Episodic integration under stress
Final Report Abstract
Integrating separate events into coherent episodes is a fundamental process of episodic memory, with important implications for clinical or education setting. Mnemonic integration relies critically on medial temporal and prefrontal areas, which are known to be sensitive to major stress mediators. Therefore, this project aimed to examine if and how impacts stress affects memory integration. To this end, we first exposed healthy participants to a standardized stressor or a control manipulation, before they completed a real life like narrative insight task in the MRI scanner. In this narrative insight task, participants first saw of series of video events. In a subsequent linking phase, some of the events were linked whereas others remained unlinked. Thereafter all events were presented again to determine whether the insight into the relationship between events changed their neural representation. We further tested participants’ memory for the presented events one week after encoding. Our results showed that, as expected, all participants gained insight into the relationship between events. At the neural level, however, stress reduced the activity of medial temporal and prefrontal areas when participants gained insight into the link between events. Moreover, stress abolished the insight-related increase in representational dissimilarity for linked events in the anterior part of the hippocampus as well as its association with measures of subsequent memory that we observed in non-stressed controls. Notably, memory performance, as assessed in a forced-choice recognition test, was even enhanced in the stress group. In addition to the influence of stress on the insight-driven memory integration, we tested whether this mnemonic integration is also dependent on whether the linking event is observed and imagined. Our data indicated that while insight via imagination was weaker than insight via direct observation, the imagination group showed better detail memory. Moreover, the imagination group showed no representational change in the anterior hippocampus or increases in frontal and striatal activity for the linked events, as was the case in the observation group. Together, the present findings provide novel insights into the mechanisms of mnemonic integration and their modulation by acute stress. Beyond their theoretical relevance, these findings could have relevant implications for understanding memory distortions in stress-related mental disorders as well as for educational settings, in which stress is common.
Publications
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Stress disrupts insight-driven mnemonic reconfiguration in the medial temporal lobe. NeuroImage, 265, 119804.
Grob, Anna-Maria; Milivojevic, Branka; Alink, Arjen; Doeller, Christian F. & Schwabe, Lars
