The differential effects of emotional salience on direct associative and relational memory during a nap

Abstract

Relational memories are formed from shared components between directly learned memory associations, flexibly linking learned information to better inform future judgments. Sleep has been found to facilitate both direct associative and relational memories. However, the impact of incorporating emotionally salient information into learned material and the interaction of emotional salience and sleep in facilitating both types of memory is unknown. Participants encoded two sets of picture pairs, with either emotionally negative or neutral objects paired with neutral faces. The same objects were present in both sets, paired with two different faces across the sets. Baseline memory for these directly paired associates was tested immediately after encoding, followed by either a 90-min nap opportunity or wakefulness. Five hours after learning, a surprise test assessed relational memory, the indirect association between two faces paired with the same object during encoding, followed by a retest of direct associative memory. Overall, negative information was remembered better than neutral for directly learned pairs. A nap facilitated both preservation of direct associative memories and formation of relational memories, compared to remaining awake. Interestingly, however, this sleep benefit was observed specifically for neutral directly paired associates, while both neutral and negative relational associations benefitted from a nap. Finally, REM sleep played opposing roles in neutral direct and relational associative memory formation, with more REM sleep leading to forgetting of direct associations but promoting relational associations, suggesting that, while not benefitting memory consolidation for directly learned details, REM sleep may foster the memory reorganization needed for relational memory.Keywords Emotion . Associative memory . Naps . Sleep . Inference . Relational memory In our encounters with the everyday stream of information, we do not encode and store all individual experiences in a veridical fashion. Rather, new information is integrated with old, and overlapping details are consolidated into schemata, or networks linked by common features of related memories, to flexibly form novel relationships (Eichenbaum, 2004;Eichenbaum & Cohen, 2001). We use these new representations derived from related memories to adaptively make inferential judgments about future experiences. However, our everyday experiences are not devoid of emotion. Emotional salience, defined by the valence (negative to positive) and arousal (calming to arousing) of an experience, is a biologically adaptive cue that can influence how an event is remembered and possibly how it is integrated in memory. In addition to the influence of emotion, sleep during the consolidation and integration period of a new memory may impact its fate. This experiment investigates the separate and interacting contributions of emotional salience and sleep to the consolidation of direct associative and relational memories, the indirect associations between two...

Setting the alarm: Word emotional attributes require consolidation to be operational.

“…They found a dissociation such that long-term memory for neutral-emotional pairs (tested after 30 minutes) did not benefit as much as neutral-only pairs from encoding in an integrative, as opposed to nonintegrative, fashion. A similar memory head-start was found in a recent nap study by Alger and Payne (2016).…”

“…and B-C" (e.g., Alger & Payne, 2016;Lau, Tucker, & Fishbein, 2010), here the binding element resides only in the spatio-temporal context of the session, in particular the fact that pictures with the same valence were all used as distractors for one another. Thus, to sum up, a true emotional Stroop interference (i.e., uncontaminated by stimulus idiosyncrasies) can be obtained from newly-learnt made-up words, as long as the test occurs after a consolidation interval, which most likely needs to include sleep.…”

Exploring the nap paradox: are mid-day sleep bouts a friend or foe?

“…However, recent work has demonstrated that REM plays a unique role in promoting relational memory [18]. When participants were presented with directly related images (eg, A – B and B – C) and a pair of indirectly rated images (A – C), REM sleep during a nap was positively correlated with memory for the related images, but correlated negatively with memory for the direct pairs.…”

“…Naps facilitate executive functioning [6,23,24], memory formation [10–18] subsequent learning [19,20] and emotional processing [21–25]. Yet, paradoxically, there are also a multitude of studies linking frequent napping with negative outcomes, especially in older populations [26–29].…”

Sleep selectively stabilizes contextual aspects of negative memories

“…These inconsistencies may be related to various experimental design factors (e.g., sleep vs. wake; full night vs. nap, split-night; sleep-deprivation; targeted memory reactivation), as well as the memory paradigm employed. Specifically, the clearer effect of sleep on hippocampus-dependent associative memories compared to item recognition could result in greater emotional benefits for memories with an associative component, but again, the available evidence is contradictory 25,[32][33][34] .…”