Overnight Improvement Research Articles

Frequent video game players resist perceptual interference.

Playing certain types of video games for a long time can improve a wide range of mental processes, from visual acuity to cognitive control. Frequent gamers have also displayed generalized improvements in perceptual learning. In the Texture Discrimination Task (TDT), a widely used perceptual learning paradigm, participants report the orientation of a target embedded in a field of lines and demonstrate robust over-night improvement. However, changing the orientation of the background lines midway through TDT training interferes with overnight improvements in overall performance on TDT. Interestingly, prior research has suggested that this effect will not occur if a one-hour break is allowed in between the changes. These results have suggested that after training is over, it may take some time for learning to become stabilized and resilient against interference. Here, we tested whether frequent gamers have faster stabilization of perceptual learning compared to non-gamers and examined the effect of daily video game playing on interference of training of TDT with one background orientation on perceptual learning of TDT with a different background orientation. As a result, we found that non-gamers showed overnight performance improvement only on one background orientation, replicating previous results with the interference in TDT. In contrast, frequent gamers demonstrated overnight improvements in performance with both background orientations, suggesting that they are better able to overcome interference in perceptual learning. This resistance to interference suggests that video game playing not only enhances the amplitude and speed of perceptual learning but also leads to faster and/or more robust stabilization of perceptual learning.

Infrequent dream recall associated with low performance but high overnight improvement on mirror-tracing.

Although sleep facilitates learning and memory, the roles of dreaming and habitual levels of recalling dreams remain unknown. This study examined if performance and overnight improvement on a rapid eye movement sleep-sensitive visuomotor task is associated differentially with habitually high or low dream recall frequency. As a relation between dream production and visuospatial skills has been demonstrated previously, one possibility is that frequency of dream recall will be linked to performance on visuomotor tasks such as the Mirror Tracing Task. We expected that habitually low dream recallers would perform more poorly on the Mirror Tracing Task than would high recallers and would show less task improvement following a night of sleep. Fifteen low and 20 high dream recallers slept one night each in the laboratory and performed the Mirror Tracing Task before and after sleep. Low recallers had overall worse baseline performance but a greater evening-to-morning improvement than did high recallers. Greater improvements in completion time in low recallers were associated with Stage 2 rather than rapid eye movement sleep. Findings support the separate notions that dreaming is related to visuomotor processes and that different levels of visuomotor skill engage different sleep- and dream-related consolidation mechanisms.

First night of CPAP: impact on memory consolidation attention and subjective experience

ObjectiveNeurocognitive deficits are common and serious consequences of obstructive sleep apnea (OSA). Currently, the gold standard treatment is continuous positive air pressure (CPAP) therapy, although the clinical responses to this intervention can be variable. This study examined the effect of one night of CPAP therapy on sleep-dependent memory consolidation, attention, and vigilance as well as subjective experience. MethodsFifteen healthy controls and 29 patients with obstructive sleep apnea of whom 14 underwent a full-night CPAP titration completed the psychomotor vigilance test (PVT) and motor sequence learning task (MST) in the evening and the morning after undergoing overnight polysomnography. All participants also completed subjective evaluations of sleep quality. ResultsParticipants with OSA showed significantly less overnight improvement on the MST compared to controls without OSA, independent of whether or not they had received CPAP treatment, while there was no significant difference between the untreated OSA and CPAP-treated patients. Within the OSA group, only those receiving CPAP exhibited faster reaction times on the PVT in the morning. Compared to untreated OSA patients, they also felt subjectively more rested and reported that they slept better. ConclusionOur results demonstrate an instant augmentation of subjective experience and, based on PVT results, attention and vigilance after one night of CPAP, but a lack of an effect on offline sleep-dependent motor memory consolidation. This dissociation may be explained by different brain structures underlying these processes, some of which might require longer continued adherence to CPAP to generate an effect.

Medial Prefrontal-Hippocampal Connectivity and Motor Memory Consolidation in Depression and Schizophrenia

BackgroundOvernight memory consolidation is disturbed in both depression and schizophrenia, creating an ideal situation to investigate the mechanisms underlying sleep-related consolidation and to distinguish disease-specific processes from common elements in their pathophysiology. MethodsWe investigated patients with depression and schizophrenia, as well as healthy control subjects (each n = 16), under a motor memory consolidation protocol with functional magnetic resonance imaging and polysomnography. ResultsIn a sequential finger-tapping task associated with the degree of hippocampal-prefrontal cortex functional connectivity during the task, significantly less overnight improvement was identified as a common deficit in both patient groups. A task-related overnight decrease in activation of the basal ganglia was observed in control subjects and schizophrenia patients; in contrast, patients with depression showed an increase. During the task, schizophrenia patients, in comparison with control subjects, additionally recruited adjacent cortical areas, which showed a decrease in functional magnetic resonance imaging activation overnight and were related to disease severity. Effective connectivity analyses revealed that the hippocampus was functionally connected to the motor task network, and the cerebellum decoupled from this network overnight. ConclusionsWhile both patient groups showed similar deficits in consolidation associated with hippocampal-prefrontal cortex connectivity, other activity patterns more specific for disease pathology differed.

Untreated Sleep-Disordered Breathing: Links to Aging-Related Decline in Sleep-Dependent Memory Consolidation

BackgroundIncreasing age is associated with a decline in cognition and motor skills, while at the same time exacerbating one's risk of developing obstructive sleep apnea (OSA). OSA-related cognitive deficits are highly prevalent and can affect various memory systems including overnight memory consolidation on a motor sequence task.Thus, the aim of our study was to examine the effect of aging on sleep-dependent motor memory consolidation in patients with and without OSA.MethodsWe studied 44 patients (19–68 years) who had been referred by a physician for a baseline polysomnography (PSG) evaluation. Based on their PSG, patients were assigned either to the OSA group (AHI>5/h), or control (Non-OSA) group (AHI<5/h).All subjects performed the Psychomotor Vigilance Task (PVT) and the Motor Sequence Learning Task (MST) in the evening and again in the morning after their PSG.ResultsDespite similar learning in the evening, OSA subjects showed significantly less overnight improvement on the MST, both for immediate (OSA −2.7%±2.8% vs. controls 12.2%±3.5%; p = 0.002) and plateau improvement (OSA 4.9%±2.3% vs. controls 21.1%±4.0%; p = 0.001). Within the OSA group, there was a significant negative correlation between overnight MST improvement and age (r2 = 0.3; p = 0.01), an effect that was not observed in the Non-OSA group (r2 = 0.08; p = 0.23)ConclusionsConsistent with previous research, healthy sleepers demonstrated a higher degree of sleep-dependent overnight improvement on the MST, an effect not mitigated by increasing age. However, the presence of untreated obstructive sleep apnea is associated with an aging-related cognitive deficit, otherwise not present in individuals without OSA. As other research has linked the presence of OSA to a higher likelihood of developing dementia, future studies are necessary to examine if the inhibition of memory consolidation is tied to the onset of neurodegenerative disease.

Do video game players resist interference with perceptual learning by training on a new task?

Long-term exposure to certain types of video games can influence a wide range of mental processes, from visual acuity to cognitive control (e.g., Cain, Landau, & Shimamura, 2012, Green & Bavelier, 2003). Video game players have also displayed generalized improvements in perceptual learning (Green, Li, & Bavelier, 2010). We investigated whether perceptual learning advantages in heavy action video gamers, compared to non-players, included resistance to interference caused by changes in stimulus properties. In the classic texture discrimination task (TDT, Karni & Sagi, 1991), participants report the orientation of an array of oblique lines embedded in a field of all vertical or all horizontal lines and demonstrate robust over-night improvement. However, changing the background line orientation midway through TDT training with no interval between the changes interferes with overnight improvements in performance on TDT with both background orientations (Yotsumoto, Chang, Watanabe, & Sasaki, 2009). Interestingly, no interference occurred with a one-hour interval between the changes. These results have suggested that after training is over, it takes some time for the learning to be stabilized and resilient against interference. Here, we examined the effect of daily video game playing on interference of training of TDT with one background orientation on perceptual learning of TDT with a different background orientation. As a result, we found that non-gamers showed no overnight performance improvements, replicating previous results with the interference TDT. In contrast, action video game players demonstrated overnight improvements in performance with both background orientations, suggesting that they are better able to overcome interference in perceptual learning. This resistance to proactive and retroactive interference suggests that video game playing not only enhances the amplitude and speed of perceptual learning but also leads to faster and/or more robust stabilization of perceptual learning. Meeting abstract presented at VSS 2013

Declarative memory consolidation during the first night in a sleep lab: The role of REM sleep and cortisol

While the consolidation of declarative memory is supported by slow wave sleep (SWS) in healthy subjects, it has been shown to be associated with rapid eye movement (REM) sleep in patients with insomnia. Sleep during a subject's first night in an unfamiliar environment is often disturbed, and this so-called first-night effect (FNE) has often been used as a model of transient insomnia. Additionally, sleeping for the first time in an unfamiliar environment can lead to increased cortisol secretion, and declarative memory consolidation likely depends on low cortisol levels, especially during the early part of the night. Accounting for intersubject variability in the FNE, we examined the relationship between sleep stages, cortisol secretion and declarative memory performance in 27 healthy young men. Declarative memory performance improved significantly after sleep. Whereas memory performance during the learning session and retrieval testing was strongly associated with cortisol secretion, the overnight gain was not. Post hoc analyses indicated that the overnight gain appears to be modulated by the extent of the FNE: a significant overnight improvement in memory performance was found only in subjects with a weak FNE (n=12). In these subjects, no association was found between any sleep stage and the improvement observed in their memory performance. In subjects with a strong FNE (n=12), however, the overnight change in memory performance was associated with the proportion of REM sleep and the total number of REMs. Disturbed sleep in an unfamiliar environment therefore appears to affect the memory consolidation process.

Selective delayed gains following motor imagery of complex movements.

Recent studies suggest that a night of sleep may play a similar functional role following motor imagery (MI) practice. Here we examined whether offline gains following MI of a finger tapping sequence depends on the degree of complexity of the motor sequence, and whether this improvement differentially affects the individual transitions of the motor-sequence pattern being learned. The data revealed greater delayed performance gains in motor skill procedures that were most difficult, with larger sleep-dependent overnight improvement for movements involving bimanual coordination. The analyses of single transitions between sequence elements further revealed greatest overnight improvement in speed for the slowest (i.e., most difficult) transitions at the re-test. These findings suggest that sleep-related performance gains for imagined movements depend on motor skill complexity, and that difficult transition movements are most effectively enhanced after a night of sleep.

Alpha Activity during Rem Sleep Contributes to Overnight Improvement in Performance on a Visual Discrimination Task

The purpose of this preliminary study was to clarify the association between cortical and subcortical activities during REM and non-REM sleep with overnight improvement of performance on a procedural memory task. Eleven healthy volunteers (M age = 23.8 yr., SD = 3.1) participated in this study which was conducted over two consecutive nights: an adaptation night and the experimental night. They underwent a visual discrimination task before and after the experimental night. A positive correlation was observed between overnight performance improvement on the visual discrimination task and EEG alpha band power during REM sleep, while no significant correlation was observed between the performance and either the amount of Stage REM sleep, REM activity, or other sleep variables. The findings corroborate other studies and suggest that cortical activity during REM sleep contributed to procedural memory consolidation and highlights the importance of measuring quantitative REM sleep components to elucidate the role of physiological sleep on memory consolidation in humans.

Sleep-related cognitive function and the K-complex in schizophrenia

Sleep parameters have been reported to be related to cognitive function in a variety of ways. Problem solving and procedural learning were found to be improved after sleep but training also affected subsequent sleep and some parameters were related to cognitive trait variables, e.g. IQ. Additional to rapid-eye-movement (REM) and slow wave sleep (SWS), micro-architectural features such as spindle activity and K-complexes have recently been the focus of interest. The study aimed at investigating the relationship of neuropsychological variables, problem solving and procedural learning with sleep parameters in stably medicated schizophrenia patients.Twenty schizophrenia out-patients participated in the study. Learning and testing occurred over a randomly balanced waking and sleep interval. The tasks were the Tower of London (ToL) and mirror tracing. Sleep EEG was analysed together with spindle activity and K-complexes.Performance improved with regard to both tasks from learning to testing irrespective of type of interval. Increasing density of K-complexes was related to a higher number of solved ToL tasks pre and post night whereas longer SWS was related to faster completion of the ToL. A higher age was related to less overnight improvement in regard to number of solved ToL tasks.K-complexes are thought to indicate intra-cortical activity paving the way for the uptake of new information. As ToL is considered a test of executive function, K-complexes appear to be linked to this domain, deficits of which are thought to be a core feature of schizophrenia.

Increased Sleep Fragmentation Leads to Impaired Off-Line Consolidation of Motor Memories in Humans

A growing literature supports a role for sleep after training in long-term memory consolidation and enhancement. Consequently, interrupted sleep should result in cognitive deficits. Recent evidence from an animal study indeed showed that optimal memory consolidation during sleep requires a certain amount of uninterrupted sleep.Sleep continuity is disrupted in various medical disorders. We compared performance on a motor sequence learning task (MST) in relatively young subjects with obstructive sleep apnea (n = 16; apnea-hypopnea index 17.1±2.6/h [SEM]) to a carefully matched control group (n = 15, apnea-hypopnea index 3.7±0.4/h, p<0.001. Apart from AHI, oxygen nadir and arousal index, there were no significant differences between groups in total sleep time, sleep efficiency and sleep architecture as well as subjective measures of sleepiness based on standard questionnaires. In addition performance on the psychomotor vigilance task (reaction time and lapses), which is highly sensitive to sleep deprivation showed no differences as well as initial learning performance during the training phase. However there was a significant difference in the primary outcome of immediate overnight improvement on the MST between the two groups (controls = 14.7±4%, patients = 1.1±3.6%; P = 0.023) as well as plateau performance (controls = 24.0±5.3%, patients = 10.1±2.0%; P = 0.017) and this difference was predicted by the arousal index (p = 0.02) rather than oxygen saturation (nadir and time below 90% saturation. Taken together, this outcome provides evidence that there is a clear minimum requirement of sleep continuity in humans to ensure optimal sleep dependent memory processes. It also provides important new information about the cognitive impact of obstructive sleep apnea and challenges its current definitions.

Reduced Sleep Spindles and Spindle Coherence in Schizophrenia: Mechanisms of Impaired Memory Consolidation?

Sleep spindles are thought to induce synaptic changes and thereby contribute to memory consolidation during sleep. Patients with schizophrenia show dramatic reductions of both spindles and sleep-dependent memory consolidation, which may be causally related. To examine the relations of sleep spindle activity to sleep-dependent consolidation of motor procedural memory, 21 chronic, medicated schizophrenia outpatients and 17 healthy volunteers underwent polysomnography on two consecutive nights. On the second night, participants were trained on the finger-tapping motor sequence task (MST) at bedtime and tested the following morning. The number, density, frequency, duration, amplitude, spectral content, and coherence of stage 2 sleep spindles were compared between groups and examined in relation to overnight changes in MST performance. Patients failed to show overnight improvement on the MST and differed significantly from control participants who did improve. Patients also exhibited marked reductions in the density (reduced 38% relative to control participants), number (reduced 36%), and coherence (reduced 19%) of sleep spindles but showed no abnormalities in the morphology of individual spindles or of sleep architecture. In patients, reduced spindle number and density predicted less overnight improvement on the MST. In addition, reduced amplitude and sigma power of individual spindles correlated with greater severity of positive symptoms. The observed sleep spindle abnormalities implicate thalamocortical network dysfunction in schizophrenia. In addition, the findings suggest that abnormal spindle generation impairs sleep-dependent memory consolidation in schizophrenia, contributes to positive symptoms, and is a promising novel target for the treatment of cognitive deficits in schizophrenia.

Sleep Optimizes Motor Skill in Older Adults

To determine whether sleep benefits motor memory in healthy elderly adults and, if so, whether the observed sleep-related benefits are comparable with those observed in healthy young adults. Repeated-measures cross-over design. Boston, Massachusetts (general community) and Harvard University. Sixteen healthy older and 15 healthy young participants. Motor sequence task (MST) performance was assessed at training and at the beginning and end of the retest session; polysomnographic sleep studies were recorded for the elderly participants. After 12 hours of daytime wakefulness, elderly participants showed a dramatic decline in MST performance on the first three retest trials, and only a nonsignificant improvement by the end of retest (the last 3 retest trials). In contrast, when the same participants trained in the morning but were retested 24 hours after training, after a day of wake plus a night of sleep, they maintained their performance at the beginning of retest and demonstrated a highly significant 17.4% improvement by the end of the retest session, essentially identical to the 17.3% improvement seen in young participants. These strikingly similar improvements occurred despite the presence of other age-related differences, including overall slower motor speed, a lag in the appearance of sleep-dependent improvement, and an absence of correlations between overnight improvement and sleep architecture or sleep spindle density in the elderly participants. These findings provide compelling evidence that sleep optimizes motor skill performance across the adult life span.

Transcranial direct current stimulation at training can improve subsequent consolidation of a visual perceptual skill

Event Abstract Back to Event Transcranial direct current stimulation at training can improve subsequent consolidation of a visual perceptual skill Katia Boumghar1*, Katja Laske1, Matthias Mölle1, Jan Born1 and Lisa Marshall1 1 Department of Neuroendocrinology, University of Lübeck, Germany In humans, transcranial direct current stimulation (tDCS) is used to induce cortical polarization and excitability shifts which can result in acute as well as longer lasting effects. Here we investigated at the behavioral level the effects of cathodal and anodal tDCS applied during learning on the overnight improvement in a visual texture discrimination task (VDT). The VDT requires learning of a procedural skill in which robust improvement is typically obtained only after post-training retention periods containing sleep. In the VDT learning and retest are spaced 24h apart. On each trial, subjects fix a central cross and activate the beginning of each trial consisting of the target and mask for which the time interval of separation (stimulus-to-mask-onset, SOA) decreases over time. Subjects are to judge the orientation of target-lines (horizontal or vertical). The subjects of both experimental groups receive on one of two weeks either anodal (cathodal) or sham stimulation over V1. Cathodal tDCS applied during learning led to a significant decrease in the discrimination threshold measured at retesting the following day, as compared to a sham stimulation control condition. No acute effect of stimulation during training was found, nor did anodal tDCS affect performance. We propose that the effect of cathodal tDCS in the VDT reflects the ability of endogenous polarization fields as induced by simple neuronal processing steps or attentional shifts to impact latent improvement in performance. Differences in the early component of the visual potential dependent upon learning on the VDT task have been reported (Pourtois et al., 2008). In order to assess possible underlying mechanisms the visual evoked potentials (VEP) are currently being recorded. Funding: Supported by BMBF, DFG. Keywords: Learning, tDCS Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Neural Bases of Memory and Learning Citation: Boumghar K, Laske K, Mölle M, Born J and Marshall L (2011). Transcranial direct current stimulation at training can improve subsequent consolidation of a visual perceptual skill. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00408 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 24 Nov 2011; Published Online: 28 Nov 2011. * Correspondence: Dr. Katia Boumghar, Department of Neuroendocrinology, University of Lübeck, Lübeck, Germany, boumghar@kfg.uni-luebeck.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Katia Boumghar Katja Laske Matthias Mölle Jan Born Lisa Marshall Google Katia Boumghar Katja Laske Matthias Mölle Jan Born Lisa Marshall Google Scholar Katia Boumghar Katja Laske Matthias Mölle Jan Born Lisa Marshall PubMed Katia Boumghar Katja Laske Matthias Mölle Jan Born Lisa Marshall Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Is sleep-dependent memory consolidation of a visuo-motor task related to dream content?

A considerable amount of studies have shown that sleep facilitates memory consolidation. For procedural memory, some findings support the association with REM sleep but the relationship between memory consolidation and dreaming has been scarcely studied. The present study did not find an effect of direct incorporations of the mirror tracing task into the dream on over-night improvement. On the other hand, bizarre, long, and intense dreams were associated with poorer performance regarding speed but also with decreased amount of errors. Whether this can be explained by altered sleep physiology or negative effects of dreams on mood and performance can not yet been answered. Future research should study more complex and demanding procedural memory tasks and the relationship between dreaming and sleep-dependent consolidation of emotional memories.

Effects on neuropsychological performance and sleep quality in patients with obstructive sleep apnea syndrome

Patients with obstructive sleep apnea syndrome (OSAS) may have impaired neuropsychological performance. The aim of the study is to assess neuropsychological function in OSAS patients before and on continous positive airway pressure (CPAP) therapy to assess different neuropsychological tests – especially of sensomotor memory – in OSAS patients, and to relate neuropsychological test results to polysomnographic findings. Therefore, 36 normal controls and 18 OSAS patients performed tests of attention capacity and memory with retrieval in the evening and the following morning. Six weeks later, the tests were repeated (patients on CPAP). Controls performed significantly better than patients in the tests of attention and of memory of facts without and on CPAP therapy. Moreover, good compliance of CPAP therapy was not associated with better performance. However, there was no significant difference between controls and patients in the tests of sensomotor memory. The neuropsychological results depended on oxygen values, the arousal index, and sleep stages. There is no group difference in overnight improvement in the neuropsychological tests, which could indicate that sleep has an important function in homeostatic regulation rather than in consolidation.

Reduced overnight consolidation of procedural learning in chronic medicated schizophrenia is related to specific sleep stages

We previously reported that patients with schizophrenia failed to demonstrate normal sleep-dependent improvement in motor procedural learning. Here, we tested whether this failure was associated with the duration of Stage 2 sleep in the last quartile of the night (S2q4) and with spindle activity during this epoch. Fourteen patients with schizophrenia and 15 demographically matched controls performed a motor sequence task (MST) before and after a night of polysomnographically monitored sleep. Patients showed no significant overnight task improvement and significantly less than controls, who did show significant improvement. While there were no group differences in overall sleep architecture, patients showed significant reductions in fast sigma frequency power (45%) and in spindle density (43%) during S2q4 sleep at the electrode proximal to the motor cortex controlling the hand that performed the MST. Although spindle activity did not correlate with overnight improvement in either group, S2q4 sleep duration in patients significantly correlated with the plateau level of overnight improvement seen at the end of the morning testing session, and slow wave sleep (SWS) duration correlated with the delay in reaching this plateau. SWS and S2q4 sleep each predicted the initial level of overnight improvement in schizophrenia, and their product explained 77% of the variance, suggesting that both sleep stages are necessary for consolidation. These findings replicate our prior observation of reduced sleep-dependent consolidation of motor procedural learning in schizophrenia and link this deficit to specific sleep stages. They provide further evidence that sleep is an important contributor to cognitive deficits in schizophrenia.

Does Sleep Promote Motor Learning? Implications for Physical Rehabilitation

Sleep following motor skill practice has repeatedly been demonstrated to enhance motor skill learning off-line (continued overnight improvements in motor skill that are not associated with additional physical practice) for young people who are healthy. Mounting evidence suggests that older people who are healthy fail to demonstrate sleep-dependent off-line motor learning. However, little is known regarding the influence of sleep on motor skill enhancement following damage to the brain. Emerging evidence suggests that individuals with brain damage, particularly following stroke, do benefit from sleep to promote off-line motor skill learning. Because rehabilitation following stroke requires learning new, and re-learning old, motor skills, awareness that individuals with stroke benefit from a period of sleep following motor skill practice to enhance skill learning could affect physical therapist practice. The objective of this article is to present the evidence demonstrating sleep-dependent off-line motor learning in young people who are healthy and the variables that may influence this beneficial sleep-dependent skill enhancement. In young people who are healthy, these variables include the stages of memory formation, the type of memory, the type of instruction provided (implicit versus explicit learning), and the task utilized. The neural mechanisms thought to be associated with sleep-dependent off-line motor learning also are considered. Research examining whether older adults who are healthy show the same benefits of sleep as do younger adults is discussed. The data suggest that older adults who are healthy do not benefit from sleep to promote off-line skill enhancement. A possible explanation for the apparent lack of sleep-dependent off-line motor learning by older adults who are healthy is presented. Last, emerging evidence showing that individuals with chronic stroke demonstrate sleep-dependent off-line motor skill learning and some of the possible mechanisms for this effect are considered.

Islet culture and counter-culture

The publication of the Edmonton protocol caused a lot of excitement by reporting an almost overnight improvement in the rate of success of clinical islet of Langerhans transplantation [1]. Conventional wisdom holds that steroid-free immunosuppression and an increased transplanted islet mass, thanks to the use of multiple donors for each recipient, were the key determinants for the success of the Edmonton protocol. However, the protocol incorporated several additional strategies in the effort to improve the results of the method. One of these was the transplantation of freshly isolated islets within 2 h of the end of the isolation procedure [1,2]. This approach was novel, but based on intuition rather than on hard data. Indeed, in the previous years, islet preparations were commonly cultured prior to transplantation [3]. In the wake of the Edmonton report, many islet transplant centers attempted to reproduce its results by implementing the same protocol, including immediate transplantation of fresh islets, as was the case in the first ever multicenter trial of islet transplantation, funded by the Immune Tolerance Network [2]. There are, however, obvious logistical advantages in culturing islets prior to transplantation: it provides flexibility in the organization and planning of the procedure, which involves interventional radiology access and anesthesiology standby, and it allows the pooling of islet preparations sequentially isolated from different donor pancreata, to increase the islet graft functional mass. Indeed, it could be shown that transplantation of cultured islets could lead to seemingly similar success rates as those described by the Edmonton group [4,5]. The question thus arises whether culturing islets for a period of time could have a beneficial or detrimental impact on islet viability and function, and on what mechanistic basis. This question is addressed by Dr. Ihm et al. in a recent issue of Transplant International [6] [Correction added after publication 31 March 2009: in the preceding sentence, this issue was corrected to a recent issue]. This is an important question and it is noteworthy that this is one of very few publications that have addressed this topic studying human islets. Results obtained in animal models may not necessarily be extrapolated to the human, because of the species-specific impact of culture on islet function [7]. The authors show that short-term culture has a beneficial effect on islet vitality and viability. Two-day culture increased islet cell ATP contents and decreased the activity of protein kinases involved in pro-apoptotic signalling. These positive findings are balanced by the increased expression of certain pro-inflammatory genes induced by short-term culture. What matters to the islet transplant community, however, is the overall impact of short-term culture on in vivo islet function. It is well known and a matter of concern that culturing islets leads to a loss of function and mass Correspondence Thierry Berney MD, MSc, Division of Visceral/ Transplantation Surgery, Geneva University Hospitals, 24 rue MIcheli-du-Crest, CH-1211 Geneva 14. Tel.: +41 22 37 23 404; fax: +41 22 37 27 707; e-mail: thierry. berney@hcuge.ch

Mid-term effects of serial sleep deprivation therapy implemented in cognitive-behavioral treatment on the neuroendocrine response to clomipramine in patients with major depression

While data dealing with neurobiological effects of sleep deprivation (SD) are mainly restricted to the acute effects of a single night, only few studies have investigated mid-term effects after repeated SD. We therefore examined the clinical and hormonal characteristics of depressive patients before and after serial SD to determine potential sustained effects, focusing especially on serotoninergic functions. One tool to investigate serotoninergic dysfunction in depression is the use of serotoninergic agents to stimulate hormonal secretion, which is assumed to normalize during a clinically effective therapy. Eighteen drug-free inpatients with unipolar major depression received cognitive-behavioral treatment for three weeks and – according to a randomized control design – additional SD therapy (six nights of total SD within three weeks, separated by nights of recovery sleep) or no SD therapy (control group). Serotoninergic function was assessed by measuring cortisol and prolactin in response to intravenously administered clomipramine (12.5 mg) before and after the treatment period. The post-treatment challenge test was performed three days after the last SD night. Apart from of a transient overnight improvement of mood induced by SD, both groups showed a comparable clinical course during the three-week treatment period. Compared to the control group, the SD-treated patients exhibited significantly decreased pre-stimulation cortisol levels and significantly increased cortisol responses to clomipramine, whereas no treatment effects were observed for prolactin. In conclusion, our findings suggest that the mid-term effects of serial SD therapy lead to a normalization of serotoninergic dysfunction, although an obvious impact on clinical symptoms was not detected.