Brief wakeful resting boosts new memories over the long term

New in, old out: Does learning a new language make you forget previously learned foreign languages?

Anecdotal evidence suggests that learning a new foreign language (FL) makes you forget previously learned FLs. To seek empirical evidence for this claim, we tested whether learning words in a previously unknown L3 hampers subsequent retrieval of their L2 translation equivalents. In two experiments, Dutch native speakers with knowledge of English (L2), but not Spanish (L3), first completed an English vocabulary test, based on which 46 participant-specific, known English words were chosen. Half of those were then learned in Spanish. Finally, participants' memory for all 46 English words was probed again in a picture naming task. In Experiment 1, all tests took place within one session. In Experiment 2, we separated the English pre-test from Spanish learning by a day and manipulated the timing of the English post-test (immediately after learning vs. 1 day later). By separating the post-test from Spanish learning, we asked whether consolidation of the new Spanish words would increase their interference strength. We found significant main effects of interference in naming latencies and accuracy: Participants speeded up less and were less accurate to recall words in English for which they had learned Spanish translations, compared with words for which they had not. Consolidation time did not significantly affect these interference effects. Thus, learning a new language indeed comes at the cost of subsequent retrieval ability in other FLs. Such interference effects set in immediately after learning and do not need time to emerge, even when the other FL has been known for a long time.

Sex-dependent impact of a short rest after lunch on hemodynamics as assessed by Doppler sonography

PURPOSE

Taking a short rest after lunch suppresses increases in blood flow to the digestive organs and maintains blood flow to the brain in the afternoon, possibly providing beneficial effects in preventing post-prandial drowsiness. The present study investigated sex-dependent influences on changes in hemodynamics produced by taking a short rest after lunch.

METHODS

Subjects comprised 20 healthy young adults (10 men, 10 women; mean age 21 ± 1 years). Doppler sonography was performed to measure blood flow in the superior mesenteric artery (SMA) and common carotid artery (CCA) before and after lunch every hour on each day, with and without a 15-min rest with eyes closed after lunch. Blood pressure and heart rate (HR) were also measured.

RESULTS

For both men and women, peak systolic velocity (PSV) in the SMA was suppressed by taking a rest. PSV in the CCA in men was increased at 0.5 h after lunch in the resting condition but was decreased in the non-resting condition (median 109%, interquartile range [IQR] 102-120% vs. median 98%, IQR 90-107%; P = 0.037). No such differences were observed in women. Although post-prandial increases in HR were observed in women, a similar increase was only found for men in the resting condition.

CONCLUSION

An increase in CCA blood flow was observed only in men. The present study suggests that a short rest after lunch could better promote the maintenance of blood flow to the brain in men than in women.

Post-encoding task engagement not attentional load is detrimental to awake consolidation

The fate of new memories depends partly on the cognitive state experienced immediately following encoding. Wakeful rest, relative to task engagement, benefits retention and this effect is typically explained through a consolidation account: rest is theorised to provide a state of minimal interference, which would otherwise disrupt consolidation. Yet, the determinants of consolidation interference, notably the contribution of attention, remain poorly characterised. Through a repeated measures design, we investigated attention load's impact on consolidation. In three phases, participants encountered a set of nonwords and underwent immediate recognition testing, experienced a 5-min delay condition, and completed a delayed recognition test for the nonwords. This cycle repeated for each phase before proceeding to the next. Delay conditions comprised of wakeful rest and two sustained attention to response tasks (SART) that were of low (SART-fixed) and high (SART-random) attention load. Immediate memory was matched across conditions, but delayed recognition was poorer after completing the SART-fixed and SART-random conditions, relative to rest. There was no difference between the two SART conditions. These data provide insights into the factors that contribute to the success of consolidation and indicate that the attention load of a task does not determine the magnitude of consolidation interference and associated forgetting.

Effect of cognitive load on time spent offline during wakefulness

Humans continuously alternate between online attention to the current environment and offline attention to internally generated thought and imagery. This may be a fundamental feature of the waking brain, but remains poorly understood. Here, we took a data-driven approach to defining online and offline states of wakefulness, using machine learning methods applied to measures of sensory responsiveness, subjective report, electroencephalogram (EEG), and pupil diameter. We tested the effect of cognitive load on the structure and prevalence of online and offline states, hypothesizing that time spent offline would increase as cognitive load of an ongoing task decreased. We also expected that alternation between online and offline states would persist even in the absence of a cognitive task. As in prior studies, we arrived at a three-state model comprised of one online state and two offline states. As predicted, when cognitive load was high, more time was spent online. Also as predicted, the same three states were present even when participants were not performing a task. These observations confirm our method is successful at isolating seconds-long periods of offline time. Varying cognitive load may be a useful way to manipulate time spent in at least one of these offline states in future experimental studies.

An online experiment that presents challenges for translating rest-related gains in visual detail memory from the laboratory to naturalistic settings

New memories are labile and consolidate over time. Contemporary findings demonstrate that, like sleep, awake quiescence supports consolidation: people remember more new memories if they experience a brief period of post-encoding quiet rest than sensory processing. Furthermore, it was recently demonstrated that the quality of new memories can also be enhanced significantly by awake quiescence. This phenomenon offers great applied potential, for example, in education and eyewitness testimony settings. However, the translation of rest-related gains from the laboratory to everyday life remains poorly characterised and findings are mixed. Here, we report follow-on evidence demonstrating that rest-related gains in visual detail memory may be more challenging to achieve in naturalistic than laboratory-based settings. In contrast to established laboratory findings, using an online version of an established consolidation paradigm, we observed no memory benefit of post-encoding quiescence, relative to an engaging perceptual task, in the retention of detailed visual memories as measured through a lure discrimination task. This null finding could not be explained by intentional rehearsal in those who rested or between-group differences in participants' demographics or mental state, including fatigue and mood. Crucially, post-experimental reports indicated that those in the rest group experienced challenges in initiating and maintaining a state of quiescence, which may account for our null finding. Based on these findings, we propose three areas of focus for future work should rest-related gains in memory be translated from the lab to field: (1) to establish the specific environmental and individual conditions that are conducive and detrimental to awake consolidation, (2) to understand the barriers to initiating and maintaining a state of quiescence in naturalistic settings, and (3) to examine how knowledge of quiescence and its cognitive benefits can encourage the initiation and maintenance of states that are conductive to awake consolidation.

Memory Consolidation during Ultra-short Offline States

Traditionally, neuroscience and psychology have studied the human brain during periods of "online" attention to the environment, while participants actively engage in processing sensory stimuli. However, emerging evidence shows that the waking brain also intermittently enters an "offline" state, during which sensory processing is inhibited and our attention shifts inward. In fact, humans may spend up to half of their waking hours offline [Wamsley, E. J., & Summer, T. Spontaneous entry into an "offline" state during wakefulness: A mechanism of memory consolidation? Journal of Cognitive Neuroscience, 32, 1714-1734, 2020; Killingsworth, M. A., & Gilbert, D. T. A wandering mind is an unhappy mind. Science, 330, 932, 2010]. The function of alternating between online and offline forms of wakefulness remains unknown. We hypothesized that rapidly switching between online and offline states enables the brain to alternate between the competing demands of encoding new information and consolidating already-encoded information. A total of 46 participants (34 female) trained on a memory task just before a 30-min retention interval, during which they completed a simple attention task while undergoing simultaneous high-density EEG and pupillometry recording. We used a data-driven method to parse this retention interval into a sequence of discrete online and offline states, with a 5-sec temporal resolution. We found evidence for three distinct states, one of which was an offline state with features well-suited to support memory consolidation, including increased EEG slow oscillation power, reduced attention to the external environment, and increased pupil diameter (a proxy for increased norepinephrine). Participants who spent more time in this offline state following encoding showed improved memory at delayed test. These observations are consistent with the hypothesis that even brief, seconds-long entry into an offline state may support the early stages of memory consolidation.

Individual differences in sensory processing sensitivity amplify effects of post-learning activity for better and for worse

Sensory processing sensitivity (SPS) is a biologically-based trait associated with greater reactivity to both positive and negative environments. Recent studies suggest that the activity following learning can support or hinder memory retention. Here, we employed a within-subject experiment to examine whether and how individual differences in SPS contribute to differences in memory retention. Sixty-four participants encoded and immediately recalled two word lists: one followed by 8-min of eyes-closed, wakeful resting; and the other by a distraction task. After 7 days, participants completed a surprise free recall test for both word lists. If participants wakefully rested after encoding, memory retention increased as a function of higher SPS. However, in the distraction condition, a negative curvilinear relationship indicated that memory retention was especially hindered for highly sensitive individuals. These results suggest that individual differences in SPS are an important factor to consider when examining the effects of environmental conditions on learning and memory.

Understanding the Need for Sleep to Improve Cognition

The restorative function of sleep is shaped by its duration, timing, continuity, subjective quality, and efficiency. Current sleep recommendations specify only nocturnal duration and have been largely derived from sleep self-reports that can be imprecise and miss relevant details. Sleep duration, preferred timing, and ability to withstand sleep deprivation are heritable traits whose expression may change with age and affect the optimal sleep prescription for an individual. Prevailing societal norms and circumstances related to work and relationships interact to influence sleep opportunity and quality. The value of allocating time for sleep is revealed by the impact of its restriction on behavior, functional brain imaging, sleep macrostructure, and late-life cognition. Augmentation of sleep slow oscillations and spindles have been proposed for enhancing sleep quality, but they inconsistently achieve their goal. Crafting bespoke sleep recommendations could benefit from large-scale, longitudinal collection of objective sleep data integrated with behavioral and self-reported data.

Do naps benefit novel word learning? Developmental differences and white matter correlates

Memory representations of newly learned words undergo changes during nocturnal sleep, as evidenced by improvements in explicit recall and lexical integration (i.e., after sleep, novel words compete with existing words during online word recognition). Some studies have revealed larger sleep-benefits in children relative to adults. However, whether daytime naps play a similar facilitatory role is unclear. We investigated the effect of a daytime nap (relative to wake) on explicit memory (recall/recognition) and lexical integration (lexical competition) of newly learned novel words in young adults and children aged 10-12 years, also exploring white matter correlates of the pre- and post-nap effects of word learning in the child group with diffusion weighted MRI. In both age groups, a nap maintained explicit memory of novel words and wake led to forgetting. However, there was an age group interaction when comparing change in recall over the nap: children showed a slight improvement whereas adults showed a slight decline. There was no evidence of lexical integration at any point. Although children spent proportionally more time in slow-wave sleep (SWS) than adults, neither SWS nor spindle parameters correlated with over-nap changes in word learning. For children, increased fractional anisotropy (FA) in the uncinate fasciculus and arcuate fasciculus were associated with the recognition of novel words immediately after learning, and FA in the right arcuate fasciculus was further associated with changes in recall of novel words over a nap, supporting the importance of these tracts in the word learning and consolidation process. These findings point to a protective role of naps in word learning (at least under the present conditions), and emphasize the need to better understand both the active and passive roles that sleep plays in supporting vocabulary consolidation over development.

Cognitive Enhancement through Differential Rope Skipping after Math Lesson

Numerous studies have shown cognitive enhancement through sport and physical exercise. Despite the variety of studies, the extent to which physical activity before or after a cognitive learning session leads to more effective cognitive enhancement remains largely unresolved. Moreover, little attention has been paid to the dependence of the motor learning approach then applied. In this study, we compare the influence of differential with uniformly rope skipping directly succeeding an acquisition phase in arithmetic mathematics. For three weeks 26 pupils, 14 female, 12 male, and 13.9 ± 0.7 years old, completed nine 15 min exercises in arithmetic math, each followed by 3 min rope skipping with heart rate measurement. Arithmetic performance was tested in a pre-, post- and retention test design. The results showed a statistically significant difference between the differential and the control groups within the development of arithmetic performance, especially in the retention test. There was no statistical difference in heart rate. It is suggested that the results provide evidence for sustainable improvements of cognitive learning performance by means of highly variable rope skipping.

Wakeful Rest Benefits Recall, but Not Recognition, of Incidentally Encoded Memory Stimuli in Younger and Older Adults

Older adults exhibit deficits in episodic memory tasks, which have often been attributed to encoding or retrieval deficits, with little attention to consolidation mechanisms. More recently, researchers have attempted to measure consolidation in the context of a behavioral experiment using the wakeful rest paradigm (i.e., a brief, quiet period of minimal stimulation, which facilitates memory performance, compared to a distractor task). Critically, older adults might not produce this effect, given established age differences in other episodic memory processes and mind-wandering. In three experiments, we directly compared younger and older adults in modified versions of the wakeful rest paradigm. Critically, we utilized incidental encoding procedures (all experiments) and abstract shape stimuli (in Experiment 3) to limit the possibility of retrieval practice or maintenance rehearsal as potential confounding mechanisms in producing the wakeful rest effect. Wakeful rest reliably and equally benefited recall of incidentally encoded words in both younger and older adults. In contrast, wakeful rest had no benefit for standard accuracy measures of recognition performance in verbal stimuli, although there was an effect in response latencies for non-verbal stimuli. Overall, these results suggest that the benefits of wakeful rest on episodic retrieval are preserved across age groups, and hence support age-independence in potential consolidation mechanisms as measured by wakeful rest. Further, these benefits do not appear to be dependent on the intentionality of encoding or variations in distractor task types. Finally, the lack of wakeful rest benefits on recognition performance might be driven by theoretical constraints on the effect or methodological limitations of recognition memory testing in the current paradigm.

The effects of wakeful rest on memory consolidation in an online memory study

Memory consolidation is the process in which memory traces are strengthened over time for later retrieval. Although some theories hold that consolidation can only occur during sleep, accumulating evidence suggests that brief periods of wakeful rest may also facilitate consolidation. Interestingly, however, Varma and colleagues reported that a demanding 2-back task following encoding produced a similar performance to a wakeful reset condition. We tested whether participants' recall would be best following a wakeful rest condition as compared to other distractor conditions, consistent with the extant wakeful rest literature, or whether we would replicate the finding by Varma and colleagues such that participants' memory benefitted from both a rest and a 2-back task following encoding. Across two experiments, we used similar (Experiment 1) and the same (Experiment 2) encoding material as used the one by Varma and colleagues, employed a wakeful rest condition adapted for online testing, and compared participants' recall across post-encoding conditions. In the first experiment, we used a between-subjects design and compared participants' cued recall performance following a period of wakeful rest, a 2-back task, or a rest + sounds condition. The second experiment more closely replicated the experimental design used by Varma and colleagues using a within-subjects manipulation. Ultimately, our findings more consistently aligned with the canonical wakeful rest finding, such that recall was better following the rest condition than all other post-encoding conditions. These results support the notion that wakeful rest may allow for consolidation by protecting recently encoded information from interference, thereby improving memory performance.

Listening to Music and Playing Activities during Recreation between Lessons Regenerate Children's Cognitive Performance at Different Times of Day

The interruption of learning processes by breaks filled with diverse activities is common in everyday life. The purpose of this study was to investigate the effects of the time of day (TOD) of playing with or without music during recess on cognitive performance regeneration among students aged between 11 and 12. Twenty-seven volunteer children (aged 12 ± 0.6 years) completed four trials at 09h45, 10h15, 14h45, and 15h15. Each test session was separated by recreation between classroom lessons with different conditions: music only (MSC), playing only (PAY), music and playing (MSC-PAY), and without music and playing (NON). During each session, oral temperature, reaction time (RT), and constant attention (CA) were measured. For all parameters, the ANOVA revealed a significant effect of the type of activity. However, no significant effect of the TOD and no significant interaction of type of activity × TOD were reported. The Bonferroni post hoc test revealed that Δ-core temperature was significantly higher during PAY and MSC-PAY compared to NON (p < 0.05). Δ-attention was higher during MSC, PAY, and MSC-PAY compared to NON (p < 0.001). Δ-attention was lower during MSC (p < 0.05), PAY (p < 0.05), and MSC-PAY (p < 0.01) compared to NON. Therefore, playing, listening to music, and playing while listening to music at recess improve the child’s ability to regenerate cognitive performance regardless of the TOD.

Wakeful resting and listening to music contrast their effects on verbal long-term memory in dependence on word concreteness

Wakeful resting and listening to music are powerful means to modulate memory. How these activities affect memory when directly compared has not been tested so far. In two experiments, participants encoded and immediately recalled two word lists followed by either 6 min wakefully resting or 6 min listening to music. The results of Experiment 1 show that both post-encoding conditions have a similar effect on memory after 1 day. In Experiment 2, we explored the possibility that less concrete words, i.e. lower in imageability than in Experiment 1, are differently affected by the two post-encoding conditions. The results of Experiment 2 show that, when words are less concrete, more words are retained after 1 day when encoding is followed by wakeful resting rather than listening to music. These findings indicate that the effects of wakeful resting and listening to music on memory consolidation are moderated by the concreteness of the encoded material.

Is the role of sleep in memory consolidation overrated?

Substantial empirical evidence suggests that sleep benefits the consolidation and reorganization of learned information. Consequently, the concept of "sleep-dependent memory consolidation" is now widely accepted by the scientific community, in addition to influencing public perceptions regarding the functions of sleep. There are, however, numerous studies that have presented findings inconsistent with the sleep-memory hypothesis. Here, we challenge the notion of "sleep-dependency" by summarizing evidence for effective memory consolidation independent of sleep. Plasticity mechanisms thought to mediate or facilitate consolidation during sleep (e.g., neuronal replay, reactivation, slow oscillations, neurochemical milieu) also operate during non-sleep states, particularly quiet wakefulness, thus allowing for the stabilization of new memories. We propose that it is not sleep per se, but the engagement of plasticity mechanisms, active during both sleep and (at least some) waking states, that constitutes the critical factor determining memory formation. Thus, rather than playing a "critical" role, sleep falls along a continuum of behavioral states that vary in their effectiveness to support memory consolidation at the neural and behavioral level.

A new angle on mental rotation ability in transgender men: Modulation by ovarian milieu

Organizational/activational theory posits that transgender individuals should perform in the direction of their gender, not their sex, on cognitive tasks that show sex differences-the largest of which are observed on visuospatial tasks. Yet, tests of this hypothesis have been mixed for transgender men (TM). One possible reason is that performance shifts associated with the hormonal milieu at testing have not been fully considered in TM. Although "activating" influences, like gender-affirming hormone therapy (GAHT), are well-characterized in this population, endogenous ones, like ovarian cycling, have gone unaddressed. To provide a more complete picture of hormonal activation, we explored an influence of ovarian milieu on visuospatial performance of TM, and its potential contributions toward effects of sex and GAHT. We administered two male-favoring mental rotation tests (MRTs), and a sex-neutral control task to 22 TM naïve to GAHT (TM-), 29 TM receiving GAHT (TM+), and cisgender men (CM; n = 24) and women (CW; n = 43), testing cycling men (TM-) and women (CW) in either early follicular phase (Follicular) or midluteal phase (Luteal). On MRTs, performance of TM- varied across the menstrual cycle, and matched that of menstrual phase-matched CW. Additionally, cycling individuals in Follicular performed as strongly as TM+ and CM, all of whom performed above individuals in Luteal. Effects did not extend to a verbal control task, on which TM+ performed below others. Rather than conforming to static categories that suggest sex- or gender-typical organization of cognitive circuits, our findings support dynamic shifts in visuospatial ability of TM, and illustrate the need to consider activating effects of hormones beyond GAHT.

Evidence for superior encoding of detailed visual memories in deaf signers

Recent evidence shows that deaf signers outperform hearing non-signers in some tests of visual attention and discrimination. Furthermore, they can retain visual information better over short periods, i.e., seconds. However, it is unknown if deaf signers’ retention of detailed visual information is superior following more extended periods. We report a study investigating this possibility. Our data revealed that deaf individuals outperformed hearing people in a visual long-term memory test that probed the fine detail of new memories. Deaf individuals also performed better in a scene-discrimination test, which correlated positively with performance on the long-term memory test. Our findings provide evidence that deaf signers can demonstrate superior visual long-term memory, possibly because of enhanced visual attention during encoding. The relative contributions of factors including sign language fluency, protracted practice, and neural plasticity are still to be established. Our findings add to evidence showing that deaf signers are at an advantage in some respects, including the retention of detailed visual memories over the longer term.

The Birth of the Mammalian Sleep

Simple Summary

Mammals evolved from reptiles as a consequence of an evolutionary bottleneck. Some diurnal reptiles extended their activity, first to twilight and then to the entire dark time. This forced the change of the visual system. Pursuing maximal sensitivity, they abandoned the filters protecting the eyes against the dangerous diurnal light, which, in turn, forced immobility in lightproof burrows during light time. This was the birth of the mammalian sleep. Then, the Cretacic-Paleogene extinction of dinosaurs leaved free the diurnal niche and allowed the expansion of a few early mammals to diurnal life and the high variability of sleep traits. On the other hand, we propose that the idling rest is a state showing homeostatic regulation. Therefore, the difference between behavioral rest and wakeful idling is rather low: both show quiescence, raised sensory thresholds, reversibility, specific sleeping-resting sites and body positions, it is a pleasing state, and both are dependent of circadian and homeostatic regulation. Indeed, the most important difference is the unconsciousness of sleep and the consciousness of wakeful idling. Thus, we propose that sleep is a mere upgrade of the wakeful rest, and both may have the same function: guaranteeing rest during a part of the daily cycle.

Abstract

Mammals evolved from small-sized reptiles that developed endothermic metabolism. This allowed filling the nocturnal niche. They traded-off visual acuity for sensitivity but became defenseless against the dangerous daylight. To avoid such danger, they rested with closed eyes in lightproof burrows during light-time. This was the birth of the mammalian sleep, the main finding of this report. Improved audition and olfaction counterweighed the visual impairments and facilitated the cortical development. This process is called “The Nocturnal Evolutionary Bottleneck”. Pre-mammals were nocturnal until the Cretacic-Paleogene extinction of dinosaurs. Some early mammals returned to diurnal activity, and this allowed the high variability in sleeping patterns observed today. The traits of Waking Idleness are almost identical to those of behavioral sleep, including homeostatic regulation. This is another important finding of this report. In summary, behavioral sleep seems to be an upgrade of Waking Idleness Indeed, the trait that never fails to show is quiescence. We conclude that the main function of sleep consists in guaranteeing it during a part of the daily cycle.

A Brief Study of Binaural Beat: A Means of Brain-Computer Interfacing

The human brain tends to follow a rhythm. Sound has a significant impact on our physical and mental health. This sound technology uses binaural beat by generating two tones of marginally different frequencies in each individual ear to facilitate the improved focus of attention, emotion, calming, and sensory organization. Binaural beat helps in memory boosting, relaxation, and work performance. Again because of hearing a binaural beat sound, brainwave stimuli can be diagnosed to pick up a person’s sensitive information. Using this technology in brain-computer interfacing, it is possible to establish a communication between the brain and the computer. Thus, it enables us to go beyond our potential. The aim of this study is to assess the impact and explore the potential contribution of binaural beat to enhancement of human brain performance.

Possible effects of short rest after lunch on hemodynamics in the afternoon

PURPOSE

Drowsiness is often experienced in the afternoon after lunch. Decreases in blood flow to the brain secondary to increases in blood flow to the digestive organs after food intake could represent an underlying cause. As various beneficial effects of short rests on mental activities have been reported, the present study investigated hemodynamics using Doppler sonography of the common carotid artery (CCA) and superior mesenteric artery (SMA) after lunch, comparing resting and non-resting cases.

METHODS

Subjects comprised 24 healthy young adults (10 men, 14 women; mean age 22 ± 1 years). Sonography was performed to measure blood flow before and after lunch on each day, with and without a 15-min lying rest with eyes closed after lunch in each subject.

RESULTS

The timing of the peak velocity-time integral in the SMA in resting cases was delayed to 1.5 h after lunch compared to 0.5 h in non-resting cases. Although end-diastolic velocity in the CCA decreased after lunch, this decrease was suppressed in resting cases compared to non-resting cases even 4.5 h after lunch (median 96%, interquartile range [IQR] 83-102% vs. median 87%, IQR 77-92%; P = 0.037). Mean velocity (MV) in the CCA maintained unchanged after lunch in resting cases (P = 0.318), whereas non-resting cases showed decreased MV after lunch (P < 0.001).

CONCLUSION

These findings suggest that a short lying rest with eyes closed suppresses increases in blood flow to the digestive organ and maintains blood flow to the brain after lunch. These hemodynamic changes might help explain the benefits of afternoon rests.

A Brief Period of Wakeful Rest after Learning Enhances Verbal Memory in Stroke Survivors

OBJECTIVE

Accumulating evidence suggests that wakeful rest (a period of minimal cognitive stimulation) enhances memory in clinical populations with memory impairment. However, no study has previously examined the efficacy of this technique in stroke survivors, despite the high prevalence of post-stroke memory difficulties. We aimed to investigate whether wakeful rest enhances verbal memory in stroke survivors and healthy controls.

METHOD

Twenty-four stroke survivors and 24 healthy controls were presented with two short stories; one story was followed by a 10-minute period of wakeful rest and the other was followed by a 10-minute visual interference task. A mixed factorial analysis of variance (ANOVA) with pairwise comparisons was used to compare participants' story retention at two time points.

RESULTS

After 15-30 minutes, stroke survivors (p = .002, d = .73), and healthy controls (p = .001, d = .76) retained more information from the story followed by wakeful rest, compared with the story followed by an interference task. While wakeful rest remained the superior condition in healthy controls after 7 days (p = .01, d = .58), the beneficial effect was not maintained in stroke survivors (p = .35, d = .19).

CONCLUSIONS

Wakeful rest is a promising technique, which significantly enhanced verbal memory after 15-30 minutes in both groups; however, no significant benefit of wakeful rest was observed after 7 days in stroke survivors. Preliminary findings suggest that wakeful rest enhances early memory consolidation processes by protecting against the effects of interference after learning in stroke survivors.

The Black Box effect: sensory stimulation after learning interferes with the retention of long-term object location memory in rats

Reducing sensory experiences during the period that immediately follows learning improves long-term memory retention in healthy humans, and even preserves memory in patients with amnesia. To date, it is entirely unclear why this is the case, and identifying the neurobiological mechanisms underpinning this effect requires suitable animal models, which are currently lacking. Here, we describe a straightforward experimental procedure in rats that future studies can use to directly address this issue. Using this method, we replicated the central findings on quiet wakefulness obtained in humans: We show that rats that spent 1 h alone in a familiar dark and quiet chamber (the Black Box) after exploring two objects in an open field expressed long-term memory for the object locations 6 h later, while rats that instead directly went back into their home cage with their cage mates did not. We discovered that both visual stimulation and being together with conspecifics contributed to the memory loss in the home cage, as exposing rats either to light or to a cage mate in the Black Box was sufficient to disrupt memory for object locations. Our results suggest that in both rats and humans, everyday sensory experiences that normally follow learning in natural settings can interfere with processes that promote long-term memory retention, thereby causing forgetting in form of retroactive interference. The processes involved in this effect are not sleep-dependent because we prevented sleep in periods of reduced sensory experience. Our findings, which also have implications for research practices, describe a potentially useful method to study the neurobiological mechanisms that might explain why normal sensory processing after learning impairs memory both in healthy humans and in patients suffering from amnesia.

Prefrontal Transcranial Direct Current Stimulation Globally Improves Learning but Does Not Selectively Potentiate the Benefits of Targeted Memory Reactivation on Awake Memory Consolidation

Targeted memory reactivation (TMR) and transcranial direct current stimulation (tDCS) can enhance memory consolidation. It is currently unknown whether TMR reinforced by simultaneous tDCS has superior efficacy. In this study, we investigated the complementary effect of TMR and bilateral tDCS on the consolidation of emotionally neutral and negative declarative memories. Participants learned neutral and negative word pairs. Each word pair was presented with an emotionally compatible sound. Following learning, participants spent a 20 min retention interval awake under four possible conditions: (1) TMR alone (i.e., replay of 50% of the associated sounds), (2) TMR combined with anodal stimulation of the left DLPFC, (3) TMR combined with anodal stimulation of the right DLPFC and (4) TMR with sham tDCS. Results evidenced selective memory enhancement for the replayed stimuli in the TMR-only and TMR-sham conditions, which confirms a specific effect of TMR on memory. However, memory was enhanced at higher levels for all learned items (irrespective of TMR) in the TMR-anodal right and TMR-anodal left tDCS conditions, suggesting that the beneficial effects of tDCS overshadow the specific effects of TMR. Emotionally negative memories were not modulated by tDCS hemispheric polarity. We conclude that electrical stimulation of the DLPFC during the post-learning period globally benefits memory consolidation but does not potentiate the specific benefits of TMR.

'Sleep-dependent' memory consolidation? Brief periods of post-training rest and sleep provide an equivalent benefit for both declarative and procedural memory

Sleep following learning facilitates the consolidation of memories. This effect has often been attributed to sleep-specific factors, such as the presence of sleep spindles or slow waves in the electroencephalogram (EEG). However, recent studies suggest that simply resting quietly while awake could confer a similar memory benefit. In the current study, we examined the effects of sleep, quiet rest, and active wakefulness on the consolidation of declarative and procedural memory. We hypothesized that sleep and eyes-closed quiet rest would both benefit memory compared with a period of active wakefulness. After completing a declarative and a procedural memory task, participants began a 30-min retention period with PSG (polysomnographic) monitoring, in which they either slept (n = 24), quietly rested with their eyes closed (n = 22), or completed a distractor task (n = 29). Following the retention period, participants were again tested on their memory for the two learning tasks. As hypothesized, sleep and quiet rest both led to better performance on the declarative and procedural memory tasks than did the distractor task. Moreover, the performance advantages conferred by rest were indistinguishable from those of sleep. These data suggest that neurobiology specific to sleep might not be necessary to induce the consolidation of memory, at least across very short retention intervals. Instead, offline memory consolidation may function opportunistically, occurring during either sleep or stimulus-free rest, provided a favorable neurobiological milieu and sufficient reduction of new encoding.

Eye-movements reveal semantic interference effects during the encoding of naturalistic scenes in long-term memory

Similarity-based semantic interference (SI) hinders memory recognition. Within long-term visual memory paradigms, the more scenes (or objects) from the same semantic category are viewed, the harder it is to recognize each individual instance. A growing body of evidence shows that overt attention is intimately linked to memory. However, it is yet to be understood whether SI mediates overt attention during scene encoding, and so explain its detrimental impact on recognition memory. In the current experiment, participants watched 372 photographs belonging to different semantic categories (e.g., a kitchen) with different frequency (4, 20, 40 or 60 images), while being eye-tracked. After 10 minutes, they were presented with the same 372 photographs plus 372 new photographs and asked whether they recognized (or not) each photo (i.e., old/new paradigm). We found that the more the SI, the poorer the recognition performance, especially for old scenes of which memory representations existed. Scenes more widely explored were better recognized, but for increasing SI, participants focused on more local regions of the scene in search for its potentially distinctive details. Attending to the centre of the display, or to scene regions rich in low-level saliency was detrimental to recognition accuracy, and as SI increased participants were more likely to rely on visual saliency. The complexity of maintaining faithful memory representations for increasing SI also manifested in longer fixation durations; in fact, a more successful encoding was also associated with shorter fixations. Our study highlights the interdependence between attention and memory during high-level processing of semantic information.

A reappraisal of acute doses of benzodiazepines as a model of anterograde amnesia

OBJECTIVE

Acute administration of benzodiazepines is considered a pharmacological model of general organic anterograde amnesias (OAA). We sought to determine which type of amnesia these drugs best model by comparing the effects of diazepam with those reported in amnesiacs regarding working memory capacity (WMC), susceptibility to retroactive interference (RI), and accelerated forgetting.

METHODS

In this double-blind, parallel-group design study, 30 undergraduates were randomly allocated to acute oral treatments with 15 mg diazepam or placebo. WMC and story recall were assessed pre- and post-treatment. Story presentation was succeeded by 10 min of RI (spotting differences in pictures) or minimal RI (doing nothing in a darkened room). Delayed story recall was assessed under diazepam and 7 days later in a drug-free session to assess accelerated forgetting.

RESULTS

Recall of stories encoded under diazepam, whether reactivated or not, was severely impaired (anterograde amnesia). However, diazepam did not impair WMC, increase susceptibility to RI, or accelerate forgetting.

CONCLUSIONS

Diazepam's amnestic effects mirror those in patients with probable severe medial temporal damage, mostly restricted to initial consolidation and differ from other OAA (Korsakoff syndrome, frontal, transient epileptic, posttraumatic amnesia, and most progressive amnesias) in terms of WMC, susceptibility to RI and accelerated forgetting.

Wakeful rest during storage and consolidation enhances priming effects for those with acquired memory impairment

A period of rest after learning results in better explicit memory for the material than a period of unrelated mental activity. This study investigated whether the same applies to priming. Thirty-four people with memory impairments due to acquired brain injury took part. In a repeated measures design, participants studied word lists; then either engaged in a relaxation technique (wakeful rest condition) or completed visuo-spatial tasks (control condition); and finally completed two priming tasks. Priming effects were significantly larger in the wakeful rest condition. This result is difficult to explain in terms of some of the explanations used to account for the benefits of wakeful rest on explicit memory, and alternative explanations are considered. One possibility is that the attentional demands of the control task resulted in inhibition of activity in neocortical areas associated with perception that contributed to the priming effect. The findings have implications for memory rehabilitation. Acquired memory impairments typically impact on explicit memory, and implicit memory is often relatively intact. It is important to find ways of enabling those with more severe explicit impairments to make best use of their implicit memory as a way of compensating for the deficits in their explicit memory.

No evidence of consolidation of evaluative conditioning during waking rest and sleep

Research on evaluative conditioning (EC) shows that attitudes can emerge from co-occurrences of stimuli, and accumulating evidence suggests that EC usually depends on memory for these stimulus contingencies. Therefore, processes known to aid memory retention may be relevant for the development of stable attitudes. One such process may be memory consolidation, assumed to be promoted by waking rest and sleep. In two pre-registered experiments, we investigated whether waking rest (vs. cognitive activity, Experiment 1) and sleep (vs. wakefulness, Experiment 2) in between conditioning and measurement of EC, consolidate contingency memory and EC. Contrary to our predictions, waking rest (vs. cognitive activity) promoted neither contingency memory nor EC effects. Sleep (vs. wakefulness) decreased forgetting of contingency memory but crucially, it did not attenuate the impact of counterconditioning on contingency memory. Sleep also did not influence EC effects, nor the reduction of EC by counterconditioning. EC effects in both experiments were predicted by contingency memory. Yet, unexpectedly, EC effects occurred in the absence of contingency memory after waking rest, but neither after sleep nor in the active control conditions. Our findings emphasise a role of contingency memory in EC, but it remains unclear whether this role changes during waking rest.

A study on episodic memory reconsolidation that tells us more about consolidation

Awake quiescence immediately after encoding is conducive to episodic memory consolidation. Retrieval can render episodic memories labile again, but reconsolidation can modify and restrengthen them. It remained unknown whether awake quiescence after retrieval supports episodic memory reconsolidation. We sought to examine this question via an object-location memory paradigm. We failed to probe the effect of quiescence on reconsolidation, but we did observe an unforeseen “delayed” effect of quiescence on consolidation. Our findings reveal that the beneficial effect of quiescence on episodic memory consolidation is not restricted to immediately following encoding but can be achieved at a delayed stage and even following a period of task engagement.

A Review of Accelerated Long-Term Forgetting in Epilepsy

Accelerated long-term forgetting (ALF) is a memory disorder that manifests by a distinct pattern of normal memory for up to an hour after learning, but an increased rate of forgetting during the subsequent hours and days. The topic of ALF has gained much attention in group studies with epilepsy patients and the phenomenon has been shown to have contradictory associations with seizures, epileptiform activity, imaging data, sleep, and antiepileptic medication. The aim of this review was to explore how clinical and imaging data could help determine the topographic and physiological substrate of ALF, and what is the possible use of this information in the clinical setting. We have reviewed 51 group studies in English to provide a synthesis of the existing findings concerning ALF in epilepsy. Analysis of recently reported data among patients with temporal lobe epilepsy, transient epileptic amnesia, and generalized and extratemporal epilepsies provided further indication that ALF is likely a disorder of late memory consolidation. The spatial substrate of ALF might be located along the parts of the hippocampal-neocortical network and novel studies reveal the increasingly possible importance of damage in extrahippocampal sites. Further research is needed to explore the mechanisms of cellular impairment in ALF and to develop effective methods of care for patients with the disorder.

Individual differences in working memory capacity moderate effects of post-learning activity on memory consolidation over the long term

Similar to sleeping after learning, a brief period of wakeful resting after encoding new information supports memory retention in contrast to task-related cognition. Recent evidence suggests that working memory capacity (WMC) is related to sleep-dependent declarative memory consolidation. We tested whether WMC moderates the effect of a brief period of wakeful resting compared to performing a distractor task subsequent to encoding a word list. Participants encoded and immediately recalled a word list followed by either an 8 min wakeful resting period (eyes closed, relaxed) or by performing an adapted version of the d2 test of attention for 8 min. At the end of the experimental session (after 12–24 min) and again, after 7 days, participants were required to complete a surprise free recall test of both word lists. Our results show that interindividual differences in WMC are a central moderating factor for the effect of post-learning activity on memory retention. The difference in word retention between a brief period of wakeful resting versus performing a selective attention task subsequent to encoding increased in higher WMC individuals over a retention interval of 12–24 min, as well as over 7 days. This effect was reversed in lower WMC individuals. Our results extend findings showing that WMC seems not only to moderate sleep-related but also wakeful resting-related memory consolidation.

Spontaneous Entry into an “Offline” State during Wakefulness: A Mechanism of Memory Consolidation?

Moments of inattention to our surroundings may be essential to optimal cognitive functioning. Here, we investigated the hypothesis that humans spontaneously switch between two opposing attentional states during wakefulness—one in which we attend to the external environment (an “online” state) and one in which we disengage from the sensory environment to focus our attention internally (an “offline” state). We created a data-driven model of this proposed alternation between “online” and “offline” attentional states in humans, on a seconds-level timescale. Participants (n = 34) completed a sustained attention to response task while undergoing simultaneous high-density EEG and pupillometry recording and intermittently reporting on their subjective experience. “Online” and “offline” attentional states were initially defined using a cluster analysis applied to multimodal measures of (1) EEG spectral power, (2) pupil diameter, (3) RT, and (4) self-reported subjective experience. We then developed a classifier that labeled trials as belonging to the online or offline cluster with &gt;95% accuracy, without requiring subjective experience data. This allowed us to classify all 5-sec trials in this manner, despite the fact that subjective experience was probed on only a small minority of trials. We report evidence of statistically discriminable “online” and “offline” states matching the hypothesized characteristics. Furthermore, the offline state strongly predicted memory retention for one of two verbal learning tasks encoded immediately prior. Together, these observations suggest that seconds-timescale alternation between online and offline states is a fundamental feature of wakefulness and that this may serve a memory processing function.

It's about time: Delay-dependent forgetting of item- and contextual-information

Once fiercely rejected, the notion of delay-dependent forgetting from long-term memory has recently resurfaced. By this notion, the duration of the study-test delay predicts the magnitude of memory degradation. Our Representation Theory of Forgetting adopts the notion of delay-dependent forgetting, alongside interference due to similarity of representations as an additional cause of forgetting-rather than its sole cause, as has been largely argued in the past. This theory maintains that the causes of forgetting depend on the underlying memory representations. Because hippocampus-based memory representations are relatively distinct from one another, by the virtue of being associated with distinct contexts, they are not as likely as non-hippocampus representations to be forgotten due to interference from similar memories. Instead, as neurobiological evidence suggests, these representations may be forgotten over the passage of time. Thus, contextual-information should be particularly sensitive to delay-dependent forgetting in comparison to item-information. In the current study we tested this hypothesis by comparing the effects of short study-test delay (~2 min) to long delay (~15 min) on forgetting. In three experiments using three different memory paradigms, we obtained various measures of item- and contextual-information. Results converged to support our predictions: whereas most measures of contextual-information showed forgetting over time, item-information was less affected by delay and, at times, was not affected at all. Finally, different patterns of time-dependent forgetting of contextual-information were observed in recall and recognition, in line with the different roles of context in these tests. Our results provide novel evidence for the specific effects of delay on hippocampus-based, contextual memory representations.

Testing the efficacy of a brief exercise intervention for enhancing exposure therapy outcomes

Recently, it has been hypothesized that a brief bout of exercise could cognitively enhance extinction learning processes theorized to underlie exposure therapy for pathological anxiety. The present study tested the exercise enhancement hypothesis in a sample of speech-anxious undergraduates (n = 84). During the first laboratory session, participants engaged in either 30 min of moderate-intensity exercise on a cycling ergometer (n = 37) or seated rest (n = 47) immediately following a brief speech exposure trial. They returned approximately one week later to give a follow-up speech. Contrary to expectation, there were no significant between-group differences in memory of a brief word list across four recall trials, which served as a manipulation check. Further, all main effects and interactions involving condition were nonsignificant. Post hoc tests revealed that participants who reported higher average perceived exertion during exercise demonstrated increases in an average anxiety composite across speeches relative to those who reported lower average perceived exertion, indicating that trying hard during the intervention predicted worse exposure trial outcomes. The implications of these findings, as well as future directions for this line of research, are explored.

Effect of postlearning meditation on memory consolidation: level of focused attention matters

Recent studies demonstrate that eyes-closed rest benefits memory consolidation, perhaps due to reduced attention to environmental stimuli. Here, we asked whether focusing attention to internal thoughts and feelings after learning similarly blocks memory consolidation. Verbal memory was tested following an eyes-closed consolidation period filled with either focused attention to breath or quiet rest. Although breath-focus did not impair memory relative to quiet rest overall, participants who reported being more successful in maintaining breath-focus during this condition showed increased forgetting. We interpret these findings as incompatible with a simple sensory-interference-based account of rest's effect on memory.

Post-encoding positive emotion impairs associative memory for English vocabulary

There is evidence that emotion induced during encoding impairs associative memory (e.g., Bisby, Horner, Bush, & Burgess, 2018), yet the effect of post-encoding emotion (particularly positive emotion) on associative memory remains largely unclear. Two experiments were conducted to examine the effect of post-encoding positive emotion on associative memory for English vocabulary. In Experiment 1, high school students memorized Chinese definitions of a list of English words, immediately recalled the Chinese definitions, watched a neutral or comic video, and took a delayed memory test 25 minutes after encoding. The result showed a significant impairing effect of post-encoding positive emotion on memory for Chinese definitions. In Experiment 2, primary school students encoded English words with their associative pictures, took an immediate test where, on each trial, they were asked to choose the correct English word that matches a picture. Following the test, they watched a neutral or comic video, and took a memory test 10 minutes after encoding. Consistent with Experiment 1, Experiment 2 showed an impairing effect of positive emotion. Taken together, these findings support the hypothesis that post-encoding positive emotion can impair associative memory, providing important implications for acquisition of vocabulary of English as a foreign language.

Comparing the Effects of Sleep and Rest on Memory Consolidation

INTRODUCTION

There is ample evidence that overnight sleep and daytime naps benefit memory retention, compared to comparable amounts of active wakefulness. Yet recent evidence also suggests that a period of post-training rest (eg, quiet wakefulness with eyes closed) provides a similar memory benefit compared to wake. However, the relative benefits of sleep vs quiet waking rest on memory remain poorly understood. Here, we assessed the extent to which sleep provides a unique memory benefit, above and beyond that conferred by quiet waking rest.

METHODS

In a sample of healthy undergraduate students (N=83), we tested the effect of 30 mins of post-learning sleep, rest, or active wake on concept learning (dot pattern classification) and declarative memory (word pair associates) across a 4-hr daytime training-retest interval.

RESULTS AND CONCLUSIONS

Contrary to our hypotheses, we found no differences in performance between the three conditions for either task. The findings are interpreted with reference to methodological considerations including the length of the experimental interval, the nature of the tasks used, and challenges inherent in creating experimental conditions that can be executed by participants.

Resting States and Memory Consolidation: A Preregistered Replication and Meta-Analysis

While several recent studies have found that a post-encoding period of quiet, eyes-closed waking rest benefits memory consolidation, others have reported null effects. To more precisely estimate this effect, we conducted a quasi-exact behavioural replication of a recent study from our lab, which found that post-training eyes-closed waking rest improved declarative memory relative to a distractor task. Contrary to our hypothesis, the observed effect was not significant; however, it did fall within the 95% confidence interval of our previous finding. Furthermore, a meta-analytic effect summarizing n = 10 similar studies indicates a moderately sized and significant benefit of waking rest for verbal memory (d = 0.38, p < 0.001). We argue that the apparently conflicting results in this literature are most parsimoniously explained by variability due to sampling and/or measurement error, in a group of studies often underpowered to detect a smaller-than-expected effect of rest. Additionally, exploratory analyses revealed that increased trait daydreaming frequency negatively correlated with memory retention during eyes-closed rest. Together with our replication and meta-analysis, these studies suggest that waking rest confers a small but significant benefit on memory consolidation, and that this benefit requires the mind to be free from attention to either external tasks or spontaneous thought.

Factors modulating the effects of waking rest on memory

Study results indicate that moments of unoccupied rest immediately after learning serve an essential cognitive function: memory consolidation. However, there also are findings suggesting that waking rest after learning has similar effects on delayed memory performance as an active wake condition, where participants work on a cognitive distractor task. Based on these studies, we highlight several potentially modulating factors of the so-called resting effect.

The effects of different protocols of physical exercise and rest on long-term memory

Whilst there are many studies comparing the different effects of exercise on long-term memory, these typically adopt varying intensities, durations, and behavioural measures. Furthermore, few studies provide direct comparisons between exercise and different types of rest. Therefore, by providing a standardised methodological design, this study will ascertain the most effective intensity and protocol of exercise for the modulation of long-term memory, whilst directly comparing it to different types rest. This was achieved using the same old/new recognition memory test and an 80-90 min retention interval. Three experiments were performed (total N = 59), each with a three-armed crossover design measuring the extent to which physical exercise and wakeful rest can influence long-term memory performance. In Experiment 1, the effects of continuous moderate intensity exercise (65-75% HR_max), passive rest (no cognitive engagement) and active rest (cognitively engaged) were explored. In Experiment 2, continuous moderate intensity exercise was compared to a type of high-intensity interval training (HIIT) and passive rest. Experiment 3 observed the effects of low- (55-65% HR_max), moderate- and high-intensity (75-85% HR_max) continuous exercise. Across the three experiments moderate intensity exercise had the greatest positive impact on memory performance. Although not significant, HIIT was more effective than passive-rest, and passive rest was more effective than active rest. Our findings suggest that it is not necessary to physically overexert oneself in order to achieve observable improvements to long-term memory. By also investigating wakeful rest, we reaffirmed the importance of the cognitive engagement during consolidation for the formation of long-term memories.

Short-term effects of video gaming on brain response during working memory performance

Breaks filled with different break activities often interrupt cognitive performance in everyday life. Previous studies have reported that both enhancing and deteriorating effects on challenging ongoing tasks such as working memory updating, depend on the type of break activity. However, neural mechanisms of these break-related alterations in working memory performance have not been studied, to date. Therefore, we conducted a brain imaging study to identify the neurobiological correlates of effects on the n-back working memory task related to different break activities. Before performing the n-back task in the magnetic resonance imaging (MRI) scanner, young adults were exposed to break activities in the MRI scanner involving (i) eyes-open resting, (ii) listening to music, and (iii) playing the video game “Angry Birds”. Heart rate was measured by a pulse oximeter during the experiment. We found that increased heart rate during gaming as well as decreased relaxation levels after a video gaming break was related to poorer n-back task performance, as compared to listening to music. On the neural level, video gaming reduced supplementary motor area activation during working memory performance. These results may indicate that video gaming during a break may affect working memory performance by interfering with arousal state and frontal cognitive control functions.

Optimising recovery in aphasia: Learning following exposure to a single dose of computer-based script training

Purpose: Intensity of therapy influences outcomes in aphasia treatment, but little is known about optimum dosage across treatment approaches. Improved understanding of the effects of dose could help facilitate clinical decisions that maximise patient outcomes. This study examines learning in individuals with aphasia following exposure to one 60-min dose of computer-delivered script training, with or without a rest break. Method: Twenty participants (6F, 14M; 17 nonfluent, 3 fluent) with chronic aphasia due to left-hemisphere stroke participated. Participants had a mean (SD) age of 56.9 (8.4) years, a mean time post onset of 55.1 (range: 6.4-396.4) months, and a mean (SD) Comprehensive Aphasia Test score of 47.8 (4.0). Participants were exposed to 60 min of training, with or without a rest break, of a three-turn conversational script about either weather or traffic. Treatment was delivered via computer using a virtual clinician that visually modelled speech and guided treatment, promoting treatment fidelity. Oral reading probes for script sentences were administered at baseline (3 times), mid-treatment, immediately post-treatment, and, at various times, up to 2 weeks post-treatment to track script acquisition and maintenance. The study also examined generalisation from a trained script to a conversation with a clinician via a generalisation probe at three time points: baseline, immediately post-treatment, and 2 weeks post-treatment. Result: Following exposure to one dose of script training, participants demonstrated statistically significant improvements in oral reading accuracy and rate of script production on trained probes from baseline to immediately post-treatment and 2 weeks post-treatment. Participants also demonstrated significant change from baseline in generalisation to a conversation with a clinician immediately post-treatment and at 2 weeks post-treatment. Conclusion: Exposure to a single dose of computer-delivered script training may facilitate learning. These results have implications for future research investigating optimal dosage and scheduling parameters.

Wakeful rest compared to vigilance reduces intrusive but not deliberate memory for traumatic videos

Intrusive memories are prominent features of post-traumatic stress disorder, but the mechanisms supporting their development, and their relationship to deliberate memories, are subject to competing theories. Are they strengthened examples of a unitary memory system, or fragmented representations lacking aspects of healthy memories? Given the importance of post-encoding processing in memory consolidation, we investigated the effects of a brief wakeful rest compared to a vigilance task immediately after the encoding of traumatic material on subsequent intrusive and deliberate memory. Across two experiments, participants watched emotionally negative film clips immediately followed by a brief wakeful rest or a simple vigilance (0-back) task. Brief wakeful rest had distinct effects on memory compared to the 0-back task, reducing intrusive memory frequency but not changing deliberate memory performance. These differential effects suggest that intrusive memory and deliberate memory reflect dissociable systems, arguing against unitary accounts. Our findings highlight the importance of post-encoding processing in the consolidation of traumatic material and the development of intrusive memories and provide a new perspective for interpreting mechanisms of therapeutic intervention.

Awake Reactivation of Prior Experiences Consolidates Memories and Biases Cognition

After experiences are encoded into memory, post-encoding reactivation mechanisms have been proposed to mediate long-term memory stabilization and transformation. Spontaneous reactivation of hippocampal representations, together with hippocampal-cortical interactions, are leading candidate mechanisms for promoting systems-level memory strengthening and reorganization. While the replay of spatial representations has been extensively studied in rodents, here we review recent fMRI work that provides evidence for spontaneous reactivation of nonspatial, episodic event representations in the human hippocampus and cortex, as well as for experience-dependent alterations in systems-level hippocampal connectivity. We focus on reactivation during awake post-encoding periods, relationships between reactivation and subsequent behavior, how reactivation is modulated by factors that influence consolidation, and the implications of persistent reactivation for biasing ongoing perception and cognition.

Even an activated long-term memory system still needs a separate short-term store: A reply to Cowan (2019)

In Norris (2017), I explained why the notion of activated LTM (long-term memory) combined with a focus of attention was unable to perform the computations required to support short-term memory (STM) and argued that those extra computations must require a separate STM system. Cowan (2019) made the alternative proposal that this full set of computations is better conceptualized as a unitary system of activated LTM. To this he added a pointer system, the ability to perform variable binding, and an unspecified model of STM that acts as a front end to LTM. This appears to be simply an exercise in relabeling. Furthermore, without a computational specification of how the components work, the model lacks the ability to simulate even the most basic STM phenomena. If the model were specified in more detail it seems almost inevitable that it would contain something instantly recognizable as an STM system. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Short-term memory based on activated long-term memory: A review in response to Norris (2017)

Short-term memory (STM), the limited information temporarily in a state of heightened accessibility, includes just-presented events and recently retrieved information. Norris (2017) argued for a prominent class of theories in which STM depends on the brain keeping a separate copy of new information, and against alternatives in which the information is held only in a portion of long-term memory (LTM) that is currently activated (aLTM). Here I question premises of Norris' case for separate-copy theories in the following ways. (a) He did not allow for implications of the common assumption (e.g., Cowan, 1999; Cowan & Chen, 2009) that aLTM can include new, rapidly formed LTM records of a trial within an STM task. (b) His conclusions from pathological cases of impaired STM along with intact LTM are tenuous; these rare cases can be explained by impairments in encoding, processing, or retrieval related to LTM rather than passive maintenance. (c) Although Norris reasonably allowed structured pointers to aLTM instead of separate copies of the actual item representations in STM, the same structured pointers may well be involved in long-term learning. (d) Last, models of STM storage can serve as the front end of an LTM learning system rather than being separate. I summarize evidence for these premises and an updated version of an alternative theory in which storage depends on aLTM (newly clarified), and, embedded within it, information enhanced by the current focus of attention (Cowan, 1988, 1999), with no need for a separate STM copy. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Benefit of wakeful resting on gist and peripheral memory retrieval in healthy younger and older adults

Retrieval is greater if new learning is followed by a period of wakeful rest, minimising the likelihood of retroactive interference. It is not known if this benefit extends to recollection of both gist and peripheral details, nor whether age affects the benefit of wakeful resting in either of these types of recollection. Forty-five younger and forty older adults were presented with prose passages for later recall followed by a period of either interference or wakeful resting. Younger participants outperformed older participants in remembering peripheral details, but not on gist memory. Wakeful resting led to higher overall recollection in both age groups, both for gist and for peripheral details. Also, wakeful resting was more beneficial for gist than peripheral memory in older but not younger adults. We discuss these novel findings and their theoretical implications for a memory consolidation account of the benefits of wakeful resting.

Post-encoding wakeful resting supports the retention of new verbal memories in children aged 13-14 years

Evidence primarily exists in adults that engaging in task-related mental activity after new learning results in increased forgetting of learned information, compared with quietly resting in the minutes that follow learning, where less forgetting is observed. The current study investigated whether the beneficial effect of post-encoding rest can be observed in children aged 13-14 years. Each child (N = 102) encoded two word lists. After the presentation and immediate recall of one word list, children wakefully rested for 10 min (resting condition), after presentation and immediate recall of the other word list, they solved visuo-spatial problems for 10 min (problem-solving condition). Seven days later, a surprise free recall test for the two word lists took place. Our results showed that children retained more words over 7 days in the resting condition than with the problem-solving condition. Post-hoc analyses revealed that the resting effect was a function of the number of words recollected during the immediate recall. Specifically, those children who recalled fewest words (≤ 13/30 words) in the immediate recall showed a significant resting effect. There was no resting effect in those who recalled a mid-range (14-16/30 words) or a high number (>16/30 words) of words. These results provide new insights into the factors that influence memory in children, and suggest that a few minutes of wakeful rest benefits memory, relative to engaging in an ongoing task. Statement of contribution What is already known on this subject? Task-related mental activity after encoding weakens memory retention more than wakeful resting. Beneficial effect of resting after encoding was found primarily in younger and older adults. What does this study add? We investigated children at the age of 13-14 years. 8-min post-encoding wakeful resting supports memory retention over 7 days. Individuals differ in the impact of a brief period of wakeful resting after learning. Only children with lower immediate memory performances profited from wakeful resting.