Negative emotional content disrupts the coherence of episodic memories

Abstract

Events are thought to be stored in episodic memory as coherent representations, in which the constituent elements are bound together so that a cue can trigger reexperience of all elements via pattern completion. Negative emotional content can strongly influence memory, but opposing theories predict strengthening or weakening of memory coherence. Across a series of experiments, participants imagined a number of person-location-object events with half of the events including a negative element (e.g., an injured person), and memory was tested across all within event associations. We show that the presence of a negative element reduces memory for associations between event elements, including between neutral elements encoded after a negative element. The presence of a negative element reduces the coherence with which a multimodal event is remembered. Our results, supported by a computational model, suggest that coherent retrieval from neutral events is supported by pattern completion, but that negative content weakens associative encoding which impairs this process. Our findings have important implications for understanding the way traumatic events are encoded and support therapeutic strategies aimed at restoring associations between negative content and its surrounding context. (PsycINFO Database Record

Figure 1

Memory for events encoded with simultaneously presented elements. (a) In Experiment 1, each encoding trial included three separate event elements (location, person and object) presented simultaneously and followed by a 2 s intertrial interval (ITI). At retrieval, a cue image was presented and participants were required to respond whether the image was old or new. If old, the participant was then presented with six options and instructed to select the image that had been originally presented with the cue image at encoding (see Methods). (b) Recognition accuracy for each element type (hits minus misses) was compared between neutral and negative events (collapsed across first and second presentation during test). (c) Associative memory performance for neutral and negative events split by the different element pair types for each event (collapsed across testing direction; chance performance = 0.17). (d) Dependency in the data was compared to independent and dependent models across neutral and negative events. Error bars represent standard error; NS = not significant. ** p = .001. *** p < .001.

Figure 2

Memory for events encoded as overlapping pairs. (a) For Experiment 2, each event was encoded over three separate blocks (i.e., separated by encoding trials for other events). Events were either encoded with the location-object pair presented on the first encoding trial (person-last encoding order) or as the final encoding trial (person first encoding order). Associative memory was testing in a similar way to Experiment 1. (b) Associative memory performance for each encoded pair across neutral and negative events split by the person-last encoding order (upper panel, location-object studied first) and person-first encoding order (lower panel, object-person studied first). Note that the person image was always the negative element within negative events. (c) Dependency for the data and the independent and dependent models, across neutral and negative events split by person-last and person-first encoding orders. Note the overall decrease in dependency from neutral to negative events. Error bars represent standard error; NS = not significant. ** p ≤ .01. *** p < .001.

Figure 3

Memory for events following a 24hr delay. a, Associative memory performance across each pair type at encoding across neutral and negative events split by the person-last encoding order (location-object pair studied first) and person-first encoding order (object-person pair studied first). b, Dependency results for neutral and negative events following a 24-hour delay between encoding and test, split by the person-last and person-first encoding orders. Error bars represent standard error; NS = not significant. ** p < .01. *** p < .001.

Figure 4

Model of associative learning and simulated results. (a) Performance and (b) Coherence (statistical dependency between retrievals from the same event) for each event type and encoding order (whether the negative element or person was presented last or first). (c) During encoding, negative events are constructed from three pairwise associations, one of which contains two neutral elements. Associative learning is reduced when the negative element (always a person) is active, so associations involving the negative element are weaker than those involving neutral events, reducing pattern completion, performance and dependency. If the neutral pair is presented after one or more negative-neutral pairs (the Negative-First Order), reactivation of the negative element can occur via the associations already learned to it, weakening the association formed between the neutral elements, further reducing pattern completion, performance and dependency.