Open Science 2.0: Towards a truly collaborative research ecosystem

Conversations about open science have reached the mainstream, yet many open science practices such as data sharing remain uncommon. Our efforts towards openness therefore need to increase in scale and aim for a more ambitious target. We need an ecosystem not only where research outputs are openly shared but also in which transparency permeates the research process from the start and lends itself to more rigorous and collaborative research. To support this vision, this Essay provides an overview of a selection of open science initiatives from the past 2 decades, focusing on methods transparency, scholarly communication, team science, and research culture, and speculates about what the future of open science could look like. It then draws on these examples to provide recommendations for how funders, institutions, journals, regulators, and other stakeholders can create an environment that is ripe for improvement.

Memory destabilization during reconsolidation: a consequence of homeostatic plasticity?

Remembering is not a static process: When retrieved, a memory can be destabilized and become prone to modifications. This phenomenon has been demonstrated in a number of brain regions, but the neuronal mechanisms that rule memory destabilization and its boundary conditions remain elusive. Using two distinct computational models that combine Hebbian plasticity and synaptic downscaling, we show that homeostatic plasticity can function as a destabilization mechanism, accounting for behavioral results of protein synthesis inhibition upon reactivation with different re-exposure times. Furthermore, by performing systematic reviews, we identify a series of overlapping molecular mechanisms between memory destabilization and synaptic downscaling, although direct experimental links between both phenomena remain scarce. In light of these results, we propose a theoretical framework where memory destabilization can emerge as an epiphenomenon of homeostatic adaptations prompted by memory retrieval.

Comparing quality of reporting between preprints and peer-reviewed articles in the biomedical literature

BACKGROUND

Preprint usage is growing rapidly in the life sciences; however, questions remain on the relative quality of preprints when compared to published articles. An objective dimension of quality that is readily measurable is completeness of reporting, as transparency can improve the reader's ability to independently interpret data and reproduce findings.

METHODS

In this observational study, we initially compared independent samples of articles published in bioRxiv and in PubMed-indexed journals in 2016 using a quality of reporting questionnaire. After that, we performed paired comparisons between preprints from bioRxiv to their own peer-reviewed versions in journals.

RESULTS

Peer-reviewed articles had, on average, higher quality of reporting than preprints, although the difference was small, with absolute differences of 5.0% [95% CI 1.4, 8.6] and 4.7% [95% CI 2.4, 7.0] of reported items in the independent samples and paired sample comparison, respectively. There were larger differences favoring peer-reviewed articles in subjective ratings of how clearly titles and abstracts presented the main findings and how easy it was to locate relevant reporting information. Changes in reporting from preprints to peer-reviewed versions did not correlate with the impact factor of the publication venue or with the time lag from bioRxiv to journal publication.

CONCLUSIONS

Our results suggest that, on average, publication in a peer-reviewed journal is associated with improvement in quality of reporting. They also show that quality of reporting in preprints in the life sciences is within a similar range as that of peer-reviewed articles, albeit slightly lower on average, supporting the idea that preprints should be considered valid scientific contributions.

Two years into the Brazilian Reproducibility Initiative: reflections on conducting a large-scale replication of Brazilian biomedical science

Scientists have increasingly recognised that low methodological and analytical rigour combined with publish-or-perish incentives can make the published scientific literature unreliable. As a response to this, large-scale systematic replications of the literature have emerged as a way to assess the problem empirically. The Brazilian Reproducibility Initiative is one such effort, aimed at estimating the reproducibility of Brazilian biomedical research. Its goal is to perform multicentre replications of a quasi-random sample of at least 60 experiments from Brazilian articles published over a 20-year period, using a set of common laboratory methods. In this article, we describe the challenges of managing a multicentre project with collaborating teams across the country, as well as its successes and failures over the first two years. We end with a brief discussion of the Initiative's current status and its possible future contributions after the project is concluded in 2021.

Using collaboration networks to identify authorship dependence in meta-analysis results

Meta-analytic methods are powerful resources to summarize the existing evidence concerning a given research question and are widely used in many academic fields. Meta-analyzes can also be used to study sources of heterogeneity and bias among results, which should be considered to avoid inaccuracies. Many of these sources can be related to study authorship, as both methodological heterogeneity and researcher bias may lead to deviations in results between different research groups. In this work, we describe a method to objectively attribute study authorship within a given meta-analysis to different research groups by using graph cluster analysis of collaboration networks. We then provide empirical examples of how the research group of origin can impact effect size in distinct types of meta-analyzes, demonstrating how non-independence between within-group results can bias effect size estimates if uncorrected. Finally, we show that multilevel random-effects models using research group as a level of analysis can be a simple tool for correcting for authorship dependence in results.

Addressing selective reporting of experiments through predefined exclusion criteria

The pressure for every research article to tell a clear story often leads researchers in the life sciences to exclude experiments that 'did not work' when they write up their results. However, this practice can lead to reporting bias if the decisions about which experiments to exclude are taken after data have been collected and analyzed. Here we discuss how to balance clarity and thoroughness when reporting the results of research, and suggest that predefining the criteria for excluding experiments might help researchers to achieve this balance.

Shifting from fear to safety through deconditioning-update

Aversive memories are at the heart of psychiatric disorders such as phobias and post-traumatic stress disorder (PTSD). Here, we present a new behavioral approach in rats that robustly attenuates aversive memories. This method consists of ‘deconditioning’ animals previously trained to associate a tone with a strong footshock by replacing it with a much weaker one during memory retrieval. Our results indicate that deconditioning-update is more effective than traditional extinction in reducing fear responses; moreover, such effects are long lasting and resistant to renewal and spontaneous recovery. Remarkably, this strategy overcame important boundary conditions for memory updating, such as remote or very strong traumatic memories. The same beneficial effect was found in other types of fear-related memories. Deconditioning was mediated by L-type voltage-gated calcium channels and is consistent with computational accounts of mismatch-induced memory updating. Our results suggest that shifting from fear to safety through deconditioning-update is a promising approach to attenuate traumatic memories.

A Freely Available, Self-Calibrating Software for Automatic Measurement of Freezing Behavior

Freezing behavior is commonly used as a measure of associative fear memory. It can be measured by a trained observer, but this task is time-consuming and subject to variation. Commercially available software packages can also be used to quantify freezing; however, they can be expensive and usually require various parameters to be adjusted by the researcher, leading to additional work and variability in results. With this in mind, we developed Phobos, a freely available, self-calibrating software that measures freezing in a set of videos using a brief manual quantification performed by the user to automatically adjust parameters. To optimize the software, we used four different video sets with different features in order to determine the most relevant parameters, the amount of videos needed for calibration and the minimum criteria to consider it reliable. The results of four different users were compared in order to test intra- and interobserver variability in manual and automated freezing scores. Our results suggest that Phobos can be an inexpensive, simple and reliable tool for measurement of fear-related behavior, with intra- and interuser variability similar to that obtained with manual scoring.

The Brazilian Reproducibility Initiative

Most efforts to estimate the reproducibility of published findings have focused on specific areas of research, even though science is usually assessed and funded on a regional or national basis. Here we describe a project to assess the reproducibility of findings in biomedical science published by researchers based in Brazil. The Brazilian Reproducibility Initiative is a systematic, multicenter effort to repeat between 60 and 100 experiments: the project will focus on a set of common methods, repeating each experiment in three different laboratories from a countrywide network. The results, due in 2021, will allow us to estimate the level of reproducibility of biomedical science in Brazil, and to investigate what aspects of the published literature might help to predict whether a finding is reproducible.

Different temporal windows for CB1 receptor involvement in contextual fear memory destabilisation in the amygdala and hippocampus

Reconsolidation is a process in which re-exposure to a reminder causes a previously acquired memory to undergo a process of destabilisation followed by subsequent restabilisation. Different molecular mechanisms have been postulated for destabilisation in the amygdala and hippocampus, including CB1 receptor activation, protein degradation and AMPA receptor exchange; however, most of the amygdala studies have used pre-reexposure interventions, while those in the hippocampus have usually performed them after reexposure. To test whether the temporal window for destabilisation is similar across both structures, we trained Lister Hooded rats in a contextual fear conditioning task, and 1 day later performed memory reexposure followed by injection of either the NMDA antagonist MK-801 (0.1 mg/kg) or saline in order to block reconsolidation. In parallel, we also performed local injections of either the CB1 antagonist SR141716A or its vehicle in the hippocampus or in the amygdala, either immediately before or immediately after reactivation. Infusion of SR141716A in the hippocampus prevented the reconsolidation-blocking effect of MK-801 when performed after reexposure, but not before it. In the amygdala, meanwhile, pre-reexposure infusions of SR141716A impaired reconsolidation blockade by MK-801, although the time-dependency of this effect was not as clear as in the hippocampus. Our results suggest the temporal windows for CB1-receptor-mediated memory destabilisation during reconsolidation vary between brain structures. Whether this reflects different time windows for engagement of these structures or different roles played by CB1 receptors in destabilisation across structures remains an open question for future studies.

On the transition from reconsolidation to extinction of contextual fear memories

Retrieval of an associative memory can lead to different phenomena. Brief reexposure sessions tend to trigger reconsolidation, whereas more extended ones trigger extinction. In appetitive and fear cued Pavlovian memories, an intermediate "null point" period has been observed where neither process seems to be engaged. Here we investigated whether this phenomenon extends to contextual fear memory. Adult rats were subjected to a contextual fear conditioning paradigm, reexposed to the context 2 d later for 3, 5, 10, 20, or 30 min, with immediate injections of MK-801 or saline following reexposure, and tested on the following day. We observed a significant effect of MK-801 with the 3- and 30-min sessions, impairing reconsolidation and extinction, respectively. However, it did not have significant effects with 5-, 10-, or 20-min sessions, even though freezing decreased from reexposure to test. Further analyses indicated that this is not likely to be due to a variable transition point at the population level. In conclusion, the results show that in contextual fear memories there is a genuine "null point" between the parameters that induce reconsolidation and extinction, as defined by the effects of MK-801, although NMDA receptor-independent decreases in freezing can still occur in these conditions.

Protocol for a Systematic Review of Effect Sizes and Statistical Power in the Rodent Fear Conditioning Literature

The concepts of effect size and statistical power are often disregarded in basic neuroscience, and most articles in the field draw their conclusions solely based on the arbitrary significance thresholds of statistical inference tests. Moreover, studies are often underpowered, making conclusions from significance tests less reliable. With this in mind, we present the protocol of a systematic review to study the distribution of effect sizes and statistical power in the rodent fear conditioning literature, and to analyze how these factors influence the description and publication of results. To do this we will conduct a search in PubMed for "fear conditioning" AND ("mouse" OR "mice" OR "rat" OR "rats") and obtain all articles published online in 2013. Experiments will be included if they: (a) describe the effect(s) of a single intervention on fear conditioning acquisition or consolidation; (b) have a control group to which the experimental group is compared; (c) use freezing as a measure of conditioned fear; and (d) have available data on mean freezing, standard deviation and sample size of each group and on the statistical significance of the comparison. We will use the extracted data to calculate the distribution of effect sizes in these experiments, as well as the distribution of statistical power curves for detecting a range of differences at a threshold of α=0.05. We will assess correlations between these variables and (a) the chances of a result being statistically significant, (b) the way the result is described in the article text, (c) measures to reduce risk of bias in the article and (d) the impact factor of the journal and the number of citations of the article. We will also perform analyses to see whether effect sizes vary systematically across species, gender, conditioning protocols or intervention types.

Dysfunction in the coagulation system and schizophrenia

Although different hypotheses have been formulated to explain schizophrenia pathogenesis, the links between them are weak. The observation that five psychotic patients on chronic warfarin therapy for deep-vein thrombosis showed long-term remission of psychotic symptoms made us suspect that abnormalities in the coagulation pathway, specifically low tissue plasminogen activator (tPA) activity, could be one of the missing links. Our hypothesis is supported by a high prevalence of conditions affecting tPA activity in drug-naive schizophrenia, such as antiphospholipid antibodies, elevated cytokine levels, hyperinsulinemia and hyperhomocysteinemia. We recently screened a group of schizophrenia patients and controls for conditions affecting tPA activity. Free-protein S deficiency was highly prevalent among patients, but not found in controls. Free-protein S and functional protein C are natural anticoagulants that form complexes that inhibit tPA inhibitors. All participants had normal protein C levels, suggesting that protein S could have a role in schizophrenia, independent of protein C. Chronic patients and those studied during acute episodes had between three and six conditions affecting tPA and/or protein S activity, while patients in remission had up to two, which led us to postulate that multiple conditions affecting tPA and/or protein S activity could contribute to the full expression of schizophrenia phenotype. This paper describes the physiological roles of tPA and protein S, reviewing how their activity influences pathogenesis and comorbidity of schizophrenia. Next, it analyzes how activity of tPA and protein S is influenced by biochemical abnormalities found in schizophrenia. Last, it suggests future directions for research, such as studies on animal models and on therapeutic approaches for schizophrenia aiming at increasing tPA and protein S activity.

Multifactoriality in Psychiatric Disorders: A Computational Study of Schizophrenia

The search for biological causes of mental disorders has up to now met with limited success, leading to growing dissatisfaction with diagnostic classifications. However, it is questionable whether most clinical syndromes should be expected to correspond to specific microscale brain alterations, as multiple low-level causes could lead to similar symptoms in different individuals. In order to evaluate the potential multifactoriality of alterations related to psychiatric illness, we performed a parametric exploration of published computational models of schizophrenia. By varying multiple parameters simultaneously, such as receptor conductances, connectivity patterns, and background excitation, we generated 5625 different versions of an attractor-based network model of schizophrenia symptoms. Among networks presenting activity within valid ranges, 154 parameter combinations out of 3002 (5.1%) presented a phenotype reminiscent of schizophrenia symptoms as defined in the original publication. We repeated this analysis in a model of schizophrenia-related deficits in spatial working memory, building 3125 different networks, and found that 41 (4.9%) out of 834 networks with valid activity presented schizophrenia-like alterations. In isolation, none of the parameters in either model showed adequate sensitivity or specificity to identify schizophrenia-like networks. Thus, in computational models of schizophrenia, even simple network phenotypes related to the disorder can be produced by a myriad of causes at the molecular and circuit levels. This suggests that unified explanations for either the full syndrome or its behavioral and network endophenotypes are unlikely to be expected at the genetic and molecular levels.

Calcineurin inhibition blocks within-, but not between-session fear extinction in mice

Memory extinction involves the formation of a new associative memory that inhibits a previously conditioned association. Nonetheless, it could also depend on weakening of the original memory trace if extinction is assumed to have multiple components. The phosphatase calcineurin (CaN) has been described as being involved in extinction but not in the initial consolidation of fear learning. With this in mind, we set to study whether CaN could have different roles in distinct components of extinction. Systemic treatment with the CaN inhibitors cyclosporin A (CsA) or FK-506, as well as i.c.v. administration of CsA, blocked within-session, but not between-session extinction or initial learning of contextual fear conditioning. Similar effects were found in multiple-session extinction of contextual fear conditioning and in auditory fear conditioning, indicating that CaN is involved in different types of short-term extinction. Meanwhile, inhibition of protein synthesis by cycloheximide (CHX) treatment did not affect within-session extinction, but disrupted fear acquisition and slightly impaired between-session extinction. Our results point to a dissociation of within- and between-session extinction of fear conditioning, with the former being more dependent on CaN activity and the latter on protein synthesis. Moreover, the modulation of within-session extinction did not affect between-session extinction, suggesting that these components are at least partially independent.

Memory labilization in reconsolidation and extinction--evidence for a common plasticity system?

Reconsolidation and extinction are two processes occurring upon memory retrieval that have received great attention in memory research over the last decade, partly due to their purported potential in the treatment of anxiety disorders. Due to their opposite behavioral effects, the two phenomena have usually been considered as separate entities, with few attempts to build a unified view of how both could be produced by similar mechanisms. Based on computational modeling, we have previously proposed that reconsolidation and extinction are behavioral outcomes of the same set of plasticity systems, albeit working at different synapses. One of these systems seems to be pharmacologically similar to the one involved in initial memory consolidation, and likely involves traditional Hebbian plasticity, while the second seems to be more involved with the labilization of existing memories and/or synaptic changes. In this article, we review the evidence for the existence of a plasticity system specifically involved in memory labilization, as well as its possible molecular requirements, anatomical substrates, synaptic mechanisms and physiological roles. Based on these data, we propose that the field of memory updating might ultimately benefit from a paradigm shift in which reconsolidation and extinction are viewed not as separate processes but as different instantiations of plasticity systems responsible for reinforcement and labilization of synaptic changes.

A phosphodiesterase 4-controlled switch between memory extinction and strengthening in the hippocampus

Established fear-related memories can undergo phenomena such as extinction or reconsolidation when recalled. Extinction probably involves the creation of a new, competing memory trace that decreases fear expression, whereas reconsolidation can mediate memory maintenance, updating, or strengthening. The factors determining whether retrieval will initiate extinction, reconsolidation, or neither of these two processes include training intensity, duration of the retrieval session, and age of the memory. However, previous studies have not shown that the same behavioral protocol can be used to induce either extinction or reconsolidation and strengthening, depending on the pharmacological intervention used. Here we show that, within an experiment that leads to extinction in control rats, memory can be strengthened if rolipram, a selective inhibitor of phosphodiesterase type 4 (PDE4), is administered into the dorsal hippocampus immediately after retrieval. The memory-enhancing effect of rolipram lasted for at least 1 week, was blocked by the protein synthesis inhibitor anisomycin, and did not occur when drug administration was not paired with retrieval. These findings indicate that the behavioral outcome of memory retrieval can be pharmacologically switched from extinction to strengthening. The cAMP/protein kinase A (PKA) signaling pathway might be a crucial mechanism determining the fate of memories after recall.

TNF-α mediates PKR-dependent memory impairment and brain IRS-1 inhibition induced by Alzheimer's β-amyloid oligomers in mice and monkeys

Alzheimer's disease (AD) and type 2 diabetes appear to share similar pathogenic mechanisms. dsRNA-dependent protein kinase (PKR) underlies peripheral insulin resistance in metabolic disorders. PKR phosphorylates eukaryotic translation initiation factor 2α (eIF2α-P), and AD brains exhibit elevated phospho-PKR and eIF2α-P levels. Whether and how PKR and eIF2α-P participate in defective brain insulin signaling and cognitive impairment in AD are unknown. We report that β-amyloid oligomers, AD-associated toxins, activate PKR in a tumor necrosis factor α (TNF-α)-dependent manner, resulting in eIF2α-P, neuronal insulin receptor substrate (IRS-1) inhibition, synapse loss, and memory impairment. Brain phospho-PKR and eIF2α-P were elevated in AD animal models, including monkeys given intracerebroventricular oligomer infusions. Oligomers failed to trigger eIF2α-P and cognitive impairment in PKR(-/-) and TNFR1(-/-) mice. Bolstering insulin signaling rescued phospho-PKR and eIF2α-P. Results reveal pathogenic mechanisms shared by AD and diabetes and establish that proinflammatory signaling mediates oligomer-induced IRS-1 inhibition and PKR-dependent synapse and memory loss.

Rising publication delays inflate journal impact factors

Journal impact factors have become an important criterion to judge the quality of scientific publications over the years, influencing the evaluation of institutions and individual researchers worldwide. However, they are also subject to a number of criticisms. Here we point out that the calculation of a journal’s impact factor is mainly based on the date of publication of its articles in print form, despite the fact that most journals now make their articles available online before that date. We analyze 61 neuroscience journals and show that delays between online and print publication of articles increased steadily over the last decade. Importantly, such a practice varies widely among journals, as some of them have no delays, while for others this period is longer than a year. Using a modified impact factor based on online rather than print publication dates, we demonstrate that online-to-print delays can artificially raise a journal’s impact factor, and that this inflation is greater for longer publication lags. We also show that correcting the effect of publication delay on impact factors changes journal rankings based on this metric. We thus suggest that indexing of articles in citation databases and calculation of citation metrics should be based on the date of an article’s online appearance, rather than on that of its publication in print.

Transcriptional profiling of striatal neurons in response to single or concurrent activation of dopamine D2, adenosine A(2A) and metabotropic glutamate type 5 receptors: focus on beta-synuclein expression

G protein-coupled receptor oligomerization is a concept which is changing the understanding of classical pharmacology. Both, oligomerization and functional interaction between adenosine A(2A,) dopamine D(2) and metabotropic glutamate type 5 receptors have been demonstrated in the striatum. However, the transcriptional consequences of receptors co-activation are still unexplored. We aim here to determine the changes in gene expression of striatal primary cultured neurons upon isolated or simultaneous receptor activation. Interestingly, we found that 95 genes of the total analyzed (15,866 transcripts and variants) changed their expression in response to simultaneous stimulation of all three receptors. Among these genes, we focused on the β-synuclein (β-Syn) gene (SCNB). Quantitative PCR verified the magnitude and direction of change in expression of SCNB. Since β-Syn belongs to the homologous synuclein family and may be considered a natural regulator of α-synuclein (α-Syn), it has been proposed that β-Syn might act protectively against α-Syn neuropathology.

Effects of low-dose D-serine on recognition and working memory in mice

RATIONALE

D -Serine is an endogenous co-agonist of the N-methyl-D: -aspartate (NMDA) receptor and has been suggested to improve cognitive deficits in schizophrenia.

OBJECTIVES

The present study investigates the effects of treatment with D -serine in mice on tasks that require recognition learning and working memory, two cognitive domains that are impaired in schizophrenia.

METHODS

We studied the effects of various regimens of systemic administration of D -serine (50 mg/kg/day) on BALB/c mice performing object recognition, T-maze alternation, and open-field exploration tasks. For the object recognition task, we also contrasted the effects of D -serine and D -cycloserine and investigated whether D -serine could reverse alterations induced by subchronic injections of the NMDA antagonist MK-801. D -Serine levels after injections were measured by high-performance liquid chromatography.

RESULTS

In the object recognition task, pre-training treatment with D -serine or D -cycloserine significantly enhanced recognition memory 24 h after training. A single administration of D -serine 30 min (but not 6 h) after training produced similar enhancement, suggesting an effect on memory consolidation. Daily treatment with D: -serine enhanced both object recognition and T-maze performance over multiple days and improved short-term memory in MK-801-treated mice. D -Serine treatment did not alter open-field exploration. Behavioral effects were accompanied by increased levels of D -serine in the hippocampus of treated animals.

CONCLUSIONS

Our results show that treatment with D -serine can improve performance in tasks related to recognition learning and working memory, suggesting that this agent can be useful for the treatment of disorders involving declines in these cognitive domains.

A mismatch-based model for memory reconsolidation and extinction in attractor networks

The processes of memory reconsolidation and extinction have received increasing attention in recent experimental research, as their potential clinical applications begin to be uncovered. A number of studies suggest that amnestic drugs injected after reexposure to a learning context can disrupt either of the two processes, depending on the behavioral protocol employed. Hypothesizing that reconsolidation represents updating of a memory trace in the hippocampus, while extinction represents formation of a new trace, we have built a neural network model in which either simple retrieval, reconsolidation or extinction of a stored attractor can occur upon contextual reexposure, depending on the similarity between the representations of the original learning and reexposure sessions. This is achieved by assuming that independent mechanisms mediate Hebbian-like synaptic strengthening and mismatch-driven labilization of synaptic changes, with protein synthesis inhibition preferentially affecting the former. Our framework provides a unified mechanistic explanation for experimental data showing (a) the effect of reexposure duration on the occurrence of reconsolidation or extinction and (b) the requirement of memory updating during reexposure to drive reconsolidation.

Morphological changes in hippocampal astrocytes induced by environmental enrichment in mice

Environmental enrichment is known to induce plastic changes in the brain, including morphological changes in hippocampal neurons, with increases in synaptic and spine densities. In recent years, the evidence for a role of astrocytes in regulating synaptic transmission and plasticity has increased, and it is likely that morphological and functional changes in astrocytes play an important role in brain plasticity. Our study was designed to evaluate changes in astrocytes induced by environmental enrichment in the CA1 region of the hippocampus, focusing on astrocytic density and on morphological changes in astrocytic processes. After 8 weeks of environmental enrichment starting at weaning, male CF-1 mice presented no significant changes in astrocyte number or in the density of glial fibrillary acidic protein (GFAP) immunoreactivity in the stratum radiatum. However, they did present changes in astrocytic morphology in the same region, as expressed by a significant increase in the ramification of astrocytic processes measured by the Sholl concentric circles method, as well as by an increase in the number and length of primary processes extending in a parallel orientation to CA1 nerve fibers. This led astrocytes to acquire a more stellate morphology, a fact which could be related to the increase in hippocampal synaptic density observed in previous studies. These findings corroborate the idea that structural changes in astrocytic networks are an integral part of plasticity processes occurring in the brain.

Targeting the NMDA receptor for fear-related disorders

The gap between basic neuroscience and clinical psychiatry in the treatment of anxiety disorders has been steadily diminishing over recent years. Among the leading advances in this field of translation research is the application of knowledge on the neurobiology of fear memory to the treatment of anxiety disorders in humans. Animal studies have identified N-methyl-D-aspartate (NMDA) receptors as crucial in fear memory acquisition and consolidation, as well as in its extinction and reconsolidation. Based on this, the NMDA receptor partial agonist D-cycloserine, which facilitates fear extinction in rodents, has been shown to increase the effect of exposure therapy in psychiatric patients for conditions such as phobias, social anxiety and obsessive-compulsive disorder. In this article, we review current strategies for targeting the NMDA receptor in the treatment of fear-related disorders, analyzing experimental results, clinical data, and recent patents in the field, while also addressing potential new approaches to explore this field of drug discovery.

A synaptic reinforcement-based model for transient amnesia following disruptions of memory consolidation and reconsolidation

The observation of memory recovery following post-training amnestic interventions has historically caused controversy over the meaning of this finding, leading some authors to question the paradigm of a consolidation period for memories. Similarly, recent demonstrations of transient amnesia caused by interventions following memory reactivation have been used to question the existence of a retrieval-driven reconsolidation process. The present work aims to approach the phenomenon of transient amnesia following disruptions of consolidation and reconsolidation, discussing how memory recovery might be explained within a framework of systems consolidation, persistent synaptic reinforcement, and multiple memory traces. With these concepts in mind, we propose that long-term consolidation processes can underlie recovery from amnesia, demonstrating the feasibility of such a hypothesis in a two-structure computational model of learning in which consolidation is dependent upon synaptic reentry reinforcement. On the basis of this, we suggest that prolonged consolidation can account for experimental findings of transient amnesia, in a way that explains differences between disruptions of consolidation and reconsolidation without the need to dwell into the discussion between storage- and retrieval-based explanations for memory impairment.

Detection of higher-order G protein-coupled receptor oligomers by a combined BRET-BiFC technique

Despite some caveats, G protein-coupled receptor oligomerization is a phenomenon that is becoming largely accepted. Within these oligomers, however, stoichiometry remains to be elucidated. Here, by using bimolecular fluorescence complementation, we visualized adenosine A(2A) receptor homodimers in living cells, showing no apparent difference in the subcellular distribution when compared to the YFP-labelled adenosine A(2A) receptor protomer. Interestingly, the combination of bimolecular fluorescence complementation and bioluminescence resonance energy transfer techniques allowed us to detect the occurrence of adenosine A(2A) receptors oligomers containing more than two protomers. These results provide new insights into the molecular composition of G protein-coupled receptor oligomers.

Duration of environmental enrichment influences the magnitude and persistence of its behavioral effects on mice

A wide range of data in the literature suggests that environmental enrichment has beneficial effects on various cognitive parameters in rodents. However, the magnitude of these effects and their persistence after the cessation of enrichment vary markedly across studies, with the use of different enrichment protocols probably playing a significant role in this variation. Using an open field habituation task as a paradigm, we investigate whether the duration and starting age of environmental enrichment affect the magnitude and persistence of its behavioral effects on male CF-1 albino mice. Our data shows that, at least in our protocol, (a) environmental enrichment, both after weaning and in early adulthood, decreases locomotion in an open field task, probably by increasing habituation; (b) a minimum enrichment period is necessary to induce this behavioral effect; (c) the effect of enrichment can persist at least partially for many months after its cessation; and (d) the degree of this persistence appears to be somewhat greater in animals exposed to longer durations of enrichment.

Temporary inactivation of the dorsal hippocampus induces a transient impairment in retrieval of aversive memory

The reconsolidation hypothesis, which predicts that consolidated memories become labile and sensitive to amnestic agents upon reactivation, has been one of the most debated topics in memory research over recent years. One of the main criticisms to this hypothesis is the fact that some studies have shown the effects of "reconsolidation blockade" to be transient. Here we show that muscimol inactivation of the dorsal hippocampus following memory reactivation produces a reversible impairment of step-down inhibitory avoidance memory in rats. Moreover, we show that the reversal of this effect is dependent on the passage of time, and not on repeated testing. The implications of the findings to the interpretation of the phenomenon of transient retrieval impairment induced by post-reactivation pharmacological interventions on memory systems are discussed.

Behavioral and genoprotective effects of Vaccinium berries intake in mice

Studies have shown that supplementation with berries rich in anthocyanins are effective in reducing oxidative stress associated with aging, and are beneficial in reversing age-related neuronal and behavioral changes. However, there are few reports on other biological activities of these polyphenols, such as genoprotective effects. The present experiments were performed to study the possible effects of 30-day administration of a lyophilized extract of Vaccinium ashei berries on cognitive performance using step-down inhibitory avoidance, open-field habituation and elevated plus-maze tasks, as well as on DNA damage in the hippocampus and cerebral cortex. The present study showed that the extract significantly enhanced long-term memory in the inhibitory avoidance task, induced an increase in the number of crossings during open-field habituation and had an anxiolytic effect in the elevated plus-maze task. Moreover, the extract reduced oxidative DNA damage in brain tissue in vitro. These results suggest that supplementation with V. ashei berries to mice improves performance on memory tasks and has a protective effect on DNA damage, possibly due to the antioxidant activity of polyphenols, including anthocyanins.

A simple webcam-based approach for the measurement of rodent locomotion and other behavioural parameters

We hereby describe a simple and inexpensive approach to evaluate the position and locomotion of rodents in an arena. The system is based on webcam registering of animal behaviour with subsequent analysis on customized software. Based on black/white differentiation, it provides rapid evaluation of animal position over a period of time, and can be used in a myriad of behavioural tasks in which locomotion, velocity or place preference are variables of interest. A brief review of the results obtained so far with this system and a discussion of other possible applications in behavioural neuroscience are also included. Such a system can be easily implemented in most laboratories and can significantly reduce the time and costs involved in behavioural analysis, especially in developing countries.

Isolated central nervous system histoplasmosis in immunocompetent hosts: a series of 11 cases

Histoplasmosis of the central nervous system occurs in a significant percentage of patients with Histoplasma capsulatum infection, but has usually been described in association with immunosuppression and/or disseminated histoplasmosis. We aim to review the clinical and laboratory features of isolated histoplasmosis of the central nervous system in the immunocompetent host by presenting a series of 11 cases with this condition. Most of these patients presented with headache, meningeal irritation signs and mental status changes, comprising a somewhat different picture from that described in immunosuppressed patients. Moreover, almost all patients had signs of ventricular dilatation in neuroimaging studies, and 8 of the 11 patients had a ventriculoperitoneal shunt at the time of diagnosis, suggesting hydrocephalus to be an important feature of this condition and/or the possibility of shunt infection by the fungus. Immunodiffusion analysis of the cerebrospinal fluid appeared to be the most efficient way to reach the diagnosis and should be considered in immunocompetent patients with chronic lymphocytic meningitis, especially in those who have ventricular shunt or live in endemic areas of Histoplasma capsulatum.

Altered behavioural response to acute stress in mice lacking cellular prion protein

Although many studies have investigated the function of cellular prion protein (PrPc), its physiologic role remains elusive. PrPc null mice have been reported to develop normally and to show normal performance in most behavioural tests. In the present study we investigated whether this also holds true after episodes of acute stress. PrPc gene ablated (Prnp0/0) and wild-type mice were subjected to restraint stress, electric foot shock, or swimming and compared with non-stressed animals. Immediately after the stressful situation, the anxiety levels and locomotion of the animals were measured using plus-maze and open-field tests. Among non-stressed animals, there was no significant difference in performance between Prnp0/0 and wild type animals in either test. However, after acute stress provoked by a foot shock or a swimming trial, Prnp0/0 animals showed a significant decrease in anxiety levels when compared with control animals. Moreover, after the swimming test, knockout mice presented decreased locomotion when compared to wild-type mice. Because of this observation, we also assessed both types of mice in a forced swimming test with the objective of better evaluating muscle function and found that Prnp0/0 animals presented reduced forced swimming capacity when compared to controls. As far as we know, this is the first report suggesting that cellular prion protein is involved in modulation of anxiety or muscular activity after acute psychic or physical stress.

Use and misuse of benzodiazepines in Brazil: a review

Benzodiazepines are among the most prescribed and consumed medication groups in the world. Although benzodiazepines are used in the treatment of several psychiatric and non-psychiatric disorders, and are generally safe and well-tolerated, the potential for misuse and abuse is considerable. This makes the study and regulation of benzodiazepine prescription and consumption an item of concern in public health around the world. Most developed countries have consistent data of benzodiazepine sales and consumption; however, data from developing countries is scarce, making health policies on the use of benzodiazepines a much tougher issue in these countries. This article aims to review the epidemiology of benzodiazepine use in Brazil, as well as to analyze how legislation, physician misinformation and economic factors might contribute to making benzodiazepine abuse a problem in the country.

Evoked potentials for the evaluation of latent hepatic encephalopathy in pediatric liver transplant candidates

BACKGROUND

Visual evoked potentials (VEPs) and brain stem auditory evoked potentials (BAEPs) have been proposed as tools in the diagnosis of subclinical hepatic encephalopathy (HE). However, little information exists to determine their usefulness in pediatric patients. This study was undertaken to evaluate both methods in the detection of subclinical HE in pediatric liver transplant candidates.

METHODS

VEPs and BAEPs were recorded in 15 pediatric liver transplant candidates with no clinical signs of HE. The wave latencies found in these examinations were then compared with those in 16 healthy controls of similar age. Laboratory data on liver function and electroencephalographic data from the patients were also recorded to examine their correlation with the evoked potentials results.

RESULTS

No differences were found in the BAEP results between patients and controls. However, in the VEPs, the liver transplant candidates had significantly prolonged N1 (N75) latencies when compared with controls; no significant delay was found in the other waves. In contrast, among the children with liver disease, higher BAEP peak latencies correlated positively with electroencephalographic abnormalities, but this correlation was not observed in VEPs.

CONCLUSIONS

Evoked potentials might be of use in detecting alterations related to HE in children. However, further studies are necessary to determine their sensitivity and specificity in this situation.

Altered ATP hydrolysis induced by pentylenetetrazol kindling in rat brain synaptosomes

The ectonucleotidase pathway is an important metabolic source of extracellular adenosine. Adenosine has potent anticonvulsant effects on various models of epilepsy. One of these models is pentylenetetrazol (PTZ) kindling, in which repeated administration of subconvulsive doses of this drug induces progressive intensification of seizure activity. In this study, we examine the effect of a single convulsive injection (60 mg/kg, i.p.) or 10 successive (35 mg/kg, i.p.) injections of PTZ on synaptosomal ectonucleotidases. Our results have shown that no changes in ectonucleotidase activities were seen at 0, 1, and 24 h or at 5 days after a single convulsive PTZ injection. However, after PTZ-kindling, rats which were more resistant to seizure development presented an increase in ATP hydrolysis in synaptosomes from hippocampus and cerebral cortex (44% and 28%, respectively). These results suggest that changes in nucleotide hydrolysis may represent an important mechanism in the modulation of chronic epileptic activity in this model.

Increased sensitivity to seizures in mice lacking cellular prion protein

PURPOSE

The physiologic role of the cellular prion protein (PrPc) is unknown. Mice devoid of PrPc develop normally and show only minor deficits. However, electrophysiologic and histologic alterations found in these mice suggest a possible role for PrPc in seizure threshold and/or epilepsy.

METHODS

We tested the sensitivity of PrPc knockout mice to seizures induced by single convulsant or repeated subconvulsant (kindling) doses of pentylenetetrazol (PTZ), and to status epilepticus (SE) induced by kainic acid or pilocarpine.

RESULTS

In PTZ kindling, seizure severity progressed faster in the PrPc knockout group, in which 92.8% reached stage 5 or death after 4 days of stimulation, as opposed to 38.4% in wild-type animals. After 10 injections, mortality was 85.7% among knockouts and 15.3% among controls. After a single PTZ injection (60 mg/kg), overall mortality due to seizures was 91% in knockout mice, but only 33% among wild-type animals. Pilocarpine-induced SE (320 mg/kg) caused an 86.7% mortality in knockouts, as opposed to 40% in wild-type animals. Finally, after kainic acid injections (10 mg/kg), 70% of the knockouts developed at least one severe seizure, and 50% showed repetitive seizures, whereas no wild-type animal exhibited observable seizures.

CONCLUSIONS

Animals lacking cellular prion protein expression are more susceptible to seizures induced by various convulsant agents. This is perhaps the most striking alteration yet found in PrPc-null mice, who at first analysis appeared to be completely normal. A possible role for PrPc in chronic and idiopathic (familial), secondary, or cryptogenic epilepsies in humans remains to be investigated.

Dose-dependent impairment of inhibitory avoidance retention in rats by immediate post-training infusion of a mitogen-activated protein kinase kinase inhibitor into cortical structures

Mitogen-activated protein kinase (MAPK) is a serine/threonine protein kinase abundantly expressed in postmitotic neurons of the developed nervous system. MAPK is activated in and required for both the induction of long-term potentiation (LTP) in hippocampal slices and the acquisition of fear conditioning training in rats. The present work was performed in order to test the effect of the specific inhibitor of MAPK kinase (MAPKK), PD 098059, on retention of a step-down inhibitory avoidance (IA). Adult male Wistar rats were bilaterally injected (0.5 microl/side) with PD 098059 (at 0.5, 5, or 50 microM) or vehicle into the entorhinal cortex or into the parietal cortex immediately after IA training using a 0.4 mA footshock. Retention testing was carried out 24 h after training. PD 098059 impaired retention when injected into the entorhinal cortex at the dose of 50 microM, but not at the doses of 5 or 0.5 microM. When infused into the parietal cortex, PD 098059 was amnestic at the doses of 5 and 50 microM. The drug had no effect when infused at the highest dose in either structure 6 h after training. Our results suggest that the MAPKK inhibitor impairs IA retention memory in a dose-dependent manner when injected immediately after training into entorhinal cortex or parietal cortex. The effective dose is variable according to the neocortical structure studied.