-resolution functional magnetic resonance imaging (fMRI), and pharmacological manipulation of cortisol in a within-participant, double-blinded procedure. Hydrocortisone led to enhanced functional connectivity between hippocampal subregions, which predicted subsequent memory enhancements for emotional information. Cortisol also modified the relationship between hippocampal representations and memory: whereas hippocampal signatures of distinctiveness predicted memory under placebo, relative integration predicted memory under cortisol. Together, these data provide novel evidence that the human hippocampus contains the necessary machinery to support emotional memory enhancements under stress.