Stress as a mnemonic filter: Interactions between medial temporal lobe encoding processes and post-encoding stress

Hippocampus. 2017 Jan;27(1):77-88. doi: 10.1002/hipo.22674. Epub 2016 Nov 8.

Abstract

Acute stress has been shown to modulate memory for recently learned information, an effect attributed to the influence of stress hormones on medial temporal lobe (MTL) consolidation processes. However, little is known about which memories will be affected when stress follows encoding. One possibility is that stress interacts with encoding processes to selectively protect memories that had elicited responses in the hippocampus and amygdala, two MTL structures important for memory formation. There is limited evidence for interactions between encoding processes and consolidation effects in humans, but recent studies of consolidation in rodents have emphasized the importance of encoding "tags" for determining the impact of consolidation manipulations on memory. Here, we used functional magnetic resonance imaging in humans to test the hypothesis that the effects of post-encoding stress depend on MTL processes observed during encoding. We found that changes in stress hormone levels were associated with an increase in the contingency of memory outcomes on hippocampal and amygdala encoding responses. That is, for participants showing high cortisol reactivity, memories became more dependent on MTL activity observed during encoding, thereby shifting the distribution of recollected events toward those that had elicited relatively high activation. Surprisingly, this effect was generally larger for neutral, compared to emotionally negative, memories. The results suggest that stress does not uniformly enhance memory, but instead selectively preserves memories tagged during encoding, effectively acting as mnemonic filter. © 2016 Wiley Periodicals, Inc.

Keywords: emotional memory; functional magnetic resonance imaging; stress.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amygdala / diagnostic imaging
  • Amygdala / physiopathology*
  • Analysis of Variance
  • Brain Mapping
  • Cold Temperature
  • Functional Laterality
  • Hippocampus / diagnostic imaging
  • Hippocampus / physiopathology*
  • Humans
  • Hydrocortisone / metabolism
  • Magnetic Resonance Imaging
  • Male
  • Memory / physiology*
  • Neuropsychological Tests
  • Pattern Recognition, Visual / physiology
  • Random Allocation
  • Regression Analysis
  • Saliva / metabolism
  • Stress, Physiological / physiology
  • Stress, Psychological / diagnostic imaging
  • Stress, Psychological / physiopathology*
  • Temporal Lobe / diagnostic imaging
  • Temporal Lobe / physiopathology*
  • Young Adult

Substances

  • Hydrocortisone