The Episodic-inhibition hypothesis

Consolidation of Episodic Memories During Sleep: Long-Term Effects of Retrieval Practice
Psychological Science OnlineFirst, published on November 23, 2009 as doi:10.1177/0956797609354074
Mihály Racsmány, Martin A. Conway, and Gyula Demeter

Two experiments investigated the long-term effects of retrieval practice. In the retrieval-practice procedure, selected items from a previously studied list are repeatedly recalled. The typical retrieval-practice effects are considerably enhanced memory for practiced items accompanied by low levels of recall, relative to baseline, for previously studied items that are associated with the practiced items but were not themselves practiced. The two experiments demonstrated that the former effect persisted over 12 hr; the latter effect also persisted over 12 hr, but only if a period of nocturnal sleep occurred during the retention interval. We propose that consolidation processes occurring during sleep, and possibly featuring some form of offline rehearsal, mediate these long-term effects of retrieval practice.

More faithful memories for those experiences

Awake replay of remote experiences in the hippocampus
Nature Neuroscience Volume 12, Number 7, July 2009
Published online at
Mattias P Karlsson & Loren M Frank

Hippocampal replay is thought to be essential for the consolidation of event memories in hippocampal-neocortical networks. Replay is present during both sleep and waking behavior, but although sleep replay involves the reactivation of stored representations in the absence of specific sensory inputs, awake replay is thought to depend on sensory input from the current environment. Here, we show that stored representations are reactivated during both waking and sleep replay. We found frequent awake replay of sequences of rat hippocampal place cells from a previous experience. This spatially remote replay was as common as local replay of the current environment and was more robust when the rat had recently been in motion than during extended periods of quiescence. Our results indicate that the hippocampus consistently replays past experiences during brief pauses in waking behavior, suggesting a role for waking replay in memory consolidation and retrieval.

Growing Older Does Not Mean Sleeping Poorly

Recent Advances in Understanding Sleep and Sleep Disturbances in Older Adults
Growing Older Does Not Mean Sleeping Poorly
Association for Psychological Science Volume 18—Number 6
Michael V. Vitiello

Despite commonly held assumptions, growing older does not necessarily result in disturbed or unsatisfying sleep. There is no reason to assume, a priori, that the sleep of an older adult is necessarily problematic; in fact, many high-functioning older adults are satisfied with their sleep. When the various factors that can disrupt sleep— poor health, primary sleep disorders, poor sleep-hygiene practices (e.g., irregular sleep schedules and poor sleeping environments), and so on—are screened out, ‘‘optimally’’ or ‘‘successfully’’ aging older adults, assuming they remain healthy, can expect to experience little further change in their sleep and are not likely to experience excessive daytime sleepiness and the concomitant need to nap regularly during the day. Nevertheless, the majority of older adults, who are not optimally aging, suffer significant sleep disturbances from a variety of causes. Fortunately, our growing understanding of how sleep changes with aging and of the causes of these changes is informing ever-improving treatments for these disturbances, thereby helping to ensure that growing older does not mean sleeping poorly.

A theory of protoconsciousness

REM sleep and dreaming: towards a theory of protoconsciousness
Nature Reviews| Neuroscience volume 10 | November 2009 | 803
J. Allan Hobson

Dreaming has fascinated and mystified humankind for ages: the bizarre and evanescent qualities of dreams have invited boundless speculation about their origin, meaning and purpose. For most of the twentieth century, scientific dream theories were mainly psychological. Since the discovery of rapid eye movement (REM) sleep, the neural underpinnings of dreaming have become increasingly well understood, and it is now possible to complement the details of these brain mechanisms with a theory of consciousness that is derived from the study of dreaming. The theory advanced here emphasizes data that suggest that REM sleep may constitute a protoconscious state, providing a virtual reality model of the world that is of functional use to the development and maintenance of waking consciousness.

True or False?

How to Tell If a Particular Memory Is True or False
Daniel M. Bernstein and Elizabeth F. Loftus
Association for Psychological Science Volume 4—Number 4

How can you tell if a particular memory belonging to you or someone else is true or false? Cognitive scientists use a variety of techniques to measure groups of memories, whereas police, lawyers, and other researchers use procedures to determine whether an individual can be believed or not. We discuss evidence from behavioral and neuroimaging studies and research on lying that have attempted to distinguish true from false memories.

We remember events, people, and places all the time, but how accurate are those memories? More specifically, how can we identify true memories from false ones? A majority of studies trying to answer this question have tended to focus on one of several possible methods of analysis, concentrating on either groups of memories being reported (e.g., studying word lists and then remembering related words that were not included in the original lists) or the person who is reporting the memories (for example, using a battery of self-report questionnaires and behavioral assessments to predict who may be susceptible to forming false memories). In a new report, Daniel M. Bernstein and Elizabeth F. Loftus suggest that a combined approach — focusing on groups of memories, on the person who is remembering, and on the individual memory — along with taking advantage of a variety of research tools available (such as imaging devices, mathematical models, analysis techniques, and statistical methods) may be the best way to determine if a memory is truth or fiction.

Join the discussion here on APS.

Transform Your Mind, Change Your Brain

In this talk, Richard J. Davidson explores recent scientific research on the neuroscience of positive human qualities and how they can be cultivated through contemplative practice. Distinctions among different forms of contemplative practices are introduced and shown to have different neural and behavioral consequences, as well as important consequences for physical health in both long-term and novice practitioners. New research also shows that meditation-based interventions delivered online can produce behavioral and neural changes. Collectively, this body of research indicates that we can cultivate adaptive neural changes and strengthen positive human qualities through systematic mental practice.

The Role of Sleep in Emotional Brain Processing

Cognitive neuroscience continues to build meaningful connections between affective behavior and human brain function. Within the biological sciences, a similar renaissance has taken place, focusing on the role of sleep in various neurocognitive processes and, most recently, on the interaction between sleep and emotional regulation. This review surveys an array of diverse findings across basic and clinical research domains, resulting in a convergent view of sleep-dependent emotional brain processing. On the basis of the unique neurobiology of sleep, the authors outline a model describing the overnight modulation of affective neural systems and the (re)processing of recent emotional experiences, both of which appear to redress the appropriate next-day reactivity of limbic and associated autonomic networks. Furthermore, a rapid eye movement (REM) sleep hypothesis of emotional-memory processing is proposed, the implications of which may provide brain-based insights into the association between sleep abnormalities and the initiation and maintenance of mood disturbances.

How we read each other's minds?

Sensing the motives and feelings of others is a natural talent for humans. But how do we do it? Here, Rebecca Saxe shares fascinating lab work that uncovers how the brain thinks about other peoples' thoughts -- and judges their actions.

Consolidation of Associative Memory

Hippocampal sharp wave/ripples during sleep for consolidation of associative memory.
Ramadan W, Eschenko O, Sara SJ.
PLoS One. 2009 Aug 20;4(8):e6697.

The beneficial effect of sleep on memory has been well-established by extensive research on humans, but the neurophysiological mechanisms remain a matter of speculation. This study addresses the hypothesis that the fast oscillations known as ripples recorded in the CA1 region of the hippocampus during slow wave sleep (SWS) may provide a physiological substrate for long term memory consolidation. We trained rats in a spatial discrimination task to retrieve palatable reward in three fixed locations. Hippocampal local field potentials and cortical EEG were recorded for 2 h after each daily training session. There was an increase in ripple density during SWS after early training sessions, in both trained rats and in rats randomly rewarded for exploring the maze. In rats learning the place -reward association, there was a striking further significant increase in ripple density correlated with subsequent improvements in behavioral performance as the rat learned the spatial discrimination aspect of the task. The results corroborate others showing an experience-dependent increase in ripple activity and associated ensemble replay after exploratory activity, but in addition, for the first time, reveal a clear further increase in ripple activity related to associative learning based on spatial discrimination.

Secrets of the Sleeping Brain

Why do we sleep? Although science has yet to explain the reason we spend one-third of our lives in this bizarre state, an exciting theory suggests that sleep can solidify newly learned memories by rewiring the architecture of brain.

Emerging neuroscience evidence also indicates that sleep can intelligently associate and integrate new memories together, performing a kind of "sleep-dependent alchemy." This phenomenon may fuel creative human insights, often reflected in dream content.

In addition to memory benefits, recent findings also suggest that sleep can "refresh" emotional brain reactivity, smoothing away the rough edges from our prior waking concerns, thereby allowing rational next-day decisions.

Exploring the mind of a killer

Psychopathic killers are the basis for some must-watch TV, but what really makes them tick? Neuroscientist Jim Fallon talks about brain scans and genetic analysis that may uncover the rotten wiring in the nature (and nurture) of murderers. In a too-strange-for-fiction twist, he shares a fascinating family history that makes his work chillingly personal.

Getting by on six hours of sleep?

The Transcriptional Repressor DEC2 Regulates Sleep Length in Mammals
Ying He, Christopher R. Jones, Nobuhiro Fujiki, Ying Xu, Bin Guo, Jimmy L. Holder, Jr., Moritz J. Rossner, Seiji Nishino, Ying-Hui Fu
Science 14 August 2009:
Vol. 325. no. 5942, pp. 866 - 870

Sleep deprivation can impair human health and performance. Habitual total sleep time and homeostatic sleep response to sleep deprivation are quantitative traits in humans. Genetic loci for these traits have been identified in model organisms, but none of these potential animal models have a corresponding human genotype and phenotype. We have identified a mutation in a transcriptional repressor (hDEC2-P385R) that is associated with a human short sleep phenotype. Activity profiles and sleep recordings of transgenic mice carrying this mutation showed increased vigilance time and less sleep time than control mice in a zeitgeber time– and sleep deprivation–dependent manner. These mice represent a model of human sleep homeostasis that provides an opportunity to probe the effect of sleep on human physical and mental health.

Extreme Sleep Durations Lead to Poor Quality of Life

Sleep Duration and Health-Related Quality of Life among Older Adults: A Population-Based Cohort in Spain
Raquel Faubel, Esther Lopez-Garcia, Pilar Guallar-Castillón, Teresa Balboa-Castillo, Juan Luis Gutiérrez-Fisac, José R. Banegas, Fernando Rodríguez-Artalejo
Volume: 32
Issue : 08
Pages : 1059-1068

Study Objectives:The few studies that have addressed the association between sleep duration and health-related quality of life (HRQL) were cross-sectional and small-sized, targeted young and middle-aged persons, and did not adjust for the main confounders.This study sought to examine the cross-sectional and longitudinal relationship between habitual sleep duration and HRQL in older adults.

Design: Prospective study conducted from 2001 through 2003. Sleep duration was self-reported in 2001, and HRQL was measured using the SF-36 questionnaire in 2001 and 2003. Analyses were adjusted for the main confounders.

Setting: Community-based study.

Participants: A cohort of 3834 persons representative of the non-institutionalized Spanish population aged 60 years and over.

Intervention: None.

Measurement and Results: In comparison with women who slept 7 hours, those with extreme sleep durations (≤ 5 or ≥ 10 h) reported worse scores on the SF-36 physical and mental scales in 2001. Among men, sleeping ≤ 5 h was associated with a worse score in the role-physical scale in 2001. The magnitude of most of these associations was comparable with the reduction in HRQL associated with aging 10 years. Sleep duration in 2001 failed to predict changes in HRQL between 2001 and 2003.

Conclusion:Extreme sleep durations are a marker of worse HRQL in the elderly.

2-stage models of sleep and memory

Evidence for 2-stage models of sleep and memory: Learning-dependent changes in spindles and theta in rats
Stuart M. Fogel, Carlyle T. Smithb, Richard J. Beninger
Brain Research Bulletin 79 (2009) 445–451

What processes are involved in the formation of enduring memory traces? Sleep has been proposed to play a role in memory consolidation and the present study provides evidence to support 2-stage models of sleep and memory including both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Previous research has shown REM sleep increases following avoidance learning and memory is impaired if REM deprivation occurs during these post-training periods indicating that REM sleep may have a role in memory consolidation processes. These discrete post-training periods have been termed REM sleep windows (RSWs). It is not known whether the electroencephalogram has unique characteristics during the RSW. Further investigation of the RSW was one of the primary goals of this study. We investigated the epidural-recorded electrophysiological learning-related changes following avoidance training in rats. Theta power increased in the learning group during the RSW, suggesting that theta is involved in memory consolidation during this period. Sleep spindles subsequently increased in slow wave sleep (SWS). The results suggest that both NREM and REM sleep are involved in sleep-dependent memory consolidation, and provide support for existing 2-stage models. Perhaps first theta increases to organize and consolidate material via hippocampal–neocortical dialogue, followed by subsequent refinement in the cortex by spindles during SWS.

Functional Brain Networks Organization

Functional Brain Networks Develop from a "Local to Distributed" Organization
Damien A. Fair, Alexander L. Cohen, Jonathan D. Power, Nico U. F. Dosenbach, Jessica A. Church,Francis M. Miezin, Bradley L. Schlaggar, Steven E. Petersen
PLoS Computational Biology | 1 May 2009 | Volume 5 | Issue 5 | e1000381

The mature human brain is organized into a collection of specialized functional networks that flexibly interact to support various cognitive functions. Studies of development often attempt to identify the organizing principles that guide the maturation of these functional networks. In this report, we combine resting state functional connectivity MRI (rs-fcMRI), graph analysis, community detection, and spring-embedding visualization techniques to analyze four separate networks defined in earlier studies. As we have previously reported, we find, across development, a trend toward ‘segregation’ (a general decrease in correlation strength) between regions close in anatomical space and ‘integration’ (an increased correlation strength) between selected regions distant in space. The generalization of these earlier trends across multiple networks suggests that this is a general developmental principle for changes in functional connectivity that would extend to large-scale graph theoretic analyses of large-scale brain networks. Communities in children are predominantly arranged by anatomical proximity, while communities in adults predominantly reflect functional relationships, as defined from adult fMRI studies. In sum, over development, the organization of multiple functional networks shifts from a local anatomical emphasis in children to a more "distributed" architecture in young adults. We argue that this "local to distributed" developmental characterization has important implications for understanding the development of neural systems underlying cognition. Further, graph metrics (e.g., clustering coefficients and average path lengths) are similar in child and adult graphs, with both showing "small-world"-like properties, while community detection by modularity optimization reveals stable communities within the graphs that are clearly different between young children and young adults. These observations suggest that early school age children and adults both have relatively efficient systems that may solve similar information processing problems in divergent ways.

Whats and Whens of sleep-dependent memory consolidation

The whats and whens of sleep-dependent memory consolidation
Susanne Diekelmann, Ines Wilhelm, Jan Born
Sleep Medicine Reviews (2009), doi:10.1016

Sleep benefits memory consolidation. The reviewed studies indicate that this consolidating effect is not revealed under all circumstances but is linked to specific psychological conditions. Specifically, we discuss to what extent memory consolidation during sleep depends on the type of learning materials, type of learning and retrieval test, different features of sleep and the subject population. Post-learning sleep enhances consolidation of declarative, procedural and emotional memories. The enhancement is greater for weakly than strongly encoded associations and more consistent for explicitly than implicitly encoded memories. Memories associated with expected reward gain preferentially access to sleep-dependent consolidation. For declarative memories, sleep benefits are more consistently revealed with recall than recognition procedures at retrieval testing. Slow wave sleep (SWS) particularly enhances declarative memories whereas rapid eye movement (REM) sleep preferentially supports procedural and emotional memory aspects. Declarative memory profits already from rather short sleep periods (1–2 h). Procedural memory profits seem more dose-dependent on the amount of sleep following the day after learning. Children’s sleep with high amounts of SWS distinctly enhances declarative memories whereas elderly and psychiatric patients with disturbed sleep show impaired sleep-associated consolidation often of declarative memories. Based on the constellation of psychological conditions identified we hypothesize that access to sleep-dependent consolidation requires memories to be encoded under control of prefrontal-hippocampal circuitry, with the same circuitry controlling subsequent consolidation during sleep.

Genetic and molecular regulation of sleep

The genetic and molecular regulation of sleep: from fruit flies to humans
Nature Reviews | Neuroscience Volume 10 | August 2009 | 549
Chiara Cirelli

It has been known for a long time that genetic factors affect sleep quantity and quality. Genetic screens have identified several mutations that affect sleep across species, pointing to an evolutionary conserved regulation of sleep. Moreover, it has also been recognized that sleep affects gene expression. These findings have given valuable insights into the molecular underpinnings of sleep regulation and function that might lead the way to more efficient treatments for sleep disorders.

Neurons that Fire Together Also Conspire Together

Neurons that Fire Together Also Conspire Together: Is Normal Sleep Circuitry Hijacked to Generate Epilepsy?
Neuron 62, June 11, 2009 (DOI 10.1016/j.neuron.2009.05.015)
Mark P. Beenhakker and John R. Huguenard

Brain circuits oscillate during sleep. The same circuits appear to generate pathological oscillations. In this review, we discuss recent advances in our understanding of how epilepsy co-opts normal, sleep-related circuits to generate seizures.

How to Tell If a Particular Memory Is True or False

How to Tell If a Particular Memory Is True or False
Perspectives on Psychological Science, Volume 4, Issue 4, Pages 370-374
Daniel M. Bernstein and Elizabeth F. Loftus

How can you tell if a particular memory belonging to you or someone else is true or false? Cognitive scientists use a variety of techniques to measure groups of memories, whereas police, lawyers, and other researchers use procedures to determine whether an individual can be believed or not. We discuss evidence from behavioral and neuroimaging studies and research on lying that have attempted to distinguish true from false memories.

How Technology May Soon "Read" Your Mind

Neuroscience has learned so much about how we think and the brain activity linked to certain thoughts that it is now possible - on a very basic scale - to read a person's mind.

Watch this CBS 60 Minutes video to learn more about how this incredible research lets scientists get a glimpse at your thoughts.

Pain and Emotion

The influence of negative emotions on pain: Behavioral effects and neural mechanisms,
NeuroImage (2009), doi:10.1016/j.neuroimage.2009.05.059
Katja Wiech, Irene Tracey

The idea that pain can lead to feelings of frustration, worry, anxiety and depression seems obvious, particularly if it is of a chronic nature. However, there is also evidence for the reverse causal relationship in which negative mood and emotion can lead to pain or exacerbate it. Here, we review findings from studies on the modulation of pain by experimentally induced mood changes and clinical mood disorders. We discuss possible neural mechanisms underlying this modulatory influence focusing on the periaqueductal grey (PAG), amygdala, anterior cingulate cortex (ACC) and anterior insula as key players in both, pain and affective processing.

Replay during sleep

Replay of rule-learning related neural patterns in the prefrontal cortex during sleep
Adrien Peyrache, Mehdi Khamassi, Karim Benchenane, Sidney I Wiener & Francesco P Battaglia
Nature Neuroscience, doi:10.1038/nn.2337

Slow-wave sleep (SWS) is important for memory consolidation. During sleep, neural patterns reflecting previously acquired information are replayed. One possible reason for this is that such replay exchanges information between hippocampus and neocortex, supporting consolidation. We recorded neuron ensembles in the rat medial prefrontal cortex (mPFC) to study memory trace reactivation during SWS following learning and execution of cross-modal strategy shifts. In general, reactivation of learning-related patterns occurred in distinct, highly synchronized transient bouts, mostly simultaneous with hippocampal sharp wave/ripple complexes (SPWRs), when hippocampal ensemble reactivation and cortico-hippocampal interaction is enhanced. During sleep following learning of a new rule, mPFC neural patterns that appeared during response selection replayed prominently, coincident with hippocampal SPWRs. This was learning dependent, as the patterns appeared only after rule acquisition. Therefore, learning, or the resulting reliable reward, influenced which patterns were most strongly encoded and successively reactivated in the hippocampal/prefrontal network.

Hippocampal theta oscillations are traveling waves

Hippocampal theta oscillations are traveling waves.
Lubenov EV, Siapas AG
Nature 2009;459(7246):534-9.

Theta oscillations clock hippocampal activity during awake behaviour and rapid eye movement (REM) sleep. These oscillations are prominent in the local field potential, and they also reflect the subthreshold membrane potential and strongly modulate the spiking of hippocampal neurons. The prevailing view is that theta oscillations are synchronized throughout the hippocampus, despite the lack of conclusive experimental evidence. In contrast, here we show that in freely behaving rats, theta oscillations in area CA1 are travelling waves that propagate roughly along the septotemporal axis of the hippocampus. Furthermore, we find that spiking in the CA1 pyramidal cell layer is modulated in a consistent travelling wave pattern. Our results demonstrate that theta oscillations pattern hippocampal activity not only in time, but also across anatomical space. The presence of travelling waves indicates that the instantaneous output of the hippocampus is topographically organized and represents a segment, rather than a point, of physical space.

That Face Looks Familiar

Does Sleep Really Influence Face Recognition Memory?
Bhavin R. Sheth, Ngan Nguyen, Davit Janvelyan
PLoS ONE 4(5): e5496. doi:10.1371/journal.pone.0005496

Mounting evidence implicates sleep in the consolidation of various kinds of memories. We investigated the effect of sleep on memory for face identity, a declarative form of memory that is indispensable for nearly all social interaction. In the acquisition phase, observers viewed faces that they were required to remember over a variable retention period (0–36 hours). In the test phase, observers viewed intermixed old and new faces and judged seeing each before. Participants were classified according to acquisition and test times into seven groups. Memory strength (d′) and response bias (c) were evaluated. Substantial time spent awake (12 hours or more) during the retention period impaired face recognition memory evaluated at test, whereas sleep per se during the retention period did little to enhance the memory. Wakefulness during retention also led to a tightening of the decision criterion. Our findings suggest that sleep passively and transiently shelters face recognition memory from waking interference (exposure) but does not actively aid in its long-term consolidation.

Physiological markers of local sleep

Physiological Markers of Local Sleep
David M. Rector, Jennifer L. Schei, Hans P. A. Van Dongen, Gregory Belenky and James M. Krueger
Eur J Neurosci 2009;29(9):1771-8.

Substantial evidence suggests that brain regions that have been disproportionately used during waking will require a greater intensity and/or duration of subsequent sleep. For example, rats use their whiskers in the dark and their eyes during the light which manifests as a greater magnitude of electroencephalogram (EEG) slow wave activity in the somatosensory and visual cortex during sleep in the corresponding light and dark periods respectively. The parsimonious interpretation of such findings is that sleep is distributed across local brain regions and is use-dependent. The fundamental properties of sleep can also be experimentally defined locally at the level of small neural assemblies such as cortical columns. In this view, sleep is orchestrated, but not fundamentally driven, by central mechanisms. We explore two physiological markers of local, use-dependent sleep, namely, an electrical marker apparent as a change in the size and shape of an electrical evoked response, and a metabolic marker evident as an evoked change in blood volume and oxygenation delivered to activated tissue. Both markers, applied to cortical columns, provide a means to investigate physiological mechanisms for the distributed homeostatic regulation of sleep, and may yield new insights into the consequences of sleep loss and sleep pathologies on waking brain function.

Slow waves and information processing

Slow waves, synaptic plasticity and information processing: insights from transcranial magnetic stimulation and high-density EEG experiments
M Massimini, G Tononi, R Huber
European Journal of Neuroscience, Vol. 29, No. 9., pp. 1761-1770.

Sleep slow waves are the main phenomenon underlying NREM sleep. They are homeostatically regulated, they are thought to be linked to learning and plasticity processes and, at the same time, they are associated with marked changes in cortical information processing. Using transcranial magnetic stimulation (TMS) and high-density (hd) EEG we can measure slow waves, induce and measure plastic changes in the cerebral cortex and directly assess corticocortical information transmission. In this manuscript we review the results of recent experiments in which TMS with hd-EEG is used to demonstrate (i) a causal link between cortical plastic changes and sleep slow waves and (ii) a causal link between slow waves and the decreased ability of thalamocortical circuits to integrate information and to generate conscious experience during NREM sleep. The data presented here suggest a unifying mechanism linking slow waves, plasticity and cortical information integration; moreover, they suggest that TMS can be used as a nonpharmacological means to controllably induce slow waves in the human cerebral cortex.

Lessons from fMRI Studies of Emotion, Personality, and Social Cognition

Perspectives on Psychological Science a Journal of the Association for Psychological Science had these recent articles. Posted below are the links to the excellent debate/discussions about fMRI statistical analyses and interesting issues for scientific psychology.

Editor's Introduction to Vul et al. (2009) and Comments
Ed Diener

Puzzlingly High Correlations in fMRI Studies of Emotion, Personality, and Social CognitionEdward Vul, Christine Harris, Piotr Winkielman, and Harold Pashler

Commentary on Vul et al.'s (2009) "Puzzlingly High Correlations in fMRI Studies of Emotion, Personality, and Social Cognition"Thomas E. Nichols and Jean-Baptist Poline

Big Correlations in Little Studies: Inflated fMRI Correlations Reflect Low Statistical Power--Commentary on Vul et al. (2009)
Tal Yarkoni

Correlations in Social Neuroscience Aren't Voodoo: Commentary on Vul et al. (2009)
Matthew D. Lieberman, Elliot T. Berkman, and Tor D. Wager

Discussion of "Puzzlingly High Correlations in fMRI Studies of Emotion, Personality, and Social Cognition" by Vul et al. (2009)
Nicole A. Lazar

Correlations and Multiple Comparisons in Functional Imaging: A Statistical Perspective (Commentary on Vul et al., 2009Martin A. Lindquist and Andrew Gelman

Understanding the Mind by Measuring the Brain: Lessons From Measuring Behavior (Commentary on Vul et al., 2009)
Lisa Feldman Barrett

Reply to Comments on "Puzzlingly High Correlations in fMRI Studies of Emotion, Personality, and Social Cognition"
Edward Vul, Christine Harris, Piotr Winkielman, and Harold Pashler

Improve creativity while sleeping / dreaming

REM, not incubation, improves creativity by priming associative networks
Denise J. Cai, Sarnoff A. Mednick, Elizabeth M. Harrison, Jennifer C. Kanady, and Sara C. Mednick

The hypothesized role of rapid eye movement (REM) sleep, which is rich in dreams, in the formation of new associations, has remained anecdotal. We examined the role of REM on creative problem solving, with the Remote Associates Test (RAT). Using a nap paradigm, we manipulated various conditions of prior exposure to elements of a creative problem. Compared with quiet rest and non-REM sleep, REM enhanced the formation of associative networks and the integration of unassociated information. Furthermore, these REM sleep benefits were not the result of an improved memory for the primed items. This study shows that compared with quiet rest and non-REM sleep, REM enhances the integration of unassociated information for creative problem solving, a process, we hypothesize, that is facilitated by cholinergic and noradrenergic neuromodulation during REM sleep.

False Memory Formation

The role of sleep in false memory formation
Neurobiology of Learning and Memory (2009), doi:10.1016/j.nlm.2009.03.007
Jessica D. Payne, Daniel L. Schacter, Ruth E. Propper, Li-Wen Huang, Erin J. Wamsley, Matthew A. Tucker, Matthew P. Walker, Robert Stickgold

Memories are not stored as exact copies of our experiences. As a result, remembering is subject not only to memory failure, but to inaccuracies and distortions as well. Although such distortions are often retained or even enhanced over time, sleep’s contribution to the development of false memories is unknown. Here, we report that a night of sleep increases both veridical and false recall in the Deese– Roediger–McDermott (DRM) paradigm, compared to an equivalent period of daytime wakefulness. But while veridical memory deteriorates across both wake and sleep, false memories are preferentially preserved by sleep, actually showing a non-significant improvement. The same selectivity of false over veridical memories was observed in a follow-up nap study. Unlike previous studies implicating deep, slow wave sleep (SWS) in declarative memory consolidation, here veridical recall correlated with decreased
SWS, a finding that was observed in both the overnight and nap studies. These findings lead to two counter intuitive conclusions – that under certain circumstances sleep can promote false memories over veridical ones, and SWS can be associated with impairment rather than facilitation of declarative memory consolidation. While these effects produce memories that are less accurate after sleep, these memories may, in the end, be more useful.

Neurons take a break during slow-wave sleep

The Human K-Complex Represents an Isolated Cortical Down-State
Science 22 May 2009:Vol. 324. no. 5930, pp. 1084 - 1087

The electroencephalogram (EEG) is a mainstay of clinical neurology and is tightly correlated with brain function, but the specific currents generating human EEG elements remain poorly specified because of a lack of microphysiological recordings. The largest event in healthy human EEGs is the K-complex (KC), which occurs in slow-wave sleep. Here, we show that KCs are generated in widespread cortical areas by outward dendritic currents in the middle and upper cortical layers, accompanied by decreased broadband EEG power and decreased neuronal firing, which demonstrate a steep decline in network activity. Thus, KCs are isolated "down-states," a fundamental cortico-thalamic processing mode already characterized in animals. This correspondence is compatible with proposed contributions of the KC to sleep preservation and memory consolidation.

Face recognition memory

Does sleep really influence face recognition memory?
PLoS ONE 2009;4(5):e5496.
Sheth BR, Nguyen N, Janvelyan D.

Mounting evidence implicates sleep in the consolidation of various kinds of memories. We investigated the effect of sleep on memory for face identity, a declarative form of memory that is indispensable for nearly all social interaction. In the acquisition phase, observers viewed faces that they were required to remember over a variable retention period (0-36 hours). In the test phase, observers viewed intermixed old and new faces and judged seeing each before. Participants were classified according to acquisition and test times into seven groups. Memory strength (d') and response bias (c) were evaluated. Substantial time spent awake (12 hours or more) during the retention period impaired face recognition memory evaluated at test, whereas sleep per se during the retention period did little to enhance the memory. Wakefulness during retention also led to a tightening of the decision criterion. Our findings suggest that sleep passively and transiently shelters face recognition memory from waking interference (exposure) but does not actively aid in its long-term consolidation.

Exercise and sleep deprivation

The impact of 100 hours of exercise and sleep deprivation on cognitive function and physical capacities.
J Sports Sci. 2009 May 11:1-10.
Lucas SJ, Anson JG, Palmer CD, Hellemans IJ, Cotter JD.

In this study, we examined the effect of 96-125 h of competitive exercise on cognitive and physical performance. Cognitive performance was assessed using the Stroop test (n = 9) before, during, and after the 2003 Southern Traverse adventure race. Strength (MVC) and strength endurance (time to failure at 70% current MVC) of the knee extensor and elbow flexor muscles were assessed before and after racing. Changes in vertical jump (n = 24) and 30-s Wingate performance (n = 27) were assessed in a different group of athletes. Complex response times were affected by the race (16% slower), although not significantly so (P = 0.18), and were dependent on exercise intensity (less so at 50% peak power output after racing). Reduction of strength (P < 0.05) of the legs (17%) and arms (11%) was equivalent (P = 0.17). Reductions in strength endurance were inconsistent (legs 18%, P = 0.09; arms 13%, P = 0.40), but were equivalent between limbs (P = 0.80). Similar reductions were observed in jump height (-8 +/- 9%, P < 0.01) and Wingate peak power (-7 +/- 15%, P = 0.04), mean power (-7 +/- 11%, P < 0.01), and end power (-10 +/- 11%, P < 0.01). We concluded that: moderate-intensity exercise may help complex decision making during sustained stress; functional performance was modestly impacted, and the upper and lower limbs were affected similarly despite being used disproportionately.

Multiple genes and multiple phenotypes

Sleep and circadian rhythm disturbances: multiple genes and multiple phenotypes.
Curr Opin Genet Dev
Wulff K, Porcheret K, Cussans E, Foster RG

Sleep is regulated by two broad mechanisms: the circadian system, which generates 24-h rhythms of sleep propensity and a wake-dependent homeostatic sleep process whereby sleep pressure increases during wake and dissipates during sleep. These, in turn, regulate multiple brain structures and neurotransmitter systems. In view of the complexity of sleep it is not surprising that there is considerable variation between individuals in both sleep timing and propensity. Furthermore, marked abnormalities in sleep are commonly encountered in psychiatric and neurodegenerative disorders. Teasing apart the genetic versus environmental contributions to normal and abnormal sleep is complex. Here we attempt to summarise what recent progress has been made, and what will be needed in the future to gain a more complete understanding of this fundamental aspect of physiology.

Early Birds and Night Owls

Homeostatic Sleep Pressure and Responses to Sustained Attention in the Suprachiasmatic Area
Christina Schmidt, Fabienne Collette, Yves Leclercq, Virginie Sterpenich, Gilles Vandewalle, Pierre Berthomier, Christian Berthomier, Christophe Phillips, Gilberte Tinguely, Annabelle Darsaud, Steffen Gais, Manuel Schabus, Martin Desseilles, Thien Thanh Dang-Vu, Eric Salmon, Evelyne Balteau, Christian Degueldre, André Luxen, Pierre Maquet, Christian Cajochen, and Philippe Peigneux

Science 24 April 2009 324: 516-519 [DOI: 10.1126/science.1167337] (in Reports)

Throughout the day, cognitive performance is under the combined influence of circadian processes and homeostatic sleep pressure. Some people perform best in the morning, whereas others are more alert in the evening. These chronotypes provide a unique way to study the effects of sleep wake regulation on the cerebral mechanisms supporting cognition. Using functional magnetic resonance imaging in extreme chronotypes, we found that maintaining attention in the evening was associated with higher activity in evening than morning chronotypes in a region of the locus coeruleus and in a suprachiasmatic area (SCA) including the circadian master clock. Activity in the SCA decreased with increasing homeostatic sleep pressure. This result shows the direct influence of the homeostatic and circadian interaction on the neural activity underpinning human behavior.

Exploring the re-wiring of the brain

Neuroscientist Michael Merzenich looks at one of the secrets of the brain's incredible power: its ability to actively re-wire itself. He's researching ways to harness the brain's plasticity to enhance our skills and recover lost function.

Think, blink or sleep on it?

Think, blink or sleep on it? The impact of modes of thought on complex decision making.
Q J Exp Psychol (Colchester). 2009 Apr;62(4):707-32. Epub 2008 Aug 23.
Newell BR, Wong KY, Cheung JC, Rakow T.

This paper examines controversial claims about the merit of "unconscious thought" for making complex decisions. In four experiments, participants were presented with complex decisions and were asked to choose the best option immediately, after a period of conscious deliberation, or after a period of distraction (said to encourage "unconscious thought processes"). In all experiments the majority of participants chose the option predicted by their own subjective attribute weighting scores, regardless of the mode of thought employed. There was little evidence for the superiority of choices made "unconsciously", but some evidence that conscious deliberation can lead to better choices. The final experiment suggested that the task is best conceptualized as one involving "online judgement" rather than one in which decisions are made after periods of deliberation or distraction. The results suggest that we should be cautious in accepting the advice to "stop thinking" about complex decisions.

Nightmares, Bad Dreams, and Emotion Dysregulation

A Review and New Neurocognitive Model of Dreaming
Current Directions in Psych Science, Volume 18—Number 2
Ross Levin and Tore Nielsen

Nightmares—vivid, emotionally dysphoric dreams—are quite common and are associated with a broad range of psychiatric conditions. However, the origin of such dreams remains largely unexplained, and there have been no attempts to reconcile repetitive traumatic nightmares with nontraumatic nightmares, dysphoric dreams that do not awaken the dreamer, or with more normative dreams. Based on recent research in cognitive neuroscience, sleep physiology, fear conditioning, and emotional-memory regulation, we propose a multilevel neurocognitive model that unites waking and sleeping as a conceptual framework for understanding a wide spectrum of disturbed dreaming. We propose that normal dreaming serves a fear-extinction function and that nightmares reflect failures in emotion regulation. We further suggest that nightmares occur as a result of two processes that we term affect load—a consequence of daily variations in emotional pressures—and affect distress—a disposition to experience events with high levels of negative emotional reactivity.

Role of Sleep in Cognition and Emotion

The Year in Cognitive Neuroscience 2009: Ann. N.Y. Acad. Sci. 1156: 168–197 (2009).
Matthew P. Walker

As critical as waking brain function is to cognition, an extensive literature now indicates that sleep supports equally important, different yet complementary operations. This review will consider recent and emerging findings implicating sleep and specific sleep-stage physiologies in the modulation, regulation, and even preparation of cognitive and emotional brain processes. First, evidence for the role of sleep in memory processing will be discussed, principally focusing on declarative memory. Second, at a neural level several mechanistic models of sleep-dependent plasticity underlying these effects will be reviewed, with a synthesis of these features offered that may explain the ordered structure of sleep, and the orderly evolution of memory stages. Third, accumulating evidence for the role of sleep in associative memory processing will be discussed,suggesting that the long-term goal of sleep may not be the strengthening of individual memory items, but, instead, their abstracted assimilation into a schema of generalized knowledge. Fourth, the newly emerging benefit of sleep in regulating emotional brain reactivity will be considered. Finally, and building on this latter topic, a novel hypothesis and framework of sleep-dependent affective brain processing will be proposed, culminating in testable predictions and translational implications for mood disorders.

Act out your dreams

Neurology. 2009 Feb 10;72(6):551-7.
Oudiette D, De Cock VC, Lavault S, Leu S, Vidailhet M, Arnulf I.

OBJECTIVE: To document unusual, nonviolent behaviors during REM sleep behavior disorder (RBD) and evaluate their frequency in Parkinson disease (PD).

BACKGROUND: Most behaviors previously described during RBD mimic attacks, suggesting they proceed from archaic defense generators in the brainstem. Feeding, drinking, sexual behaviors, urination, and defecation have not been documented yet in RBD.

METHODS: We collected 24 cases of nonviolent behaviors during idiopathic and symptomatic RBD (narcolepsy, dementia with Lewy bodies, PD), reported or observed in videopolysomnography. The frequency of violent and nonviolent behaviors during RBD was evaluated by face to face interview of patients and their cosleepers in a prospective series of 100 patients with PD.

RESULTS: Incidental cases of nonviolent behaviors during RBD included masturbating-like behavior and coitus-like pelvic thrusting, mimicking eating and drinking, urinating and defecating, displaying pleasant behaviors (laughing, singing, dancing, whistling, smoking a fictive cigarette, clapping and gesturing "thumbs up"), greeting, flying, building a stair, dealing textiles, inspecting the army, searching a treasure, and giving lessons. Speeches were mumbled or contained logical sentences with normal prosody. In PD with RBD (n = 60), 18% of patients displayed nonviolent behaviors. In this series (but not in incidental cases), all RBD patients with nonviolent behaviors also showed violent behaviors.

CONCLUSIONS: Although they are less frequent than violent behaviors, nonviolent behaviors during REM sleep behavior disorder (RBD) fill a large spectrum including learned speeches and culture-specific behaviors, suggesting they proceed from the cortex activation. Sexual behaviors during RBD may expose patients and cosleepers to forensic consequences.

Human Emotional Memory

REM Sleep, Prefrontal Theta, and the Consolidation of Human Emotional Memory
Cerebral Cortex May 2009;19:1158--1166
Masaki Nishida, Jori Pearsall, Randy L. Buckner and Matthew P. Walker

Both emotion and sleep are independently known to modulate declarative memory. Memory can be facilitated by emotion, leading to enhanced consolidation across increasing time delays. Sleep also facilitates offline memory processing, resulting in superior recall the next day. Here we explore whether rapid eye movement (REM) sleep, and aspects of its unique neurophysiology, underlie these convergent influences on memory. Using a nap paradigm, we measured the consolidation of neutral and negative emotional memories, and the association with REM-sleep electrophysiology. Subjects that napped showed a consolidation benefit for emotional but not neutral memories. The No-Nap control group showed no evidence of a consolidation benefit for either memory type. Within the Nap group, the extent of emotional memory facilitation was significantly correlated with the amount of REM sleep and also with right-dominant prefrontal theta power during REM. Together, these data support the role of REM-sleep neurobiology in the consolidation of emotional human memories, findings that have direct translational implications for affective psychiatric and mood disorders.

Brain Cells Have 'Memory'

Neuron, Volume 61, Issue 5, 12 March 2009, Pages 801-809
Philip O'Herron and Rüdiger von der Heydt

Whether the visual system uses a buffer to store image information and the duration of that storage have been debated intensely in recent psychophysical studies. The long phases of stable perception of reversible figures suggest a memory that persists for seconds. But persistence of similar duration has not been found in signals of the visual cortex. Here, we show that figure-ground signals in the visual cortex can persist for a second or more after the removal of the figure-ground cues. When new figure-ground information is presented, the signals adjust rapidly, but when a figure display is changed to an ambiguous edge display, the signals decay slowly—a behavior that is characteristic of memory devices. Figure-ground signals represent the layout of objects in a scene, and we propose that a short-term memory for object layout is important in providing continuity of perception in the rapid stream of images flooding our eyes.

The five ages of the brain

Throughout life our brains undergo more changes than any other part of the body. These can be broadly divided into five stages, each profoundly affecting our abilities and behaviour. Read this article on New Scientist on 'The five ages of the brain', looking at how the brain changes as we grow and how these transformations are reflected in our lives.

It breaks the life span down into 'five ages', with a short article for each - tackling gestation, childhood, adolescence, adulthood and old age.

A Biochemical Pathway For Blocking Your Worst Fears?

mGluR5 Has a Critical Role in Inhibitory Learning
Jian Xu, Yongling Zhu, Anis Contractor, and Stephen F. Heinemann1

The mechanisms that contribute to the extinction of previously acquired memories are not well understood. These processes, often referred to as inhibitory learning, are thought to be parallel learning mechanisms that require a reacquisition of new information and suppression of previously acquired experiences in order to adapt to novel situations. Using newly generated metabotropic glutamate receptor 5 (mGluR5) knock-out mice, we investigated the role of mGluR5 in the acquisition and reversal of an associative conditioned task and a spatial reference task. We found that acquisition of fear conditioning is partially impaired in mice lacking mGluR5. More markedly, we found that extinction of both contextual and auditory fear was completely abolished in mGluR5 knock-out mice. In the Morris Water Maze test (MWM), mGluR5 knock-out mice exhibited mild deficits in the rate of acquisition of the regular water maze task, but again had significant deficits in the reversal task, despite overall spatial memory being intact. Together, these results demonstrate that mGluR5 is critical to the function of neural circuits that are required for inhibitory learning mechanisms, and suggest that targeting metabotropic receptors may be useful in treating psychiatric disorders in which aversive memories are inappropriately retained.

Brain decline begins at age 27

When does age-related cognitive decline begin?
Timothy A. Salthouse
Neurobiology of Aging 30 (2009) 507–514

Cross-sectional comparisons have consistently revealed that increased age is associated with lower levels of cognitive performance, even in the range from 18 to 60 years of age. However, the validity of cross-sectional comparisons of cognitive functioning in young and middle-aged adults has been questioned because of the discrepant age trends found in longitudinal and cross-sectional analyses. The results of the current project suggest that a major factor contributing to the discrepancy is the masking of age-related declines in longitudinal comparisons by large positive effects associated with prior test experience. Results from three methods of estimating retest effects in this project, together with results from studies comparing non-human animals raised in constant environments and from studies examining neurobiological variables not susceptible to retest effects, converge on a conclusion that some aspects of age-related cognitive decline begin in healthy educated adults when they are in their 20s and 30s.

Emotion Perception

Emotion perception in emotionless face images suggests a norm-based representation
Donald Neth, Aleix M. Martinez
Volume 9, Number 1, Article 5, Pages 1-11, Journal Of Vision

Perception of facial expressions of emotion is generally assumed to correspond to underlying muscle movement. However, it is often observed that some individuals have sadder or angrier faces, even for neutral, motionless faces. Here, we report on one such effect caused by simple static configural changes. In particular, we show four variations in the relative vertical position of the nose, mouth, eyes, and eyebrows that affect the perception of emotion in neutral faces. The first two configurations make the vertical distance between the eyes and mouth shorter than average, resulting in the perception of an angrier face. The other two configurations make this distance larger than average, resulting in the perception of sadness. These perceptions increase with the amount of configural change, suggesting a representation based on variations from a norm (prototypical) face.

American Recovery and Reinvestment Act of 2009

Got this from APA today.

Apply for an NIH grant for research that you can do in two years.
Of the NIH $10 billion, at least $200 million over the next two years is for a new initiative called NIH Challenge Grants in Health and Science Research, to fund 200 or more grants at $1 million each. The program will support research on "Challenge Topics," and first on the list is Behavior, Behavioral Change, and Prevention. This is a unique opportunity to conduct research in a short time frame. The application deadline is April 27, 2009, and grants will begin this fall. See:

If you recently applied to NIH or NSF and received good reviews but were not funded,contact the program officer who oversaw the process.
At the end of the last federal fiscal year, about 14,000 applications were approved for funding but went unfunded. NIH is planning to review these applications to see if any would benefit from two-year funding. This will not be done in a formulaic manner; rather, grants will be analyzed on a case-by-case basis. Program officers will be involved in this process, so it can only help to contact them to discuss your application.

NSF is also planning to fund recently approved but unfunded proposals. Call the NSF program officer in your area if you think your proposal might be in this category.

If you have an existing grant, you may be eligible for a supplement.
The stimulus funding may also be available to expand an existing NIH grant. Some funding will be awarded through a competitive process, while other funding will be administratively allocated. Few details are available at this time, and each Institute and agency will determine its priorities for supplemental funding. Another reason to call NIH or NSF staff.

A word of advice.
This funding is part of the Recovery Act, so it's meant to create jobs and stimulate the economy, all in a transparent and trackable way. If you do any of the above, be sure to pay particular attention to the economic impact of your grant: How many jobs will it create? How will you measure and track spending? Job creation? If you are at, or are partnering with, an institution located in an under-represented geographic area, please highlight that, since geographic location may be a criterion for grant awards. After all, the economy needs to be stimulated throughout the United States.

Read more about it here.

Why Sleep Is Needed To Form Memories

Mechanisms of Sleep-Dependent Consolidation of Cortical Plasticity
Sara J. Aton, Julie Seibt, Michelle Dumoulin, Sushil K. Jha, Nicholas Steinmetz, Tammi Coleman, Nirinjini Naidoo, and Marcos G. Frank
DOI 10.1016/j.neuron.2009.01.007

Sleep is thought to consolidate changes in synaptic strength, but the underlying mechanisms are unknown. We investigated the cellular events involved in this process during ocular dominance plasticity (ODP)—a canonical form of in vivo cortical plasticity triggered by monocular deprivation (MD) and consolidated by sleep via undetermined, activity-dependent mechanisms. We find that sleep consolidates ODP primarily by strengthening cortical responses to nondeprived eye stimulation. Consolidation is inhibited by reversible, intracortical antagonism of NMDA receptors (NMDARs) or cAMP-dependent protein kinase (PKA) during post-MD sleep. Consolidation is also associated with sleep-dependent increases in the activity of remodeling neurons and in the phosphorylation of proteins required for potentiation of glutamatergic synapses. These findingsdemonstrate that synaptic strengthening via NMDAR and PKA activity is a key step in sleep-dependent consolidation of ODP.

Molecule that helps the sleep-deprived to mentally rebound

Control and Function of the Homeostatic Sleep Response by
Adenosine A1 Receptors

Theresa E. Bjorness, Christine L. Kelly, Tianshu Gao, Virginia Poffenberger, and Robert W. Greene
Department of Psychiatry, University of Texas Southwestern, Dallas, Texas 75390

During sleep, the mammalian CNS undergoes widespread, synchronized slow-wave activity (SWA) that directly varies with previous waking duration (Borbe´ly, 1982; Dijk et al., 1990). When sleep is restricted, an enhanced SWA response follows in the next sleep period. The enhancement of SWA is associated with improved cognitive performance (Huber et al., 2004), but it is unclear either how the SWA is enhanced or whetherSWAis needed to maintain normal cognitive performance.Aconditional, CNS knock-out of the adenosine receptor, AdoA1R gene, shows selective attenuation of the SWA rebound response to restricted sleep, but sleep duration is not affected. During sleep restriction, wild phenotype animals express a rebound SWA response and maintain cognitive performance in a working memory task. However, the knock-out animals not only show a reduced rebound SWA response but they also fail to maintain normal cognitive function, although this function is normal when sleep is not restricted. Thus, AdoA1R activation is needed for normal rebound SWA, and when the SWA rebound is reduced, there is a failure to maintain working memory function, suggesting a functional role for SWA homeostasis.

What Happens When You Sleep?

Another nice article from the National Sleep Foundation.

When we sleep well, we wake up feeling refreshed and alert for our daily activities. Sleep affects how we look, feel and perform on a daily basis, and can have a major impact on our overall quality of life.

To get the most out of our sleep, both quantity and quality are important. Teens need at least 8½ hours—and on average 9¼ hours—a night of uninterrupted sleep to leave their bodies and minds rejuvenated for the next day. If sleep is cut short, the body doesn’t have time to complete all of the phases needed for muscle repair, memory consolidation and release of hormones regulating growth and appetite. Then we wake up less prepared to concentrate, make decisions, or engage fully in school and social activities.
How Does Sleep Contribute to All of These Things?

Sleep architecture follows a pattern of alternating REM (rapid eye movement) and NREM (non-rapid eye movement) sleep throughout a typical night in a cycle that repeats itself about every 90 minutes.
What role does each state and stage of sleep play?

NREM (75% of night): As we begin to fall asleep, we enter NREM sleep, which is composed of stages 1-4

Stage 1

* Between being awake and falling asleep
* Light sleep

Stage 2

* Onset of sleep
* Becoming disengaged from surroundings
* Breathing and heart rate are regular
* Body temperature drops (so sleeping in a cool room is helpful)

Stages 3 and 4

* Deepest and most restorative sleep
* Blood pressure drops
* Breathing becomes slower
* Muscles are relaxed
* Blood supply to muscles increases
* Tissue growth and repair occurs
* Energy is restored
* Hormones are released, such as: Growth hormone, essential for growth and development, including muscle development

REM (25% of night): First occurs about 90 minutes after falling asleep and recurs about every 90 minutes, getting longer later in the night

* Provides energy to brain and body
* Supports daytime performance
* Brain is active and dreams occur
* Eyes dart back and forth
* Body becomes immobile and relaxed, as muscles are turned off

In addition, levels of the hormone cortisol dip at bed time and increase over the night to promote alertness in morning.

Sleep helps us thrive by contributing to a healthy immune system, and can also balance our appetites by helping to regulate levels of the hormones ghrelin and leptin, which play a role in our feelings of hunger and fullness. So when we’re sleep deprived, we may feel the need to eat more, which can lead to weight gain.

The one-third of our lives that we spend sleeping, far from being “unproductive,” plays a direct role in how full, energetic and successful the other two-thirds of our lives can be.

25 Random Facts about Sleep

The National Sleep Foundation has created a list of 25 random facts about sleep.

  1. Man is the only mammal that willingly delays sleep.

  2. The higher the altitude, the greater the sleep disruption. Generally, sleep disturbance becomes greater at altitudes of 13,200 feet or more. The disturbance is thought to be caused by diminished oxygen levels and accompanying changes in respiration. Most people adjust to new altitudes in approximately two to three weeks — from Jet Lag and Sleep.

  3. In general, exercising regularly makes it easier to fall asleep and contributes to sounder sleep. However, exercising sporadically or right before going to bed will make falling asleep more difficult — from Sleep Tips.

  4. Divorced, widowed and separated people report more insomnia — from Sleep Aids and Insomnia.

  5. Six in ten healthcare professionals do not feel that they have enough time to have a discussion with their patients about insomnia during regular office visits — from the Sleeping Smart Sleep Report Card.

  6. More than eight in ten survey respondents think that people often or sometimes misuse prescription sleep aids — from the Sleeping Smart Sleep Report Card.

  7. Caffeine has been called the most popular drug in the world. All over the world people consume caffeine on a daily basis in coffee, tea, cocoa, chocolate, some soft drinks, and some drugs — from Caffeine and Sleep.

  8. In general, most healthy adults need seven to nine hours of sleep a night. However, some individuals are able to function without sleepiness or drowsiness after as little as six hours of sleep. Others can’t perform at their peak unless they’ve slept ten hours — from ABC's of ZZZZs — When You Can't Sleep.

  9. We naturally feel tired at two different times of the day: about 2:00 AM and 2:00 PM. It is this natural dip in alertness that is primarily responsible for the post-lunch dip — from Ingredients for Slumber: How Food and Beverages May Affect Your Sleep.

  10. Sleep is just as important as diet and exercise.

  11. According to the International Classifications of Sleep Disorders, shift workers are at increased risk for a variety of chronic illnesses such as cardiovascular and gastrointestinal diseases.

  12. Newborns sleep a total of 10.5 to 18 hours a day on an irregular schedule with periods of one to three hours spent awake — from Children and Sleep.

  13. When infants are put to bed drowsy but not asleep, they are more likely to become "self- soothers," which enables them to fall asleep independently at bedtime and put themselves back to sleep during the night — from Children and Sleep.

  14. Eighty-two percent of healthcare professionals believe that it is the responsibility of both the patient and the healthcare professional to bring up symptoms of insomnia during an appointment — from the Sleeping Smart Sleep Report Card.

  15. The body never adjusts to shift work!

  16. There are individual differences in the need to nap. Some adults and children need to nap. However, the majority of teenagers probably nap in the afternoon because they are not sleeping enough at night — Daniel Lewin, PhD, Ask the Sleep Expert: Sleep and Teens.

  17. Snoring is the primary cause of sleep disruption for approximately 90 million American adults; 37 million on a regular basis — from Aging and Sleep.

  18. Scientists still don't know — and probably never will — if animals dream during REM sleep, as humans do — from Dreams and Sleep.

  19. Some studies show promise for the use of melatonin in shortening the time it takes to fall asleep and reducing the number of awakenings, but not necessarily total sleep time. Other studies show no benefit at all with melatonin — from Melatonin and Sleep.

  20. One of the primary causes of excessive sleepiness among Americans is self-imposed sleep deprivation — from Excessive Sleepiness and Sleep.

  21. According to the results of NSF's 2008 Sleep in America poll, 36 percent of American drive drowsy or fall asleep while driving.

  22. According to the results of NSF's 2008 Sleep in America poll, a surprising 34 percent of respondents reported their employer allows them to nap during breaks and 16 percent provide a place to do so.

  23. People who don’t get enough sleep are more likely to have bigger appetites due to the fact that their leptin levels (leptin is an appetite-regulating hormone) fall, promoting appetite increase — from Diet, Exercise and Sleep.

  24. Rates of insomnia increase as a function of age, but most often the sleep disturbance is attributable to some other medical condition — from the Sleeping Smart Study Hall.

  25. And in case you missed our post on Tips for Beating the Winter Blues, did you know seasonal affective disorder is believed to be influenced by the changing patterns of light and darkness that occur with the approach of winter?

Boost resistance to interference

The sleeping brain's influence on verbal memory: boosting resistance to interference.
Jeffrey M. Ellenbogen, Justin C. Hulbert, Ying Jiang, Robert Stickgold
PLoS ONE 2009;4(1):e4117.

Memories evolve. After learning something new, the brain initiates a complex set of post-learning processing that facilitates recall (i.e., consolidation). Evidence points to sleep as one of the determinants of that change. But whenever a behavioral study of episodic memory shows a benefit of sleep, critics assert that sleep only leads to a temporary shelter from the damaging effects of interference that would otherwise accrue during wakefulness. To evaluate the potentially active role of sleep for verbal memory, we compared memory recall after sleep, with and without interference before testing. We demonstrated that recall performance for verbal memory was greater after sleep than after wakefulness. And when using interference testing, that difference was even more pronounced. By introducing interference after sleep, this study confirms an experimental paradigm that demonstrates the active role of sleep in consolidating memory, and unmasks the large magnitude of that benefit.