Procedural Memory Consolidation Research Articles

Impaired off-line memory consolidation in depression

Sleep is critically involved in the consolidation of procedural memory. In major depression (MD) and during antidepressant pharmacotherapy, changes in sleep EEG are well documented. Here, we test if off-line motor memory consolidation is impaired in MD. 50 medicated patients with an acute episode of MD, 50 normal controls and 12 patients with a remitted episode of MD were assessed using a sequential finger tapping task before and after a night of sleep. Although depressed patients and control subjects did not differ in practice-dependent learning, healthy subjects showed markedly overnight improvements in tapping performance of 18% while patients failed to show any improvement. This pattern became even more striking when the subjects were divided by an age threshold of 30years: In the 30+yrs group the healthy subjects showed 16% overnight increase in motor performance, whereas the patients showed -10% overnight decrease. In contrast, patients and controls in the </=30yrs group showed virtually the same motor performance, as well as remitted patients and controls in the 30+yrs group. In addition, the younger controls showed stronger overnight improvements than the older controls. This pattern might be interpreted as a synergistic interaction between age and depression: Off-line motor memory consolidation is not affected in young patients, but severely impaired in older patients with an acute episode of MD. This impairment seems to recover after remission from depression.

Sleep Induced Mu-Beta Rhythm Modulations in Motor Sequence Memory Consolidation

Event Abstract Back to Event Sleep Induced Mu-Beta Rhythm Modulations in Motor Sequence Memory Consolidation Genevieve Albouy1*, Francoise Lecaignard2, Jeremie Mattout1, Claude Delpuech3, Pierre-Emmanuel Aguera1, Pierre-Herve Luppi4, Alain Nicolas4, Pierre Maquet5 and Olivier Bertrand1 1 University of Lyon, INSERM U821, France 2 CERMEP, Imagerie du Vivant, MEG Dept, France 3 CERMEP/INSERM U821, France 4 University of Lyon, CNRS UMR 5167, France 5 University of Liège, Cyclotron Research Centre, Belgium The neural correlates of motor sequence memory consolidation have already been studied but its electrophysiological correlates remain scarcely described. The aim of the present study was to determine the influence of sleep on the electrophysiological correlates of motor sequence memory consolidation, using magnetoencephalography (275-channel MEG). Subjects were scanned during training on a sequential finger tapping task (FTT). After training, they were divided in two groups whether they slept (N=15) or were totally sleep-deprived (N=16) on the following night. Three days after training, a second MEG session consisted in the retest on the FTT for the two groups. Using ELAN software package (INSERM U821, Lyon), both sessions were analysed in the time frequency (TF) domain, during practice and inter-tapping rest periods. Subsequent group source reconstruction analyses of significant effects during training were performed using SPM8 (Wellcome Department of Imaging Neuroscience, London, UK). TF analyses on the training session show a progressive desynchronization, i.e. a power decrease, of mu (10-15 Hz) and beta (20-25 Hz) oscillations over bilateral and medial central areas during practice of the learned sequence. The anatomical sources of this effect in the beta band were localised in bilateral sensorimotor cortices (pre- and post-central gyri). An overall sleep-dependent increase in the amplitude of mu-beta oscillations was observed over controlateral and medial central areas during both practice periods and inter-tapping rest periods following practice of the learned sequence. Interestingly, in sleepers, a beta power increase was observed specifically for the learned sequence during inter-tapping rest periods. In contrast, no changes in mu-beta oscillatory activity were observed after sleep deprivation. These results provide the first electrophysiological evidence of sleep-dependent reorganisation of motor cortex activity during procedural sequence memory consolidation. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: Neurocognition and Functional Connectivity Citation: Albouy G, Lecaignard F, Mattout J, Delpuech C, Aguera P, Luppi P, Nicolas A, Maquet P and Bertrand O (2010). Sleep Induced Mu-Beta Rhythm Modulations in Motor Sequence Memory Consolidation. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00393 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: 08 Apr 2010; Published Online: 08 Apr 2010. * Correspondence: Genevieve Albouy, University of Lyon, INSERM U821, Bron, France, gmalbouy@club-internet.fr 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 Genevieve Albouy Francoise Lecaignard Jeremie Mattout Claude Delpuech Pierre-Emmanuel Aguera Pierre-Herve Luppi Alain Nicolas Pierre Maquet Olivier Bertrand Google Genevieve Albouy Francoise Lecaignard Jeremie Mattout Claude Delpuech Pierre-Emmanuel Aguera Pierre-Herve Luppi Alain Nicolas Pierre Maquet Olivier Bertrand Google Scholar Genevieve Albouy Francoise Lecaignard Jeremie Mattout Claude Delpuech Pierre-Emmanuel Aguera Pierre-Herve Luppi Alain Nicolas Pierre Maquet Olivier Bertrand PubMed Genevieve Albouy Francoise Lecaignard Jeremie Mattout Claude Delpuech Pierre-Emmanuel Aguera Pierre-Herve Luppi Alain Nicolas Pierre Maquet Olivier Bertrand 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.

068 EFFECT OF CHRONIC PHYSICAL EXERCISE ON ANXIETY IN PATIENTS WITH CHRONIC PRIMARY INSOMNIA

s of 3rd International Congress of the Association of Sleep Medicine (WASM) / Sleep Medicine 10, Suppl. 2 (2009) S1–S83 S19 Objectives: The aim of this study was to test the hypothesis that ongoing hyperarousal processes during sleep, as indexed by EEG beta activity, mediates previously shown deficits in memory consolidation during sleep in patients with primary insomnia. Methods: General neurocognitive and memory performance (procedural mirror-tracing task, declarative visual and verbal learning task) was assessed before and after one night of polysomnographic monitoring in 18 patients with primary insomnia (7 men, aged 45.5±4.5 years) and 34 sex, age and IQ matched healthy subjects. EEG spectral analysis was performed for epochs of NREM sleep. Results: Insomnia patients showed significantly increased EEG beta activity during NREM sleep (16-32 Hz), decreased overnight procedural memory consolidation (MANOVA, p 36 hours), and/or focused solely on global assessments of negative mood. Objective: To determine the effects of experimental sleep restriction and sleep disruption, two common and distinct forms of sleep loss, on negative and positive mood. Methods: Fifty-three healthy adults (62.2% female, age 26±6.1) spent five consecutive nights on an inpatient research unit. After a baseline sleep night, participantswere randomized to one of three conditions: Forced Awakenings (FA), Restricted Sleep (RS), or Control (C) for the following three nights. FA underwent one forced awakening each hour for an 8-hour sleep opportunity (seven random 20-min. and one 60-min. awakening). RS slept undisturbed for no more than 280 mins. C slept undisturbed for 8 hrs. The Profile of Mood States (POMS) was given prior to bedtime each night. POMS total negative (POMS-N) and positive (POMS-P) mood scales were utilized by aggregating responses to negative and positive valence items. Results: Independent 3 Condition (C, FA, RS) × 4 Time (Baseline, Night 1, Night 2, Night 3) mixed-model ANOVAs were conducted with POMS-N and POMS-P as DVs. Follow-up single-df comparisons focused on changes in POMS-N and POMS-P across nights for RS vs. Control and FA vs. Control. The omnibus Condition × Time effect was significant (p<0.05) for POMS-N and POMS-P. Comparisons for POMS-N revealed that FA and RS yielded greater increases in POMS-N than C (p<0.05). For POMS-P, FA yielded greater decreases in POMS-P than C (p<0.05). A post hoc comparison showed that FA tended to yield greater decreases in POMS-P than RS (p=0.06). Both RS and FA demonstrated equivalent total sleep time. Conclusion: Partial sleep loss by disruption or curtailment has detrimental effects on mood. Moreover, fragmented sleep contributed to greater decrements in positive mood than restricted sleep. These data have important implications for the well-being of individuals who have repeated awakenings or voluntarily restrict their sleep. The mechanisms of these effects, mental health consequences, and the novel finding that fragmented (but not restricted) sleep contributes robustly to anhedonia require additional inquiry. Support: NINDS R21NS051771 (MTS) and MH075884 (PJQ) 070 BODY MASS INDEX, EATING ATTITUDES AND SLEEP DISTURBANCE IN YOUNG ADULTS M.J. Soares1, S.C. Bos1, B. Maia1, A.T. Pereira1, M. Marques1, J. Valente1, A.A. Gomes2, A. Macedo1, M.H. Azevedo1. 1Institute of Medical Psychology, Faculty of Medicine, University of Coimbra, Coimbra, Portugal; 2Educational Sciences Department, University of Aveiro, Aveiro, Portugal Objective: To examine the association between body mass index, eating attitudes, and self-reported sleep disturbances in university students. Methods: Self-reported current body weight and height were used to calculate BMI (BMI; KG/M2). The Eating Attitudes Test-40 (EAT40 Garner & Garfinkel, 1979) was used to measure eating attitudes and behaviors (Diet Concerns, DC; Bulimic Behaviors, BB, Social Pressure to Eat, EAT). Sleep disturbance was assessed with two items: (1) I have difficulty in falling asleep -DIS and (2) I wake up many times during the night -DMS. Each item was scored on a 5-point scale ranging from 0 (never) to 5 (always). An overall index of sleep disturbance score (SDI) was calculated from the sum of the scores of the individual items. The sample consisted of 544 female (M age=19.5 years, SD=1.56) and 326 male (M age=19.8 years, SD=1.68) undergraduate students. Results: In the total sample, subjectswith a BMI lower than 19 or between 19 and 22 had significantly more difficulties initiating sleep (M=1.83; SD=1.04; p<.05 and M=1.77; SD=1.07; p<.05, respectively) than subjects with a BMI higher than 24 (M=1.50; SD=1.04). Eating disorder behavior (DC, BB, SPE and EAT total score) was positively and significantly associated with DIS, DMS and SDI (values ranging from r=0.09 to r=0.21; p<0.05). The exception was that DC was not associated to sleep measures in males, while in females it was not associated to DMS. Insomniacs (subjects who often, very often or

A double dissociation of memory impairments in major depression

Objective: While declarative memory impairments are well known in major depression, most studies show preserved procedural memory in depressed patients. We tested if sleep-dependent procedural and declarative memory consolidation are impaired in major depression. Methods: 30 medicated patients with an acute episode of major depression and 30 normal controls were assessed using a procedural (sequential finger tapping) and a declarative (paired associates) memory task before and after a night of sleep. Results: Although depressed patients and control subjects did not differ in practice-dependent learning of the procedural task in the awake state, healthy subjects showed overnight improvements in tapping performance of 11.5%, while the patients' performance decreased overnight by 10.7%. This pattern was reversed for the declarative task: While patients learned 33.5% less word pairs than controls in the awake state, overnight changes did not differ between the two groups. Conclusions: Our results suggest a double dissociation of memory consolidation processes in major depression: Sleep-dependent memory consolidation in major depression is impaired for procedural, but not declarative tasks. The same tasks in the awake state show a reversed pattern, with performance in declarative but not procedural tasks being impaired in major depression.

Sleep and memory consolidation in the elderly

The significance of sleep for memory consolidation has been investigated for several years. Even though aging affects both sleep and memory, only very few studies have addressed this topic in the context of aging so far. Recent findings with regard to sleep-related memory consolidation in old age suggest that processes of procedural memory consolidation during REM sleep as well as declarative memory consolidation during slow wave sleep are impaired in older adults. Posttraining increases in stage 2 sleep spindles also seem to be less pronounced in old age. Apart from age-related changes in sleep characteristics such as duration and microstructure of specific sleep stages, age-related changes at the neurochemical level, especially the cholinergic system, play an important role in this context. In addition, structural and functional changes of the brain with increasing age could adversely affect the efficiency of sleep-related memory consolidation in old age. In light of structural, functional and neurochemical changes of the brain with dementia as well as characteristic changes in sleep quality as part of the disorder, this patient group is of particular interest for the study of sleep-related memory consolidation in old age. The same applies to old age depression, which has not been studied systematically in this context so far.

Effects of Early and Late Rest Breaks during Training on Overnight Memory Consolidation of a Keyboard Melody

In two experiments, we tested the extent to which overnight procedural memory consolidation is affected by extended rest breaks during training. In the first experiment, nonmusicians practiced a 5-element keypress sequence with their nondominant hand in 12 30-s practice intervals separated by 30-s pauses. In the second experiment, nonpianist musicians practiced a 13-note keyboard melody using the same procedures. In both experiments, approximately one-third of the subjects took a 5-min break after the first three blocks of practice; another third took a break after nine blocks of practice; the remaining participants did not take an extended break. All were trained in the evening and were retested the following morning. Participants in both experiments made dramatic improvements over the course of the training and retest sessions, and participants who took an extended rest break early in practice made the largest gains in performance between the end of training and the beginning of retest.

Effects of daytime naps on procedural and declarative memory in patients with schizophrenia

Sleep has been identified as a state that optimizes the consolidation of newly acquired information in memory. Straight memory deficits and sleep disturbances are well-known in patients with schizophrenia. This study tested the hypothesis that patients with schizophrenia have a deficit in procedural and declarative memory consolidation after a short midday nap when compared to healthy controls and patients with remitted to moderate major depression. Following a normal night’s sleep, 22 healthy subjects, 20 patients with major depression and 21 patients with schizophrenia were studied in a napping and wake condition in a random-order cross-over design, early in the afternoon. To test declarative memory, the Rey–Osterrieth Complex Figure Test respectively the Taylor Complex Figure Test and, for procedural learning, a mirror tracing task were performed. The present study is the first to demonstrate significant differences between individuals with schizophrenia, depression and healthy matched controls with regard to measures of sleep and memory performance after a short period of daytime sleep (napping). In particular we found that a daytime nap of only about 40 min led to improvement of declarative memory performance in all investigated groups, whereas no beneficial effect was seen on procedural performance in the group of medicated patients with schizophrenia in contrast to healthy controls and patients with remitted to moderate major depression.

Enhancing influence of intranasal interleukin‐6 on slowwave activity and memory consolidation during sleep

The cytokine IL-6 has been considered to exert neuromodulating influences on the brain, with promoting influences on sleep. Sleep enhances the consolidation of memories, and, in particular, late nocturnal sleep also represents a period of enhanced IL-6 signaling, due to a distinctly enhanced availability of soluble IL-6 receptors during this period, enabling trans-signaling of IL-6 to neurons. Thus, a contribution of IL-6 to sleep-dependent memory consolidation is hypothesized. To test this hypothesis, we compared effects of intranasally administered IL-6 (vs. placebo) on sleep-dependent consolidation of declarative (neutral and emotional texts, 2-dimensional object location) and procedural (finger sequence tapping) memories in 17 healthy young men. IL-6 distinctly improved the sleep-related consolidation of emotional text material (P<0.03), which benefits mostly from sleep in the second night-half, in which rapid eye movement sleep (REM) dominates the non-REM-REM sleep cycle. During this second night-half, the amount of electroencephalogram slow-wave activity (0.5-4 Hz) distinctly increased after IL-6 (P<0.01). Other types of memory were not affected. The ability of IL-6 to enhance sleep-associated emotional memory consolidation highlights an example of a functional interaction between the central nervous and immune system.

Contribution of night and day sleep vs. simple passage of time to the consolidation of motor sequence and visuomotor adaptation learning

There is increasing evidence supporting the notion that the contribution of sleep to consolidation of motor skills depends on the nature of the task used in practice. We compared the role of three post-training conditions in the expression of delayed gains on two different motor skill learning tasks: finger tapping sequence learning (FTSL) and visuomotor adaptation (VMA). Subjects in the DaySleep and ImmDaySleep conditions were trained in the morning and at noon, respectively, afforded a 90-min nap early in the afternoon and were re-tested 12 h post-training. In the NightSleep condition, subjects were trained in the evening on either of the two learning paradigms and re-tested 12 h later following sleep, while subjects in the NoSleep condition underwent their training session in the morning and were re-tested 12 h later without any intervening sleep. The results of the FTSL task revealed that post-training sleep (day-time nap or night-time sleep) significantly promoted the expression of delayed gains at 12 h post-training, especially if sleep was afforded immediately after training. In the VMA task, however, there were no significant differences in the gains expressed at 12 h post-training in the three conditions. These findings suggest that "off-line" performance gains reflecting consolidation processes in the FTSL task benefit from sleep, even a short nap, while the simple passage of time is as effective as time in sleep for consolidation of VMA to occur. They also imply that procedural memory consolidation processes differ depending on the nature of task demands.

Slow wave sleep and REM sleep awakenings do not affect sleep dependent memory consolidation.

The effects of REM sleep and slow wave sleep (SWS) deprivation on sleep-dependent motor and declarative memory consolidation. Randomized, within-subject, cross-over study. Weekly (women: monthly) sleep laboratory visits, with retest 60 hours later. Twelve healthy subjects (6 men) aged between 20 and 30 years. REM sleep deprivation, SWS deprivation, or undisturbed sleep. We deprived subjects once each of REM sleep and SWS, and once let them sleep undisturbed through the night. After each night, we tested declarative and procedural memory consolidation. We tested memory performance by a verbal paired associate task and a sequential finger-tapping task at 21:00 on the study night and again 60 hours later. Although REM sleep and SWS awakenings led to a significant reduction of the respective sleep stages, memory consolidation remained unaffected. We also found a significant correlation between the declarative task and sleep spindles in the undisturbed condition, especially the sleep spindles in the first third of the night. We suggest that word-pair learning relies on stage 2 sleep spindles and requires little SWS. Their sleep dependent consolidation is not affected by SWS deprivation. Simple motor tasks may either be consolidated in stage 2 sleep or depend on only small amounts of REM sleep. Their sleep dependent consolidation is not influenced by REM sleep deprivation.

Slow Wave Sleep and REM Sleep Awakenings Do Not Affect Sleep Dependent Memory Consolidation

The effects of REM sleep and slow wave sleep (SWS) deprivation on sleep-dependent motor and declarative memory consolidation. Randomized, within-subject, cross-over study Weekly (women: monthly) sleep laboratory visits, with retest 60 hours later Twelve healthy subjects (6 men) aged between 20 and 30 years REM sleep deprivation, SWS deprivation, or undisturbed sleep Measurements and Results: We deprived subjects once each of REM sleep and SWS, and once let them sleep undisturbed through the night. After each night, we tested declarative and procedural memory consolidation. We tested memory performance by a verbal paired associate task and a sequential finger-tapping task at 21:00 on the study night and again 60 hours later. Although REM sleep and SWS awakenings led to a significant reduction of the respective sleep stages, memory consolidation remained unaffected. We also found a significant correlation between the declarative task and sleep spindles in the undisturbed condition, especially the sleep spindles in the first third of the night. We suggest that word-pair learning relies on stage 2 sleep spindles and requires little SWS. Their sleep dependent consolidation is not affected by SWS deprivation. Simple motor tasks may either be consolidated in stage 2 sleep or depend on only small amounts of REM sleep. Their sleep dependent consolidation is not influenced by REM sleep deprivation.

Still Missing Some Significant Ingredients

Still Missing Some Significant Ingredients

Sleep in children enhances preferentially emotional declarative but not procedural memories

Although the consolidation of several memory systems is enhanced by sleep in adults, recent studies suggest that sleep supports declarative memory but not procedural memory in children. In the current study, the influence of sleep on emotional declarative memory (recognition task) and procedural memory (mirror tracing task) in 20 healthy children (10–13 years of age) was examined. After sleep, children showed an improvement in declarative memory. Separate analysis with respect to the emotional stimulus content revealed that sleep enhances the recognition of emotional stimuli ( p > .001) rather than neutral stimuli ( p = .084). In the procedural task, however, no sleep-enhanced memory improvement was observed. The results indicate that sleep in children, comparable to adults, enhances predominantly emotional declarative memory; however, in contrast to adults, it has no effect on the consolidation of procedural memory.

The whats and whens of sleep-dependent memory consolidation

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.

The Effects of Donepezil on Postlearning Sleep EEG of Healthy Older Adults

Aging is associated with cholinergic hypofunction and memory decline. Cholinergic activity also plays a crucial role in sleep-dependent memory consolidation. The acetylcholinesterase inhibitor (AChE-I) donepezil has been found to increase sleep-related procedural memory consolidation in healthy older adults in a previous study. Data of the former study were reanalyzed with regard to the effects of donepezil on the sleep EEG of healthy older adults. This analysis was conducted with a special focus on spectral parameters of sleep, which have previously been linked to plasticity-related processes during sleep, i.e., sigma and delta activity. Forty-two participants (aged: 60-77 years) received 5 mg of the AChE-I donepezil orally 30 min before bedtime in a placebo-controlled, double-blind design. Power values for EEG delta, theta, alpha1, alpha 2, sigma, beta and gamma frequency bands were calculated for stage 2 NREM sleep, SWS and REM sleep. In line with our hypotheses, the AChE-I donepezil led to an increase in sigma activity during stage 2 NREM sleep and delta activity during slow wave sleep. These results suggest that an AChE-I facilitates processes of sleep-dependent memory consolidation in older adults.

Intranasal growth hormone-releasing hormone (GHRH) impairs declarative memory consolidation and GH secretion during nocturnal wakefulness

Context and aim: The activity of the somatotropic system displays a secretory maximum during early sleep which is a period known to be essential for memory consolidation. While blocking the sleep-onset associated surge in growth hormone (GH) secretion does not affect memory performance, the contribution of growth hormone-releasing hormone (GHRH) to memory formation is unclear. We assessed the influence of intranasal GHRH on memory consolidation in waking men. Design and subjects: Twelve healthy young men (mean age 23.3+/-1.0 years) were investigated twice (GHRH and placebo) during nocturnal wakefulness. Declarative and procedural memory consolidation was examined by means of a word pair and a finger tapping task, respectively. Learning took place around 2030h, i.e., before subjects were intranasally administered 600µg GHRH and saline solution, respectively. Recall was tested at 0900h in the morning. Levels of GH, ACTH, cortisol, catecholamines, insulin and blood glucose were assessed throughout the night. Results: The number of word pairs recalled in the morning (expressed as the percentage of word pairs acquired at learning) was reduced in the GHRH condition (72.3±4.1%) compared to placebo (81.3±6.4%; p&lt;0.05). Finger tapping was not influenced. A small but distinct GH peak observed in the control condition around 2330h was blunted by intranasal GHRH administration. Conclusion: Intranasal GHRH administration impairs declarative but not procedural memory consolidation during nocturnal wakefulness. GHRH treatment also impairs GH release during the first night-half, suggesting that the effects of intranasal GHRH are mediated via an ultrashort negative feedback loop that controls GH secretion.

Anodal transcranial direct stimulation enhances motor dexterity and procedural memory consolidation

Dynamic recruitment of primary motor cortex (M1) has been identified during within-session and inter-session motor learning. Anodal transcranial direct current stimulation (A-tDCS) has been demonstrated to increase cortical excitability.

Procedural learning and sleep hippocampal low frequencies in humans

Recent evidence suggests that slow EEG rhythms are involved in post-learning plasticity. However, the relationships between memory consolidation and hippocampal EEG features remain unclear. Here, we assessed the effects of both procedural and declarative learning on qualitative and quantitative measures of sleep by recording stereo-EEG (SEEG) directly from the hippocampus and the neocortex in a group of epileptic patients undergoing pre-surgical evaluations. Following a baseline night, sleep was recorded after administration of a declarative (paired-associate word list learning task) and a procedural (sequential finger tapping) task. Patients were tested before going to bed (test) and after sleep in the following morning (retest). At retest, we found that patients recalled correctly more word pairs compared to the pre-sleep test (declarative task), and they were slightly faster in performing the motor task (procedural task). Standard polysomnography showed an increase in the amount of slow-wave sleep (SWS) only after procedural learning, paralleled by an increase of hippocampal SEEG power in the very low frequency range (VLF, 0.5–1 Hz) during the first NREM sleep cycle. Moreover, procedural performance enhancement and SEEG power increase in the hippocampal VLF were significantly correlated, indicating a link between procedural memory consolidation and slow hippocampal SEEG rhythms. These findings are consistent with the hypothesis of synaptic homeostasis occurring during sleep, suggesting that hippocampal slow oscillations are associated with local processes of post-learning synaptic downscaling.

Visual–Procedural Memory Consolidation during Sleep Blocked by Glutamatergic Receptor Antagonists

Visual cortex plasticity is enhanced by sleep. It is hypothesized that a reactivation of glutamatergic synapses is essential for this form of plasticity to occur after learning. To test this hypothesis, human subjects practiced a visual texture discrimination skill known to require post-training sleep for improvements to occur. During sleep, glutamatergic transmission was inhibited by administration of the two glutamate antagonists, caroverine and ketamine, targeting the ionotropic NMDA and AMPA receptors. Both substances given during consolidation sleep in a placebo controlled crossover design were able to prevent improvement of the skill measured the next morning. An off-line activation of glutamatergic synapses therefore seems to play a critical part in the consolidation of plastic changes in the visual cortex.

Sleep in children improves memory performance on declarative but not procedural tasks

Sleep supports the consolidation of memory in adults. Childhood is a period hallmarked by huge demands of brain plasticity as well as great amounts of efficient sleep. Whether sleep supports memory consolidation in children as in adults is unclear. We compared effects of nocturnal sleep (versus daytime wakefulness) on consolidation of declarative (word-pair associates, two-dimensional [2D] object location), and procedural memories (finger sequence tapping) in 15 children (6-8 yr) and 15 adults. Beneficial effects of sleep on retention of declarative memories were comparable in children and adults. However, opposite to adults, children showed smaller improvement in finger-tapping skill across retention sleep than wakefulness, indicating that sleep-dependent procedural memory consolidation depends on developmental stage.