Slow cortical potentials & Spontaneous Fluctuations

Electrophysiological correlates of the brain's intrinsic large-scale functional architecture
PNAS October 14, 2008 vol. 105 no. 41 16039-16044

Spontaneous fluctuations in the blood-oxygen-level-dependent (BOLD) signals demonstrate consistent temporal correlations within large-scale brain networks associated with different functions. The neurophysiological correlates of this phenomenon remain elusive. Here, we show in humans that the slow cortical potentials recorded by electrocorticography demonstrate a correlation structure similar to that of spontaneous BOLD fluctuations across wakefulness, slow-wave sleep, and rapid-eye-movement sleep. Gamma frequency power also showed a similar correlation structure but only during wakefulness and rapid-eye-movement sleep. Our results provide an important bridge between the large-scale brain networks readily revealed by spontaneous BOLD signals and their underlying neurophysiology.

Influenced by reward?

How does reward expectation influence cognition in the human brain?
J Cogn Neurosci. 2008 Nov;20(11):1980-92.Click here to read

The prospect of reward changes how we think and behave. We investigated how this occurs in the brain using a novel continuous performance task in which fluctuating reward expectations biased cognitive processes between competing spatial and verbal tasks. Critically, effects of reward expectancy could be distinguished from induced changes in task-related networks. Behavioral data confirm specific bias toward a reward-relevant modality. Increased reward expectation improves reaction time and accuracy in the relevant dimension while reducing sensitivity to modulations of stimuli characteristics in the irrelevant dimension. Analysis of functional magnetic resonance imaging data shows that the proximity to reward over successive trials is associated with increased activity of the medial frontal cortex regardless of the modality. However, there are modality-specific changes in brain activity in the lateral frontal, parietal, and temporal cortex. Analysis of effective connectivity suggests that reward expectancy enhances coupling in both early visual pathways and within the prefrontal cortex. These distributed changes in task-related cortical networks arise from subjects' representations of future events and likelihood of reward.

Are you getting enough sleep?

The National Sleep Foundation’s 2008 Sleep in America poll reports the average American spends 6 hours and 55 minutes in bed — with 6 hours and 40 minutes spent actually sleeping.

The standard 8-hour business day is no longer the norm in America. NSF’s 2008 Sleep in America poll reports the average American’s work day is now 9 hours and 28 minutes. The average time spent in bed is 6 hours and 55 minutes - with 6 hours and 40 minutes spent actually sleeping. NSF recommends getting at least 7 to 9 hours of sleep each night.

According to the Sleep Foundation poll results, 42 percent of people chose 7-8 hours, 31 percent chose 8-9 hours, 14 percent chose more than 9 hours, 10 percent chose 5-6 hours and 3 percent chose less than 5 hours. The first thing experts will tell you about sleep is that there is no "magic number." Not only do different age groups need different amounts of sleep, but sleep needs are also individual.

Click here to read more about why you shouldn't skimp on sleep.

Sex Differences in Cognitive Estimation

Sex Differences in Cognitive Estimation During Sleep Deprivation: Effects of Stimulant Countermeasures
Int J Neurosci 2008;118(11):1547-57.

Stimulant medications restore simple alertness during sleep loss, but it is not clear how they affect complex executive functions, particularly in light of sex differences in cerebral organization. The effectiveness of caffeine, modafinil, dextroamphetamine, or placebo for sustaining performance on the Biber Cognitive Estimation Test (BCET) was compared in 29 men and 25 women following 46 hr of sleep deprivation. Stimulants had differential effects on BCET performance as a function of the sex of the subjects. Women receiving placebo or caffeine scored significantly worse than males, while modafinil and dextroamphetamine were effective at sustaining BCET performance of men andwomen.

Circadian Clock Could Help Learning Retention

Hippocampal-dependent learning requires a functional circadian system
PNAS October 7, 2008 vol. 105 no. 40 15593-15598

Decades of studies have shown that eliminating circadian rhythms of mammals does not compromise their health or longevity in the laboratory in any obvious way. These observations have raised questions about the functional significance of the mammalian circadian system, but have been difficult to address for lack of an appropriate animal model. Surgical ablation of the suprachiasmatic nucleus (SCN) and clock gene knockouts eliminate rhythms, but also damage adjacent brain regions or cause developmental effects that may impair cognitive or other physiological functions. We developed a method that avoids these problems and eliminates rhythms by noninvasive means in Siberian hamsters (Phodopus sungorus). The present study evaluated cognitive function in arrhythmic animals by using a hippocampal-dependent learning task. Control hamsters exhibited normal circadian modulation of performance in a delayed novel-object recognition task. By contrast, arrhythmic animals could not discriminate a novel object from a familiar one only 20 or 60 min after training. Memory performance was not related to prior sleep history as sleep manipulations had no effect on performance. The GABA antagonist pentylenetetrazol restored learning without restoring circadian rhythms. We conclude that the circadian system is involved in memory function in a manner that is independent of sleep. Circadian influence on learning may be exerted via cyclic GABA output from the SCN to target sites involved in learning. Arrhythmic hamsters may have failed to perform this task because of chronic inhibitory signaling from the SCN that interfered with the plastic mechanisms that encode learning in the hippocampus.

Spontaneous neural activity during human slow wave sleep

Spontaneous neural activity during human slow wave sleep
Proc Natl Acad Sci U S A 2008;105(39):15160-5.

Slow wave sleep (SWS) is associated with spontaneous brain oscillations that are thought to participate in sleep homeostasis and to support the processing of information related to the experiences of the previous awake period. At the cellular level, during SWS, a slow oscillation (<1 Hz) synchronizes firing patterns in large neuronal populations and is reflected on electroencephalography (EEG) recordings as large-amplitude, low-frequency waves. By using simultaneous EEG and event-related functional magnetic resonance imaging (fMRI), we characterized the transient changes in brain activity consistently associated with slow waves (>140 μV) and delta waves (75–140 μV) during SWS in 14 non-sleep-deprived normal human volunteers. Significant increases in activity were associated with these waves in several cortical areas, including the inferior frontal, medial prefrontal, precuneus, and posterior cingulate areas. Compared with baseline activity, slow waves are associated with significant activity in the parahippocampal gyrus, cerebellum, and brainstem, whereas delta waves are related to frontal responses. No decrease in activity was observed. This study demonstrates that SWS is not a state of brain quiescence, but rather is an active state during which brain activity is consistently synchronized to the slow oscillation in specific cerebral regions. The partial overlap between the response pattern related to SWS waves and the waking default mode network is consistent with the fascinating hypothesis that brain responses synchronized by the slow oscillation restore microwake-like activity patterns that facilitate neuronal interactions.

The Blank Slate

Steven Pinker's book The Blank Slate argues that all humans are born with some innate traits. Here, Pinker talks about his thesis, and why some people found it incredibly upsetting.

Is Sleep Essential?

Is Sleep Essential?
Chiara Cirelli, Giulio Tononi
PLoS Biol 2008;6(8):e216.

Everybody knows that sleep is important, yet the function of sleep seems like the mythological phoenix: “Che vi sia ciascun lo dice, dove sia nessun lo sa” (“that there is one they all say, where it may be no one knows,” Wolfgang Amadeus Mozart and Lorenzo da Ponte [1790], Così fan tutte). But what if the search for an essential function of sleep is misguided? What if sleep is not required but rather a kind of extreme indolence that animals indulge in when they have no more pressing needs, such as eating or reproducing? In many circumstances sleeping may be a less dangerous choice than roaming around, wasting energy and exposing oneself to predators. Also, if sleep is just one out of a repertoire of available behaviors that is useful without being essential, it is easier to explain why sleep duration varies so much across species. This “null hypothesis” would explain why nobody has yet identified a core function of sleep. But how strong is the evidence supporting it? And are there counterexamples?

Reactivation of Single Neurons

Internally Generated Reactivation of Single Neurons in Human Hippocampus During Free Recall
Hagar Gelbard-Sagiv, Roy Mukamel, Michal Harel, Rafael Malach, Itzhak Fried
Science DOI: 10.1126/science.1164685

The emergence of memory, a trace of things past, into human consciousness is one of the greatest mysteries of the human mind. Whereas the neuronal basis of recognition memory can be probed experimentally in human and nonhuman primates, the study of free recall requires that the mind declare the occurrence of a recalled memory (an event intrinsic to the organism and invisible to an observer). Here, we report the activity of single neurons in the human hippocampus and surrounding areas when subjects first view television episodes consisting of audiovisual sequences and again later when they freely recall these episodes. A subset of these neurons exhibited selective firing, which often persisted throughout and following specific episodes for as long as 12 seconds. Verbal reports of memories of these specific episodes at the time of free recall were preceded by selective reactivation of the same hippocampal and entorhinal cortex neurons. We suggest that this reactivation is an internally generated neuronal correlate of the subjective experience of spontaneous emergence of human recollection.

Spatial and contextual memories

Sleep modulates the neural substrates of both spatial and contextual memory consolidation.
Geraldine Rauchs, Pierre Orban, Christina Schmidt, Genevieve Albouy, Evelyne Balteau, Christian Degueldre, Caroline Schnackers, Virginie Sterpenich, Gilberte Tinguely, Andre Luxen, Pierre Maquet, Philippe Peigneux
PLoS ONE 2008;3(8):e2949.

Background: It is known that sleep reshapes the neural representations that subtend the memories acquired while navigating in a virtual environment. However, navigation is not process-pure, as manifold learning components contribute to performance, notably the spatial and contextual memory constituents. In this context, it remains unclear whether post-training sleep globally promotes consolidation of all of the memory components embedded in virtual navigation, or rather favors the development of specific representations.

Methods: Here, we investigated the effect of post-training sleep on the neural substrates of the consolidation of spatial and contextual memories acquired while navigating in a complex 3D, naturalistic virtual town. Using fMRI, we mapped regional cerebral activity during various tasks designed to tap either the spatial or the contextual memory component, or both, 72 h after encoding with or without sleep deprivation during the first post-training night.

Results: Behavioral performance was not dependent upon post-training sleep deprivation, neither in a natural setting that engages both spatial and contextual memory processes nor when looking more specifically at each of these memory
representations. At the neuronal level however, analyses that focused on contextual memory revealed distinct correlations between performance and neuronal activity in frontal areas associated with recollection processes after post-training sleep,
and in the parahippocampal gyrus associated with familiarity processes in sleep-deprived participants. Likewise, efficient spatial memory was associated with posterior cortical activity after sleep whereas it correlated with parahippocampal/
medial temporal activity after sleep deprivation. Finally, variations in place-finding efficiency in a natural setting encompassing spatial and contextual elements were associated with caudate activity after post-training sleep, suggesting
the automation of navigation.

Conclusion: These data indicate that post-training sleep modulates the neural substrates of the consolidation of both the spatial and contextual memories acquired during virtual navigation.

Emotional Context

Decoding of affective facial expressions in the context of emotional situations
Monika Sommera, Katrin Döhnela, Jörg Meinhardtb and Göran Hajaka
Neuropsychologia Volume 46, Issue 11, September 2008, Pages 2615-2621

Background: The ability to recognize other persons’ affective states and to link these with aspects of the current situation arises early in development and is precursor functions of a Theory of Mind (ToM). Until now, studies investigated either the processing of affective faces or affective pictures.

Methods: In the present study, we tried to realize a scenario more similar to every day situations. We employed fMRI and used a picture matching task to explore the neural correlates associated with the integration and decoding of facial affective expressions in the context of affective situations. In the emotion condition, the participants judged an emotional facial expression with respect to the content of an emotional picture. In the two other conditions, participants indicated colour matches on the background of either affective or scrambled pictures.

Results: In contrast to colour matching on scrambled pictures, colour matching on emotional pictures resulted in longer reaction times and increased activation of the bilateral fusiform and occipital gyrus. These results indicated that, although task irrelevant, participants may attend to the emotional background of the pictures. The emotion task was associated with higher reaction times and with activation of the bilateral fusiform and occipital gyrus. Additionally, emotion attribution induced left amygdala activity. Possibly, attention processes and amygdala projections modulated the activation found in the occipital and fusiform areas. Furthermore, the involvement of the amygdala in the ToM precursor ability to link facial expressions with an emotional situation may indicate that the amygdala is involved in the development of stable ToM abilities.

Age-Related Insomnia

Age-Related Reduction in the Maximal Capacity for Sleep—Implications for Insomnia
Elizabeth B. Klerman and Derk-Jan Dijk
Current Biology 18, 1–6, August 5, 2008

Background: Sleep changes markedly across the life span and complaints about insomnia are prevalent in older people. Whether age-related alterations in sleep are due to modifications in social factors, circadian physiology, homeostatic drive, or
the ability to sleep remains unresolved.

Methods: We assessed habitual sleep duration at home and then quantified daytime sleep propensity, sleep duration, and sleep structure in an inpatient protocol that included extended sleep opportunities covering 2/3 of the circadian cycle (12 hr at night and 4 hr in the afternoon) for 3–7 days in 18 older and 35 younger healthy men and women.

Results: At baseline, older subjects had less daytime sleep propensity than did younger subjects. Total daily sleep duration, which was initially longer than habitual sleep duration, declined during the experiment to asymptotic values that were 1.5 hr shorter in older (7.4 6 0.4 SEM, hour) than in younger subjects (8.9 6 0.4). Rapid eye-movement sleep and non-rapid-eye-movement sleep contributed about equally to this reduction.

Conclusions: Thus, in the absence of social and circadian constraints, both daytime sleep propensity and the maximal capacity for sleep are reduced in older people. These data have important implications for understanding age-related insomnia.

How Sleep affects Memory and Congition

Functional neuroimaging insights into how sleep and sleep deprivation affect memory and cognition.
Chee Michael WL and Chuah Lisa YM b
Current Opinion in Neurology. 24(4):417-423, August 2008.

Purpose of review: The review summarizes current knowledge about what fMRI has revealed regarding the neurobehavioral correlates of sleep deprivation and sleep-dependent memory consolidation.

Recent findings: Functional imaging studies of sleep deprivation have characterized its effects on a number of cognitive domains, the best studied of these being working memory. There is a growing appreciation that it is important to consider inter individual differences in vulnerability to sleep deprivation, task and task difficulty when interpreting imaging results. Our understanding of the role of sleep and the dynamic evolution of offline memory consolidation has benefited greatly from human imaging studies. Both hippocampal-dependent and hippocampal-independent memory systems have been studied.

Summary: Functional imaging studies contrasting sleep-deprived and well-rested brains provide substantial evidence that sleep is highly important for optimal cognitive function and learning. The experimental paradigms developed to date merit evaluation in clinical settings to determine the impact of sleep disruption in sleep disorders.

Computer that works like the brain?

Researcher Kwabena Boahen is looking for ways to mimic the brain's supercomputing powers in silicon -- because the messy, redundant processes inside our heads actually make for a small, light, superfast computer.

Emotion Modulates Default Activity

Emotional Experience Modulates Brain Activity During Fixation Periods Between Tasks
Sean Pitroda, Mike Angstadt, Michael S. McCloskey, Emil F. Coccaro, K. Luan Phan
Neuroscience Letters

Background: Functional imaging studies have begun to identify a set of brain regions whose brain activity is greater during 'rest' (e.g., fixation) states than during cognitive tasks. It has been posited that these regions constitute a network that supports the brain's default mode, which is temporarily suspended during specific goal-directed behaviors. Exogenous tasks that require cognitive effort are thought to command reallocation of resources away from the brain's default state. However, it remains unknown if brain activity during fixation periods between active task periods is influenced by previous task-related emotional content.

Methods: We examined brain activity during periods of FIXATION (viewing and rating gray-scale images) interspersed among periods of viewing and rating complex images ('PICTURE') with positive, negative, and neutral affective content.

Results: We show that a selected group of brain regions (PCC, precuneus, IPL, vACC) do exhibit activity that is greater during FIXATION (>PICTURE); these regions have previously been implicated in the "default brain network". In addition, we report that activity within precuneus and IPL in the FIXATION period is attenuated by the precedent processing of images with positive and negative emotional content, relative to non-emotional content.

Conclusion: These data suggest that the activity within regions implicated in the default network is modulated by the presence of environmental stimuli with motivational salience and, thus, adds to our understanding of the brain function during periods of low cognitive, emotional, or sensory demand.

Persistence of Emotional Memories Over Time

Role of Amygdala Connectivity in the Persistence of Emotional Memories Over Time: An Event-Related fMRI Investigation
Maureen Ritchey, Florin Dolcos and Roberto Cabeza
Cerebral Cortex, 2008

Background: According to the consolidation hypothesis, enhanced memory for emotional information reflects the modulatory effect of the amygdala on the medial temporal lobe (MTL) memory system during consolidation. Although there is evidence that amygdala--MTL connectivity enhances memory for emotional stimuli, it remains unclear whether this enhancement increases over time, as consolidation processes

Methods: They used functional magnetic resonance imaging to measure encoding activity predicting memory for emotionally negative and neutral pictures after short (20-min) versus long (1-week) delays.

Results: Memory measures distinguished between vivid remembering (recollection) and feelings of knowing (familiarity). Consistent with the consolidation hypothesis, the persistence of recollection over time (long divided by short) was greater for emotional than neutral pictures. Activity in the amygdala predicted subsequent memory to a greater extent for emotional than neutral pictures. Although this advantage did not vary with delay, the contribution of amygdala--MTL connectivity to subsequent memory for emotional items increased over time. Moreover, both this increase in connectivity and amygdala activity itself were correlated with individual differences in recollection persistence for emotional but not neutral pictures.

Conclusion: These results suggest that the amygdala and its connectivity with the MTL are critical to sustaining emotional memories over time, consistent with the consolidation hypothesis.

Small-world network organization during sleep

The functional connectivity of different EEG bands moves towards small-world network organization during sleep.
Ferri R, Rundo F, Bruni O, Terzano MG, Stam CJ.
Clin Neurophysiol. 2008 Sep;119(9):2026-36.

Background: To analyze the functional connectivity patterns of the different EEG
bands during wakefulness and sleep (different sleep stages and cyclic alternating
pattern (CAP) conditions), using concepts derived from Graph Theory.

Methods: They evaluated spatial patterns of EEG band synchronization between all possible pairs of electrodes (19) placed over the scalp of 10 sleeping healthy young normal subjects using two graph theoretical measures: the clustering coefficient (Cp) and the characteristic path length (Lp). The measures were obtained during wakefulness and the different sleep stages/CAP conditions from the real EEG connectivity networks and randomized control (surrogate) networks (Cp-s and Lp-s).

Results: They found the values of Cp and Lp compatible with a small-world network organization in all sleep stages and for all EEG bands. All bands below 15Hz showed an increase of these features during sleep (and during CAP-A phases in particular), compared to wakefulness.

Conclusion: The results of this study seem to confirm the initial hypothesis that during sleep there exists a clear trend for the functional connectivity of the EEG to move forward to an organization more similar to that of a small-world network, at least for the frequency bands lower than 15Hz. Sleep network "reconfiguration" might be one of the key mechanisms for the understanding of the "global" and "local" neural plasticity taking place during sleep.

Positive Psychology

Martin Seligman talks about psychology -- as a field of study and as it works one-on-one with each patient and each practitioner. As it moves beyond a focus on disease, what can modern psychology help us to become?

Authorship Plagiarism

Plagiarism is the unauthorized use or close imitation of the language and thoughts of another author and the representation of them as one's own original work. (Wiki)

Now let's think of that definition in the context of authorship in science.

According to the study by Swazey, Anderson and Lewis the rates of plagiarism and inappropriate authorship were reported to be similar by both faculty and students. They found that inappropriate authorship was slightly more frequent than plagiarism with one the twist: While plagiarism was about three times more likely to be committed by students than by faculty, inappropriate authorship was about three times more likely to be committed by faculty than by students.

I think the National Academy of Sciences in the study of scientific misconduct should include the most frequent and important issue of possible misconduct relevant to the designation of authorship besides aspects like fabrication, falsification, and plagiarism.

Brain Age

Found this on Brain Waves.

Cognitive Drug Research teamed up with Portfolio to develop an online test to determine your brain age (it takes 7 minutes). Very cool, but pay attention, you might be surprised to learn how old your brain is, I was 26!! Might want to try a brain fitness product.

Link to the test.

Neuroscience Peer Review

Read about this consortium of journals that enables reviews to be transferred from one journal to another!

I definitely like this concept. This will reduce the time and effort involved in the peer review of submissions and speed publications of the results. This system is completely voluntary for authors. If the reviews from the first journal do not seem likely to facilitate acceptance at another journal, the authors can send the paper directly to the second journal as a fresh submission. However, if the author feels that the reviews may be helpful,transferring them can accelerate the editorial process.

Here is a link to the participating journals.

For reviewers besides reducing the load they also have the option to release their names along with the review in the event that the paper is transferred to another journal. I like transparency and hence support this idea.

Anyways, a definite thumbs up from me for the whole process. The flexibility is the system should suffice everyone to participate in it.

Emotional interactions

Functional grouping and cortical–subcortical interactions in emotion: A meta-analysis of neuroimaging studies
Hedy Kobera, Lisa Feldman Barrettb, Josh Josepha, Eliza Bliss-Moreaub, Kristen Lindquistb and Tor D. Wager
Article in Press, NeuroImage 2008

Background & Methods: We performed an updated quantitative meta-analysis of 162 neuroimaging studies of emotion using a novel multi-level kernel-based approach, focusing on locating brain regions consistently activated in emotional tasks and their functional organization into distributed functional groups, independent of semantically defined emotion category labels (e.g., “anger,” “fear”). Such brain-based analyses are critical if our ways of labeling emotions are to be evaluated and revised based on consistency with brain data. Consistent activations were limited to specific cortical sub-regions, including multiple functional areas within medial, orbital, and inferior lateral frontal cortices. Consistent with a wealth of animal literature, multiple subcortical activations were identified, including amygdala, ventral striatum, thalamus, hypothalamus, and periaqueductal gray. We used multivariate parcellation and clustering techniques to identify groups of co-activated brain regions across studies.

Results: These analyses identified six distributed functional groups, including medial and lateral frontal groups, two posterior cortical groups, and paralimbic and core limbic/brainstem groups. These functional groups provide information on potential organization of brain regions into large-scale networks. Specific follow-up analyses focused on amygdala, periaqueductal gray (PAG), and hypothalamic (Hy) activations, and identified frontal cortical areas co-activated with these core limbic structures. While multiple areas of frontal cortex co-activated with amygdala sub-regions, a specific region of dorsomedial prefrontal cortex (dmPFC, Brodmann's Area 9/32) was the only area co-activated with both PAG and Hy. Subsequent mediation analyses were consistent with a pathway from dmPFC through PAG to Hy.

Conclusions: These results suggest that medial frontal areas are more closely associated with core limbic activation than their lateral counterparts, and that dmPFC may play a particularly important role in the cognitive generation of emotional states.

Dysfunction of the default mode network?

Failure to deactivate in the prefrontal cortex in schizophrenia: dysfunction of the default mode network?
Pomarol-Clotet E, Salvador R, Sarró S, Gomar J, Vila F, Martínez A, Guerrero A, Ortiz-Gil J, Sans-Sansa B, Capdevila A, Cebamanos JM, McKenna PJ.
Psychological Medicine

Background: Functional imaging studies using working memory tasks have documented both prefrontal cortex (PFC) hypo- and hyperactivation in schizophrenia. However, these studies have often failed to consider the potential role of task-related deactivation.

Methods: Thirty-two patients with chronic schizophrenia and 32 age- and sex-matched normal controls underwent functional magnetic resonance imaging (fMRI) scanning while performing baseline, 1-back and 2-back versions of the n-back task. Linear models were used to obtain maps of activations and deactivations in the groups.

Results: The controls showed activation in the expected frontal regions. There were also clusters of deactivation, particularly in the anterior cingulate/ventromedial PFC and the posterior cingulate cortex/precuneus. Compared to the controls, the schizophrenic patients showed reduced activation in the right dorsolateral prefrontal cortex (DLPFC) and other frontal areas. There was also an area in the anterior cingulate/ventromedial PFC where the patients showed apparently greater activation than the controls. This represented a failure of deactivation in the schizophrenic patients. Failure to activate was a function of the patients' impaired performance on the n-back task, whereas the failure to deactivate was less performance dependent.

Conclusions: Patients with schizophrenia show both failure to activate and failure to deactivate during performance of a working memory task. The area of failure of deactivation is in the anterior prefrontal/anterior cingulate cortex and corresponds to one of the two midline components of the ‘default mode network’ implicated in functions related to maintaining one's sense of self.

Sleep Deprivation effects

Sleep deprivation reduces perceived emotional intelligence and constructive thinking skills
William D.S. Killgore, Ellen T. Kahn-Greene, Erica L. Lipizzi, Rachel A. Newman, Gary H. Kamimori, Thomas J. Balkin
Sleep Medicine

Background: Insufficient sleep can adversely affect a variety of cognitive abilities, ranging from simple alertness to higher-order executive functions. Although the effects of sleep loss on mood and cognition are well documented, there have been no controlled studies examining its effects on perceived emotional intelligence (EQ) and constructive thinking, abilities that require the integration of affect and cognition and are central to adaptive functioning.

Patients and methods: Twenty-six healthy volunteers completed the Bar-On Emotional Quotient Inventory (EQi) and the Constructive Thinking Inventory (CTI) at rested baseline and again after 55.5 and 58 h of continuous wakefulness, respectively.

Results: Relative to baseline, sleep deprivation was associated with lower scores on Total EQ (decreased global emotional intelligence), Intrapersonal functioning (reduced self-regard, assertiveness, sense of independence, and self-actualization), Interpersonal functioning (reduced empathy toward others and quality of interpersonal relationships), Stress Management skills (reduced impulse control and difficulty with delay of gratification), and Behavioral Coping (reduced positive thinking and action orientation). Esoteric Thinking (greater reliance on formal superstitions and magical thinking processes) was increased.

Conclusions: These findings are consistent with the neurobehavioral model suggesting that sleep loss produces temporary changes in cerebral metabolism, cognition, emotion, and behavior consistent with mild prefrontal lobe dysfunction.

Jet Lagged? Try Skipping Lunch

Differential Rescue of Light- and Food-Entrainable Circadian Rhythms
Patrick M. Fuller, Jun Lu, Clifford B. Saper
Science 2008

Background: When food is plentiful, circadian rhythms of animals are powerfully entrained by the light-dark cycle. However, if animals have access to food only during their normal sleep cycle, they will shift most of their circadian rhythms to match the food availability.

Methods: They studied the basis for entrainment of circadian rhythms by food and light in mice with targeted disruption of the clock gene Bmal1, which lack circadian rhythmicity.

Results: Injection of a viral vector containing the Bmal1 gene into the suprachiasmatic nuclei of the hypothalamus restored light-entrainable, but not food-entrainable, circadian rhythms. In contrast, restoration of the Bmal1 gene only in the dorsomedial hypothalamic nucleus restored the ability of animals to entrain to food but not to light.

Conclusions: These results demonstrate that the dorsomedial hypothalamus contains a Bmal1-based oscillator that can drive food entrainment of circadian rhythms.

Why Do Some People Sleepwalk?

Found this explanation for why sleepwalking occurs in this month's Scientific American Mind.

Neurologist Antonio Oliviero of the National Hospital for Paraplegics in Toledo, Spain, explains:

Sleep disorders such as sleepwalking arise when normal physiological systems are active at inappropriate times. We do not yet understand why the brain issues commands to the muscles during certain phases of sleep, but we do know that these commands are usually suppressed by other neurological mechanisms. At times this suppression can be incomplete—because of genetic or environmental factors or physical immaturity—and actions that normally occur during wakefulness emerge in sleep.

People can perform a variety of activities while asleep, from simply sitting up in bed to more complex behavior such as housecleaning or driving a car. Individuals in this trancelike state are difficult to rouse, and if awoken they are often confused and unaware of the events that have taken place. Sleepwalking most often occurs during childhood, perhaps because children spend more time in the “deep sleep” phase of slumber. Physical activity only happens during the non–rapid eye movement (NREM) cycle of deep sleep, which precedes the dreaming state of REM sleep.

Recently my team proposed a possible physiological mechanism underlying sleepwalking. During normal sleep the chemical messenger gamma-aminobutyric acid (GABA) acts as an inhibitor that stifles the activity of the brain’s motor system. In children the neurons that release this neurotransmitter are still developing and have not yet fully established a network of connections to keep motor activity under control. As a result, many kids have insufficient amounts of GABA, leaving their motor neurons capable of commanding the body to move even during sleep. In some, this inhibitory system may remain underdeveloped—or be rendered less effective by environmental factors—and sleepwalking can persist into adulthood.

Sleepwalking runs in families, indicating that there is a genetic component. The identical twin of a person who sleepwalks often, for example, typically shares this nocturnal habit. Studies have also shown that frequent sleepwalking is associated with sleep deprivation, fever, stress and intake of drugs, especially sedatives, hypnotics, antipsychotics, stimulants and antihistamines.