Summary: A new study reveals that intentional memory control—deciding what to remember or forget—is more powerful than emotional influence when forming long-term memories. Participants were more likely to recall words they were told to remember than those carrying emotional weight, even though emotion sometimes strengthened recall or caused false memories.
Interestingly, sleep itself did not enhance memory performance, though certain sleep brain waves, such as sleep spindles, were linked to better recall of emotional material. These findings suggest that conscious intention plays a stronger role than emotion or sleep in shaping what the brain stores and forgets.
Key Facts:
- Intent Beats Emotion: Directed memory (“remember this”) was more effective than emotional content for recall.
- Sleep Brain Waves Matter: Sleep spindles aided recall of emotional cues, but overall sleep had no major effect.
- False Memories: Negative emotional words increased the likelihood of recalling events that never occurred.
Source: Frontiers
A good night’s sleep has long been understood to help us consolidate new memories, but we don’t understand how.
Associations with negative feelings like fear or stress can improve recall, but intentionally trying to remember can also be effective. But these two mechanisms are very different — one involuntary, one deliberate.
Which influences memory most?
To investigate, researchers asked participants to remember or forget words, some of which had negative emotional associations. They found that instructions improved recall more than emotion.
“What we intend to remember and to forget can be powerful,” said Dr Laura Kurdziel of Merrimack College, lead author of the article in Frontiers in Behavioral Neuroscience. “We have more control over our memories than we often think we do.”
Sleep on it
Researchers performed two matching studies — one where 45 participants completed the task online, and one where 53 participants visited the lab. Half of each group received their words to remember in the morning and then tested their memories that evening.
The other half received their words in the evening and were tested on the following morning, after sleeping.
For the evening group of lab-based participants, the team supplied electroencephalogram (EEG) headbands that measured their brain activity while they slept. All participants took part in two sessions.
At the first session, participants watched 100 words appear on a screen, each followed by a cue to remember or forget. Half of the selected words had negative emotional connotations, and the other half were neutral.
Immediately afterwards, participants were shown another set of 100 words and asked if they recognized them. 50 of these were from the previous task, but 50 were ‘foils’ which they hadn’t seen before.
At the second session, 12 hours later, the scientists asked participants to report as many of the words they’d been asked to remember as possible. The scientists then analyzed the participants’ performance and EEG data.
Building a memory palace
They found that when it comes to memory, instructions do indeed work better than emotion. People were more likely to recall words they had been asked to remember. However, emotions did play a part: words participants had been asked to remember that had negative connotations were more likely to be remembered.
This suggests that although instructions were the primary influence on recall, emotional cues could amplify the effect of instructions. Emotions also increased the chances of false memories: negative foils were more likely to be misremembered as words participants had been asked to remember.
“During encoding, we will devote more attentional resources to words that we are told explicitly to remember,” said Kurdziel.
“Along similar lines, cognitive control systems can ‘tag’ information as relevant, biasing the hippocampus to prioritize it. This increases the likelihood that the memory will be reactivated during sleep and transferred to long-term storage.
“Lastly, instructions don’t just enhance relevant items, they also suppress irrelevant ones. By inhibiting competing memories, remember-cued items face less interference, which improves recall.”
Unexpectedly, whether participants had slept had no effect on how well they recalled words. However, the different types of brain wave activity measured by the EEG were linked to recall. For example, higher levels of REM theta power, a measure of REM sleep, were associated with the misremembering of negative foils.
“Sleep spindles were associated with better recall of negative, remember-cued words,” said Kurdziel, referring to a kind of brain wave that looks like a burst of spikes on the brain wave recordings. “Sleep spindles are widely implicated in the transfer of information from temporary hippocampal storage to more stable representations in the neocortex.”
“By contrast, slow wave sleep was negatively correlated with total recall,” Kurdziel continued.
“This was somewhat unexpected — slow wave sleep is often associated with improvements in declarative memory. However, it has also been theorized to facilitate active forgetting of irrelevant or redundant information.”
This could indicate that sleeping only consolidates some memories — prioritizing things you’re motivated to remember over things which are emotional — and that sleeping in general is less significant than your brain’s activity during sleep. However, more research is needed to confirm this.
“The number of participants who provided usable EEG data was relatively small, which reduces confidence in the strength of sleep–memory associations,” explained Kurdziel.
“Additionally, the sample consisted primarily of college students, making it difficult to generalize the findings to broader populations.”
Key Questions Answered:
A: Emotional content can enhance recall slightly but also increases false memories.
A: No general memory boost was found, though certain brain waves during sleep correlated with recall accuracy.
A: Intentionally deciding what to remember had the greatest impact on long-term recall.
About this memory and neuroscience research news
Author: Angharad Brewer Gillham
Source: Frontiers
Contact: Angharad Brewer Gillham – Frontiers
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Top-Down Instruction Outweighs Emotional Salience: Nocturnal Sleep Physiology Indicates Selective Memory Consolidation” by Laura Kurdziel et al. Frontiers in Behavioral Neuroscience
Abstract
Top-Down Instruction Outweighs Emotional Salience: Nocturnal Sleep Physiology Indicates Selective Memory Consolidation
Introduction: Sleep plays a crucial role in memory consolidation, not only stabilizing newly encoded information but also potentially supporting forgetting. Yet it remains unclear how sleep prioritizes what is retained or discarded when multiple salience cues, such as emotional valence and top-down instructional goals, compete for consolidation.
Methods: In two studies, we examined how emotional content and intentional memory instruction interact to shape memory performance across a 12 h interval that included either nocturnal sleep or wakefulness.
Participants completed a directed forgetting paradigm with neutral and negatively valenced words, followed by immediate recognition and delayed free recall.
Results: In both Study 1 (online) and Study 2 (in-lab), behavioral results showed that instruction to remember significantly enhanced recognition and recall, whereas emotion alone did not produce consistent benefits; however, sleep condition did not impact memory performance. In Study 2 (in-lab), which included overnight EEG monitoring, physiological markers of sleep revealed meaningful correlates of memory performance.
Specifically, sleep spindle activity predicted recall for negative remember-cued words, while Slow Wave Sleep (SWS) and delta power were negatively correlated with total recall, suggesting a trade-off between deep sleep and memory accessibility. REM theta power was associated with increased false recall of emotionally negative foils, consistent with emotional memory generalization.
Discussion: Importantly, these findings extend prior nap-based research by demonstrating that full-night sleep physiology reflects selective consolidation mechanisms even in the absence of overt behavioral effects. Overall, results underscore the primacy of top-down instruction over emotional salience in shaping memory, and highlight the utility of sleep physiology for understanding selective memory consolidation.
