Showing papers on "Sleep and memory published in 2009"
TL;DR: An extensive and critical review of the rapidly growing literature on sleep-dependent memory consolidation is provided, but rather than simply reviewing this literature, the authors have taken this opportunity to ask several important questions concerning off-line memory processing.
77 citations
TL;DR: The results suggest that both NREM and REM sleep are involved in sleep-dependent memory consolidation, and provide support for existing 2-stage models of sleep and memory including both non-rapid eye movement and rapid eye movement sleep.
75 citations
TL;DR: It is found that the bees sleep more during the dark phase of the day compared with the light phase, and retention for extinction learning was significantly reduced, indicating that consolidation of extinction memory but not acquisition memory was affected by sleep deprivation.
Abstract: Sleep-like behavior has been studied in honeybees before, but the relationship between sleep and memory formation has not been explored. Here we describe a new approach to address the question if sleep in bees, like in other animals, improves memory consolidation. Restrained bees were observed by a web camera, and their antennal activities were used as indicators of sleep. We found that the bees sleep more during the dark phase of the day compared with the light phase. Sleep phases were characterized by two distinct patterns of antennal activities: symmetrical activity, more prominent during the dark phase; and asymmetrical activity, more common during the light phase. Sleep-deprived bees showed rebound the following day, confirming effective deprivation of sleep. After appetitive conditioning of the bees to various olfactory stimuli, we observed their sleep. Bees conditioned to odor with sugar reward showed lesser sleep compared with bees that were exposed to either reward alone or air alone. Next, we asked whether sleep deprivation affects memory consolidation. While sleep deprivation had no effect on retention scores after odor acquisition, retention for extinction learning was significantly reduced, indicating that consolidation of extinction memory but not acquisition memory was affected by sleep deprivation.
66 citations
TL;DR: It is suggested that donepezil can improve delayed recognition in sleep-deprived persons by improving attention as well as enhancing memory encoding and the utility of combined fMRI-behavior evaluation in psychopharmacological studies.
Abstract: SLEEP AND MEMORY ARE STRONGLY INTERLINKED. SLEEP IS VITAL TO MEMORY CONSOLIDATION1–3 AND SLEEP DEPRIVATION RESULTS IN THE IMPAIRMENT OF short-term as well as long-term memory.4 In theory, the impact of sleep deprivation on memory might be reduced by directly influencing its component processes, encoding, consolidation and retrieval, or indirectly by enhancing arousal and/or attention.
The best-known countermeasures, caffeine, amphetamines and modafinil, all boost arousal and vigilant attention5 and to date, the more direct approach has not yielded much success. For example, while CX717, an ampakine, could theoretically improve memory through glutaminergic mechanisms, promising results obtained with primates6 were not similarly realized in a human study.7
Here, we evaluated the enhancement of cholinergic transmission with the long acting cholinesterase inhibitor, donepezil, as a means of ameliorating memory deficits in sleep deprivation, using a combination of behavioral and functional magnetic resonance imaging (fMRI) measures. Augmenting cholinergic transmission could benefit cognition in sleep-deprived individuals via multiple mechanisms: promoting wakefulness,8 through top-down increases in attention,9 increasing the signal-to-noise ratio of processing within visual sensory cortex,10,11 and enhancing LTP in hippocampal circuits.12 Additionally, cholinesterase inhibitors secondarily influence dopaminergic and noradrenergic neurotransmission.13 fMRI provides a noninvasive means of identifying the neuroanatomical locus of drug action that could help discern the functional relevance of these putative mechanisms.14
The neurobehavioral effects of manipulating cholinergic transmission in the context of non-sleep-deprived, healthy adults, performing tasks tapping attention and memory, have been well characterized in several functional imaging studies.15–21 In these studies, increasing cholinergic transmission generally improved attention and short-term memory whereas antagonists like scopolamine induced decline in long-term, episodic memory. Behavior-only studies using donepezil have yielded positive22 and negative23 results.
Reflecting the multiple mechanisms through which acetylcholine can modulate cognition across different tasks,24 the locus of drug effect(s) has varied across different studies. Drug induced modulation of neural activity has been reported in top-down control regions such as the frontal17 and parietal lobes,15,20 regions involved in visual processing such as the extrastriate visual cortex17,25 and the fusiform cortex19 as well as brain regions involved in memory encoding such as the hippocampal formation19,21 and the lateral prefrontal cortex.19
Another source of the varied results in these psychopharmacological-imaging studies is the point along the neurotransmitter signaling continuum that a subject lies. Recent studies involving cholinergic agents in elderly volunteers,15,23 sleep-deprived volunteers,25 as well as a pharmacogenetic study involving modafinil in sleep-deprived persons,26 have reinforced the notion that there exists a bell-shaped response curve to neurotransmitter augmentation.27,28 This is particularly relevant to the present study because the cognitive deficits experienced following sleep deprivation reportedly show trait-like inter-individual variation.29,30 One can reasonably postulate that inter-individual variation in reduced cholinergic drive might mediate vulnerability to sleep deprivation and that there would be a corresponding range of response to exogenous cholinergic augmentation (Supplementary Figure 1, available at www.journalsleep.org).
In this report, we evaluated two hypotheses. Firstly, in accordance with a sister study25 that evaluated visual short-term memory, we anticipated that donepezil would benefit episodic memory performance in persons vulnerable to the effects of sleep deprivation, but not otherwise. Secondly, we predicted that we would find correlation between donepezil-induced modulation of brain activation and memory improvement in left lateral prefrontal cortex, a region that participates in successful word encoding. This would be in line with the thesis that while cholinergic neurons have widespread projections in the cerebral cortex, modulation in brain activation can occur in a task-specific manner.14,31
In consideration of these goals, we conducted a double-blind, placebo-controlled, cross-over functional imaging study (Figure 1) that involved 26 healthy young adult participants. In this within-subject design, volunteers were scanned 4 times, twice following a normal night's sleep and twice after 24 hours of total sleep deprivation. During scanning, participants encoded words while they performed a semantic judgment task. A 5 mg dose of donepezil was compared to placebo. Delayed recognition memory (reflecting episodic memory), non-responses (reflecting attentional lapses), and judgment accuracy at encoding were the main behavioral measures of interest. Task-related activation associated with successfully encoded words was the main imaging variable of interest. As we studied the same subjects in both the present and previous report, we minimized the likelihood that between-subject anatomical variation would confound the localization of drug-induced fMRI signal modulation.
Figure 1
A schematic of the study timeline. B1, B2, and B3 denote briefing and screening sessions while S1, S2, S3, and S4 denote scanning sessions. The drug (placebo, donepezil) and state (rested wakefulness, sleep deprivation) conditions were counterbalanced ...
65 citations
TL;DR: It is found that post-reactivation RSD whether from 0 to 6h or 6 to 12h had no effect on the reconsolidation of both cued and contextual fear memory, however, the present results did not exclude the potential roles of non-rapid eye movement sleep in the reconsideration of fear memory or sleep inThe reconsolidations of other memory paradigms.
14 citations
[...]
TL;DR: Brain-imaging and gene-expression studies have provided limited evidence that sleep may facilitate the gradual redistribution of memory traces throughout the brain, but it remains unclear whether sleep-dependent consolidation is mediated by permissive or instructive mechanisms.
Abstract: Current behavioural evidence indicates that sleep plays a central role in memory
consolidation. Neural events during post-learning sleep share key features with both
early and late stages of memory consolidation. For example, recent studies have shown
neuronal changes during post-learning sleep which reflect early synaptic changes
associated with consolidation, including activation of shared intracellular pathways and
modifications of synaptic strength. Sleep may also play a role in later stages of
consolidation involving propagation of memory traces throughout the brain. However,
to date the precise molecular and physiological aspects of sleep required for this process
remain unknown. The behavioural effects of sleep may be mediated by the large-scale,
global changes in neuronal activity, synchrony and intracellular communication that
accompany this vigilance state, or by synapse-specific ‘replay’ of activity patterns
associated with prior learning.
10 citations
Journal Article•
[...]
TL;DR: Although recorded observations about the benefits of sleep on memory date back to ancient Rome, recent research has provided exciting evidence related to different types of memory and the role sleep can perform in learning and memory consolidation.
Abstract: Forgetfulness is a common complaint of people who do not get enough sleep, whether it is due to sleep deprivation from an overly busy schedule or the result of insomnia. People often find that it is more difficult both to learn and remember things when they are unable to achieve sufficient sleep on a regular basis. Although recorded observations about the benefits of sleep on memory date back to ancient Rome, recent research has provided exciting evidence related to different types of memory and the role sleep can perform in learning and memory consolidation. Research findings now suggest that different types of sleep can affect different types of memory It appears that sleep also can influence emotional aspects of our memory Some studies 1 even suggest that certain types of memory can be enhanced during sleep with instrumentation capable of promoting greater slow wave activity.
2 citations
01 Nov 2009