Memory For Word Pairs Research Articles

Closed-loop auditory stimulation of slow-wave sleep in chronic insomnia: a pilot study.

Insomnia is a prevalent and disabling condition whose treatment is not always effective. This pilot study explores the feasibility and effects of closed-loop auditory stimulation (CLAS) as a potential non-invasive intervention to improve sleep, its subjective quality, and memory consolidation in patients with insomnia. A total of 27 patients with chronic insomnia underwent a crossover, sham-controlled study with 2 nights of either CLAS or sham stimulation. Polysomnography was used to record sleep parameters, while questionnaires and a word-pair memory task were administered to assess subjective sleep quality and memory consolidation. The initial analyses included 17 patients who completed the study, met the inclusion criteria, and received CLAS. From those, 10 (58%) received only a small number of stimuli. In the remaining seven (41%) patients with sufficient CLAS, we evaluated the acute and whole-night effect on sleep. CLAS led to a significant immediate increase in slow oscillation (0.5-1 Hz) amplitude and activity, and reduced delta (1-4 Hz) and sigma/sleep spindle (12-15 Hz) activity during slow-wave sleep across the whole night. All these fundamental sleep rhythms are implicated in sleep-dependent memory consolidation. Yet, CLAS did not change sleep-dependent memory consolidation or sleep macrostructure characteristics, number of arousals, or subjective perception of sleep quality. Results showed CLAS to be feasible in patients with insomnia. However, a high variance in the efficacy of our automated stimulation approach suggests that further research is needed to optimise stimulation protocols to better unlock potential CLAS benefits for sleep structure and subjective sleep quality in such clinical settings.

Why do judgments of learning modify memory? Evidence from identical pairs and relatedness judgments.

Research has observed that monitoring one's own learning modifies memory for some materials but not for others. Specifically, making judgments of learning (JOLs) while learning word pairs improves subsequent cued-recall memory performance for related word pairs but not for unrelated word pairs. Theories that have attempted to explain this pattern of results assume that people attend to and process cue-target relatedness during learning more when making JOLs than they spontaneously do when not making JOLs. The present research directly tested this relatedness-processing assumption with unrelated and related word pairs as well as with hitherto unexamined materials: identical word pairs. In three experiments, participants studied word pairs while either making or not making JOLs. Results revealed that making JOLs improved memory for related word pairs as well as for identical word pairs, but not for unrelated word pairs. Importantly, in two of the experiments, participants were further asked to judge at test whether each cue appeared with an unrelated, related, or identical target before attempting to recall it. Results revealed that making JOLs improved the accuracy of these relatedness judgments independently from its effect on recall, thus providing direct evidence that people process cue-target relatedness when making JOLs more than they spontaneously do when not making JOLs. These findings contribute to a more comprehensive understanding of why judging one's own learning can modify memory and, more broadly, suggest that instructions to monitor learning can direct people's attention to information that is not or less processed otherwise. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Guessing can benefit memory for related word pairs even when feedback is delayed

Trying to guess what the correct answer to a question might be can facilitate future learning of this answer when presented in the form of corrective feedback. One issue that determines the effectiveness of guessing as a learning strategy is the timing of the presentation of feedback: it can be presented either immediately after the guess, or after a delay. Whereas the timing of feedback is of little importance for complex materials such as trivia questions, previous research suggests that for simpler materials such as related word pairs guessing seems to benefit learning only when feedback is immediate. In order to test whether this always has to be the case, we conducted two experiments in which we increased the richness of study materials by superimposing the to-be-learned word pairs over unrelated context pictures. We then manipulated the match between contexts at study and at test (Experiment 1) and at the time of feedback delivery (Experiment 2). Contrary to previous studies showing no benefits of guessing with delayed feedback, our results show that learning related word pairs can benefit from guessing even when feedback is delayed. These benefits of guessing occur if participants are reminded via reinstated contexts of the guessing stage at the time of feedback delivery. Our results help constrain theories of guessing benefits and extend theories of reminding.

Using EEG microstates to examine post-encoding quiet rest and subsequent word-pair memory

Evidence suggests that the brain preferentially consolidates memories during “offline” periods, in which an individual is not performing a task and their attention is otherwise undirected, including spans of quiet, resting wakefulness. Moreover, research has demonstrated that factors such as the initial encoding strength of information influence which memories receive the greatest benefit. Recent studies have begun to investigate these periods of post-learning quiet rest using EEG microstate analysis to observe the electrical dynamics of the brain during these stretches of memory consolidation, specifically finding an increase in the amount of the canonical microstate D during a post-encoding rest period. Here, we implement an exploratory analysis to probe the activity of EEG microstates during a post-encoding session of quiet rest in order to scrutinize the impact of learning on microstate dynamics and to further understand the role these microstates play in the consolidation of memories. We examined 54 subjects (41 female) as they completed a word-pair memory task designed to use repetition to vary the initial encoding strength of the word-pair memories. In this study, we were able to replicate previous research in which there was a significant increase (p < .05) in the amount of microstate D (often associated with the dorsal attention network) during post-encoding rest. This change was accompanied by a significant decrease (p < .05) in the amount of microstate C (often associated with the default mode network). We also found preliminary evidence indicating a positive relationship between the amount of microstate D and improved memory for weakly encoded memories, which merits further exploration.

CORRECTION OF TINNITUS AND NEUROPSYCHOLOGICAL STATUS OF PATIENTS WITH CEREBRAL ATHEROSCLEROSIS AND ESSENTIAL HYPERTENSION USING CITICOLINE AS PART OF COMPREHENSIVE THERAPY

Objective : to analyze the effect of neuroprotective therapy with citicoline in combination with hypotensive and hypolipidemic therapy on the correction of tinnitus and neuropsychological status in patients with atherosclerosis of the brachiocephalic and cerebral arteries and essential hypertension. Materials and methods. We examined 86 patients aged between 60 and 68 years with essential hypertension and atherosclerosis of the brachiocephalic and cerebral arteries. All patients were diagnosed with decompensated tinnitus that affected their quality of life. The Multidimensional Fatigue Inventory (MFI) was used to assess the severity of asthenic syndrome. The cognitive status was evaluated using the Schulte tables, word pair memory tests, and phrase pair memory tests. Study participants were divided into two groups. Patients in Group 1 ( n = 43) received nootropic therapy with citicoline at a dose of 1000 mg/day for 3 months in addition to standard hypotensive, hypolipidemic, and antiplatelet therapies. We found that citicoline as a part of comprehensive therapy facilitated regression of actual and moderate tinnitus in patients with atherosclerosis of the brachiocephalic and cerebral arteries and essential hypertension. This optimized the neurovegetative status of patients and improved their cognitive functions.

Judgments of learning (JOLs) selectively improve memory depending on the type of test.

JOL reactivity refers to the finding that making judgments of learning (JOLs) while studying material influences later memory for that material. Findings of JOL reactivity have been mixed, with some experiments reporting changes to memory when participants make JOLs and others finding no influence of JOLs. Soderstrom, Clark, Halamish, and Bjork (Journal of Experimental Psychology: Learning, Memory, and Cognition, 41(2), 553-558, 2015) proposed that JOL reactivity will only occur if the final test is sensitive to the same cues used to inform JOLs. The current study evaluated this account by manipulating the type of final test. In four experiments, participants studied mixed lists of related and unrelated word pairs and either made JOLs or did not make JOLs. Making JOLs generally enhanced memory for related word pairs when a cued-recall test was administered. However, during free recall, JOLs had no influence on memory for target information, likely because cue-target associations (which are used to inform JOLs) are less beneficial in the absence of cues. JOLs improved item recognition memory for words that were studied in related pairs, although the effect was small. Collectively, data from a meta-analysis of these experiments indicate that JOL reactivity depends on the type of final test, with reactivity most likely to occur when the final test is sensitive to the same cues used to inform JOLs. Future work should continue examining different tests and study materials in order to develop a comprehensive theory of JOL reactivity.

Effect of Rocking Movements on Afternoon Sleep.

Study ObjectivesGentle rocking movements provided by a moving bed have been proposed as a promising non-pharmacological way to promote sleep. In rodents the sleep promoting effect of rocking movements depended on the peak acceleration (named “stimulation intensity”) perceived by the vestibular system. We set out to verify previous reports on the sleep promoting effect of rocking movements and to investigate the importance of stimulation intensity in this process.MethodsSide-to-side rocking movements along a pendulum trajectory with different peak accelerations (control: 0 m/s2, low intensity: 0.15 m/s2, medium intensity: 0.25 m/s2, high intensity: 0.35 m/s2) were provided for 45 min during an afternoon nap opportunity. Participants were assigned to a low intensity group (n = 10) experiencing control, low and medium intensity stimulation or a high intensity group (n = 12) experiencing control, medium and high intensity stimulation. Sleep and sleep-related memory performance were assessed using polysomnography and a word-pair memory task, respectively.ResultsParticipants transitioned faster into deep sleep under the influence of medium intensity rocking as was evident by a faster buildup of delta power compared to the control condition (n = 22). The faster buildup did not affect sleep architecture, since e.g., the proportion of the nap spent in deep sleep or latencies did not change. Previously reported effects like a shorter latency to stage N2 and a higher density of sleep spindles were not observed. Sleep quality during control naps of the low intensity group was worse than in the high intensity group. In the low intensity group, we also observed a significant increase in delta power throughout the nap, as well as a higher density of slow oscillations both under the influence of low and medium intensity vestibular stimulation. No such effects were observed in the high intensity group.ConclusionRocking movements may promote nap sleep in young adults. Due to a difference in sleep quality during control naps between the low and high intensity group no conclusion regarding the influence of stimulation intensity were possible. Thus, optimal stimulation settings in humans need further investigation.

Closed-Loop Acoustic Stimulation Enhances Sleep Oscillations But Not Memory Performance.

Slow oscillations and spindle activity during non-rapid eye movement sleep have been implicated in memory consolidation. Closed-loop acoustic stimulation has previously been shown to enhance slow oscillations and spindle activity during sleep and improve verbal associative memory. We assessed the effect of closed-loop acoustic stimulation during a daytime nap on a virtual reality spatial navigation task in 12 healthy human subjects in a randomized within-subject crossover design. We show robust enhancement of slow oscillation and spindle activity during sleep. However, no effects on behavioral performance were observed when comparing real versus sham stimulation. To explore whether memory enhancement effects were task specific and dependent on nocturnal sleep, in a second experiment with 19 healthy subjects, we aimed to replicate a previous study that used closed-loop acoustic stimulation to enhance memory for word pairs. The methods used were as close as possible to those used in the original study, except that we used a double-blind protocol, in which both subject and experimenter were unaware of the test condition. Again, we successfully enhanced slow oscillation and spindle power, but again did not strengthen associative memory performance with stimulation. We conclude that enhancement of sleep oscillations may be insufficient to enhance memory performance in spatial navigation or verbal association tasks, and provide possible explanations for lack of behavioral replication.

Direct Stimulation of Human Hippocampus During Verbal Associative Encoding Enhances Subsequent Memory Recollection.

Previous studies have reported conflicting results regarding the effect of direct electrical stimulation of the human hippocampus on memory performance. A major function of the hippocampus is to form associations between individual elements of experience. However, the effect of direct hippocampal stimulation on associative memory remains largely inconclusive, with most evidence coming from studies employing non-invasive stimulation. Here, we therefore tested the hypothesis that direct electrical stimulation of the hippocampus specifically enhances hippocampal-dependent associative memory. To test this hypothesis, we recruited surgical patients with implanted subdural electrodes to perform a word pair memory task during which the hippocampus was stimulated. Our results indicate that stimulation of the hippocampus during encoding helped to build strong associative memories and enhanced recollection in subsequent trials. Moreover, stimulation significantly increased theta power in the lateral middle temporal cortex during successful memory encoding. Overall, our findings indicate that hippocampal stimulation positively impacts performance during a word pair memory task, suggesting that successful memory encoding involves the temporal cortex, which may act together with the hippocampus.

Commentary: Effects of Sleep on Word Pair Memory in Children-Separating Item and Source Memory Aspects.

Commentary: Effects of Sleep on Word Pair Memory in Children-Separating Item and Source Memory Aspects.

Cognitive performance and emotion are indifferent to ambient color

AbstractFolklore has it that ambient color has the power to relax or arouse the observer and enhance performance when executing cognitive tasks. We picked a number of commercially available colors that allegedly have the power to alter cognitive performance and the emotional state, and exposed subjects to them while solving a battery of cognitive tasks. The colors were “Cool Down Pink”, which is said to produce relaxing effects and reduce effort, “Energy Red”, allegedly enhancing performance via increased arousal, “Relaxing Blue”, which is said to enhance attention and concentration, as well as white as a control. In a between‐subjects design, a total of 170 high school students carried out five tasks (number series completion, mental rotation, and memory for word categories, word pairs, and geometrical figures) while exposed to one of the four colors. The emotional state of the subjects was measured before the beginning and at the end of the experiment. The ambient colors did not have the predicted effects, neither on cognitive performance nor on the emotional state of the participants.

Effects of Sleep on Word Pair Memory in Children - Separating Item and Source Memory Aspects.

Word paired-associate learning is a well-established task to demonstrate sleep-dependent memory consolidation in adults as well as children. Sleep has also been proposed to benefit episodic features of memory, i.e., a memory for an event (item) bound into the spatiotemporal context it has been experienced in (source). We aimed to explore if sleep enhances word pair memory in children by strengthening the episodic features of the memory, in particular. Sixty-one children (8–12 years) studied two lists of word pairs with 1 h in between. Retrieval testing comprised cued recall of the target word of each word pair (item memory) and recalling in which list the word pair had appeared in (source memory). Retrieval was tested either after 1 h (short retention interval) or after 11 h, with this long retention interval covering either nocturnal sleep or daytime wakefulness. Compared with the wake interval, sleep enhanced separate recall of both word pairs and the lists per se, while recall of the combination of the word pair and the list it had appeared in remained unaffected by sleep. An additional comparison with adult controls (n = 37) suggested that item-source bound memory (combined recall of word pair and list) is generally diminished in children. Our results argue against the view that the sleep-induced enhancement in paired-associate learning in children is a consequence of sleep specifically enhancing the episodic features of the memory representation. On the contrary, sleep in children might strengthen item and source representations in isolation, while leaving the episodic memory representations (item-source binding) unaffected.

No evidence for a role of reconsolidation in updating of paired associates

ABSTRACTReconsolidation theory states that memories are labilized through reactivation, making them prone to change, before being re-consolidated. When information in memory requires updating, reconsolidation theory therefore predicts that reminders of previously learned information should facilitate updating of that information and should thus improve memory for the updated information. In two experiments, we tested this prediction by investigating memory for word pairs over a short time-scale. Participants studied word pairs (A–B), some of which were subsequently updated with word pairs that shared the first word (A–C). Half of the A–C pairs received a pre-study reminder of the first word in the pair so as to reactivate and labilize A–B memory. In a recognition memory test targeting the A–C list, reminders by and large had no effect on memory. Results thus failed to support the predictions of reconsolidation theory.

Never forget a name: white matter connectivity predicts person memory.

Through learning and practice, we can acquire numerous skills, ranging from the simple (whistling) to the complex (memorizing operettas in a foreign language). It has been proposed that complex learning requires a network of brain regions that interact with one another via white matter pathways. One candidate white matter pathway, the uncinate fasciculus (UF), has exhibited mixed results for this hypothesis: some studies have shown UF involvement across a range of memory tasks, while other studies report null results. Here, we tested the hypothesis that the UF supports associative memory processes and that this tract can be parcellated into sub-tracts that support specific types of memory. Healthy young adults performed behavioral tasks (two face-name learning tasks, one word pair memory task) and underwent a diffusion-weighted imaging scan. Our results revealed that variation in UF microstructure was significantly associated with individual differences in performance on both face-name tasks, as well as the word association memory task. A UF sub-tract, functionally defined by its connectivity between face-selective regions in the anterior temporal lobe and orbitofrontal cortex, selectively predicted face-name learning. In contrast, connectivity between the fusiform face patch and both anterior face patches had no predictive validity. These findings suggest that there is a robust and replicable relationship between the UF and associative learning and memory. Moreover, this large white matter pathway can be subdivided to reveal discrete functional profiles.

Overlapping effects of age on associative memory and the anterior hippocampus from middle to older age

The anterior hippocampus has been implicated in associative memory, and along with hippocampal volume, this type of memory declines with age. However, few cross-sectional studies include middle-aged samples, making it unclear at what point these age-related changes occur. In addition, although men and women have been shown to differ in associative memory and rates of age-related hippocampal atrophy, sex-differences in aging are rarely studied. To address these issues, we assessed memory for word-pairs, hippocampal volume and activation during encoding and retrieval, across middle-aged (n=39) and older (n=44) participants, specifically in relation to sex. Older adults showed significantly poorer associative memory compared to middle-aged adults, paralleled by smaller anterior hippocampi and less activation during successful retrieval. The age-by-sex interaction observed in memory performance was also mirrored in the volume and activation of the hippocampus, indicating more pronounced age-effects in men as compared to women. These results indicate a specific role of the anterior hippocampus in verbal associative memory and suggest they both decline between middle-age and older age.

The role of encoding strategy in younger and older adult associative recognition: A think-aloud analysis.

Older adults have especially poor recognition memory for word pairs, and research suggests this associative deficit manifests primarily in older adults' higher rates of false alarms. This could result from older adults either failing to generate meaningful (deep) mediators at study, or failing to benefit from having generated deep mediators at test. Younger and older adults performed a recognition memory task for words and word pairs. A think-aloud analysis of their spontaneous encoding strategies (repetition, shallow mediators, deep mediators) revealed that generation of deep mediators did not differ between younger and older adults, and was associated with high hit rates for items and associates in both age groups. However, generation of deep mediators was inversely related to false alarm rates in younger adults but not older adults. A trial-level analysis of encoding strategies and recognition responses revealed that younger adults benefited from having generated deep mediators when presented with corresponding recombined pairs at test as shown in their lower false alarm rates. In contrast, older adults who generated deep mediators during study (e.g., to blanket-figure) did not benefit from having done so when they encountered the corresponding recombined pairs at test (blanket-summer and district-figure). Their false alarm rates to pairs at test were unrelated to generation of deep mediators at study. These results suggest that many older adults have difficulty retrieving their mediators when presented with recombined pairs at test, or their mediators are not distinct enough to distinguish intact pairs from recombined pairs at test, or some combination of both. (PsycINFO Database Record

Abstract POSTER-CTRL-1205: Neurocognitive evaluation of a cognitive training intervention in ovarian and gynecologic cancer survivors

Abstract Purpose: Our prior work indicates that a group-based cognitive training intervention can improve memory and attention in cancer survivors. This study examined potential for training transfer on two cognitive tasks and corresponding changes in neural activation patterns as measured by fMRI prior to and following the cognitive training intervention. Methods: Seven gynecologic cancer (ovarian, breast, uterine) survivors (mean age: 64 years, mean time since primary treatment: 7.2 years) underwent a 7-week cognitive rehabilitation intervention delivered in group format. Participants were evaluated with a comprehensive cognitive battery and two experimental cognitive tasks prior to and following treatment. A word pair task required participants to learn pairs of words and later indicate whether words had been seen before (Item condition) or whether words had been paired together at learning (Relational condition). A verbal working memory task required participants to learn a set of 3, 5, or 7 letters and confirm or deny the presence of a probe letter. Participants also underwent fMRI scanning during word pair and verbal working memory tasks prior to and following treatment. Results: Participants showed significant improvement following intervention in accuracy in the Relational condition, in which strong associations between presented word pairs were required for successful performance, t(3)=5.21, p&amp;lt; .05. By contrast, accuracy did not increase significantly in the Item condition following intervention, t(3)=.48, p=.66). There was also a significant improvement in accuracy for the intermediate load (5-item) condition of the verbal working memory task following intervention, t(3)=4.17, p&amp;lt;.05. fMRI analyses revealed activation in a frontoparietal network during both the word pairs and verbal working memory tasks. Future analyses will investigate changes in recruitment of this network following intervention. Conclusions: Cancer survivors show evidence of specific transfer of memory skills following a group-based cognitive training intervention as demonstrated by improvement on the word memory task- relational item. In addition, there was a trend toward improvement on a working memory task. Neuroimaging results suggest frontoparietal network involvement for the cognitive task as well as some indication of a more efficient neural response following training. These results suggest that cognitive training may have a beneficial impact on both behavioral measures of cognition as well as neural activation markers. Citation Format: H. Gray, M. K. Askren Thomas, K. Anderson, D. David, A. Singh, K. Murphy, S. Willis, H. Mendoza, M.M. Cherrier. Neurocognitive evaluation of a cognitive training intervention in ovarian and gynecologic cancer survivors [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-CTRL-1205.

Cueing vocabulary in awake subjects during the day has no effect on memory

It is assumed that the beneficial effect of sleep on memory relies on spontaneous reactivation of memories during sleep. We recently showed that reactivation by re-exposure to previously learned foreign vocabulary cues during sleep benefits vocabulary learning. Cueing foreign vocabulary during active or passive wakefulness at night did not improve memory, suggesting that memory benefits of cueing are specific to sleep. However, the ineffectiveness of cueing during wakefulness might also be explained by increased tiredness of the participants in this former study. To exclude tiredness as a confounding factor, we tested the effect of vocabulary cueing during active and passive daytime wakefulness. It was hypothesized that cueing during waking does not improve memory consolidation, even when participants are well rested. A total of 32 subjects learned 120 Dutch–German word pairs. During a 3 h retention interval, parts of the previously learned Dutch words were replayed. Subjects of the active waking group (N = 16) were distracted from hearing the Dutch words by an n-back task, while subjects of the passive waking group (N = 16) were not distracted. After the retention interval, memory for word pairs was tested by a cued recall. Replay of Dutch words during daytime wake did not improve later memory for the German translation in either of the waking groups. We observed no difference in recall performance between cued and uncued words, neither in the active waking nor in the passive waking group. Cueing Dutch words during wakefulness does not exert beneficial effects on memory, even when subjects are well rested and under full control of their cognitive capacities. This result gives further evidence that the beneficial effects of cueing are solely specific to sleep.

Reduced habituation in patients with schizophrenia

BackgroundNeural habituation, the decrease in brain response to repeated stimulation, is a basic form of learning. There is strong evidence for behavioral and physiological habituation deficits in schizophrenia, and one previous study found reduced neural habituation within the hippocampus. However, it is unknown whether neural habituation deficits are specific to faces and limited to the hippocampus. Here we studied habituation of several brain regions in schizophrenia, using both face and object stimuli. Post-scan memory measures were administered to test for a link between hippocampal habituation and memory performance. MethodsDuring an fMRI scan, 23 patients with schizophrenia and 21 control subjects viewed blocks of a repeated neutral face or neutral object, and blocks of different neutral faces and neutral objects. Habituation in the hippocampus, primary visual cortex and fusiform face area (FFA) was compared between groups. Memory for faces, words, and word pairs was assessed after the scan. ResultsPatients showed reduced habituation to faces in the hippocampus and primary visual cortex, but not the FFA. Healthy control subjects exhibited a pattern of hippocampal discrimination that distinguished between repeated and different images for both faces and objects, and schizophrenia patients did not. Hippocampal discrimination was positively correlated with memory for word pairs. ConclusionPatients with schizophrenia showed reduced habituation of the hippocampus and visual cortex, and a lack of neural discrimination between old and new images in the hippocampus. Hippocampal discrimination correlated with memory performance, suggesting reduced habituation may contribute to the memory deficits commonly observed in schizophrenia.

Memory for Semantically Related and Unrelated Declarative Information: The Benefit of Sleep, the Cost of Wake

Numerous studies have examined sleep's influence on a range of hippocampus-dependent declarative memory tasks, from text learning to spatial navigation. In this study, we examined the impact of sleep, wake, and time-of-day influences on the processing of declarative information with strong semantic links (semantically related word pairs) and information requiring the formation of novel associations (unrelated word pairs). Participants encoded a set of related or unrelated word pairs at either 9am or 9pm, and were then tested after an interval of 30 min, 12 hr, or 24 hr. The time of day at which subjects were trained had no effect on training performance or initial memory of either word pair type. At 12 hr retest, memory overall was superior following a night of sleep compared to a day of wakefulness. However, this performance difference was a result of a pronounced deterioration in memory for unrelated word pairs across wake; there was no sleep-wake difference for related word pairs. At 24 hr retest, with all subjects having received both a full night of sleep and a full day of wakefulness, we found that memory was superior when sleep occurred shortly after learning rather than following a full day of wakefulness. Lastly, we present evidence that the rate of deterioration across wakefulness was significantly diminished when a night of sleep preceded the wake period compared to when no sleep preceded wake, suggesting that sleep served to stabilize the memories against the deleterious effects of subsequent wakefulness. Overall, our results demonstrate that 1) the impact of 12 hr of waking interference on memory retention is strongly determined by word-pair type, 2) sleep is most beneficial to memory 24 hr later if it occurs shortly after learning, and 3) sleep does in fact stabilize declarative memories, diminishing the negative impact of subsequent wakefulness.