Sleep and school education

Sleep has emerged in the past decades as a key process for memory consolidation and restructuring. Given the universality of sleep across cultures, the need to reduce educational inequality, the low implementation cost of a sleep-based pedagogy, and its global scalability, it is surprising that the potential of improved sleep as a means of enhancing school education has remained largely unexploited. Students of various socio-economic status often suffer from sleep deficits. In principle, the optimization of sleep schedules both before and after classes should produce large positive benefits for learning. Here we review the biological and psychological phenomena underlying the cognitive role of sleep, present the few published studies on sleep and learning that have been performed in schools, and discuss potential applications of sleep to the school setting. Translational research on sleep and learning has never seemed more appropriate.

Naps in school can enhance the duration of declarative memories learned by adolescents

Sleep helps the consolidation of declarative memories in the laboratory, but the pro-mnemonic effect of daytime naps in schools is yet to be fully characterized. While a few studies indicate that sleep can indeed benefit school learning, it remains unclear how best to use it. Here we set out to evaluate the influence of daytime naps on the duration of declarative memories learned in school by students of 10–15 years old. A total of 584 students from 6th grade were investigated. Students within a regular classroom were exposed to a 15-min lecture on new declarative contents, absent from the standard curriculum for this age group. The students were then randomly sorted into nap and non-nap groups. Students in the nap group were conducted to a quiet room with mats, received sleep masks and were invited to sleep. At the same time, students in the non-nap group attended regular school classes given by their usual teacher (Experiment I), or English classes given by another experimenter (Experiment II). These 2 versions of the study differed in a number of ways. In Experiment I (n = 371), students were pre-tested on lecture-related contents before the lecture, were invited to nap for up to 2 h, and after 1, 2, or 5 days received surprise tests with similar content but different wording and question order. In Experiment II (n = 213), students were invited to nap for up to 50 min (duration of a regular class); surprise tests were applied immediately after the lecture, and repeated after 5, 30, or 110 days. Experiment I showed a significant ∼10% gain in test scores for both nap and non-nap groups 1 day after learning, in comparison with pre-test scores. This gain was sustained in the nap group after 2 and 5 days, but in the non-nap group it decayed completely after 5 days. In Experiment II, the nap group showed significantly higher scores than the non-nap group at all times tested, thus precluding specific conclusions. The results suggest that sleep can be used to enhance the duration of memory contents learned in school.

Dinâmica da Plasticidade Sináptica em neurônios do hipocampo durante ciclos de sono: um estudo computacional

Several research lines show that sleep favors memory consolidation and learning. It has been proposed that the cognitive role of sleep is derived from a global scaling of synaptic weights, able to homeostatically restore the ability to learn new things, erasing memories overnight. This phenomenon is typical of slow-wave sleep (SWS) and characterized by non-Hebbian mechanisms, i.e., mechanisms independent of synchronous neuronal activity. Another view holds that sleep also triggers the specific enhancement of synaptic connections, carrying out the embossing of certain mnemonic traces within a lattice of synaptic weights rescaled each night. Such an embossing is understood as the combination of Hebbian and non-Hebbian mechanisms, capable of increasing and decreasing respectively the synaptic weights in complementary circuits, leading to selective memory improvement and a restructuring of synaptic configuration (SC) that can be crucial for the generation of new behaviors ( insights ). The empirical findings indicate that initiation of Hebbian plasticity during sleep occurs in the transition of the SWS to the stage of rapid eye movement (REM), possibly due to the significant differences between the firing rates regimes of the stages and the up-regulation of factors involved in longterm synaptic plasticity. In this study the theories of homeostasis and embossing were compared using an artificial neural network (ANN) fed with action potentials recorded in the hippocampus of rats during the sleep-wake cycle. In the simulation in which the ANN did not apply the long-term plasticity mechanisms during sleep (SWS-transition REM), the synaptic weights distribution was re-scaled inexorably, for its mean value proportional to the input firing rate, erasing the synaptic weights pattern that had been established initially. In contrast, when the long-term plasticity is modeled during the transition SWSREM, an increase of synaptic weights were observed in the range of initial/low values, redistributing effectively the weights in a way to reinforce a subset of synapses over time. The results suggest that a positive regulation coming from the long-term plasticity can completely change the role of sleep: its absence leads to forgetting; its presence leads to a positive mnemonic change

Estudo da topologia de redes de conexão funcional no córtex sensorial primário e hipocampo durante o sono de ondas lentas

Complex network analysis is a powerful tool into research of complex systems like brain networks. This work aims to describe the topological changes in neural functional connectivity networks of neocortex and hippocampus during slow-wave sleep (SWS) in animals submited to a novel experience exposure. Slow-wave sleep is an important sleep stage where occurs reverberations of electrical activities patterns of wakeness, playing a fundamental role in memory consolidation. Although its importance there s a lack of studies that characterize the topological dynamical of functional connectivity networks during that sleep stage. There s no studies that describe the topological modifications that novel exposure leads to this networks. We have observed that several topological properties have been modified after novel exposure and this modification remains for a long time. Major part of this changes in topological properties by novel exposure are related to fault tolerance

Caracterização dos acoplamentos fase-amplitude na região CA1 do hopocampo

Brain oscillation are not completely independent, but able to interact with each other through cross-frequency coupling (CFC) in at least four different ways: power-to-power, phase-to-phase, phase-to-frequency and phase-to-power. Recent evidence suggests that not only the rhythms per se, but also their interactions are involved in the execution of cognitive tasks, mainly those requiring selective attention, information flow and memory consolidation. It was recently proposed that fast gamma oscillations (60 150 Hz) convey spatial information from the medial entorhinal cortex to the CA1 region of the hippocampus by means of theta (4-12 Hz) phase coupling. Despite these findings, however, little is known about general characteristics of CFCs in several brain regions. In this work we recorded local field potentials using multielectrode arrays aimed at the CA1 region of the dorsal hippocampus for chronic recording. Cross-frequency coupling was evaluated by using comodulogram analysis, a CFC tool recently developted (Tort et al. 2008, Tort et al. 2010). All data analyses were performed using MATLAB (MathWorks Inc). Here we describe two functionally distinct oscillations within the fast gamma frequency range, both coupled to the theta rhythm during active exploration and REM sleep: an oscillation with peak activity at ~80 Hz, and a faster oscillation centered at ~140 Hz. The two oscillations are differentially modulated by the phase of theta depending on the CA1 layer; theta-80 Hz coupling is strongest at stratum lacunosum-moleculare, while theta-140 Hz coupling is strongest at stratum oriens-alveus. This laminar profile suggests that the ~80 Hz oscillation originates from entorhinal cortex inputs to deeper CA1 layers, while the ~140 Hz oscillation reflects CA1 activity in superficial layers. We further show that the ~140 Hz oscillation differs from sharp-wave associated ripple oscillations in several key characteristics. Our results demonstrate the existence of novel theta-associated high-frequency oscillations, and suggest a redefinition of fast gamma oscillations

Diferenças funcionais das regiões hipocampais na formação da memória do tipo o quê", "quando" e "onde" em ratos

Episodic memory refers to the recollection of what, where and when a specific event occurred. Hippocampus is a key structure in this type of memory. Computational models suggest that the dentate gyrus (DG) and the CA3 hippocampal subregions are involved in pattern separation and the rapid acquisition of episodic memories, while CA1 is involved in memory consolidation. However there are few studies with animal models that access simultaneously the aspects ‗what-where-when . Recently, an object recognition episodic-like memory task in rodents was proposed. This task consists of two sample trials and a test phase. In sample trial one, the rat is exposed to four copies of an object. In sample trial two, one hour later, the rat is exposed to four copies of a different object. In the test phase, 1 h later, two copies of each of the objects previously used are presented. One copy of the object used in sample trial one is located in a different place, and therefore it is expected to be the most explored object.However, the short retention delay of the task narrows its applications. This study verifies if this task can be evoked after 24h and whether the pharmacological inactivation of the DG/CA3 and CA1 subregions could differentially impair the acquisition of the task described. Validation of the task with a longer interval (24h) was accomplished (animals showed spatiotemporal object discrimination and scopolamine (1 mg/kg, ip) injected pos-training impaired performance). Afterwards, the GABA agonist muscimol, (0,250 μg/μl; volume = 0,5 μl) or saline were injected in the hippocampal subregions fifteen minutes before training. Pre-training inactivation of the DG/CA3 subregions impaired the spatial discrimination of the objects (‗where ), while the temporal discrimination (‗when ) was preserved. Rats treated with muscimol in the CA1 subregion explored all the objects equally well, irrespective of place or presentation time. Our results corroborate the computational models that postulate a role for DG/CA3 in spatial pattern separation, and a role for CA1 in the consolidation process of different mnemonic episodes

Taxa de disparo e ativação de assembléias no hipocampo de ratos durante o processamento de uma memória aversiva

Hebb postulated that memory could be stored thanks to the synchronous activity of many neurons, building a neural assembly. Knowing of the importance of the hippocampal structure to the formation of new explicit memories, we used electrophysiological recording of multiple neurons to access the relevance of rate coding from neural firing rates in comparison to the temporal coding of neural assemblies activity in the consolidation of an aversive memory in rats. Animals were trained at the discriminative avoidance task using a modified elevated plus-maze. During experimental sessions, slow wave sleep periods (SWS) were recorded. Our results show an increase in the identified neural assemblies activity during post-training SWS, but not for the neural firing rate. In summary, we demonstrate that for this particular task, the relevant information needed for a proper memory consolidation lies within the temporal patters of synchronized neural activity, not in its firing rate

Avaliação dos efeitos do biperideno, diazepam e neuropeptídeos S sobre a memória e a ansiedade na tarefa do labirinto em T elevado em camundongos

Anxiety is an emotional phenomenon, and normally it is interpreted as an adaptative behavior front to adversities. In its pathological form, anxiety can severely affect aspects related to the personal and professional life. Studies have shown a close relationship between anxiety disorders and aversive memory processing. Considering that the pharmacotherapy of anxiety disorders is still limited, innovative anxiolytic agents are needed. In this regard, neuropeptides systems are interesting therapeutic targets to the treatment of psychopathologies. Neuropeptide S (NPS), a 20-aminoacid peptide, is the endogenous ligand of a G-protein coupled receptor (NPSR), which has been reported to evoke hyperlocomotion, awakefull states, besides anxiolysis and memory improvements in rodents. This study aimed to investigate the effects of biperiden (BPR; an amnesic drug), diazepam (DZP; an anxiolytic drug) and NPS at three distinct times: pre-training, post-training, and pre-test, in order to assess anxiety and memory process in the same animal model. The elevated Tmaze (ETM) is an apparatus derived from the elevated plus-maze test, which consists of one enclosed and two open arms. The procedure is based on the avoidance of open spaces learned during training session, in which mice were exposed to the enclosed arm as many times as needed to stay 300 s. In the test session, memory is assessed by re-exposing the mouse to the enclosed arm and the latency to enter an open arm was recorded. When injected pre-training, BPR (1 mg/kg) impaired learning and memory processing; DZP (1 and 2 mg/kg) evoked anxiolysis, but only at the dose of 2 mg/kg impaired memory; and NPS 0.1 nmol induced anxiolysis without affecting memory. Post-training injection of DZP (2 mg/kg) or BPR (1 and 3 mg/kg) did not affect memory consolidation, while the post-trainning administration of NPS 1 nmol, but not 0.1 nmol, improved memory in mice. Indeed, pre-trainning administration of NPS 1 nmol did not prevent memory impairment elicited by BPR (2 mg/kg, injected before training). In the open field test, BPR 1 mg/kg and NPS 1 nmol induced hyperlocomotion in mice. In conclusion, the proposed ETM task is practical for the detection of the anxiolytic and amnesic effects of drugs. The anxiolytic and memory enhancement effects of NPS were detected in the ETM task, and reinforce the role of NPS system as an interesting therapeutic target to the treatment of anxiety disorders

Alterações do ciclo sono-vigília moduladas por Dopamina e suas consequências Mnemônicas

Neuroscience is on a rise of discoveries. Its wide interdisciplinary approach facilitates a more complex understanding of the brain, covering various areas in depth. However, many phenomena that fascinate human kind are far from being fully elucidated, such as the formation of memories and sleep. In this study we investigated the role of the dopaminergic system in the process of memory consolidation and modulation of the phases of sleep-wake cycle. We used two groups of animals: wildtype mice and hiperdopaminergic mice, heterozygous for the gene encoding the dopamine transporter protein. We observed in wild-type mice that the partial blockade of the D2 dopamine receptor by the drug haloperidol caused deficits in memory consolidation for object recognition, as well as a significant reduction in the duration of rapid eye movement sleep (REM). We also found a mnemonic deficit without pharmacological intervention in hiperdopaminergic animals; this deficit was reversed with haloperidol. The results suggest that dopamine plays a key role in memory consolidation for object recognition. The data also support a functional relationship between the dopaminergic system and the modulation of REM sleep

Efeitos do tratamento com lítio na memória aversiva, comportamentos relacionados à ansiedade e depressão e na expressão de BDNF em ratos

Lithium (Li) is the first choice to treat bipolar disorder, a psychiatric illness characterized by mood oscillations between mania and depression. However, studies have demonstrated that this drug might influence mnemonic process due to its neuroprotector, antiapoptotic and neurogenic effects. The use of Li in the treatment of cognitive deficits caused by brain injury or neurodegenerative disorders have been widely studied, and this drug shows to be effective in preventing or even alleviating the memory impairment. The effects of Li on anxiety and depression are controversial and the relationship of the effects of lithium on memory, anxiety and depression remain unknown. In this context, this study aims to: evaluate the effects of acute and chronic administration of lithium carbonate in aversive memory and anxiety, simultaneously, using the plus maze discriminative avoidance task (PMDAT); test the antidepressant effect of the drug through the forced swimming test (FS) and analyze brainderived neurotrophic factor (BDNF) expression in structures related to memory and emotion. To evaluation of the acute effects, male Wistar rats were submitted to i.p. administration of lithium carbonate (50, 100 or 200 mg/kg) one hour before the training session (PMDAT) or lithium carbonate (50 or 100 mg/kg) one hour before the test session (FS). To evaluation of the chronic effects, the doses administered were 50 or 100 mg/kg or vehicle once a day for 21 days before the beginning of behavioral tasks (PMDAT and FS). Afterwards, the animals were euthanized and their brains removed and submitted to immunohistochemistry procedure to quantify BDNF. The animals that received acute treatment with 100 and 200 mg/kg of Li did not discriminated between the enclosed arms (aversive and non-aversive) in the training session of PMDAT, showing that these animal did not learned the task. This lack of discrimination was also observed in the test session, showing that the animals did not recall the aversive task. We also observed an increased exploration of the open arms of these same groups, indicating an anxiolytic effect. The same groups showed a reduction of locomotor activity, however, this effect does not seem to be related with the anxiolytic effect of the drug. Chronic treatment with Li did not promote alterations on learning or memory processes. Nevertheless, we observed a reduction of open arms exploration by animals treated with 50 mg/kg when compared to the other groups, showing an anxiogenic effect caused by this dose. This effect it is not related to locomotor alterations since there were no alterations in these parameters. Both acute and chronic treatment were ineffective in the FS. Chronic treatment with lithium was not able to modify BDNF expression in hippocampus, amygdala and pre-frontal cortex. These results suggest that acute administration of lithium promote impairments on learning in an aversive task, blocking the occurrence of memory consolidation and retrieval. The reduction of anxiety following acute treatment may have prevented the learning of the aversive task, as it has been found that optimum levels of anxiety are necessary for the occurrence of learning with emotional context. With continued, treatment the animals recover the ability to learn and recall the task. Indeed, they do not show differences in relation to control group, and the lack of alterations on BDNF expression corroborates this result. Possibly, the regimen of treatment used was not able to promote cognitive improvement. Li showed acute anxiolytic effect, however chronic administration 4 promoted the opposite effect. More studies are necessary to clarify the potential beneficial effect of Li on aversive memory

Efeitos da privação do sono em tarefas cognitivas

Learning and memory are important mechanism for species, since its allows to recognize conspecifics, routes and food place. Sleep is one of behaviors known by facilitate learning, it is a widespread phenomenon, present in most of vertebrates lives and highly investigated in many aspects. It is known that sleep deprivation modifies physiologic behavioral processes in animals, however, sleep function in organism is still debatable. Hypothesis range from energy conservation to memory consolidation, with different roles in animal’s evolution. The zebrafish (Danio rerio) emerg e in the last years as vertebrate model in genetics and developmental biology and quickly become popular in behavioral studies, as learning and memory. Despite the fact that zebrafish is a diurnal animal and have well characterized sleep behavior, zebrafish fish still has advantages due to its small size and low cost of maintenance, whichestablishes this species as interesting model for research on sleep. In this study we aimed to analyze the effects of partial and total sleep deprivation on learning acquisition, as well the concomitant administration of alcohol and melatonin. For this, the research was divided in three phases, each one with a different kind of conditioning: (1) object Recognition, (2) avoidance conditioning and (3) appetitive conditioning. The results showed the fish partially sleep deprived and totally sleep deprived + et hanol could perform the tasks just like the control group, however, fish totally sleep deprived and totally sleep deprived + melatonin showed impairments in attention and memory during the tests. Our results suggest that only one night of sleep deprivation is enough to harm the zebrafish performance in cognitive tasks. In addition, ethanol exposure on the night previously the test seems to suppress the negative effects of sleep deprivation, while the melatonin treatment seems not to be enough to promote sleep state, at least on the protocol applied here.

Efeitos da privação do sono em tarefas cognitivas

Learning and memory are important mechanism for species, since its allows to recognize conspecifics, routes and food place. Sleep is one of behaviors known by facilitate learning, it is a widespread phenomenon, present in most of vertebrates lives and highly investigated in many aspects. It is known that sleep deprivation modifies physiologic behavioral processes in animals, however, sleep function in organism is still debatable. Hypothesis range from energy conservation to memory consolidation, with different roles in animal’s evolution. The zebrafish (Danio rerio) emerg e in the last years as vertebrate model in genetics and developmental biology and quickly become popular in behavioral studies, as learning and memory. Despite the fact that zebrafish is a diurnal animal and have well characterized sleep behavior, zebrafish fish still has advantages due to its small size and low cost of maintenance, whichestablishes this species as interesting model for research on sleep. In this study we aimed to analyze the effects of partial and total sleep deprivation on learning acquisition, as well the concomitant administration of alcohol and melatonin. For this, the research was divided in three phases, each one with a different kind of conditioning: (1) object Recognition, (2) avoidance conditioning and (3) appetitive conditioning. The results showed the fish partially sleep deprived and totally sleep deprived + et hanol could perform the tasks just like the control group, however, fish totally sleep deprived and totally sleep deprived + melatonin showed impairments in attention and memory during the tests. Our results suggest that only one night of sleep deprivation is enough to harm the zebrafish performance in cognitive tasks. In addition, ethanol exposure on the night previously the test seems to suppress the negative effects of sleep deprivation, while the melatonin treatment seems not to be enough to promote sleep state, at least on the protocol applied here.

Sleep and school education

Sleep has emerged in the past decades as a key process for memory consolidation and restructuring. Given the universality of sleep across cultures, the need to reduce educational inequality, the low implementation cost of a sleep-based pedagogy, and its global scalability, it is surprising that the potential of improved sleep as a means of enhancing school education has remained largely unexploited. Students of various socio-economic status often suffer from sleep deficits. In principle, the optimization of sleep schedules both before and after classes should produce large positive benefits for learning. Here we review the biological and psychological phenomena underlying the cognitive role of sleep, present the few published studies on sleep and learning that have been performed in schools, and discuss potential applications of sleep to the school setting. Translational research on sleep and learning has never seemed more appropriate.

Naps in school can enhance the duration of declarative memories learned by adolescents

Sleep helps the consolidation of declarative memories in the laboratory, but the pro-mnemonic effect of daytime naps in schools is yet to be fully characterized. While a few studies indicate that sleep can indeed benefit school learning, it remains unclear how best to use it. Here we set out to evaluate the influence of daytime naps on the duration of declarative memories learned in school by students of 10–15 years old. A total of 584 students from 6th grade were investigated. Students within a regular classroom were exposed to a 15-min lecture on new declarative contents, absent from the standard curriculum for this age group. The students were then randomly sorted into nap and non-nap groups. Students in the nap group were conducted to a quiet room with mats, received sleep masks and were invited to sleep. At the same time, students in the non-nap group attended regular school classes given by their usual teacher (Experiment I), or English classes given by another experimenter (Experiment II). These 2 versions of the study differed in a number of ways. In Experiment I (n = 371), students were pre-tested on lecture-related contents before the lecture, were invited to nap for up to 2 h, and after 1, 2, or 5 days received surprise tests with similar content but different wording and question order. In Experiment II (n = 213), students were invited to nap for up to 50 min (duration of a regular class); surprise tests were applied immediately after the lecture, and repeated after 5, 30, or 110 days. Experiment I showed a significant ∼10% gain in test scores for both nap and non-nap groups 1 day after learning, in comparison with pre-test scores. This gain was sustained in the nap group after 2 and 5 days, but in the non-nap group it decayed completely after 5 days. In Experiment II, the nap group showed significantly higher scores than the non-nap group at all times tested, thus precluding specific conclusions. The results suggest that sleep can be used to enhance the duration of memory contents learned in school.