Genome-wide association studies (GWASs) are the method most often used by geneticists to interrogate the human genome, and they provide a cost-effective way to identify the genetic variants underpinning complex traits and diseases. Most initial GWASs have focused on genetically homogeneous cohorts from European populations given the limited availability of ethnic minority samples and so as to limit population stratification effects. Transethnic studies have been invaluable in explaining the heritability of common quantitative traits, such as height, and in examining the genetic architecture of complex diseases, such as type 2 diabetes. They provide an opportunity for large-scale signal replication in independent populations and for cross-population meta-analyses to boost statistical power. In addition, transethnic GWASs enable prioritization of candidate genes, fine-mapping of functional variants, and potentially identification of SNPs associated with disease risk in admixed populations, by taking advantage of natural differences in genomic linkage disequilibrium across ethnically diverse populations. Recent efforts to assess the biological function of variants identified by GWAS have highlighted the need for large-scale replication, meta-analyses and fine-mapping across worldwide populations of ethnically diverse genetic ancestries. Here, we review recent advances and new approaches that are important to consider when performing, designing or interpreting transethnic GWASs, and we highlight existing challenges, such as the limited ability to handle heterogeneity in linkage disequilibrium across populations and limitations in dissecting complex architectures, such as those found in recently admixed populations.The online version of this article (doi:10.1186/s13073-014-0091-5) contains supplementary material, which is available to authorized users. Large-scale genome-wide association studies (GWASs) have led to the discovery of thousands of genetic signals across the human genome associated with human diseases and quantitative traits . These fDespite significant advances in high-throughput genotyping platforms, more powerful human genome reference panels and accurate imputation methods, major challenges remain. One is the apparent gap between the estimated disease heritability attributable to genetic factors (based on family and population genetics studies) and the small proportions of the total genetic heritability evident for most traits and common diseases explained through GWASs . This gabona fide disease-causing genetic variants are known to vary between populations and because environmental exposures can also be altered, there has been much interest recently in the design and implementation of transethnic studies.Various approaches have been proposed to test the models put forth by the genetics community to explain the observed missing heritability -6]. Rar. Rar6]. Furthermore, with the sheer numbers of individuals required to detect small to modest effect sizes, the bolstering of all populations available across large disease-analysis consortia is becoming more common, particularly in the study of quantitative traits where common international laboratory standards are used ,13]-[15-[1513]- and and18] aa priori appropriate study populations is difficult. For example, the currently available methods for performing transethnic meta-analysis still face limitations in power and also have limited ability to estimate joint effect sizes in the presence of effect heterogeneity.We conclude by noting the many challenges that remain in using samples from multiple diverse populations. Aside from limitations in sample sizes, with limited availability of genotyping and sequencing data from ethnic minorities, the ability to identify Transethnic studies are increasingly being used to increase study power by increasing the total study sample size. This is in part because there are limited sample sizes available for many diseases and because several consortia across the world have been established in countries whose populations are of diverse ancestries. The largest transethnic studies so far include studies of factors involved in metabolic and cardiovascular diseases, including high-density lipoprotein and low-density lipoprotein (LDL) levels , ischemiAlthough a common goal in each of these large-scale transethnic GWASs is still disease/trait locus discovery, these studies also simultaneously make use of other features of transethnic study designs in four ways. First, they provide an independent replication sample set that can overcome concerns about sub-population or cryptic population stratification effects in single-population GWASs  and thatbona fide associations identified for a disease or trait in one population also affect other populations of different genetic ancestries. In the era of genomic medicine, the identification of such SNPs that can predict disease risk or therapeutic response is helpful in evaluating potential clinical or disease-predictive utility. Moreover, because GWAS association signals represent only a statistical correlation between genetic variations and disease or phenotype status, rather than causation, they are sensitive to sources of confounding and bias. Concerns about false positives are further amplified because of the large number of comparisons, as most standard GWAS platforms capture several hundred thousand to millions of variants and several tens of millions of variants following imputation.One of the most common motivations for pursuing transethnic GWASs is to evaluate whether TCF7L2 variant for type 2 diabetes (T2D) and the variant in the 9p.21 region for coronary artery disease. However, such consistent replications are likely to be the exception rather than the rule, because many disease or trait-associated SNPs reaching genome-wide significance do not directly replicate in studies of populations from a different ancestry. Although the TCF7L2 and 9p.21 variants have moderate disease odds ratios (1.25 to 1.3), they have high minor allele frequencies (MAFs), which significantly aided their detection.Consequently, the initial goals of early transethnic studies had been to replicate the associations identified in one population in a second population with a distinct ancestry. At first these efforts aimed to directly replicate SNP-specific associations , but it soon became apparent that achieving direct replication in an independent cohort posed significant challenges. Some SNPs have been consistently replicated across multiple ancestral populations - for example, the primary Although some initial putative associations are undoubtedly spurious , the lack of direct replication could also be attributable to technical and biological factors, even for a true association ,30]. Fo. Fo30]. PTPN22 in RA and inflammatory bowel disease , IN, INPTPN2diabetes ,40], IL, ILPTPN2n asthma  and TCF72 in T2D ,42]. Th. ThPTPN2A recent large-scale review of published transethnic GWAS results across 28 diseases in European, East Asian and African ancestries  showed tAs power is a function of both the strength of the association (effect size) and the MAF of the associated variant, limitations in transethnic replicability of variants resulting from limited allelic polymorphisms in a replicating population is a notable challenge. This is particularly the case in transethnic replication studies that incorporate resequencing data, which attempt to replicate findings of rare variants associated with disease. Recently, newer methods have been proposed for boosting the power of random effects models to provide multi-variant, gene-based testing that can be implemented in rare-variant transethnic association study designs .a priori a replication population of interest and also help reduce the frequency of performing `replication' studies in populations in which the associated variant is either non-polymorphic or too rare.Finally, despite these successes, new methods that can assess naturally occurring differences in population allele frequencies and LD structure are needed because it remains difficult to know which SNPs are expected or, conversely, not expected to be `replicable' given inherent genomic architectural differences. Such methods could help identify Pnominal <0.05 in a second cohort to be a replication signal, in most cases, when an independent GWAS has been performed it is more statistically rigorous to maintain a genome-wide significance threshold at P <5 × 10-8 in European populations . Th. ThPnomiIn the past few years, many global genomics consortia with enormous patient datasets have been used either in cross-continental mega-analyses directly or, more frequently, in summary statistic meta-analyses to better account for the wide ranges of genotyping platforms, genetic ancestry, environmental exposures, and other sources of sample heterogeneity. Two exemplary consortia that have published extensively using large transethnic cohorts include the T2D consortium and the RA consortium ,47]. Ov. Ov47]. Although the publication of data from these transethnic studies is becoming increasingly frequent, these methods face several challenges, notably the presence of both genotype and phenotype heterogeneity. For example, not all SNPs found in one population are polymorphic in another, some disease-associated SNPs have vastly different MAFs across different populations ,51], an, an51], Existing methods for cross-cohort meta-analysis assume, for the large part, one of two theoretical frameworks: fixed effects (FE) and random effects (RE) -55]. Th. Th55]. Although in the presence of heterogeneity the RE model is more statistically sound, RE methods operate under a fairly conservative assumption that even null associations can have greatly varying effect sizes. Consequently, in these traditional methods, heterogeneity in the effects observed across populations results either in a down-estimate of the effect size because some populations do not show this association (when one obtains a mean estimate of effect), or in an overestimate of the standard errors that reduces the overall confidence of the association signal identified (by adjusting for heterogeneity). These are the main reasons that neither of these approaches are ideal when considering multiple, ethnically diverse cohorts together in a transethnic GWAS. Their advantages and limitations have been addressed thoroughly elsewhere ,57]..57].Two recent approaches, including alternate random effects (RE-HE)  and MANTAlthough the RE-HE method is not specific to transethnic studies, it is clear that implementing this model would be particularly helpful. In contrast, Morris  introducet al. ,,,59]. Fu. Fu59]. et al. , who demAlthough MANTRA and RE-HE methods cannot be truly compared directly because the former uses a Bayesian framework, at the Bayes' factor significance threshold recommended by Morris , MANTRA However, the use of these new approaches is still limited, and most recent studies have applied one or a combination of the traditional FE or RE meta-analysis models -63]. We. We63]. An inherent advantage of transethnic studies is that demonstrating that signals are shared across multiple distant ancestral populations can help guard against false positives identified by GWASs due to population-stratification-related confounding. Although numerous methods have been identified in attempts to overcome such risks, they remain a challenge and concern, which is why independent replication, particularly in a second cohort, is still the gold standard in the GWAS community. Furthermore, because association signals in homogeneous populations are identified across a conserved LD block, it is not clear which SNP is the most strongly associated with a given phenotype, and consequently is most likely the functional or causal variant.Furthermore, in the past few years, the genomics community has shifted its focus from locus discovery to identifying casual or functional variants, in response to heavy criticisms of the limited utility of GWAS results and in an effort to better establish whether there is significant utility of such genetic information. Although most GWAS signals are found in non-coding regions of the genome (either intronic or intergenic regions), it is thought that some common association signals are proxies that `synthetically tag' the rarer causal or functional mutations in LD . Based oAlthough resequencing techniques are becoming widely available and more economically feasible, genotyping is still advantageous in the study of variants with MAFs greater than 1 to 5%.This is particularly true with the now widely available, high-density population-based genome references, such as the 1000 Genomes project and the ongoing UK-10 K and Genome Netherlands projects ,68]. To. To68]. Towards this goal, transethnic GWAS designs use naturally occurring differences in the LD patterns surrounding the locus of interest to help identify the likely causal or functional variants(s). Specifically, it is expected that the causal or functional variation would be associated with disease or trait status even in different populations in which the ancestral or derived haplotype frequencies differ significantly because of population drift or under selective pressures. Consequently, this allows the dissection of the key functional variant from other variants that are tagging signals on the same haplotype, because the non-causal tagging signals will be less likely to be preserved across diverse populations. This is particularly helpful, for instance, in using populations with more diverse haplotypes (such as African populations) to help refine signals from a less diverse group (such as European). Similarly, local ancestry analysis in admixture populations such as Mexican or Native American populations can also be helpful in refining a signal spanning a large LD block (see below).Methods such as MANTRA, as discussed above, have also been effectively implemented in several transethnic fine-mapping studies - for example, across 14 central adiposity loci  and to dOne of the major observations from transethnic studies is the limited direct replicability of signals identified in one population associated with a given phenotype in a second population of differing ancestry. However, as demonstrated elegantly by Wijmenga and colleagues  for fourThus, although genetic studies of a range of phenotypes across different populations have not yielded associated loci common to all or even the majority of investigated ancestry groups, this could be for a variety of reasons independent of whether this is a truly shared risk- or phenotype-associated variant: population-specific variants, differences in allele frequencies, different patterns of LD across respective populations, and/or low statistical power from modest sample sizes, as discussed above.One traditional technique used to identify disease-association or phenotype-associated regions of the genome, which was used and advanced before the advent of high-density genotyping platforms and the GWAS era, was the use of ancestry-informative markers in admixture mapping ,77]. Ad. Ad77]. The theoretical framework for admixture-based genetic mapping analysis is complex and beyond the scope of this review, but it is summarized briefly in Figure et al. ,,,82], bu, bu82], et al. , who proAlternatives to adjusting for ancestry differences by using linear mixed model approaches, which have gained popularity recently, have only been applied so far to closely related populations, not to transethnic GWASs. Consequently, directly merging genotypes from either ancestrally divergent populations or those that have undergone varying degrees of admixture using traditional association testing frameworks  to adjust for population substructure does not sufficiently control for the risk of confounding ,81],,. An inheAdmixture mapping approaches, which uses significantly fewer tests across the genome, have been successfully used to study several traits and phenotypes, including blood pressure phenotypes in African Americans, for which no robust associations had previously been observed using conventional GWAS approaches . AdmixtuAs the cost of genotyping and high-throughput sequencing technologies continues to drop, consortium-driven worldwide GWASs of complex diseases and phenotypes will probably continue to expand to ever larger cohorts, additional phenotypes and wider ethnic groups. In addition, coupled with current deep phenotyping and electronic medical record mining efforts, genomic medicine is entering an exciting era of phenomics and phenome-wide association studies (PheWASs), in which characterization of genetic and environmental effects across all traits and diseases might be within reach. Applying the methods discussed here for transethnic GWASs to PheWASs could be powerful, given the known stratification of related phenotypes and disease risk among ethnic groups.Without a doubt, new findings from transethnic studies will enrich our understanding of several issues. First, the degree to which genetic associations are shared or population-specific in the presence of either shared or disparate genetic architecture; second, how architectural differences in LD patterns might affect the pattern of genetic association; and third, whether ethnically stratified disease prevalence is directly attributable to genetic or gene-environment interactions. New methods, such as MANTRA and RE-HE, as discussed here, offer more robust and better powered approaches to performing transethnic meta-analyses.a priori which loci should have a good chance of being shared versus being population-specific. Nor is it clear which populations (including admixed ancestries) should be investigated to optimize the chance for locus discovery versus fine-mapping.As the number of GWASs using transethnic and admixed populations increases, they present new opportunities for novel study designs using linkage information at either the variant level or the higher gene or pathway levels. However, numerous challenges remain for transethnic studies. Specific association markers typically demonstrate limited replicability in genetically distant cohorts and it is usually not known Wijmenga and colleagues, in their review of existing literature-reported transethnic GWAS replication rates across different study populations , observeet al. [Another relevant question that has not been thoroughly explored is whether specific populations are more amenable or useful in a transethnic or admixture analysis; identifying optimal methods to answer this question in a locus-specific manner will be difficult. Some methods have been proposed: constructing marker panels for admixture studies using an information-theory-based measure, the expected mutual information score ; identifet al.  to consiFinally, work has also been done to examine how information on LD structure differences across ethnically diverse populations, and variant molecular function, can be used in a Bayesian framework to improve the power of association testing . Althoug


Tumor hypoxia is strongly associated with an adverse prognosis in cancer, irrespective of treatment modality. Analysis of this association has revealed that hypoxia signalling pathways mediated by hypoxia inducible factor (HIF) are up-regulated in cancer, not only by micro-environment hypoxia, but also by diverse oncogenic signal pathways. Pan-genomic analysis of the HIF transcriptional cascade has demonstrated the massive extent of its actions on gene expression at multiple levels. Direct HIF targets include not only coding RNAs, but regulatory long non-coding RNAs, micro-RNAs and translational control proteins. Physiological pathways that are targeted by the HIF system are not restricted to those with direct actions in oxygen homeostasis, but include biosynthetic metabolic pathways as well as molecules acting on cell differentiation, proliferation, migration and survival decisions. Interestingly, isoform/isoenzyme specific patterns of metabolic gene expression that are induced by HIF map well onto those defined in rapidly proliferating normoxic tumor cells, which are also directly targeted by oncogenic pathways operating in parallel. The implication of oncogenic switching of these massive ‘hard-wired’ parallel physiological pathways for cancer phenotypes will be discussed.


Ischemic heart disease (IHD) is characterized by an imbalance between oxygen supply and demand, most frequently caused by coronary artery disease (CAD) that reduces myocardial perfusion. In some patients, IHD is ascribed to microvascular dysfunction (MVD): microcirculatory disturbances that reduce myocardial perfusion at the level of myocardial pre-arterioles and arterioles. In a minority of cases, chest pain and reductions in myocardial flow reserve may even occur in patients without any other demonstrable systemic or cardiac disease. In this topical review, we address whether these findings might be caused by impaired myocardial oxygen extraction, caused by capillary flow disturbances further downstream. Myocardial blood flow (MBF) increases approximately linearly with oxygen utilization, but efficient oxygen extraction at high MBF values is known to depend on the parallel reduction of capillary transit time heterogeneity (CTH). Consequently, changes in capillary wall morphology or blood viscosity may impair myocardial oxygen extraction by preventing capillary flow homogenization. Indeed, a recent re-analysis of oxygen transport in tissue shows that elevated CTH can reduce tissue oxygenation by causing a functional shunt of oxygenated blood through the tissue. We review the combined effects of MBF, CTH, and tissue oxygen tension on myocardial oxygen supply. We show that as CTH increases, normal vasodilator responses must be attenuated in order to reduce the degree of functional shunting and improve blood-tissue oxygen concentration gradients to allow sufficient myocardial oxygenation. Theoretically, CTH can reach levels such that increased metabolic demands cannot be met, resulting in tissue hypoxia and angina in the absence of flow-limiting CAD or MVD. We discuss these predictions in the context of MVD, myocardial infarction, and reperfusion injury. Ischemic heart disease (IHD) can be viewed as an imbalance between oxygen supply and demand . The conIn some patients, or in some phases of the disease, MVD appears to be associated with disturbances in myocardial oxygen extraction, rather than reductions in MBF per se. In patients with diabetes and hypertension, chest pain and reductions in CFR can develop prior to the onset of their microvascular complications. Indeed, some MVD patients show no demonstrable systemic or cardiac disease, a disease entity previously referred to as cardiac syndrome X although it is important to recognize that only 40 % of this heterogeneous patient group have signs of MVD . Taken tRose and colleagues first demonstrated that the efficient extraction of diffusible substances in the myocardium at high MBF can be explained by concomitant reductions in capillary transit time heterogeneity (CTH), as derived from indicator dilution studies , 89. Fig1 receptors)  in tissue or in venous blood [15O2 data in isolated hearts, and the predicted myocardial oxygen utilization shown to be in good agreement with direct measurements using Fick’s principle [Oxygen transport models have been used extensively in the attempt to understand the relation between MBF and metabolism, and to derive myocardial oxygen metabolism based on dynamic recordings of [us blood , 65, 115us blood , 92, 107us blood —see Fig.rinciple . With itThe extended flow-diffusion equation models oxygen availability with as few parameters as possible in order to examine how blood flow, CTH and tissue oxygen tension, combined, can support a given metabolic demand, while permitting intuitive visualization of these limitations in three-dimensional plots such as Fig. 15O2 data, Schwanke et al. [max) [max, our model therefore predicts that apparent PS for oxygen in the myocardium (where OEF is remarkably constant) increases linearly with MBF, as Schwanke et al. [The classical flow-diffusion equation , as welle et al.  found the et al. . The extl. [max) . Providee et al.  observedmax, is actively regulated, possibly via pericyte dilation [The CTH phenomenon, and the potential ‘oxygen loss’ due to functional shunting through capillary paths with short transit times, has received much less attention , 89 thandilation , to meetdilation , with hidilation . Similardilation .We hypothesize that the model parameters of the extended flow-diffusion model  hold information about myocardial oxygen availability that cannot be gleaned from MBF measurements alone. The coronary microcirculation can be assessed by a number of techniques, albeit direct observation of capillary flow patterns in the myocardium itself remains challenging , 83. MyoThe presence of age- or risk-factor-related changes in capillary morphology constitutes a key difference between human IHD and the animal models that are typically used in the study of myocardial ischemia and reperfusion injury. Given the putative effects of capillary flow disturbances described here, this difference could affect the extent to which cardioprotective strategies developed in animal models with normal regulation of CTH translate into successful human therapies. We speculate that the use of animal models with capillary changes characteristic of human disease  may provide more realistic models of human disease.This review re-emphasizes the importance of biophysical modeling as a means of understanding the relation between myocardial blood supply and the metabolic needs of the myocardium. Combining such models with cutting-edge imaging techniques, we speculate that studies of the importance of capillary flow distributions in MVD, myocardial ischemia, and reperfusion injury may be within reach in both animal models and humans. Meanwhile, we must develop a thorough understanding of capillary function, including that of the glycocalyx, of endothelial cells, and of the regulation and pharmacological modulation of pericyte tone.


Animals have evolved to survive, and even thrive, in different environments. Genetic adaptations may have indirectly created phenotypes that also resulted in a longer lifespan. One example of this phenomenon is the preternaturally long-lived naked mole-rat. This strictly subterranean rodent tolerates hypoxia, hypercapnia, and soil-based toxins. Naked mole-rats also exhibit pronounced resistance to cancer and an attenuated decline of many physiological characteristics that often decline as mammals age. Elucidating mechanisms that give rise to their unique phenotypes will lead to better understanding of subterranean ecophysiology and biology of aging. Comparative genomics could be a useful tool in this regard. Since the publication of a naked mole-rat genome assembly in 2011, analyses of genomic and transcriptomic data have enabled a clearer understanding of mole-rat evolutionary history and suggested molecular pathways  that may explain the extraordinarily longevity and unique health traits of this species. However, careful scrutiny and re-analysis suggest that some identified features result from incorrect or imprecise annotation and assembly of the naked mole-rat genome: in addition, some of these conclusions  are rejected when the analysis includes additional, more closely related species. We describe how the combination of better study design, improved genomic sequencing techniques, and new bioinformatic and data analytical tools will improve comparative genomics and ultimately bridge the gap between traditional model and nonmodel organisms. E. coli must also be true of elephants” , as well as genetic regulation of the metabolic pathways that inflict age-related damage, is likely to be directly involved in organismal longevity  or ubiquitously shared  across evolutionarily distinct clades Martin . ComparaComparative genomics is a powerful tool that exploits millions of years of evolution to identify the natural mechanisms that may have led not only to prolonged longevity, but also to different phenotypes associated with disparate resistance to cancer and other diseases. These genomic variations, rooted in evolution, are likely to be well conserved and possibly directly pertinent to human health and lifespan. In keeping with the maxim of the Nobel laureate August Krogh, that for every biological question there is an animal model ideally suited to tackle that research focus  can extend lifespan of Caenorhabditis elegans  or a disruption in proteostasis , as they do in the laboratory. Rather, their death in the wild more commonly results directly from stochastic and random events   live underground and are protected from climatic extremes, germs, and predation , (b) can escape hostile habitats , or (c) have effective body armor   include species that are considered truly eusocial  occupy underground niches. Although some of these evolutionarily divergent species lead a solitary existence and others live communally, they share many morphological and physiological traits considered adaptive to life below ground Tables . All molThe naked mole-rat is endemic to the arid and semi-arid regions of north east Africa  of the naked mole-rat genome  effort . Yet, approximately 50 % of the RNAseq reads from the naked mole-rat align to the unannotated parts of its genome . BetterIn summary, technological improvements will provide us with genomic data of far greater resolution than what is available today. Similarly, more carefully controlled comparative studies using state-of-the-art bioinformatics tools will yield high-quality, unambiguous data. As a direct result of these improvements, greater insights into the unique traits of naked mole-rat will become possible, particularly when combined with phenotypic profiling. Improving access to the secrets within the naked mole-rat genome will elucidate the mechanisms naked mole-rats employ to resist the vagaries of aging and prevent age-associated diseases from gaining hold.


Meles meles) naturally infected with bovine tuberculosis (bTB). At the point of infection, infected male and female badgers had equal mortality risk, refuting the hypothesis that acquisition of infection occurs in males with coincidentally high mortality. Males and females exhibited similar levels of heterogeneity in mortality risk, refuting the hypothesis that maleness is only a proxy for disease susceptibility. Instead, sex differences were caused by a more rapid increase in male mortality rates following infection. Males are indeed more susceptible to bTB, probably due to immunological differences between the sexes. We recommend this mortality trajectory approach for the study of infection in animal populations.In animal populations, males are commonly more susceptible to disease-induced mortality than females. However, three competing mechanisms can cause this sex bias: weak males may simultaneously be more prone to exposure to infection and mortality; being ‘male’ may be an imperfect proxy for the underlying driver of disease-induced mortality; or males may experience increased severity of disease-induced effects compared with females. Here, we infer the drivers of sex-specific epidemiology by decomposing fixed mortality rates into mortality trajectories and comparing their parameters. We applied Bayesian survival trajectory analysis to a 22-year longitudinal study of a population of badgers ( Males are usually more likely than females to acquire infection and die from disease once infected . HoweverThe most obvious driver of sex differences in infectious disease-induced mortality is that disease affects males more than it does females due to weaker, or simply different, physiologies . GeneticAlternatively, behavioural and ecological differences between the sexes might indirectly make males simultaneously more likely to acquire infection and die from other causes. In many species, including humans , males aA third potential driver of sex differences is that infection may have disproportionate effects on substandard males that are already in poor body condition, resulting in observable differences in heterogeneity in response to infection between the sexes. In this case, maleness is simply a proxy for susceptibility to disease: the true driver is poor body condition, but more males than females tend to be in this state.Classical statistical approaches to demographic or epidemiological analysis of surveys of wild animal populations tend to estimate fixed mortality parameters for pre-defined classes of population members . Fixed mortality parameters assume that infected individuals experience an exponential decay in the numbers surviving over the infection period, and thus fail to consider infection as a more complex, time-varying process. Fixed mortality parameters also fail to reveal immunological or behavioural causes. In reality, mortality trajectories will be more complicated than the exponential process, and differences in the parameters of mortality curves among classes of individuals can reveal important epidemiological processes. If males are coincidentally more likely to develop disease and die of other causes, we predict elevated male mortality at the point of infection. If males are more susceptible to disease because the male class harbours the greater share of substandard individuals, we predict less heterogeneity in disease-induced mortality among males than among females. Finally, if males are genuinely more susceptible to disease-induced effects, we predict that the rate of increase in mortality, post-infection, will be greater in males than in females.Meles meles) naturally infected with Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB).One reason for the paucity of time-varying mortality trajectories of infected hosts in wild populations is that individuals cannot be monitored continuously from time of infection to death. However, age-specific mortality functions are commonly used in human and wildlife demographic analyses, and a recently developed method can estimate age-specific mortality trajectories while accommodating uncertainty in dates of birth and death . We emplSex differences in epidemiological traits have been observed in bTB-infected badgers, with males suffering increased mortality during early disease stages and faster progression into advanced diseased states , where tper se. We show that bTB infection alters mortality trajectories of badgers. We describe differences in mortality trajectories between uninfected and infected states, and, by focusing attention on variation over time, the role of sex in shaping heterogeneity in disease response. The ability of BaSTA to account for unknown date of infection provides opportunities to explore disease-specific mortality trajectories in this and other wild mammal populations, paving the way for a better understanding of the role of sex in epidemiology.In summary, we have applied a new methodology for analysing longitudinal demographic data, which provides mortality trajectories rather than discrete rates of mortality during different stages of disease progression. We suggest that this methodology can be used to obtain mortality trajectories that depend on infection duration, rather than age 2.(a)M. bovis using an enzyme-linked immunosorbent assay . Blood M. bovis . BadgersM. bovis ,22). SecM. bovis ,24 and cM. bovis . Violati(b)To account for uncertainty in infection date, we fitted BaSTA  to captuBaSTA models ‘birth’ years  and death years as latent variables, drawing inference on age- or time-since-infection-specific mortality despite missing data. For the uninfected badgers analysed, prior information on the year of birth was obtainable when badgers were first caught as cubs or yearlings, therefore under such circumstances birth dates were incorporated, consisting of 1011 known birth dates. With regard to the infected badgers, we cannot be certain when an individual entered a diseased state, therefore no date was included. Dates of death were recorded when badgers were found dead: time of death was known for 214 uninfected badgers and 48 infected badgers.Exponential. The simplest trajectory models consist of a single constant mortality parameter that assumes mortality is independent of the duration of infection, equivalent to the fixed discrete rates we commonly see in wildlife disease analyses.(i) Gompertz. These models consist of two parameters; an initial mortality and an exponential increase in mortality parameter [(ii) arameter .Weibull. This model has two parameters, a shape and a scale [(iii)  a scale ,27. The Logistic. This model has three parameters [(iv) rameters . It is srameters .Four mortality functions, each able to describe different trends in mortality, were compared :(i) ExpTo ensure model convergence, initial trials of four Markov chain Monte Carlo (MCMC) iterated samplings (chains) were run for each model, followed by 100 000 iterations on four chains with a burn-in of 20 000 for each analysis. Convergence was assessed both visually ensuring mixing of the chains and formally within the model calculating the potential scale reduction . When  on (DIC)  was usedon (DIC)  calibraton (DIC) . This al(c)μ) to time since infection (x),b0 represents mortality at the point of infection, b1 describes the rate of mortality increase post-infection and b2 highlights deceleration in mortality rates.b0; Hypothesis 1. If sex differences in mortality are caused by a coincidental predisposition to die and to also become infected, we would expect to find differences in mortality at the point of infection b0; .b0) but sex-related differences in the subsequent rate of increase in mortality post-infection  and the rate of mortality increase (b1). Once infected, the logistic mortality function (equation (2.1)) was most supported, consisting of an additional deceleration parameter , , , ; Logistic priors b0, b1, b2: , , , ).The Gompertz model was most supported for uninfected badgers , consisteter b2; . As the Inferred life expectancies decreased once badgers became infected. Life expectancies were consistently shorter in males than in females. To the nearest month, male average life expectancies were estimated to be 32 months for uninfected badgers and 22 months for infected badgers. Female average life expectancies were found to be 40 months for uninfected badgers and 35 months for infected badgers. When they are uninfected, this equates to males having on average a 20% lower life expectancy compared with females, with the acquisition of infection increasing this difference to 37%.Sex-related differences among uninfected badgers were due to higher initial mortality parameter values in males, suggesting that they are predisposed at birth to have a higher initial mortality than females KLDC: 1; . Their sb2). At the point of infection, there is no identifiable difference in mortality between the sexes, with significant posterior overlap  in the trajectories of uninfected individuals suggests that infection promotes an increase in heterogeneity in mortality among badgers . These results support our hypothesis 2, that differences between male and female infected badgers are due to a substantial difference in the post-infection rate of increase of mortality (b1).Infection alters mortality patterns in badgers, with trajectories of infected animals supported by a logistic framework, consisting of an additional deceleration parameter  explanation for higher rates of increase in mortality risk in male badgers is the possibility that infection itself causes changes in behaviour that increase the likelihood of death. Pathogens can manipulate host behaviour ,45, incrThis confirmation that male badgers suffer elevated rates of increase in disease-induced mortality might help inform management strategies designed to reduce bTB prevalence in the wildlife reservoir, or to reduce rates of transmission between badgers and cattle. However, the dynamics of bTB in wildlife and livestock are sufficiently complex  that manWe uncover the counterintuitive result that males have similar mortality to females upon becoming infected, despite having higher natural mortality. This may be due to earlier onset of infection in males. That is, males have higher probability of infection  and therUnderstanding how the risk of mortality changes as infection progresses provides a key to explaining and predicting the population dynamics of infected hosts, and ultimately informs the development of better intervention strategies for disease control. We demonstrate the utility of a Bayesian modelling framework, developed specifically for age-related survival analysis, but translated here for the analysis of disease-induced mortality trajectories in wildlife populations. Trajectories, as opposed to discrete rates of mortality, can highlight heterogeneity in disease response and stages of maximum vulnerability, and allow comparison of mortality trends between cohorts and classes of infected hosts. Trajectory analysis has revealed key sex-related differences in bTB epidemiology in badgers, and we recommend its application to surveys of disease-induced mortality in other populations and species.


Diabetic kidney disease is the leading cause of end-stage renal disease. Albuminuria is recognized as the most important prognostic factor for chronic kidney disease progression. For this reason, blockade of renin-angiotensin system remains the main recommended strategy, with either angiotensin converting enzyme inhibitors or angiotensin II receptor blockers. However, other antiproteinuric treatments have begun to be studied, such as direct renin inhibitors or aldosterone blockers. Beyond antiproteinuric treatments, other drugs such as pentoxifylline or bardoxolone have yielded conflicting results. Finally, alternative pathogenic pathways are being explored, and emerging therapies including antifibrotic agents, endothelin receptor antagonists, or transcription factors show promising results. The aim of this review is to explain the advances in newer agents to treat diabetic kidney disease, along with the background of the renin-angiotensin system blockade. Diabetes mellitus (DM) and chronic kidney disease (CKD) have become two of the fastest growing pathologies worldwide , 2, whilDespite emerging strategies and constant investigation, no current single treatment has been able to reverse or at least stop DKD progression. At best, some of the measures can partially slow the speed at which renal function is lost.There are several possible reasons for this fact. First, most clinical trials have been addressed to evaluate the effect on albuminuria. Although albuminuria probably remains as the most influencing prognostic factor, up to one-fourth of normoalbuminuric diabetic patients will eventually develop CKD –6. This In this review, we summarize the available evidence regarding classical treatments for diabetic nephropathy, as well as novel agents, paths, and targets under basic and clinical investigation.DKD occurs in approximately 20% of diabetic patients, and it can appear despite a good glycemic control . NeverthGiven the pathogenetic importance of intraglomerular hypertension in the initiation of DKD, earlier guidelines recommended a stricter blood pressure control in diabetic patients . The latOverweight and obesity are frequent comorbidities to diabetes and play an important role in the pathogenesis of CKD . This maDietary advice in DKD patients is a complex issue: it compels carbohydrate consumption regulation, but the frequent concurrence of comorbidities also requires a low-salt diet for hypertension, fat-free for dyslipidemia, and hypocaloric intake for obesity. There is evidence of the benefits of moderate protein restriction up to 0.8 g/kg/day –33, and Cigarette smoking has been linked to the appearance and progression of DKD, probably due to oxidative stress stimulation, and the cessation of this habit has also been associated with slower progression of the nephropathy –36. If nOne of the most important risk factors for kidney disease progression in diabetic patients is the onset and persistence of proteinuria . The useMany clinical trials have been performed in this respect. A different approach that has attracted much attention has aimed to demonstrate the usefulness of combining two or even three of these drugs. The efficacy for lowering proteinuria with the combination of renin-angiotensin-aldosterone system blockers is at least the same as using one of them at maximum dosage. However, published studies have not succeeded in demonstrating these positive outcomes with the same adverse effects . While using ARB or ACEI to lower proteinuria in DKD and in proteinuric CKD is considered mandatory (evidence grade 1A), the lack of positive studies has encouraged a change in current recommendations against the use of dual blockade –43. In sIn a more detailed analysis of these trials , ACEI anThe unsolved issue is probably to find the optimal drug doses. The ROAD study showed that uptitration to the highest tolerated dose can be an interesting strategy to avoid adverse effects while achieving the maximum reduction in proteinuria . In thisThe controversy about an early treatment of nonproteinuric diabetic patients still remains. In the ROADMAP trial, proteinuria had a delayed onset in those patients treated with olmesartan, although at the expense of higher rates of cardiovascular events . This beAnother option that has been proposed is the use of a selective inhibitor of human renin in combination with an ACEI, an ARB, or an aldosterone blocker. Aliskiren is a direct renin inhibitor that has been tested as an antiproteinuric agent in DKD. The AVOID trial generated important evidence about the efficacy of this drug with a nonsignificant rise of adverse effects . However, the security profile of this treatment was questioned after the premature stop of the ALTITUDE trial due to a higher rate of adverse effects in an intermediate analysis , 46. ForThe benefits of the addition of an aldosterone blocker to the standard therapy in DKD have been noted in some clinical trials , 55. BeyRegarding the use of eplerenone, only one clinical trial has assessed the antiproteinuric value of this aldosterone blocker . EpsteinIn spite of these good results, and given that these trials were only performed in early CKD stages, we must still be cautious until larger studies with long-term follow-up are published. Potential adverse events must still be closely monitored, especially hypotension, hyperkalemia, and renal failure .Blocking renin-angiotensin system is not always enough to avoid proteinuria, so other approaches have been proposed. The formerly unexplored fields of inflammation and oxidative stress now become more important as targets for new treatments. Unfortunately, most of the studies performed yield incomplete conclusions or results that have not been confirmed in other studies .Bardoxolone methyl is an antioxidant agent that activates Keap1-Nfr2 [nuclear 1 factor (erythroid-derived 2)-related factor 2] pathway and regulates inflammation in the kidney. However, the inhibition of this pathway focusing on slowing CKD progression in diabetic animals has produced controversial conclusions , 62. Nrf2) that were randomized to placebo or various doses of bardoxolone for 52 weeks [In humans, two relevant clinical trials have been published with bardoxolone methyl in DKD. The BEAM trial included 227 CKD patients  on the control of proteinuria in CKD concludes that these drugs provide a significant reduction in proteinuria in addition to rennin-angiotensin system blockade. However, except the VITAL trial, the rest of the included studies were small in sample size, and the underlying conditions differed between them (like the etiology of the proteinuric state) .Both insulin resistance and diabetes are linked to inflammation. This fact has generated a growing interest in anti-inflammatory therapies to slow diabetes and DKD progression . Indeed,α) that has demonstrated an antiproteinuric effect in DKD [Pentoxifylline is a methylxanthine derivative and a nonspecific phosphodiesterase inhibitor of tumor necrosis factor  after the first year of treatment and maintained a statistically significant difference with placebo after 24 months . Our groSome studies have tried to show beneficial effects of other drugs such as statins, aspirin, or rapamycin –80. ThesAn increasing knowledge of pathogenic mechanisms in DKD beyond proteinuria has enhanced studies of new molecules that could interfere in CKD progression . bosentan, molecules with higher selectivity on ETA over ETB like sitaxsentan and avosentan also showed these adverse events, which led to early termination of several trials [ atrasentan on renal endpoints in type-2 diabetic patients [Endothelins are small vasoactive peptides that influence hypertension and CKD through various mechanisms, including endothelial dysfunction, vasoconstriction, cell damage, and albuminuria , 82. Thel trials –85. Currpatients , but it  taurine, luteolin, D-saccharic 1,4-lactone, silybin, or hemin) have proved to diminish kidney damage in animal models by normalizing superoxide dismutase, inducing hemoxygenase, or inhibiting NADPH oxidase [ N-Acetylcysteine, which has been tested in many clinical trials for the prevention of contrast-induced nephropathy with controversial results [ Probucol is another antioxidant drug that has shown nephroprotective capacity besides its hypolipidemic use [Oxidative stress is part of the hyperglycemic-generated renal dysfunction. Several vitamin analogs and other molecules that inhibit redox reactions  system has also been related to kidney damage . Baricit for DKD . D3-RA showed beneficial effects on albuminuria and glomerulosclerosis [ sarpogrelate, which is more known for its antiplatelet action, has also demonstrated renal anti-inflammatory and antiproteinuric effects [ ACTH has also shown efficacy in reducing proteinuria in DKD [Transcription processes can also be indirectly regulated through neurohormonal paths. The most studied pathway in this area is vitamin D receptor activation, but other ways are under evaluation. On the one hand, dopamine has been involved in blood flow regulation and hyperfiltration in earlier diabetic kidney disease. Experimental antagonism of D3 receptor withclerosis , but res effects , 123 anda in DKD . apelin [ activated protein C [Finally, reinforcement of endogenous mechanisms that are inherently protective against hyperglycemia-derived kidney damage has also been tried. For example, exogenous administration of the adipocytokine apelin , 126 or rotein C  has renorotein C , 129.α inhibition with infliximab or etanercept has been shown to decrease albuminuria and slow CKD progression in animal models, but further investigation in humans is required [More downstream regulation of inflammatory and fibrosis cascades is also being explored. Treatments that inhibit cell adhesion and accumulation and cytokine production appear promising. In fact, TNF-required –132.β) blockade has been achieved through pirfenidone, currently approved for lung and liver fibrosis. Pilot studies showed a renal benefit but were halted due to adverse effects [ Tranilast, currently approved for allergic states and keloids, showed a reduction in albuminuria in a small pilot study with diabetic patients [β monoclonal antibodies, such as fresolimumab, in various proteinuric nephropathies [β blockers have been tested in animal models but have not yet arrived to human subjects [Transforming growth factor beta  has also been implied in the process of renal fibrosis in DKD.n in DKD  but has  CCX 140-B, TLK-19705, RS102895, PF-04634817, or BMS-813160) have shown positive experimental results and some of them are being evaluated in clinical trials [Reduction of chemokine production is also a potential treatment target in DKD. Several antagonists of the receptors CCR2 and CCR2/5 of the MCP-1 pathway , mainly involved in extracellular matrix regulation . Moleculduration , 148. SoFinally, one of the newest therapeutic approaches is based on developing molecules that target microRNA (miRNA) pathways . These s pimagedine or pyridoxamine, showed beneficial effects on animal models [Hyperglycemia-derived advanced glycation end-products (AGE) are known to have a pathogenic effect through the activation of their receptor (RAGE), causing protein dysfunction and altered collagen turnover activating metalloproteinases , 153. Inl models  but negal models –158. AST-120, also called kremezin, a spherical carbon preparation [ Ai Xi Te and Niaoduqing granted a possible benefit in slowing the speed of renal loss, but without clear evidence [Several oral adsorbents for uremic toxins have been tested, based on the hypothesis that reducing intestinal absorption of some of these toxins would diminish systemic inflammation and immune system activation. The most studied compound has beenparation . Initialparation , 161, buparation . A recenevidence .Finally, other approaches are still in earlier stages of investigation. These include infusion of endovenous mesenchymal precursor cells or modulation of immune response through regulatory T cells or autophagy –166. palosuran, a urotensin-II receptor antagonist [ sulodexide, a glycosaminoglycan with anti-inflammatory properties in animal models [Many other attempts have revealed unsuccessful, despite arriving to phase II or III, clinical trials. This has been the case oftagonist , or sulol models –170.


Attention deficit hyperactivity disorder (ADHD) is characterized by severe and age-inappropriate levels of hyperactivity, impulsivity and inattention. ADHD is a heterogeneous disorder, and the majority of patients show comorbid or associated problems from other psychiatric disorders. Also, ADHD is associated with cognitive and motivational problems as well as resting-state abnormalities, associated with impaired brain activity in distinct neuronal networks. This needs to be considered in a multimodal treatment, of which neurofeedback (NF) may be a promising component. During NF, specific brain activity is fed-back using visual or auditory signals, allowing the participants to gain control over these otherwise unaware neuronal processes. NF may be used to directly improve underlying neuronal deficits, and/or to establish more general self-regulatory skills that may be used to compensate behavioral difficulties. The current manuscript describes pathophysiological characteristics of ADHD, heterogeneity of ADHD subtypes and gender differences, as well as frequently associated behavioral problems such as oppositional defiant/conduct or tic disorder. It is discussed how NF may be helpful as a treatment approach within these contexts. Difficulties with Inattention or Hyperactivity and Impulsivity as the core symptoms of Attention deficit Hyperactivity disorder (ADHD) are a frequent psychosocial burden. With an early onset during childhood, ADHD is often persisting throughout life. It is a heterogeneous disorder, and a challenge to treat. In light of this heterogeneity, the most promising treatment approach should be multimodal in nature  and to decrease theta (4–8 Hz) activity, or to train slow cortical potentials (SCP) in order to modulate cortical excitability); and successful trials are positively reinforced.Neurofeedback (NF) as a non-pharmacological intervention for ADHD utilizes cognitive-behavioral therapeutic elements to gain access on and practice brain activity  may improve performance and may ameliorate neuropsychological deficits found in ADHD, but direct effects on ADHD symptoms may be limited  usually shows a fronto-central negativity peaking around 200–400 ms after onset of the stimulus which is larger for the Nogo than for the Go condition, particularly when the Nogo condition is rare. The same effect can be observed when the target is primed with either congruent or incongruent distractors. The so called N2 and the N2-enhancement were originally attributed to (response) inhibition Kok, , but recWhile several studies using Continous Performance Tests (CPT) or Go-Nogo-tasks in children did not find conflict-specific differences in N2 between ADHD and controls  and error processing (error negativity) may operate with theta (or maybe even lower delta) frequency  NF of brain activity in the bilateral prefrontal cortex (implicated in executive functions and response inhibition) showed effectiveness in behavioral symptom ratings and executive functions, but may require fewer sessions than EEG or EMG NF  evoke a centrally negative SCP that terminates with the presentation of the next stimulus , frontal cortex, thalamus and midbrain dopaminergic nuclei  revealed coherent activity fluctuations with low frequency  in ADHD should be equal to the prevalence in the total population—in fact it is at least 20-times higher, and the reasons for this are still under debate. Research indicates that some comorbidities may in fact be a separate clinical entity , whilst others may in many ways an addition of difficulties present in either disorder . In any case, heterogeneity in ADHD may further complicate treatment.The Diagnostic and Statistical Manual distinguishes Hyperactive/Impulsive (ADHD-H) and Inattention (ADHD-I) symptom clusters in the diagnosis of ADHD APA, , but it However, on the neuropsychological level children with ADHD-I show similar performance problems as ADHD-C in a wide range of demands . In a large multicenter randomized controlled trial of a combination of theta-beta/SCP NF training for children with ADHD, we found comparable effects for symptoms of inattention as well as hyperactivity/impulsivity  axis and expressed in the release of cortisol, which was moderately inverse associated with aggressive symptoms  resulting from dysfunctions in the paralimbic system including orbito-frontal and superior-temporal areas and the ACC as well as the limbic system , whilst problems with “cool” attentional orienting and response preparation may be less severe than expected from an additive model of impairments found in both pure ADHD and ODD/CD.There is evidence that children with comorbid ADHD + ODD/CD may show particularly problems with self-regulation, whilst cognitive deficits may be less severe than expected from typical findings from ADHD and ODD/CD, suggesting that NF interventions may use these cognitive resources and may dwell on the enhancement or compensation of diminished self-regulation skills accordingly. Since ADHD may precede ODD/CD in child development, early interventions may be particularly promising. Moreover, combined NF SCP and theta/beta training yielded, besides particular reductions of teacher and parent-rated ADHD symptoms, also effects on parent-rated oppositional behavior and conduct problems when compared to a standardized computer attention training  are characterized by involuntary, sudden, short, repetitive and non-rhythmic fragments of usual movements and/or vocal expressions. Tics are ranging from mild  to severe  intensity and simple  to complex  extent that do not fulfil any subjective purpose Leckman, . TD are Tics do often occur in bouts and are particularly present during stress or in positive or negative emotional situations. Particularly patients older than 10 years may realize sensory-motor phenomena  before and/or after tic, and are often able to suppress their tics for a limited period of time  additive in ADHD and TD (Roessner et al., TD is probably associated with disturbances in cortico-striato-thalamo-cortical neuronal networks which may be partly compensated by increased prefrontal activity instrumental in tic suppression (Leckman et al., A recent imaging study in adults generally replicated an earlier study of Bohlhalter by further elucidating the progression of brain activity in the cortico-striato-thalamo-cortical circuit preceding a tic and additionally suggesting the role of DMN activity in tic generation (Bohlhalter et al., Moreover, studies on excitability of the motor system using transcranial magnetic stimulation indicated reduced motor inhibition in individuals with TD (Ziemann et al., Studies on higher order cognitive functions in TD suggest that patients may not show general impairments, but may at most be affected as a consequence of their tics or potential compensatory mechanisms; studies addressing the co-existence of TD + ADHD often found deficits explained by ADHD following an additive model (Schuerholz et al., Functional imaging studies particularly in adults with TD yielded mixed results, and the interpretation of functional data in TD may be complicated by the interplay of both activity reflecting pathophysiological mechanisms and potential compensatory activity required during tic control (Gerard and Peterson, In sum, ADHD + TD is probably not a separate clinical entity as it is the case for ADHD + ODD/CD. Individuals with ADHD + TD may share difficulties associated with both disorders often following an additive model, which may however be a special challenge to treat. SCP-NF may be used to ameliorate diminished slow-wave activity during preparation, which may be a common psychopathological impairment in both ADHD and Tic disorders. Typical interventions used in the treatment of TD that rely on intact cognitive control mechanisms or executive functions such as habit reversal may be less effective when ADHD is associated.Nevertheless, NF may be a promising component of a multi-modal therapy, as it combines training of potentially problematic brain activity with direct feedback and reward.In previous intervention studies, Theta-SMR-protocols have been applied in Tic-/Tourette disorder, from a traditionally point of view aiming at inhibiting over-activity in senso-motor cortical regions Tansey, . There iADHD as a neurodevelopmental disorder is associated with pathophysiological problems during cognitive demands, reward processing and during rest. It is further complicated by a number of heterogeneities regarding clinical characteristics, sex differences, and frequent comorbid disorders. The current manuscript introduced associated pathophysiological characteristics and discussed their potential relevance for NF intervention in ADHD.It is argued that cognitive deficits during preparation for an upcoming event and response inhibition problems associated with deficient activity in the prefrontal cortex and in the ACC, as well as impaired resting-state brain activity may be ameliorated by respective NF trainings. Tomographic NF interventions using high density EEG recordings, fMRI or NIRS targeting specific brain areas may allow more direct training of brain activity impaired in ADHD. Motivational problems during reward processing may rather be compensated by the acquisition of self-regulation skills.NF interventions may be used for hyperactive/impulsive and inattentive subtypes, and may not require sex-specific adaptations. It may in general be useful for children with comorbid ADHD and conduct disorders characterized in many ways by sub-additive cognitive deficits of both pure disorders but pronounced self-regulation deficits, as well as for ADHD and associated Tic disorder characterized largely by additive impairments.Taken together, NF intervention in ADHD may be applied in order to ameliorate specific deficits, and/or to acquire self-regulation skills to use them for the compensation of difficulties in other domains.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Rapid muscle fatigue during functional electrical stimulation (FES)-evoked muscle contractions in individuals with spinal cord injury (SCI) is a significant limitation to attaining health benefits of FES-exercise. Delaying the onset of muscle fatigue is often cited as an important goal linked to FES clinical efficacy. Although the basic concept of fatigue-resistance has a long history, recent advances in biomedical engineering, physiotherapy and clinical exercise science have achieved improved clinical benefits, especially for reducing muscle fatigue during FES-exercise. This review evaluated the methodological quality of strategies underlying muscle fatigue-resistance that have been used to optimize FES therapeutic approaches. The review also sought to synthesize the effectiveness of these strategies for persons with SCI in order to establish their functional impacts and clinical relevance.Published scientific literature pertaining to the reduction of FES-induced muscle fatigue was identified through searches of the following databases: Science Direct, Medline, IEEE Xplore, SpringerLink, PubMed and Nature, from the earliest returned record until June 2015. Titles and abstracts were screened to obtain 35 studies that met the inclusion criteria for this systematic review.Following the evaluation of methodological quality (mean (SD), 50 (6) %) of the reviewed studies using the Downs and Black scale, the largest treatment effects reported to reduce muscle fatigue mainly investigated isometric contractions of limited functional and clinical relevance (n = 28). Some investigations (n = 13) lacked randomisation, while others were characterised by small sample sizes with low statistical power. Nevertheless, the clinical significance of emerging trends to improve fatigue-resistance during FES included (i) optimizing electrode positioning, (ii) fine-tuning of stimulation patterns and other FES parameters, (iii) adjustments to the mode and frequency of exercise training, and (iv) biofeedback-assisted FES-exercise to promote selective recruitment of fatigue-resistant motor units.Although the need for further in-depth clinical trials  was clearly warranted to establish external validity of outcomes, current evidence was sufficient to support the validity of certain techniques for rapid fatigue-reduction in order to promote FES therapy as an integral part of SCI rehabilitation. It is anticipated that this information will be valuable to clinicians and other allied health professionals administering FES as a treatment option in rehabilitation and aid the development of effective rehabilitation interventions. As a-2)) , due to -2)) . Current-2)) , 7. Cons-2)) .Neuromuscular electrical stimulation (NMES) applied over the human neuromusculature produces muscle contractions by depolarizing motor axons beneath the stimulating electrodes . The genThe low ‘take-up’ of FES interventions within conventional clinical practice, should not be assumed to indicate any lack of medical benefits, since scientific understanding of electrical stimulus-induced fatigue in the clinical population is still rudimentary , 20. Prei.e., AB and persons with SCI), only the manipulation of neuromuscular stimulus parameters was considered to improve FES contractions [i.e., multi current pathway FES). Although the authors’ paradigm produced more forceful muscle contractions, the rapid-fatigue cycle did not show any significant improvements compared with traditional FES strategies. Clearly, in the clinical environment, more widely accepted and ‘FES-efficient’ strategies need to be devised, and a comprehensive insight into an effective management of rapid muscle fatigue is needed.The current review sought to synthesize knowledge about effectiveness of fatigue-reduction strategies for persons with SCI in order to establish their functional impact and clinical relevance. Earlier, there have been some historical reviews on the implications and management of muscle fatigue in clinical populations, such as Binder-Macleod and Snyder-Mackler  and Maffractions . Subsequractions , 27. Recractions  suggesteInitially, 1933 articles within the electronic databases of Science Direct, Medline, IEEE Xplore, SpringerLink, PubMed, and Nature, and 2 additional articles identified through other sources (online request) were obtained from the earliest returned record until June 2015. The relevant search terms included ‘spinal cord injury’, ‘paralysis’, ‘paraplegia’, ‘tetraplegia’ with ‘muscle fatigue’, ‘reduction’, ‘delay’, ‘functional electrical stimulation’, ‘electrical stimulation’, therapy’, ‘contractions’, ‘walking’, ‘standing’ and ‘cycling’. The synonyms for the terms  were also included on the list of search terms. Further, we conducted a free search in Google Scholar using the reference listed in the primary citations in order to accommodate a wider context. Electrode databases were searched online through the University of Malaya, Malaysia library. However, the literature search was restricted to the English language only.i.e., assessed the ability of muscle to sustain a significant longer duration of repeated contractions following the administration of a specific strategy; (iii) at least one outcome quantified the improvement/or otherwise of resistance of rapid muscle fatigue in terms of endurance, force output (or its derivatives), number of contractions and contractile speed; (iv) study outcomes were measured based on a well-defined muscle fatigue reducing strategy. Studies with unclear protocol or data presentation were excluded. Four major categories of strategies were clearly evident i.e. optimization of electrode positioning, fine-tuning of stimulation patterns and other FES parameters, adjustments to the mode and frequency of exercise training, and biofeedback-assisted FES-exercise.The eligibility criteria were set to accommodate the focus of the review which sought to evaluate the methodological quality as well as synthesize the effectiveness of muscle fatigue-reduction strategies during FES exercise for functional and therapeutic benefits in persons with SCI. The titles and abstracts of all identified studies were screened to determine eligibility. In the event that the title or abstract did not provide adequate information, such article was retrieved for full review. In a second round of filtering, the full text of all potentially relevant studies were reviewed against the following inclusion criteria by two reviewers (MOI and NAH): (i) the study participants were humans with SCI; (ii) the study objective involved the delayed onset of muscle fatigue In order to reduce the risk of bias, two reviewers (MOI and NAH) were independently involved in extraction of data for all outcomes derived from the four identified fatigue resistance strategies. Other reviewers (AKA and NH) verified the validity of the data before a final compilation, while two others (NH and GMD) checked the technical soundness, clarity and the flow of the study. Information on participants’ physical characteristics, study objectives, methodologies, interventions, outcomes/results and limitations, and future research suggestions were retained.i.e., 17, 22 and 27) were considered inapplicable to the objective of the current review and, therefore, not graded. Thereafter, we noted significant variations between the levels of spinal lesion of the participants. In general, subjects with complete and incomplete lesions, as well as those with acute and chronic injuries were grouped together. A meta-analysis could not be conducted due to significant variations in the methods used to evaluate the outcomes, subject heterogeneity and diverse experimental methodologies. The maximum score on the D&B scale was normalised to 100% as some criteria were relevant to some studies and irrelevant to others.The quality of the studies was measured using the Downs and Black (D&B) Scale  relevanti.e., isometric versus non-isometric- isotonic/isokinetic). The characteristics of the included studies are presented in Tables At the outset, 1935 citations were generated and 1900 failed to fit the inclusion criteria. Thirty-five studies met the inclusion criteria and were critically analysed for this review . Out of i.e. meeting up to an average of 50% of the criteria  and randomisation of study participants to the intervention groups (criterion 23). However, all studies specified the eligibility criteria, and measured key outcomes in up to 100% of the initial participants except Godfrey et al., 2002 [The quality of the included studies was moderate l., 2002  and Scotl., 2002  which deOut of the 35 included studies, thirty-one were peer-reviewed journal articles, three were case studies or pilot investigations, and one conference paper. There were no RCTs in the scope of interest, and most studies lack control conditions. Subject heterogeneity and diverse methodology partially limited a quantitative or meta-analytical comparison between studies, and amongst strategies. Most of the studies were published from 2005 to 2014 highlighting an increased interest recently in this field.i.e., pulse width, frequency, amplitude) [Functional electrical stimulation to evoke muscle contractions is typically effected through the modification of key stimulus parameters (plitude) , the effN-let pulse trains  showed a significantly longer torque time integral (TTi) when compared to the traditional single-pulsed stimulation. This stimulation pattern enabled the optimization of force production per stimulation pulse. However, the small sample size of this study and a marked between-subject variability led to the heterogeneity of responses amongst individuals. Two studies, one by Griffin et al., [i.e., from a constant frequency trains  to a double frequency train  separated by longer intervals were used)) demonstrated improvements in fatigue resistance [Karu and colleagues , origina et al.,  with mat et al.,  with widsistance , whereassistance . In addiIn contrast, Thomas et al.,  evaluatei.e., muscle force and work output) following FES cycling [During repetitive electrical stimulation, progressive increases of stimulation frequency and intensity (PIFI) has been shown to generate extended contractions . Kebaets cycling , isometrA case study by Graupe and co-workers , demonstIn contrast, Graham et al.,  and Thrai.e., those that were near to each other). This limitation may be responsible for the lack of popularity of this strategy.A study by Godfrey and colleagues,  advocateA study by Decker and colleagues  investigApart from a preliminary study by Graupe and colleagues  which rei.e., final torque normalized to maximum torque), fatigue time  [i.e., over the entire trial). The administration of the optimal parameters of stimulation appears to be essential for the sustenance of FES-induced functional activity. In summary, the potential for minimizing rapid muscle fatigue during FES-evoked functional activities through the modulation of neuromuscular stimulus parameters is quite evident, and this remains an important research domain for optimization of FES therapy [Based on the available evidence, the effectiveness of modification of stimulation pattern to prevent rapid muscle fatigue is typically assessed through comparison of the fatigue index (by 3 dB) , and tor therapy , 43.Five studies investigated the importance of electrode position to reduce the fatigue characteristics of FES-induced muscle contractions in SCI population . PopovicIn general, the proper placement of stimulation electrodes over motor points of the target muscle is necessary for optimal muscle fibre recruitment. Additionally, the use of multi-electrode cathode has been recommended over a single cathode electrode. Clear understanding of the anatomical landmarks where sufficient motor units maybe recruited has been identified as an important precursor for selective recruitment of fatigue-resistant motor units. Thus, the application of multi-electrode stimulation arrays has not only been applied to selectively recruit the motor unit for efficient motor control, but has equally been validated to be more effective to offset rapid muscle fatigue.i.e., repetitive high-frequency stimulation (HFS) and more continuous low-frequency stimulation (LFS)) on the strength, contractile properties, and fatigability of paralyzed quadriceps muscle. Authors showed that fatigue resistance increased significantly (P<0.05) from 2 weeks of LFS training (by 43%) but not (P>0.05) with HFS training even after 12 weeks of training.While some previous studies have sought to improve fatigue-resistance via technical or technological approaches to neuromuscular stimulation, such as modulating neuromuscular pulse trains or deploying multi-electrode arrays, less research has addressed whether better fatigue-resistance might be achieved by improved muscle training paradigms for patients. Rehabilitation of persons with SCI involves continuous training and exercise in order to achieve the desired outcomes via task specific training . Ten stuButler et al.,  evaluateOwing to the difficulty of translating the neurological changes into functional outcomes, rehabilitation intervention in persons with SCI has been focused extensively on functional training. Improved adaptable response and fatigue resistance ability of paralyzed muscles to functional training have been demonstrated in FES induced cycling. Gerrits et al.,  evaluateTwo independent studies , 60 repoIn the interim, FES exercise therapy in persons with SCI is of considerable clinical value, especially as it increases contraction time and fatigue resistance due to the high percentage of fatigue-resistance fibres associated with the loading effect following exercise . FES exei.e., through feedback controller to regulate muscle torque) significantly enhanced the generated gastrocnemius and soleus muscles’ mean and peak torques even when the pattern of stimulation was randomised [The effectiveness of recent application of biopotential-controlled FES exercise in reducing rapid fatigue during FES training was assessed by two studies , 61. Shindomised . SimilarThis systematic review has established that previous studies demonstrated only partial success for ameliorating rapid muscle fatigue during FES muscle contractions in persons with SCI. Muscle force and its derivatives were identified as the key indices of fatigue. The available evidence revealed a number of important strategies often cited to delay the onset of muscle fatigue including the optimization of electrode positioning, modification of patterns of stimulation and its parameters, optimization of the mode and frequency of exercise training, and biofeedback-controlled FES exercise. These modalities generally resulted in selective recruitment of fatigue resistant motor units , 62. TheThe long-time goal of FES technology has been to restore functional tasks and form an integral part of SCI management. A major step in this direction is to identify fatigue resistance strategies in order to achieve an effective therapy. Modification of stimulation parameters has been mostly explored among the strategies identified. Out of eighteen studies that sought to titrate neuromuscular stimulus parameters, Graupe and colleagues  was a prPeckham et al.,  originalAlthough the physical deconditioning secondary to SCI can be favourably altered by exercise interventions, some authors have argued that improvement of physical functionality does not entirely rely on exercise since the restoration of functional capacity depend on many other factors . Among tAccordingly, an extensive muscle training to promote conditioning should be complemented with other regimens with consideration to specific level and completeness of injury in order to gain useful insight into key physiological functions necessary to improve muscle fatigue resistance. In all, reduction of rapid muscle fatigue during FES therapy in persons with SCI, being a complex task, has been managed using multiple, often concurrent, strategies. However, these are still mostly confined to the research laboratories based on the settings of most studies we reviewed. An integrated approach towards fatigue reduction may allow a successful deployment of the strategies for therapeutic trials in clinical settings and outdoor where the full potential of FES therapy can be derived. Currently, comparisons between the effectiveness of each of these strategies are difficult because of the lack of standardisation of the protocols, training procedures and stimulation parameters administered in different studies even within the same category of strategy. Accordingly, the immense potentials in the generation of fatigue resistant contractions bespeak the importance of randomised controlled trials (RCTs) to document the efficacy of available strategies. While further research is apparently required, preliminary data on the available strategies are promising. Although there is significant impact of each strategy which could serve as basis for further investigations, a combination of the strategies appears to be more effective.Furthermore, it is axiomatic that the earlier the FES therapy commences following the injury the better will be the outcome, and the associated inactivity-atrophic changes in paralyzed muscles are reversible even after 20 years . Apart fEvidence indicates that most fatigue reduction investigations were conducted during isometric contractions of skeletal muscles. However, validation of those strategies during non-isometric conditions which are observed within functional tasks will be more clinically relevant. Equally, few muscle groups such as quadriceps and thenar have been evaluated, the test on the other functionally relevant muscle groups will determine how broadly the current strategies can be generalized. Therefore, further research trials are required before a definitive conclusion can be drawn on the effectiveness of FES fatigue reducing strategies in clinical population during functional activities. In all, the relationship among the strategies seems to be complementary , since ti.e., unnatural recruitment patterns). The emerging trend is tending toward a systematic approach to the administration of the optimal stimulation parameters [Despite an extensive evidence-based knowledge establishing the decreased fatigue resistance following SCI, little research has been performed to subvert this trend. Therefore, the prevalent incidence of SCI could not be matched with the studies in this field. Available efforts to automatically minimize this phenomenon remained limited, creating a wide knowledge gaps for the development of an ideal FES device. There may be device dependent limitations in FES therapy due to the manifestation of innate nature of the FES device and its effect on muscle physiology  have been validated as physiological sensing modalities. These sensors are promising in the design of biofeedback systems to achieve a ‘closed looped’ FES control in clinical populations [i.e., generated muscle force during fresh and fatiguing contractions), and the knee-joint dynamics [As identified from the literature, studies on the application of FES are marked with heterogeneity of stimulation patterns that may be responsible for the wide variation of outcomes. This problem may be partly ameliorated by an automated biofeedback-controlled FES which could be used to control the stimulation parameters to suit the fatigue state of different muscles. Development and validation of sensors to modulate and automate the stimulation pattern in FES muscle contractions in order to mimic the physiological coordination of muscular activities remain a wide knowledge gap. Indirect measures of neural activities including electromyogram (EMG) , electroulations . They madynamics  for the i.e., by boosting the lactate threshold during high intensity exercise) and promote endurance, time to fatigue and calorie expenditure during FES exercise. However, the available studies are marked with limitations including investigation on small case series with no control groups and were conducted without consideration to other circulatory dysfunction following SCI  [There are indications of improved FES exercise outcome in SCI populations if combined with dietary supplementations. Nutrition such as whey protein and carbohydrate supplement , and othbserved) . Apart fbserved) . NeverthThe results of this review are limited to studies written in English language and included in the databases used to identify the articles. Other studies may exist outside these domains which we were unable to retrieve. Selection bias is another potential limitation of systematic reviews. However, we attempted to minimize the bias by searching for both randomized and non-randomized studies and stating clearly the quality of each study. Incidentally, there was no randomized controlled trial in the scope of interest. This was assessed independently by two reviewers. There may be other limitations beyond our control such as publication bias. Frequently, only studies with positive results are submitted to peer reviewed journals for publication. This situation may bias results toward positive treatment effects. We endeavour to widen the search scope from the earliest time to the most recent, June 2015 to limit such effect. Nevertheless, an interesting trend in rapid fatigue management could still be objectively inferred.The strategies for the rapid muscle fatigue reduction in SCI population have been highlighted in order to advance the clinical knowledge and practices, particularly in the management of persons with SCI. Inference from current state of evidence warrants the assessment of each method during functional task essential for activity of daily living as there is large treatment effect only on isometric contractions. We highlighted the emerging evidence on modulation of FES parameters, electrode positioning to enable asynchronous stimulation, and application of biopotential controlled FES exercising and muscle conditioning through exercise as the major fatigue reducing strategies. Despite the huge opportunities in the substantial independence leading to an improved quality of life for the FES candidates, the level of current evidence shows that the effective fatigue management in FES-induced contractions is still rudimentary. Most studies were conducted within short duration and were too modest, therefore, of limited clinical relevance. Many aspects of the studies were insufficiently researched to draw definitive conclusions. Moreover, several reviewed studies were marked with inadequate randomization, therefore caution should be exercised in interpreting authors’ conclusions. However, the highlighted proof of concepts provide basis for more systematic studies in a wider test population. Although the recent improvement in the commonly used strategies and current interest are of importance, evaluation of the strategies while employing more vigorous methodological design, particularly, in non-isometric contraction settings will be more clinically relevant.S1 File(DOCX)Click here for additional data file.S2 File(DOCX)Click here for additional data file.


Several observations support the hypothesis that differences in synaptic and regional cerebral plasticity between the sexes account for the high ratio of males to females in autism. First, males are more susceptible than females to perturbations in genes involved in synaptic plasticity. Second, sex-related differences in non-autistic brain structure and function are observed in highly variable regions, namely, the heteromodal associative cortices, and overlap with structural particularities and enhanced activity of perceptual associative regions in autistic individuals. Finally, functional cortical reallocations following brain lesions in non-autistic adults  are sex-dependent. Interactions between genetic sex and hormones may therefore result in higher synaptic and consecutively regional plasticity in perceptual brain areas in males than in females. The onset of autism may largely involve mutations altering synaptic plasticity that create a plastic reaction affecting the most variable and sexually dimorphic brain regions. The sex ratio bias in autism may arise because males have a lower threshold than females for the development of this plastic reaction following a genetic or environmental event. Boys have a 4 to 7 higher-fold risk of developing autism than girls ,  correspond to the experience-dependent dedication of a cerebral region to a cognitive function that does not typically map to this region in the general population, for example cross-modal plasticity that occurs in sensory-impaired individuals , , 151], aIn the two previous sections, we listed the striking similarities between male-female and AS-non AS differences in brain imaging areas that are related to plasticity mechanisms, and proposed that structure and connectivity patterns in the mature brain reflect previous experience-dependent plasticity. Although indirect, this evidence suggests that the idea of a central role of cerebral plasticity in AS male bias, based on genetic and animal findings, can be extended to human cognition. Indeed, qualitative examination of structural and functional differences between autistic and non-autistic individuals indicates a striking overlap between regions of major anatomical, connectivity-related and even functional Figure  and 2. TSexual divergence of developmental trajectories also suggests that the plastic reaction happens in different regions in boys and girls, resulting in a different autistic phenotype in men and women. This explains why males and females may be diagnosed according to different symptoms and/or using different weights attributed to the three diagnostic areas ,159. A mWe will now review sex differences in fetal hormonal effects, memory formation, stress response plasticity, and reaction to brain injury in adults. These sex differences result from both hormonal and non hormonal sex-specific mechanisms of brain plasticity, which lead to a sex difference in the adaptive response of the brain to several types of injury, regardless of age.The brain is influenced by maternal, placental, and fetal hormones during early development . DevelopAccording to the extreme male brain (EMB) theory, the effect of fetal testosterone (fT) may account for male bias in autism ,167; see67; see1.. This impaired the vocalization behavior of rat pups of both sexes. In adolescence, the female offspring spent less time engaging in social interactions and exhibited impaired heterosexual interactions as adults. Although the affected behaviors can be classified as social, this model does not mimic the complexity of autistic features in humans. Furthermore, the social impairments in this rat model disappeared in adulthood. Nevertheless, these results indicate the sexually dimorphic consequences of high T levels. Thus, similar hormone levels probably have differential effects in males and females, mainly because of the compensatory reduction of T production in the male fetus in response to high maternal exposure, which cannot occur in the female fetus. Alternatively, in males, high T levels may not be sufficient to produce autistic-like behaviors and other mechanisms may be necessary. In summary, interactions between hormones and genes should be considered in the physiopathology of autism. For instance, androgens and estrogens differentially regulate the RORA gene, a candidate susceptibility gene for autism, the expression of which is low in the frontal cortex of autistic individuals [The complex role of fT in autism has been further documented in a rat model in which a hyper-androgenic environment was created by high T levels during pregnancy . This imividuals . The proividuals .in vitro cultures of rat hippocampus from either sex, whereas synaptic loss is induced by estrogen depletion in vivo specifically in females [Sensory experience drives the formation and elimination of synapses resulting in experience-dependent plasticity . Plastic females . These dvia tonic suppression in adult male rats [Brain-derived neurotrophic factor (BDNF), one of the key molecules modulating brain plasticity, induces long-lasting potentiation of synapses during specific learning and memory processes . BDNF inale rats . Strong ale rats . Therefoale rats .The effects of stress on hippocampal neurogenesis and synaptogenesis are also sexually dimorphic. Chronic restraint stress produces atrophy of the dendritic tree of CA3 neurons, exclusively in the apical field in males and only in the basal field in females . ChronicFemales are protected against stroke and its inflammatory effects both at a young age and post-menopause, when sex differences in circulating hormones are minimal . HoweverNitric oxide synthase-1 (NOS1) is an enzyme involved in several forms of plasticity including hippocampal-dependent learning and memory, experience-dependent plasticity in the barrel cortex, and LTP in the hippocampus and neocortex. LTP is absent in male but not female αNOS1 knockout mice, indicating that residual LTP in females is not nitric oxide-dependent. Experience-dependent potentiation resulting from single-whisker experience  is significantly impaired in male αNOS1 knockout mice but does not affect females, suggesting that cortical plasticity relies more on NOS in males than in females. Therefore, synaptic neocortical plasticity mechanisms differ between males and females, including both basic plasticity induction pathways and the ability of plasticity mechanisms to compensate for the loss of αNOS1 .Sex differences in the functional outcome of traumatic brain injury (TBI) have long been recognized . In animStudies examining concussive injuries of various origins have identified hormone disruption as a key factor underlying sex differences in the outcome of concussion ,207. OneMultiple sclerosis (MS) involves the destruction of the nerve cover in brain and spinal cord white matter, developing either continuously without remission or to complete remission interspersed with successive attacks. Compensatory plasticity plays a major role in clinical relapses in MS. The sex ratio favoring women has been increasing from 2:1 to 3:1 in the past few decades .Compensatory plasticity in MS can involve regional rededication  or microstructural modification . MS patients with a lateralized motor deficit display high ipsilateral and contra-lateral activity in cortical motor areas, which are less activated or not activated at all in control individuals. The enhancement of activity in cortical motor regions is correlated with brain damage ,212 and The relationship between sex differences in functional compensation in adults and during early developmental cortical reallocation remains to be established. Nonetheless, differences in tissue repair support the idea that women are at a disadvantage regarding their plastic reaction to brain injury, as a result of combined genetic and hormonal effects . This maRecent studies investigating sex-differences in autism have attempted to distinguish sex differences in diagnosis and phenotype from the search for ‘general models of etiology and etiological-developmental mechanisms’ . With thGenetic, transcriptomic, and animal model studies demonstrate the central role of brain plasticity in autism because many mutations involved in AS affect synaptic structure, function, and plasticity. In addition, indirect but nonetheless strong arguments from animal models, brain imaging, development, and studies of the brain transcriptome and plasticity in adulthood suggest that an enhanced plastic reaction is involved in the sex ratio bias in autism. The protective effect of the female sex against these mutations and the presence of sexual dimorphism in pathways involved in synaptic plasticity support the idea that: 1) a similar genetic event may trigger a different plastic reaction in males and females; and 2) plasticity is more likely to be disrupted in males than in females. Other indirect evidence comes from adult sex differences in reconstructive and compensatory brain plasticity.A review of studies examining sexual dimorphism from brain imaging data of non-autistic and autistic individuals indicates that regions displaying functional, structural, and connectivity enhancements overlap with those in the perceptual  associative cortex that is more connected in males than in females. This convergence, observed in the mature brain, may originate from sexually dimorphic changes occurring during prenatal and early postnatal brain development because gene expression and hormone secretion are highly dependent on biological sex during these periods.As a new basis for the understanding of sex ratio bias in autism, we now hypothesize that autistic phenotypes result from plastic reactions involving the most plastic, sexually dimorphic brain regions, in individuals whose threshold for this reaction is lowered by genetic or environmental causes. A severe mutation targeting essential synaptic structures may impair synapse formation and trigger a compensatory, abnormal plastic reaction in individuals with a low threshold. In this situation, highly penetrant mutations would cause a monogenic, syndromic phenotype with low IQ whereby the mutated genes are also expressed in other cells and tissues. When less severe mutations occur, the cognitive function of the individual is mainly preserved, while the mutation triggers a mostly typical, but disproportional, plastic reaction. In this paper, we reviewed the arguments indicating that such an occurrence is more likely in males than in females because males have a lower threshold for plastic reactions. The fact that autism-related differences continue to develop throughout life suggests that sexually dimorphic regional plasticity, evident in non-autistic individuals, plays a role in the developmental transformation of the autistic brain. This chain of events applies to autistic individuals with a high IQ, who are disproportionately male, and thus accounts for male-bias in the autistic sex ratio. It also predicts that sex differences in the autistic phenotype are constrained by topographical, chronological, and systemic differences in plasticity.non-hormonal sex-dependent mechanisms, microstructural experience-dependent plasticity, and importantly, reallocation rules, is clearly a new research avenue, which will extend our understanding of sex bias in autism to factors beyond the hormonal effects documented by the EBM model  and in various forms . Brain imaging studies have indicated that the changes in AS individuals, in particular those without ID, are regional and compatible with plastic reactions; however, it remains to be demonstrated whether these two levels of enhanced synaptic and regional plasticity are associated in the same person and whether they differ in males and females. Finally, studies assessing domain-specific strengths in women may determine the targets of sex-specific experience-dependent plasticity.