Prediction Errors for Aversive Events Shape Long-Term Memory Formation through a Distinct Neural Mechanism.

Abstract

Prediction errors (PEs) have been known for decades to guide associative learning, but their role in episodic memory formation has been discovered only recently. To identify the neural mechanisms underlying the impact of aversive PEs on long-term memory formation, we used functional magnetic resonance imaging, while participants saw a series of unique stimuli and estimated the probability that an aversive shock would follow. Our behavioral data showed that negative PEs (i.e., omission of an expected outcome) were associated with superior recognition of the predictive stimuli, whereas positive PEs (i.e., presentation of an unexpected outcome) impaired subsequent memory. While medial temporal lobe (MTL) activity during stimulus encoding was overall associated with enhanced memory, memory-enhancing effects of negative PEs were linked to even decreased MTL activation. Additional large-scale network analyses showed PE-related increases in crosstalk between the "salience network" and a frontoparietal network commonly implicated in memory formation for expectancy-congruent events. These effects could not be explained by mere changes in physiological arousal or the prediction itself. Our results suggest that the superior memory for events associated with negative aversive PEs is driven by a potentially distinct neural mechanism that might serve to set these memories apart from those with expected outcomes.