Abstract
Stress influences episodic memory formation via noradrenaline and glucocorticoid effects on amygdala and hippocampus. A common finding is the improvement of memory for central aspects of a stressful episode. This is putatively related to changes in the neural representations of specific experiences, i.e., their memory traces. Here we show that the memory improvement for objects that were encountered in a stressful episode relates to differences in the neural representations of these objects in the amygdala. Using functional magnetic resonance imaging, we found that stress specifically altered the representations of central objects: compared to control objects, they became more similar to one another and more distinct from objects that were not part of this episode. Furthermore, higher similarity of central objects to the main stressor-the faces of the stress-inducing committee members-predicted better memory. This suggests that the central objects were closely integrated into a stressor-centered memory representation. Our findings provide mechanistic insights into how stress shapes the memory trace and have profound implications for neurocognitive models of stressful and emotional memory.
Highlights
Psychosocial stress exerts profound effects on episodic memory encoding and consolidation.[1,2] Among others, stress induces the release of noradrenaline and glucocorticoids, which influence neural processing in amygdala, hippocampus, and various other brain regions.[3]
We show that the memory improvement for objects that were encountered in a stressful episode relates to differences in the neural representations of these objects in the amygdala
Conceptualization of similarities as distances in representational space high similarity similarity low the recognition memory test as well as during the functional magnetic resonance imaging (fMRI) recordings, we presented pictures of the 24 objects from the (f-)Trier social stress test (TSST) session together with 24 ‘‘difficult’’ distractors and 24 ‘‘easy’’ distractors
Summary
Psychosocial stress exerts profound effects on episodic memory encoding and consolidation.[1,2] Among others, stress induces the release of noradrenaline and glucocorticoids, which influence neural processing in amygdala, hippocampus, and various other brain regions.[3] Effects on activity in the amygdala seem to be important for memories of stressful and emotional events.[3,4] While stress during encoding may be detrimental,[5] several studies have shown that memory for central aspects of a stressful episode is enhanced, suggesting that stress exerts distinct influences on some memory contents and leaves others relatively unaffected.[5,6,7] how stress influences the neural representations of specific events has remained elusive, in particular in the human brain. Previous studies employed RSA to characterize how individual items are represented in human episodic memory[10,11] and showed how they are modulated by various cognitive and emotional factors that influence memory.[11,12]
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