This paper tells the story of how hormesis became recognized as a fundamental concept in biology, affecting toxicology, microbiology, medicine, public health, agriculture, and all areas related to enhancing biological performance. This paper assesses how hormesis enhances resilience to normal aging and protects against a broad spectrum of neurodegenerative, cardiovascular, and other diseases, as well as trauma and other threats to health and well-being. This paper also explains the application of hormesis to several neurodegenerative diseases such as Parkinson’s and Huntington’s disease, macrophage polarization and its systematic adaptive protections, and the role of hormesis in enhancing stem cell functioning and medical applications. The dose response concept is central to biology, medicine, and public health . It reprWithin this context consider how the radiation genetics research community approached the concept of dose response for radiation-induced mutation which was discovered by Muller . Within This dose response hypothesis was based on the study of mutations in mature spermatozoa of Drosophila. At the time of this hypothesis formation and its applications to risk assessment, it was not known that DNA repair existed let alone that it became lost or fully degraded as spermatogonia transitioned to mature spermatozoa. Thus, when the US NAS Genetics Panel  made theThis belief in linearity at low doses would be challenged by another contemporary prominent radiation geneticist, William Russell, Oak Ridge National Laboratories, using the mouse specific locus test with over two million mice in his iterative radiation-induced mutational studies  would be stridently and unrelentingly challenged and ridiculed by leaders within traditional medicine ,38,39, mThe next several decades would provide substantial documentation that hormetic dose responses were common, and occurred in a broad range of microbial, plant, and animal models, suggesting widespread generality ,44,45. LDespite the considerable diversity of biological models, inducing agents, and endpoints showing hormetic dose responses, they have one highly consistent characteristic in common, that is, their quantitative features are similar. This was also the case whether the low dose stimulation occurred via a direct stimulation or via an overcompensation to an initial toxicity response . The stiThese biologically profound developments occurred via the study of vast numbers of dose responses and their quantitative, and mechanistic features. Furthermore, the quantitative features of the hormetic dose response also were biologically modeled and reflected an allometric pattern that was similar to those that relate a vast range of key biological parameters to body weight and/or body surface . These cSince hormesis defines the magnitude and limits of biological plasticity it has widespread and significant implications for drug development, disease resistance and other activities designed to enhance biological performance and to acquire resilience via procedures such as pre-and post-conditioning ,10. SincThe evaluation of the maximum hormetic stimulatory response represents a type of biological optima. Exactly where that optimal hormetic stimulation response resides in the zone below the threshold is important to determine in the testing of possible therapeutic agents. It is frequently located in a zone usually 10–20 fold below the estimated threshold. Using the hormesis data base ,47 we haThe hormetic dose response has important implications for the fields of hazard assessment, risk assessment for carcinogens, endocrine disruption, for pharmaceuticals/natural products that enhance biological performance, and pre/post conditioning activities that upregulate adaptive mechanisms, enhancing resilience.Hormesis is helpful in guiding the hazard assessment process in several ways. It provides a scientific basis for the selection of biological models for evaluation especially as it relates to background disease incidence. It provides a dose response model framework to assist in the selection of the number of doses, the dose spacing, and sample sizes to be employed. Hormesis also affects decisions concerning repeat sampling over time to assess possible compensatory responses. These hormetic-based insights are useful and likely to enhance the quality and utility of such studies, increasing confidence in the findings while also providing biostatistical model validation. Nonetheless, these factors can be problematic since they make experiments more expensive and longer to complete. Furthermore, in order to be successful in locating doses below the threshold one must know where the threshold is likely to occur in order to better target the low dose hormetic stimulatory zone with appropriate study designs. This would also usually require additional preliminary experiments to better clarify the dose zone within which a threshold may be likely to occur. These experimental challenges can make it difficult to assess hormetic hypotheses and to provide reproducible findings for low dose responses. This can be troublesome if the control group is especially variable. Further, it is important to have well documented information on control group variation. Failure to take such factors into consideration has the potential to reduce confidence concerning whether observed hormetic-like biphasic dose responses are reproducible effects or simply due to background variation.−4  move away from their use of the LNT as the default model in cancer risk assessment and consider the use of non-linear dose response models such as hormesis. Calabrese et al.  proposed−4 . This moLow doses of some endocrine disrupting agents act via biphasic dose responses that conform very closely to the quantitative features of the hormetic dose response. For example, in some animal models low doses of bisphenol A (BPA) biphasically affected prostate size, with a maximum enhancement in the hormetic response zone . A similA wide range of pharmaceutical products display hormetic features, including anxiolytic  54] and and54] aThe search for viable treatments for Parkinson’s and Huntington’s Diseases (HD) use a variety of predictive experimental models. Calabrese et al. ,62 have The role of mechanism in hormesis has shown marked advances over the past decade. During the 1990s as the concept of hormesis was beginning to be explored in depth, there were many reproducible examples of hormesis, but any mechanistic basis for such responses was very limited and often speculative. This has changed with major advances in the area of cell signaling pathways and their linkage with receptors activating biological processes. In 2013, Calabrese  documentA major development over the past two decades has been the recognition that macrophages can be reprogrammed toward pro-oxidative  or anti-inflammatory forms . In the case of preconditioning, this process acts to polarize macrophages toward the M2 form, facilitating protective/reparative/anti-inflammatory responses. We have recently hypothesized that macrophage reprogramming with polarization to M1 or M2 macrophage forms may be mediated via concentration gradients of signaling agents. A comprehensive assessment revealed many substances can mediate macrophage polarization following a concentration gradient that conforms to an hormetic dose response ,71. ThisA substantial literature exists on the occurrence of hormetic dose responses in a broad spectrum of stem cells. These stem cell hormetic responses have involved both direct stimulatory dose response features as well as those induced within a preconditioning framework. The quantitative features of the hormetic dose response for stem cells are similar to all other cell types . ParticuThis paper is set within the theme of this special journal issue—“day break hormesis”. Even though hormesis is scientifically “coming of age” it was first reported in the 1880s, with considerable research providing a large number of well executed studies through the past century in many biological areas ,30,46,47The past century of challenges to hormesis has become less influential with its effects becoming diluted in an asymptotic-like regression. The past 30 years of intense research focus on hormesis has worked its way through this quagmire of historical antipathies and scientific challenges, with major advances establishing the generality of hormesis and its potential medical, public health, and agricultural implications.Hormesis is now becoming prominent in leading textbooks in toxicology, pharmacology, and related biomedical areas. It has greatly profited from outstanding leadership in the areas of biogerontology, neuroscience/neurodegenerative diseases, exercise science, and other areas of public health interest. Hormesis is becoming seen as a central biological concept that can help researchers answer key biological questions in many domains. Thus, while it has been a 130 year wait, I am sure that Hugo Schulz would be proud that hormesis has finally reached its own scientific tipping point as reflected in this special issue on day break hormesis.


Regenerating lost or damaged tissue is the primary goal of Tissue Engineering. 3D bioprinting technologies have been widely applied in many research areas of tissue regeneration and disease modeling with unprecedented spatial resolution and tissue-like complexity. However, the extraction of tissue architecture and the generation of high-resolution blueprints are challenging tasks for tissue regeneration. Traditionally, such spatial information is obtained from a collection of microscopic images and then combined together to visualize regions of interest. To fabricate such engineered tissues, rendered microscopic images are transformed to code to inform a 3D bioprinting process. If this process is augmented with data-driven approaches and streamlined with machine intelligence, identification of an optimal blueprint can become an achievable task for functional tissue regeneration. In this review, our perspective is guided by an emerging paradigm to generate a blueprint for regeneration with machine intelligence. First, we reviewed recent articles with respect to our perspective for machine intelligence-driven information retrieval and fabrication. After briefly introducing recent trends in information retrieval methods from publicly available data, our discussion is focused on recent works that use machine intelligence to discover tissue architectures from imaging and spectral data. Then, our focus is on utilizing optimization approaches to increase print fidelity and enhance biomimicry with machine learning (ML) strategies to acquire a blueprint ready for 3D bioprinting. Tissue Engineering (TE) has advanced over the last few decades to tackle challenging problems in tissue regeneration  approaches are common statistical quality control techniques, utilizing systematic randomization to inform experiment planning, execution, as well as model fitting of the results. Although DOE approaches are widely utilized for optimization Allen, , these sGenerating a blueprint for 3DBP via a systematic strategy will be particularly useful in several aspects . Although collecting existing image data is the first step, currently existing IR systems are less effective for customized functionalities for tissue image data. Instead, online image data are collected manually or using relatively simple text-based engines. Examples are Yale Image Finder , detailed biochemical information , tissue anatomy and overall architecture  need to be combined systematically to generate a collective template for 3DBP. Multi-modality imaging is a way to obtain tissue information, but often requires specific computer programs as well as dedicated imaging techniques  ML methods directly targeting imaging data  method, used a hybrid multiple subgradient descent bundle (MSGDB) method in conjunction with an Adam algorithm to reduce satellite droplet formation and increase printing precision and stability in piezoelectric drop-on-demand bioprinting  for 3DBP employs a hill-climbing algorithm to optimize print fidelity through the exploration of print parameters  with GA was utilized to identify the diameter and spacing of PLGA [poly(lactic-co-glycolic acid)] scaffold that best promotes the required scaffold degradation profile , which relied on the minimization of line thickness and shear stress to optimize the final construct (Webb and Doyle, To enhance functionality of bone tissue scaffolds, one research group attempted to optimize the scaffold topology and material properties with two different engineering strategies (Uth et al., The studies discussed in this section begin to consider both print fidelity and biomimicry regarding parameter optimization; this research lays a foundation to continue to strive toward MI-based systematic approaches for creating patient-specific 3DBP tissue constructs.As MI-based approaches emerge, a few cases utilized ML approaches to accelerate the rate of production in 3D printing with fewer errors, artifacts and bias. The majority of printed features are based on simplified or artificial patterns that are less relevant to tissue or organ architectures. A blueprint was created from tissues to fabricate engineered cardiac muscle (Gao et al., While the limitations of ML are easily found in many potential applications of 3DBP and TE, the field of ML has a rich history for solutions to tackle such limitations. For example, uncertainty analysis has been an active area with Bayesian learning. To improve the interpretability of a learned model, a number of cases for the model and variable selection are found in literature (Hastie et al., It is our intention to emphasize the term of MI to be used for the future direction to overcome many existing problems with “the conventional ML,” including the uncertainty quantification, induction bias, and machine reasoning. Elaborating this perspective with an unbiased manner is beyond the scope of the manuscript prepared for a mini review. Nevertheless, the domain of ML is evolving fast, primarily motivated to deal with the new challenges of Big Data problems and high-throughput experiments. Thanks to recent advances in DL and other associated ML methods, many limitations, previously considered as roadblocks, are effectively or practically resolved.MI processes are no longer regarded as a black-box model, but rather processes that can be explained with expected behaviors (Gilpin et al., JJ and JK conceived the overall topics of discussion. All authors wrote, read, and approved the final manuscript.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.


Diabetic kidney disease affects up to forty percent of patients with diabetes during their lifespan. Prevention and treatment of diabetic kidney disease is currently based on optimal glucose and blood pressure control. Renin–angiotensin aldosterone inhibitors are considered the mainstay treatment for hypertension in diabetic patients, especially in the presence of albuminuria. Whether strict blood pressure reduction entails a favorable renal outcome also in non-albuminuric patients is at present unclear. Results of several clinical trials suggest that an overly aggressive blood pressure reduction, especially in the context of profound pharmacologic inhibition of the renin–angiotensin–aldosterone system may result in a paradoxical worsening of renal function. On the basis of this evidence, it is proposed that blood pressure reduction should be tailored in each individual patient according to renal phenotype. Diabetic kidney disease (DKD) is a relatively common and feared complication of both type 1 and 2 diabetes. It affects 30% to 40% of diabetic patients over their lifespan and negatively impacts their cardiovascular risk burden and overall survival .A recently published retrospective study while confirming that long-term, strict control of BP is associated to a reduction of albuminuria suggested that the related benefit in terms of glomerular filtration rate (GFR) preservation may be smaller than anticipated because of a paradoxical worsening in renal function at very low BP levels . As a maExperimental and clinical studies have convincingly demonstrated the involvement of increased activity of the RAAS both at the systemic and tissue level in the development and progression of diabetic renal damage . Thus, RAlbuminuria is a known marker of kidney damage with an established prognostic role both in cardiovascular and in renal risk. Recent, long-term studies confirm that a decrease in albuminuria obtained with optimal BP control is associated with better cardiovascular and renal outcome, while an increase in urine albumin excretion over time entails worse prognosis ,12. ThusWhile lower BP values and maximal pharmacologic inhibition of the RAAS have consistently been shown to improve renal outcome in diabetic patients presenting with the traditional “albuminuric” renal phenotype, it is uncertain whether a similar therapeutic strategy should be applied in the absence of albuminuria. Thus, on the basis of more recent epidemiological data, it has been proposed that antihypertensive treatment should be individualized both in terms of target BP values and possibly, in terms of antihypertensive drugs combination according to different presenting renal phenotypes .GFR and albuminuria are usually considered to be valid biomarkers that can be used to monitor renal function and to assess the effectiveness of therapeutic strategies for renal protection . The resMany diabetic hypertensive patients may suffer from autonomic neuropathy, and therefore, from orthostatic hypotension and other features of impaired systemic hemodynamics. Thus, in clinical practice, seated or standing BP should be used as a target for treatment and great care should be paid when titrating antihypertensive drugs, especially peripheral alfa-blocking drugs. In addition, the timing of drug administration should be tailored in each individual patient and attention should be paid to avoid the risk of haemodynamic changes in patients in the presence of diarrhea or hypovolemia.RAAS inhibitors are considered the mainstay treatment for a variety of cardiovascular conditions such as of hypertension, diabetes, proteinuria, and heart failure and myocardial infarction because of their beneficial effects on cardiovascular protection . In partRecently, sodium/glucose cotransporter 2 inhibitors (SGLT2-is) have received attention as a class of promising hypoglycemic agents with additional ability to slow down the progression of diabetic kidney disease. They improve glucose metabolism by inhibiting glucose reabsorption at the proximal part of the renal tubule, thereby increasing glycosuria. Moreover, SGLT2-is have been shown to improve the systemic hemodynamic profile by reducing BP and promoting weight loss. While renal changes observed with the use of these agents may be due to multiple pathogenic mechanisms, a large part of their renal protective effect seems to be mediated by their ability to favorably interfere with renal hemodynamics. In fact, SGLT2-is attenuate hyperfiltration and lower intra-glomerular pressure by increasing afferent arteriolar vaso-constriction, as a consequence of tubular glomerular feed-back activation at the macula densa . BesidesIt has been estimated that by using SGLT2-is in addition to RAAS-is, an additional 30%–40% renal protection benefit could be obtained in clinical practice. While this approach looks very promising and deserves to be implemented in a general systematic way in diabetic patients at renal risk, it may hardly represent the ultimate strategy to effectively prevent this devastating micro-vascular complication. From what we know of the complex, multifactorial mechanisms underlying the pathogenesis of diabetic renal disease, it is conceivable that, in order to obtain additional reno-protection, mechanisms that differ from glomerular hemodynamics should also be targeted. In fact, it is feasible that by combining SGLT2-is and RAAS-is, intra-glomerular pressure  may be reduced to a point beyond which further reduction may entail harm  rather than a long-term benefit. In this perspective, other attractive agents such as neprilysin-inhibitors or GLP1R-A, which exert their renal protective action by means of different mechanisms, may soon prove their incremental value in providing kidney protection. Neprilysin inhibitors have potential in improving glucose homeostasis in patients with diabetes through increasing muscle sensitivity to glucose uptake and hepatic sensitivity to insulin. The simultaneous use of RAAS-is can make-up for the negative effects of increasing angiotensin II levels through neprilysin inhibition. The association of these two drugs could provide an efficacious cardiovascular and renal protection in combination with positive effects on glucose homeostasis .In conclusion, optimal BP reduction by antihypertensive treatment currently remains the most effective and safe intervention to convey renal and cardiovascular protection in patients with diabetic kidney disease. RAAS-I should be considered the treatment of choice, although ideal BP values remain a matter of debate. Lower targets are recommended in the presence of overt albuminuria, a condition that entails greater risk of renal progression. A paradoxical J-curve relationship between BP reduction and renal morbidity may limit the benefit of aggressive treatment strategies, especially in the frail, elderly patients with non-albuminuric renal impairment.


SYNGAP1 haploinsufficiency causes a severe NDD defined by autistic traits, cognitive impairment, and epilepsy. To determine if this gene retains therapeutically-relevant biological functions into adulthood, we performed a gene restoration technique in a mouse model for SYNGAP1 haploinsufficiency. Adult restoration of SynGAP protein improved behavioral and electrophysiological measures of memory and seizure. This included the elimination of interictal events that worsened during sleep. These events may be a biomarker for generalized cortical dysfunction in SYNGAP1 disorders because they also worsened during sleep in the human patient population. We conclude that SynGAP protein retains biological functions throughout adulthood and that non-developmental functions may contribute to disease phenotypes. Thus, treatments that target debilitating aspects of severe NDDs, such as medically-refractory seizures and cognitive impairment, may be effective in adult patients.It remains unclear to what extent neurodevelopmental disorder (NDD) risk genes retain functions into adulthood and how they may influence disease phenotypes.  Neurodevelopmental disorders (NDDs), including intellectual disability (ID), autism spectrum disorder (ASD), and epilepsy result in treatment-resistant behavioral abnormalities. Many severe NDDs are characterized by cognitive impairments and medically-refractory seizures . In someHistorically, the patho-neurobiology underlying NDD symptomatology is thought to arise from impaired brain development. However, studies in animal models of genetic risk factors causally-linked to syndromic NDDs have shown improvement in meaningful measures of brain function and behavior in response to adult-initiated therapeutic interventions . These fAdult reversal studies have been carried out in animal models for only a few syndromic NDD genes . In thesSYNGAP1 is a recently discovered NDD gene . It has a reported incidence of 1-4/10,000 individuals, or 0.5–1.0% of ID cases , which have ~50% reduction in SynGAP protein levels  animal model that enables whole-body SynGAP protein re-expression at different stages of life (Syngap1 Lox-stop Het mice (+/ls)Syngap1 to hemizygous mice expressing a tamoxifen (TMX)-inducible form of Cre recombinase. Upon Cre activation, an artificial exon containing a premature stop codon is excised from the Syngap1 gene, leading to re-activation of the targeted allele and restoration of SynGAP protein levels. To test for seizure susceptibility, we used the flurothyl seizure induction paradigm, which has been used previously to uncover phenotypes in constitutive Syngap1 Het knockout mice , but not with the presence of Cre-ER, in the first two stages of seizure TMX(-) mice  is one outcome of pathogenic ariation . EE is aariation . Syngap1seizures . Therefo of life . This moout mice . In this seizure . There w WT mice , which iout mice . Importa(-) mice .Syngap1 Lox-Stop Het mice, or mice with Syngap1 pathogenicity reversed starting at PND60 (Syngap1 mice in the second seizure stage (Syngap1 Lox-Stop mice was significantly increased compared to Cre(-) Syngap1 Hets in the first two stages of the test  events in addition to occasional electrographic seizure events  WT and Cre(+) Lox-Stop Het mice. In addition to left and right sub-cranial EEG electrodes, a depth electrode was lowered into CA1 to acquire a hippocampal local field potential (hLFP). A study utilizing chronic recordings in these animals consisted of two phases. Phase one was geared toward identifying putative genotype-dependent differences in neurophysiological signals between Cre(+) WT and Cre(+) Lox-Stop mice. Phase II, in which all animals in Phase I underwent a procedure to induce Cre recombinase immediately following Phase I studies, was geared toward determining how putative neurophysiological abnormalities in each animal were impacted by restoration of SynGAP levels in Cre(+) Lox-Stop Het mice. In Phase I recordings, we observed frequent high amplitude IIS events that generalized across the three recording channels in Lox-Stop mice /Lox-Stop Het mice, we explored how this approach impacts neurophysiological correlates of seizure susceptibility. Prior studies have shown through EEG recordings that constitutive e events . Interice events . We reastop mice . This ficontrols . We alsocontrols . We tookcontrols . These dSyngap1 mice have parallels in humans expressing pathogenic SYNGAP1 variants. While IIS events are commonly observed in both humans and animal models expressing genetic risk variants linked to epilepsy, worsening of these events during sleep is uncommon and is a symptom of a distinct cluster of epilepsy syndromes, such as electrical status epilepticus in sleep (ESES)/continuous spikes and waves during slow sleep (CSWS) . In each of these unique patient entries, there were clear references to IIS activity  . Therefopulation . In thisactivity . However signals . These cSyngap1 pathogenicity on changes to cognitive function  with an adverse event (e.g. mild foot-shock). Memory is inferred from a behavior change, such as freezing and/or immobility, when the animal is placed back in the training environment hours or days later. We, and others, have previously reported that Syngap1 Het mice have normal expression of contextual fear 1 day (1d) after training  exhibit a deficit in contextual memory deficit when tested 26-30d after training  Syngap1 Het mice were no different from corresponding Cre(+) WT Syngap1 mice (Syngap1 Lox-Stop Hets  as was patient S3-080 [c.3190 C > T (p.Q1064X)]. Each patient had a scalp electroencephalogram with a minimum of 21 electrode recordings in a standard 10–20 distribution and a minimum of 45 min of recording which were reviewed by board-certified neurophysiologists as part of clinical care. The electroencephalograms were further manually reviewed by a board-certified neurologist (JLH) and representative epochs were captured.The parents of patients S3-060 and S3-080, which are distinct patients from those represented in st clonic, T/C, and THE). In behavioral studies, we included Cohen’s d for Syngap1+/+ vs. Syngap1+/(-)or(ls) as a measure of effect size when means were found to be significant between relevant groups. Explorations of data sets showed reasonably normal distributions and homogeneity of variances as assessed by Levene’s test for equality of variances as well as Box’s test for equality of covariance matrices. A nonparametric permutation test (5000 shuffles) was used to assess differences in oscillatory activity.Statistical tests for mouse seizure and fear conditioning data were conducted using SPSS and R packages importing Excel files containing raw data. Based on our prior experience with these behaviors, a general parametric statistical approach was used to assess data sets. Unpaired t tests for experiments with two groups comparing genotypes and two-factor ANOVAs with Bonferroni pair-wise comparisons for experiments with four groups assessing contingencies of Cre and genotype factors were performed to assess activity suppression ratio values associated with fear conditioning. MANOVAs were performed to assess Cre/genotype contingencies for the multiple levels of factors associated with seizure threshold . Two other reviewers remain anonymous.Thank you for submitting your work entitled "Adult Reversal of Memory and Excitability Impairments in a Model of Syngap1 Pathogenicity" for consideration by As you will see from the reviewers' comments, they accepted the conclusions of the work but thought that its impact was modest at this stage given that similar observations have been made for other neurodevelopment disorders, and that the mechanistic distinction between Syngap 1 early deficits and those that were reversible in the adult are not further explored here. Thus we think the manuscript at this stage is better suited to a more specialized journal.Reviewer #1:The study by Creson et al. adds to previous work from the Rumbaugh lab on behavioral effects of synGAP haploinsufficiency. The new work shows that cognitive deficiency measured by the long-term contextual fear memory paradigm can be reversed by re-expression of a full complement of synGAP in adulthood. This finding is in contrast to their earlier finding regarding cognition measured by spontaneous alternation in a T-maze paradigm, which is believed to measure working memory. Earlier work from the Rumbaugh lab had shown that haploinsufficient mice are deficient in the alternation task, and the deficiency is not restored by re-expression of synGAP in adulthood. In that study, the authors, apparently over-generalized prematurely, by concluding that "repairing the pathogenic mutations in adulthood did not improve behavior and cognition."In the present study, the authors further show that reduced seizure threshold produced by synGAP haploinsufficiency is reversed by re-expression in adulthood.The study is important because it indicates that the seizure susceptibility and certain aspects of cognitive disability that accompany synGAP haploinsufficiency may be improved by correcting the defect in adulthood. The study leads to the interesting question: Which behavioral tasks are "permanently" damaged by the disruption of critical periods caused by synGAP haploinsufficiency, and which behavioral tasks are not "permanently" damaged? The answer could shed light on which brain functions can be affected by ongoing brain plasticity in adulthood.eLife.The study appears well executed. The only major weakness of the manuscript is a lack of clarity resulting from over-generalization of results, and/or from the absence of important experimental details that should be supplied for the general readership of eLife, to repeatedly generalize from a few cases to all cases.In the Introduction, the authors again show a tendency to overgeneralize from very specific results by stating that historically, pathology leading to neurodevelopmental disorders was thought to arise exclusively from impaired brain development. They then cite several studies of particular disorders around 2008 that led to the "revolutionary idea" that "therapeutic intervention may be beneficial in adult NDD patients with fully mature brains." The authors should make the introductory paragraph more accurate, and more useful, by referring to the specific disorders (i.e. Rett Syndrome and tuberous sclerosis) for which improvement after treatment of adults was noted. It seems clear that some NDD's will not be improved by treatment in adulthood; whereas others may be. It is confusing, especially to the general readership of a journal like The phrase, "critical period that is essential for the assembly and excitatory balance of developing forebrain circuits" is obscure. I believe the authors mean – the " critical period during which a normal ratio of excitatory and inhibitory synapses are formed in particular brain regions. Without this normal ratio, the circuits can become overly excitable, leading to pathological function."At the beginning of the Discussion, the authors state, "The principle finding of this study is that genetic reversal of Syngap1 pathogenicity in adult mice improves deficits in memory and excitability." This is another overgeneralization that is potentially confusing. The authors should state, "The principal finding of this study is that genetic reversal of Syngap1 pathogenicity in adult mice improves deficits in long-term contextual memory and in seizure thresholds." In the next sentence, the authors should change the ending; "… that mediate working memory." The paradox that the authors refer to arises solely from their own overgeneralization. The significance of the authors work would be more broadly accepted if they refrained from over-generalization in the first place.Reviewer #2:In this manuscript, the authors show that Syngap1 heterozygous knockout mice exhibit impaired remote memory for contextual fear when tested 30 days after training, despite having normal contextual memory when tested 1 day after training. Interestingly, the authors crossed Syngap1 Lox-stop heterozygous mice to hemizygous tamoxifen-inducible Cre mice and show that re-expressing Syngap1 in adult mice reversed the remote memory deficit. The authors proceed to demonstrate that seizure threshold, but not sensorimotor gating, phenotypes are reversed by re-expressing Syngap1 in adults. The authors conclude that genetic reversal of Syngap1 pathogenicity in adult can improve impaired cognition altered excitability.eLife. As noted by the authors, similar findings in other mouse models of intellectual disability/autism spectrum disorder have demonstrated and in this manuscript there are no experiments designed to get at the mechanism or brain region where re-expression of Syngap1 is exerting this effect in adulthood. In addition, there is an interesting finding that is not explained: there is no remote memory phenotypes if the Syngap1 heterozygous mutant mice are tested one day after training, suggesting the retrieval of the memory prevents the remote memory impairment. How is does this observation impact the interpretation of the remote memory phenotype?The findings are interesting, but I am not sure whether they rise to the level of importance and novelty to warrant being published as a short report in eLife.In closing, although the findings are interesting and potentially important for understanding pathologies in adult Syngap1 mutant mice, I am not sure that they warrant publication in Reviewer #3:eLife. The seizures and remote memory phenotypes are very interesting, but they remain mostly unexplored in this manuscript. The finding that it is possible to reverse in adults certain behavioral and physiological phenotypes in neurodevelopmental mouse mutants is interesting and clinically relevant, but it is not novel, since it has been demonstrated repeatedly in multiple neurodevelopmental conditions.The manuscript by Thomas Creson et al. reported that re-expression in adults can reverse some behavioral and seizure abnormalities even though SynGAP loss disrupts neurodevelopment. Specifically, the authors showed evidence that 1) re-expression of SynGAP in adults reverses remote memory deficit in a SynGap1 Het mice with 50% SynGAP loss; 2) re-expression of SynGAP in adults also alleviates seizures in SynGap1 Het mice. These findings are interesting and worth publishing but they do not reach the level of significance expected for  [Editors’ note: the manuscript was revised and accepted after re-review.]Reviewer #1:[…] The study appears well executed. The only major weakness of the manuscript is a lack of clarity resulting from over-generalization of results, and/or from the absence of important experimental details that should be supplied for the general readership of eLife.In the Introduction, the authors again show a tendency to overgeneralize from very specific results by stating that historically, pathology leading to neurodevelopmental disorders was thought to arise exclusively from impaired brain development. They then cite several studies of particular disorders around 2008 that led to the "revolutionary idea" that "therapeutic intervention may be beneficial in adult NDD patients with fully mature brains." The authors should make the introductory paragraph more accurate, and more useful, by referring to the specific disorders (i.e. Rett Syndrome and tuberous sclerosis) for which improvement after treatment of adults was noted. It seems clear that some NDD's will not be improved by treatment in adulthood; whereas others may be. It is confusing, especially to the general readership of a journal like eLife, to repeatedly generalize from a few cases to all cases.We have rewritten the Introduction based on the comments of the reviewer. We now draw a distinction between the earlier modeling work on syndromic risk factors that impact the whole body, and our newer work, which deals with the biology of risk factors that principally cause severe NDDs, such as SYNGAP1.The phrase, "critical period that is essential for the assembly and excitatory balance of developing forebrain circuits" is obscure. I believe the authors mean – the " critical period during which a normal ratio of excitatory and inhibitory synapses are formed in particular brain regions. Without this normal ratio, the circuits can become overly excitable, leading to pathological function."Thank you for pointing this out. We have changed the statement to read, “Sygnap1 heterozygosity disrupts a developmental critical period, which a normal ratio of excitatory and inhibitory synapses are formed in particular brain regions. Without this normal ratio, circuits can become overly excitable, which may contribute to pathological brain function .”At the beginning of the Discussion, the authors state, "The principle finding of this study is that genetic reversal of Syngap1 pathogenicity in adult mice improves deficits in memory and excitability." This is another overgeneralization that is potentially confusing. The authors should state, "The principal finding of this study is that genetic reversal of Syngap1 pathogenicity in adult mice improves deficits in long-term contextual memory and in seizure thresholds." In the next sentence, the authors should change the ending; "… that mediate working memory." The paradox that the authors refer to arises solely from their own overgeneralization. The significance of the authors work would be more broadly accepted if they refrained from over-generalization in the first place.We appreciate the advice from the reviewer, and we will be mindful of overgeneralizations in the future. We have rewritten the manuscript based on the substantial new data included in the study. In the new version of the manuscript, this statement has been changed to, “The principal finding in this study is that genetic reversal of Syngap1 pathogenicity in adult mice reverses deficits in remote memory, lowers seizure threshold, re-balances neural excitability, and improves hippocampal/cortical function. On the surface, these exciting results are somewhat paradoxical given that we have previously found that Syngap1 pathogenicity causes hardwired impairments in the development of forebrain circuits that mediate a subset of previously tested cognitive functions .”Reviewer #2:[…] The findings are interesting, but I am not sure whether they rise to the level of importance and novelty to warrant being published as a short report in eLife. As noted by the authors, similar findings in other mouse models of intellectual disability/autism spectrum disorder have demonstrated and in this manuscript there are no experiments designed to get at the mechanism or brain region where re-expression of Syngap1 is exerting this effect in adulthood.Over the past year, we have performed substantial new experiments that: 1) get at the mechanism and brain regions that SynGAP re-expression may be exerting its influence, and 2) provide translational relevance to the mouse reversal studies. We believe that these new experiments increase the novelty and the general interest of our study.Behavioral improvements reflecting improved cognitive function and reduced seizure susceptibility in the mouse model are now strengthened by data demonstrating a corresponding improvement in neurophysiological signals that predict seizure susceptibility and learning ability. These new studies demonstrate that protein replacement reversed both in vivo neurophysiological and behavioral phenotypes related to memory and seizure, two of the most clinically-relevant phenotypes associated with severe NDDs. Phenotypic reversal of cognitive deficits in this study was accompanied by chronic in vivo neurophysiological analysis in mice before and after gene restoration. This prospective design, which followed individual mice over two months, allowed us to measure how hippocampal and cortical function changed in individual animals after protein restoration in adulthood. In these new studies, we observed an increase in hippocampal theta power (a biomarker for memory formation) and an elimination of generalized paroxysmal spiking across the forebrain (a biomarker for seizure susceptibility) in mutant mice that underwent gene restoration. These clear improvements in hippocampal and cortical function provide mechanistic insight into how behavioral measures of seizure and memory improved after protein re-expression in adult animals. The combined improvement in both in vivo neurophysiology and behavior in response to adult gene repair provides very strong evidence that increasing the levels of pathologically low protein caused by severe genetic variants can broadly improve the function of the hippocampus and cortex even in mature animals.We also now provide data from human SYNGAP1 patients that provide translational context to the electrophysiological studies in mice that are described above. We collected data from human patients that harbor similar genetic pathogenicity as the mouse models (i.e. haploinsufficiency of SYNGAP1/Syngap1). We found that both mouse models and human patients exhibited analogous pathological EEG waveforms, which was the tendency of interictal activity to increase during periods of sleep. In mice, the pathological waveforms biased toward sleep were abolished after adult-initiated protein restoration. Therefore, these pathological EEG waveforms are a promising candidate biomarker for generalized cortical dysfunction in this genetically-defined NDD. We have confidence in the validity of these signals as a candidate biomarker because the signals worsened during sleep in both species. Sleep-driven worsening of pathological EEG signals is associated with declining cognitive function in NDD patients. Therefore, abolishment of these signals in mice, combined with improved behavioral measures of long-term memory, suggest that EEG signals can be a proxy measure for generalized improvements in cognitive function in single-gene causes of NDDs. Past clinical trials for NDD treatments searching for improved cognitive function in patients have relied on subjective endpoints, such as parent-reported surveys. These endpoints suffer from a very high placebo effect, which can run up to 30%. EEG studies are easily performed in the clinic, even in children with severe NDDs, and signals collected from EEG are highly quantifiable. The objective nature of EEG signals suggest that they may be less prone to measurement bias leading to a lower placebo effect, and therefore may be more useful in clinical trials that test the efficacy of emerging therapies for genetically-defined NDDs.In addition, there is an interesting finding that is not explained: there is no remote memory phenotypes if the Syngap1 heterozygous mutant mice are tested one day after training, suggesting the retrieval of the memory prevents the remote memory impairment. How is does this observation impact the interpretation of the remote memory phenotype?We reasoned that if retrieval at 1-day after training can prevent 30-day retrieval deficits, then networks that either consolidate and/or retrieved remote memory must be structurally intact in adult Syngap1 mice. We therefore hypothesized that these structurally-intact memory-linked circuits likely suffer from functional deficits caused by the persistent reduction of SynGAP protein expressed in the forebrain. It follows that restoring SynGAP protein in these circuits, even in adulthood, would improve memory performance in these mice. Our behavioral data supports this hypothesis. Importantly, our new in vivo ePhys data also supports this conclusion because we see clear evidence of improved hippocampal and cortical function in Syngap1 mutants after protein re-expression in adulthood. Moreover, we have shown in a past study, that adult restoration of SynGAP protein in Syngap1 Hets also rescues LTP in the CA1. Together, these data support the hypothesis that the Syngap1 gene retains functions in the adult brain to control the function and plasticity of forebrain circuits that promote memory and balance network excitability.In closing, although the findings are interesting and potentially important for understanding pathologies in adult Syngap1 mutant mice, I am not sure that they warrant publication in eLife.We hope that the addition of human EEG data and the in vivo ePhys studies in Syngap1 rescue mice raise the enthusiasm of the reviewer.Reviewer #3:The manuscript by Thomas Creson et al. reported that re-expression in adults can reverse some behavioral and seizure abnormalities even though SynGAP loss disrupts neurodevelopment. Specifically, the authors showed evidence that 1) re-expression of SynGAP in adults reverses remote memory deficit in a SynGap1 Het mice with 50% SynGAP loss; 2) re-expression of SynGAP in adults also alleviates seizures in SynGap1 Het mice. These findings are interesting and worth publishing but they do not reach the level of significance expected for eLife. The seizures and remote memory phenotypes are very interesting, but they remain mostly unexplored in this manuscript. The finding that it is possible to reverse in adults certain behavioral and physiological phenotypes in neurodevelopmental mouse mutants is interesting and clinically relevant, but it is not novel, since it has been demonstrated repeatedly in multiple neurodevelopmental conditions.We thank the reviewer for the insightful comments. The major concern, that the reversal of behaviors in adulthood in Syngap1 mice was largely unexplored in the original manuscript, has been dealt with in the revised manuscript. We now include two new and substantial experiments in the revised study to further explore the reversal phenotypes in this mouse model. We believe that these new experiments increase the novelty and the general interest of our study.in vivo neurophysiological and behavioral phenotypes related to memory and seizure, two of the most clinically-relevant phenotypes associated with severe NDDs. Phenotypic reversal of cognitive deficits in this study was accompanied by chronic in vivo neurophysiological analysis in mice before and after gene restoration. This prospective design, which followed individual mice over two months, allowed us to measure how hippocampal and cortical function changed in individual animals after protein restoration in adulthood. In these new studies, we observed an increase in hippocampal theta power (a biomarker for memory formation) and an elimination of generalized paroxysmal spiking across the forebrain (a biomarker for seizure susceptibility) in mutant mice that underwent gene restoration. These clear improvements in hippocampal and cortical function provide mechanistic insight into how behavioral measures of seizure and memory improved after protein re-expression in adult animals. The combined improvement in both in vivo neurophysiology and behavior in response to adult gene repair provides very strong evidence that increasing the levels of pathologically low protein caused by severe genetic variants can broadly improve the function of the hippocampus and cortex even in mature animals.Behavioral improvements reflecting improved cognitive function and reduced seizure susceptibility in the mouse model are now strengthened by data demonstrating a corresponding improvement in neurophysiological signals that predict seizure susceptibility and learning ability. These new studies demonstrate that protein replacement reversed both We also now provide data from human SYNGAP1 patients that provide translational context to the electrophysiological studies in mice that are described above. We collected data from human patients that harbor similar genetic pathogenicity as the mouse models (i.e. haploinsufficiency of SYNGAP1/Syngap1). We found that both mouse models and human patients exhibited analogous pathological EEG waveforms, which was the tendency of interictal activity to increase during periods of sleep. In mice, the pathological waveforms biased toward sleep were abolished after adult-initiated protein restoration. Therefore, these pathological EEG waveforms are a promising candidate biomarker for generalized cortical dysfunction in this genetically-defined NDD. We have confidence in the validity of these signals as a candidate biomarker because the signals worsened during sleep in both species. Sleep-driven worsening of pathological EEG signals is associated with declining cognitive function in NDD patients. Therefore, abolishment of these signals in mice, combined with improved behavioral measures of long-term memory, suggest that EEG signals can be a proxy measure for generalized improvements in cognitive function in single-gene causes of NDDs. Past clinical trials for NDD treatments searching for improved cognitive function in patients have relied on subjective endpoints, such as parent-reported surveys. These endpoints suffer from a very high placebo effect, which can run up to 30%. EEG studies are easily performed in the clinic, even in children with severe NDDs, and signals collected from EEG are highly quantifiable. The objective nature of EEG signals suggest that they may be less prone to measurement bias leading to a lower placebo effect, and therefore may be more useful in clinical trials that test the efficacy of emerging therapies for genetically-defined NDDs.


Daytime and nighttime thermal infrared observations acquired by the ASTER and MODIS instruments onboard the NASA Terra spacecraft have produced a dataset that can be used to map thermophysical properties across large regions, which have implications on surface processes, thermal environments and habitat suitability for desert species. ASTER scenes acquired between 2004 and 2012 are combined using new mosaicking and data-fusion techniques to produce a map of daytime and nighttime land surface temperature with coverage exclusive of the effects of clouds and weather. These data are combined with Landsat 7 visible imagery to generate a consistent map of apparent thermal inertia (ATI), which is related to the presence of exposed bedrock, rocks, fine-grained sediments and water on the surface. The resulting datasets are compared to known geomorphic units and surface types to generate an interpreted mechanical composition map of the entire Mojave Desert at 100 m per pixel that is most sensitive to large clast size distinctions in grain size distribution.  High-resolution climate and ecological modeling in arid regions are aided with an understanding of surface characteristics such as rock exposure, soil induration, texture and mechanical composition at fine-scales because these characteristics affect the micro and macro habitat and ultimately determine the assemblage of plant and animal species that may occur ,2,3,4. TData describing surface conditions in the desert regions of the United States are often limited to geologic, geomorphic and pedologic maps, which are generally only resolved at coarse spatial resolutions greater than 1 km, or are only available for specific areas where detailed ground surveys have been completed. Where surveys have been conducted for larger areas, the methods used are often inconsistent from one survey to another, requiring post-hoc standardization across survey areas and loss of geologic detail . For exaRemote sensing datasets provide an opportunity to quantify the areal variation of physical properties of the Earth’s surface using spatially-extensive and consistent methods. This is especially applicable in the Mojave Desert  EcoregioTwo thermophysical properties dominate the surface temperatures of geologic surfaces exposed to daily solar radiation: reflectance and thermal inertia. Reflectance is the ratio of reflected energy to incident solar energy at the given incidence angle, which can be derived from multispectral satellite imagery . ThermalDeriving ATI images with daytime and nighttime LST and daytime reflectivity is straightforward for surfaces with low topography ,21,22, aA limitation of currently available high-resolution remote sensing imagery is that the probability of acquiring cloud-free coverage over a large region and narrow time span is low. As a result, regional mapping necessitates the use of scenes acquired from multiple seasons and even years, thereby introducing scene-to-scene variability in mosaics. Efforts to overcome this limitation have resulted in mosaicking techniques for thermal infrared imagery from the ASTER instrument acquired at different dates, and has resulted in data products such as the North American ASTER Land Surface Emissivity Database (NAALSED) . AlthougAdvances in mosaicking methods have also emerged from the planetary remote sensing community. Data returned from the 2001 Mars Odyssey Thermal Emission Imaging System (THEMIS)  also sho2/sr/micron) that can be separated into a brightness temperature and a five-band emissivity spectrum [2) as that measured by ASTER over the wavelengths integrated by the five band passes. ASTER is ideal for high spatial resolution mapping, but most locations on the Earth are observed every 16 days at best, and many regions are not regularly observed. MODIS is a set of two identical instruments on board the NASA Earth Observing System (EOS) Terra and Aqua satellites [The ASTER instrument on-board the NASA Terra spacecraft collects multispectral imagery at spatial resolutions of 15 m in visible and near-infrared (VNIR), 30 m in shortwave infrared (SWIR) and 90 m in thermal infrared (TIR) wavelengths . TIR datspectrum  highlightellites  that colA total of 159 ASTER scenes were compiled to create nighttime and daytime LST datasets, acquired from May 2004 through November 2011 . Differehttp://search.earthdata.nasa.gov). Daytime and nighttime ASTER TIR scenes were obtained as calibrated surface radiance (AST_09T), on which we applied an instrument noise reduction step prior to the emissivity-temperature separation. A total of 85 and 74 scenes were used for each of the daytime and nighttime TIR mosaics, respectively. MODIS daytime and nighttime atmospherically-corrected and calibrated LST and emissivity products (MYD11A1) were used to evaluate the accuracy of the mosaicking algorithms. The composite 2010 Landsat 7 dataset was compiled with Google Earth Engine (http://earthengine.google.org) using the Landsat Ecosystem Disturbance Adaptive Processing System method [ASTER and MODIS data products were obtained through the NASA Earth Observing System Data and Information System portal, currently available as the EarthData search portal  and row  correlated noise from multispectral data sets [deplaid algorithm can be applied to any multispectral dataset where the absolute radiance differences between spectral bands are relatively small, as is the case for multispectral thermal infrared radiance. This is required because the deplaid algorithm uses inter-band variation to determine the location and magnitude of line- and row-correlated noise. We modified the deplaid algorithm for ASTER imagery by adding an additional step of segmenting each image into horizontal components for redundant noise calculations. In order to remove the detector noise in ASTER-derived temperature imagery, the deplaid algorithm is run on multi-band radiance data that can later be separated into temperature and emissivity components. All nighttime scenes were processed using the deplaid algorithm on radiometrically-calibrated and atmospherically-corrected AST_09T radiance imagery to generate new five-band radiance data with significantly reduced detector noise. Nighttime ASTER thermal observations with lower surface temperatures have low signal to noise ratios and produce images with characteristically high detector noise that can be seen as image striping. Similar detector noise has been identified and characterized in other multispectral imaging systems and has been known to propagate and intensify with data processing such as emissivity-temperature separation . A post-ata sets , which hata sets . The dephttp://davinci.asu.edu). Following the noise-reduction step on the five-band AST_09T data, surface temperature and emissivity were separated using the ENVI software emissivity normalization process to produce single-band brightness temperature images equivalent to the ASTER land surface temperature (LST) product (AST_08), hereafter referred to as LST. Geographic reprojection of individual scenes and the mosaicking of images in each orbit track into image strips were also performed on LST data using ENVI A. Cross-level_adjust, identifies overlapping pixels between adjacent image strips and determines the linear gain and offset correction between the two adjacent strips within the overlapping pixels. This is used to modify pixel values of one image strip to correspond to the overlapping values of the other image strip. The original core strip retains almost all of its original values, while each successive strip has a gain and offset applied, and results in images that are blended to produce consistently scaled temperatures across the mosaic  misalignments in projection between images, inconsistent temperature changes due to weather, clouds or seasonal temperature inversions, and statistical error in correlation that propagates from one successive strip to the next . The decEven when acquired on the same date and time, there are still inherent differences between ASTER and MODIS LST products due to the differences in the temperature retrieval algorithm used by each as well as differences in their respective spatial resolution . HoweverField surveys were conducted at 40 sites using representative surface type classes that could be compared to validate and interpret the range of ATI values seen across the region . Sites wDifference images were used to identify discrepancies between the eLST and MODIS LST, and were generated by resampling all datasets to 1 km resolution and subtracting ASTER eLST for day and night to the respective MODIS LST (MYD11A1) dataset. For the nighttime mosaic, 95% of the temperature values lie between −1 and 10 C difference from MODIS, with no distinguishable difference in distribution between the core and the remainder of the mosaic a. For thnight ≥ Tday, where Tnight and Tday are the nighttime and daytime temperatures, respectively. Vegetation affects the ATI values as a function of cover and density, and the corresponding water content can be mapped using VNIR vegetation indices generated with the Landsat reflectivity mosaic. In previous work, the MODIS normalized difference vegetation index (NDVI) value at which the ATI values show anomalous values occurred around NDVI ≥ 0.2 [A number of surface substrate types have the potential to display ATI values that are not indicative of the true mechanical composition of the surface . ATI valVI ≥ 0.2 , therefoVI ≥ 0.2 . We find a strong relationship between surface type  across the 40 field sites investigated, with ATI values following a decreasing trend from bedrock to silt/clay . In geneFor example, we found overlap in ATI values among many of the sandy surface type classes that are the result of several conditions. First, there is a lack of variability in thermal conductivity at finer grain sizes due to the relationship between atmospheric pressure and thermal inertia ,47. TherThe range of ATI values in our sites containing coarse gravel and blocky surfaces is most likely the result of these characteristics, because the coarse gravel and blocky sites we investigated displayed high variability in sediment provenance and geomorphology. Another condition causing high variability in ATI values is heterogeneity in the spatial distribution of surface materials at the 100-m scale. This is especially noticeable for bedrock surfaces, where large contiguous areas of exposed bedrock are rare, and is complicated by cliffs and other high-angle slopes. Care was taken to choose bedrock field sites that were uniform and horizontal, but contiguous exposed bedrock greater than 100 m in size were rare. At the other end of the ATI scale, the grain sizes most likely produced from a single geologic process  are the most likely to have a homogenous distribution at the multiple-pixel scale.With the extensive spatial and temporal ASTER dataset collected over the past two decades, mosaics of nighttime and daytime LST can be produced to model thermophysical properties over large regions that span many orbit tracks. Our data-fusion technique complements a number of different methods that have been used recently to generate mosaics with ASTER ,32,48 asThe ATI dataset described here represents a modeled value that integrates incident solar radiation, surface reflection and near-surface conduction into a mappable class value. While the high spatial resolution (100 m/pixel) used in this research is appropriate for geomorphology and ecological modeling efforts, it is not high enough to characterize heterogeneous surface textures and thermophysical characteristics at the subpixel level. That is, each value may represent a mixture of materials, and additional insight is required for appropriate interpretation. Values for ATI are interpreted for the Mojave, and are based on a coarse-component of surface materials. The resulting scale can differentiate between unconsolidated fine-grained sediments, blocky and bedrock surfaces, but not between classes of fine grain sizes. Close inspection of the ATI image shows structure across all surface types in the Mojave, suggesting that these methods may be sensitive to surface characteristics that must first be validated by field-based mapping methods. Laboratory or sandbox tests of materials with different mechanical compositions would likely be able to further constrain the applicability of ATI mapping on natural surfaces.


Transcranial direct current stimulation (tDCS) is a non-invasive neural modulation technique to remediate many neural deficits. tDCS involves the application of a direct current (1–2 mA) which modulates the resting membrane potential of cortical neurons  determine larger effects , and the head is segmented into different compartments representing brain tissues  in reading ability  may also influence the combination treatment outcome (Elmasry et al., Adopting behavioral remediation or instructional treatment for reading difficulties have been documented as being able to improve brain activations (Temple et al., Evidence has shown EEG + tDCS, fMRI+ tDCS, or fNIRS + tDCS can be used to monitor tDCS-induced changes of the neural activities involved in sustained attention (Miller et al., Currently, the field of tDCS-based reading interventions is still at its infancy and the related literature is relatively sparse compared to other tDCS-based research. It is therefore too early to conclude that tDCS is generally effective in this field, and we should have an objective assessment of the limitations of this technique and of the conditions in which there is limited or even negative effect. In this opinion article, we have put forth some recommendations that merit more attention in future tDCS-based reading interventions. Further evidence from larger-scale RCTs is especially required for those dyslexic individuals so as to define reproducible stimulation parameters for certain groups of samples. Based on empirical evidence and safe ethical grounds (Kekic et al., YZ wrote the article. XZ revised each draft of the article. YZ, XZ, and HS helped to conceive the opinion. YC, LZ, XX and XZ contributed to data collection.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.


As the proportion of older adults in the world’s total population continues to grow, the adverse health outcomes of age-related hearing loss are becoming increasingly recognized. While research has shown that age-related hearing loss is the single greatest modifiable risk factor for dementia, use of hearing aids remains low worldwide, even in many middle- and high-income countries. Reasons for poor uptake of hearing aids are likely to involve a combination of factors, ranging from increasing costs of hearing aid technology to a widespread lack of insurance coverage. This article aims to identify the current state of access to hearing aids, focusing on eight middle- and high-income countries. We discuss how to facilitate greater access to hearing aids for patients by addressing changes in how devices are regulated, technological advancements in hearing devices, the need to adjust reimbursement schemes and the importance of adaptation among the community workforce for hearing-care. Since the 1990s, worldwide efforts to screen for hearing loss in early childhood, followed by appropriate paediatric hearing interventions, have followed from evidence that hearing loss markedly impacts a child’s intellectual, social, and emotional development.,,,This focus on a life-course approach to hearing loss is timely given the projected global increase in the number and relative proportion of older adults over the next 30 years.–,–,Research over the past decade has now demonstrated the broad impact that age-related hearing loss has on the functioning of older adults and future health outcomes.In this article we explore the financing and delivery systems for hearing aids for adults in several countries that are currently facing the challenges of an ageing society. We discuss areas where innovative policies and strategies could be employed to increase access to hearing aids.We gathered data for this article through a wide search of the grey literature from August 2018 to April 2019, which included white papers, government reports, government websites, industry reports and regulatory association guidelines. The search was limited to English language sources. We used personal correspondence with academic and industry experts to address gaps in publicly available data.We focus on eight middle- and high-income countries . We chose these countries to demonstrate variations across five factors that affect how hearing aids and related services are delivered: (i) availability of insurance coverage; (ii) training and scope of practice of hearing-care providers; (iii) pathways for obtaining hearing aids; (iv) where patients obtain their devices; and (v) how sales of hearing aids are regulated .The costs associated with purchase of a hearing aid may be covered by public insurance, private insurance or out-of-pocket payments by the patient at the point of purchase (or combinations of these).,,,,,–Public insurance for hearing aid purchases and services varies widely across countries by the population covered, device options and generosity of benefits. In the United Kingdom, all patients have access to public coverage of the costs of hearing aids whereas Australia and the United States restrict social insurance coverage of hearing aids to older adults who meet qualifying criteria, such as low income.,–Private insurance and out-of-pocket payments are the main means of financial access to hearing aids for a high proportion of patients worldwide .,,,,–,,–The two major categories of hearing aid providers, according to the scope of care required, are audiologists and hearing aid dispensers , with contributions from various other professionals .,,,,,The purchasing pathway refers to the steps through which a patient requiring a hearing aid must proceed, starting from the identification of a deficit in hearing to the point they acquire a hearing aid. In most countries providing public insurance, patients must receive a diagnostic hearing test and consult an audiologist, a general physician or an ear, nose and throat specialist before being eligible to purchase a hearing aid .Other countries are less stringent on the requirement of visiting a hearing-care professional before purchasing hearing aids. In the Netherlands, patients can proceed directly to a hearing-aid dispenser for a hearing assessment and purchase of devices . In Australia, Germany and the United Kingdom, patients who are not receiving public insurance coverage can directly purchase hearing aids from hearing-aid dispensers . China also allows patients who visit hearing-aid shops or clinics outside of hospitals to purchase their devices directly . In Japan, where insurance is non-existent, patients are free to purchase hearing aids at their own discretion .,,One pathway to purchasing devices is at the hospital or office of the hearing-care provider where patients undergo their medical consultations and diagnostic testing. However, patients are increasingly using conveniently located and diversified retail clinics, which range from small private vendors to large chain stores .,In the eight countries examined, hearing aids are classified as medical devices within regulatory bodies that dictate strict criteria that must be met before sale in the market. Current regulations around the sale of hearing aids can limit access for some patients due to the requirement for medical clearance by a designated health professional before purchase. However, it is important to note that while hearing aids are regulated, devices classified as personal sound amplification products are generally not .28,34Box 1Hearing aids are regulated by the United States Food and Drug Administration (FDA) as class I or class II medical devices. They are defined as “any wearable instrument or device designed for, offered for the purpose of, or represented as aiding persons with or compensating for, impaired hearing” (21 CFR 801.420).Personal sound amplification products are over-the-counter electronic devices that are not regulated by the FDA. The FDA has issued guidance that these devices are “intended to amplify environmental sound for non-hearing impaired users… They are not intended to compensate for hearing impairment or to address listening situations that are typically associated with and indicative of hearing loss.”While funding and delivery of hearing care vary substantially from country to country, there are several common areas where innovations could potentially lead to easier access and increased uptake of hearing aids for adults with hearing loss.Current regulations in most countries stipulate that hearing aids can only be sold or dispensed through a licensed provider to maximize the safety and efficacy of devices. For example, with older analogue hearing aids, calibrating and properly fitting a hearing aid could involve crafting a custom ear-mould to minimize audio feedback and manually adjusting trim potentiometers on the hearing aid to set appropriate levels of gain.,,Over the past 10–15 years, however, innovations have been made in digital circuitry and technologies that allow hearing aids to be self-fitted and set to appropriate levels of audio output to avoid hearing damage. Research demonstrates that such hearing aids are both safe and effective for adults with mild-to-moderate hearing loss, but regulatory models in most countries preclude such devices from being sold directly to patients.,,Recent initiatives in the United States from the National Academies of Science, Engineering and Medicine and the White House President’s Council of Advisors on Science and Technology, suggest a new regulatory model to allow for greater access to hearing aids.,A crucial building block for the feasibility of over-the-counter sales regulations in any country is reliable technology. Advances in digital amplification technologies over the past few decades have led to the emergence of products that could meet the needs of a direct-to-consumer amplification device. In the United States, this resulted in a class of unregulated amplification devices called personal sound amplification products, some of which have similar traits as traditional hearing aids .28,43 ThMany of these devices include now-standard digital hearing aid technologies such as noise-reduction algorithms, directionality and linked remote microphones to tackle hearing in difficult situations. Some key innovations too are empowering individuals with hearing loss to benefit better from amplification products. Feedback suppression and advances in durable plastics allow for non-custom ear tips. Additionally, integration with smartphone applications allows for self-adjustment of hearing aids by the user, with the phone delivering a hearing test and the device performing in situ customization to prescriptive targets. Moreover, changes in battery technology allow for rechargeable units that are easier to manipulate.,,,,While previous research revealed that low-cost, inappropriate technology produces poor electroacoustic results, recent studies have demonstrated that some direct-to-consumer devices are technologically similar to traditional hearing aids.For many health systems, the availability of over-the-counter or direct-to-consumer hearing aids has the potential to disrupt the delivery model for hearing aids and hearing services. Systems that pay for hearing-care services independently of devices may be able to adapt more readily than systems (such as in the United States) that operate on a predominantly bundled reimbursement model where the reimbursement of hearing-care services is routinely coupled with the cost of the device. As these systems evolve with the changing distribution landscape, two important factors require consideration.First, ensuring that patients can continue to access hearing-care services independent of the hearing technology used is of importance. Hearing-care services, provided by audiologists or other hearing-care providers, are a fundamental component to successful hearing aid use. These tasks include orienting individuals to the device, providing fitting and customization specific to the patient’s hearing needs, and providing supportive communication strategies and techniques.A second important factor is the reimbursement of new hearing-aid devices in an expanded marketplace. Ensuring that the availability of over-the-counter hearing aids does not lead to the elimination of insurance coverage is important. Given that the most common pathway to purchase hearing aids is through hearing-care providers, policy-makers must consider how to adapt to a wider array of products available for over-the-counter purchase. The extent of change required depends greatly on how the system of reimbursement currently operates. For example, in the United Kingdom, where publicly-funded insurance coverage is widespread and choice of devices covered by insurance is limited, adapting to an expanded hearing aid marketplace will require substantial change.,,In addition to the potential impact of a shifting hearing aid market on the ability for patients to access devices, the persistently low uptake of hearing aids worldwide indicates that the health behaviour of patients plays a major role in hearing care.,,Community-delivered hearing care broadly encompasses care delivered beyond traditional clinic-based services and incorporates task-sharing through paraprofessionals, such as community health workers, health aides or peer mentors. The community health worker model has been widely adapted for use in diverse settings in low- and middle-income countries.Oyendo Bien consists of group aural rehabilitation sessions for older adults with hearing loss who live along the United States–Mexico border, led by promotoras .,Growing efforts around the world are using community-delivered hearing care to older adults. In the United States, two programmes in low-resource settings have been developed. A country’s hearing health-care system plays an important role in how well society can address the global health priority of hearing loss. A steadily ageing global population and the generally low prevalence of hearing aid use makes it imperative that innovations in policy and practice are implemented to meet the evolving challenges that hearing loss will present in the near future. The wide spectrum of delivery models, hearing-care providers and reimbursement models that we have highlighted in this article provides an overview of the current state of hearing health care across higher-income countries and the possibilities for advancement. Innovations in hearing aid regulation, technology, reimbursement schemes and workforce models provide tangible actions for WHO Member States to consider in addressing the growing global burden of hearing loss and making hearing health a political priority.


The term “metabolism” describes the thermodynamic underpinnings of living systems that have been investigated by scientists for centuries . The stuBecause viruses construct viral progeny from stolen biomolecules , the primary tier of research into the virus-host-metabolism relationship has focused on metabolic pathways that provide these needed materials. Two excellent reviews that highlight this tier of the virus-metabolism interface were published a few years ago , 3. But Listeria monocytogenes, and also analogous proxies to these infections, poly(I:C)  and lipopolysaccharide . Overall, the study demonstrated opposing outcomes of fasting and feeding during the two infections. Specifically, higher glucose metabolism (feeding) was protective during viral infection but lethal during bacterial inflammation, whereas ketogenic metabolism (fasting) was protective during bacterial infection but detrimental during viral inflammation. The proposed model for this phenomenon suggests that viral inflammation and bacterial inflammation are qualitatively unique in terms of the glucose utilization patterns they induce and the ensuing inflammatory response. However, it remains unknown whether this simple model will hold for all viral and bacterial infections, because every infectious agent (and infectious proxies such as LPS and Poly(I:C)) can induce unique cellular/organismal responses. In this context, it is important to remember that studies about the effects of bacterial infection on mammalian cell metabolism may be confounded by the fact that bacteria are cellular and, unlike viruses, encode a metabolic network, and are confined by their own metabolic constraints. Therefore, it may be hard to disentangle just whose metabolism is being altered under experimental conditions, making the study of metabolism during viral infection easier to interpret. Indeed, immune activation with LPS has recently been shown to induce an energy preservation program in mice, where thermoregulation in turn modulates metabolic activity, generating a tolerance to inflammation [An ambitious study recently explored whether the old folk wisdom of “starving a fever and feeding a cold” has any biological validity . In thisammation . This enThese important studies provide a foundation for further exploration into the effects of feeding and fasting metabolism and the effect of immune-controlled thermoregulation on metabolism during other important viral and bacterial infections, which could have a powerful impact on the clinical treatment of various infectious diseases.+ T cells, which adopt a range of cellular states from naïve to effector T cells, are differentially susceptible to HIV-1 infection based on their levels of metabolic activity. Specifically, CD4+ cells exhibit a hierarchy of metabolic profiles of differing activity levels of glycolysis and oxidative phosphorylation (OXPHOS). This metabolic spectrum matches the cells’ susceptibility to HIV-1 infection, in which cells undergoing the highest levels of glycolysis and OXPHOS are the most susceptible, and those with the lowest are the least susceptible. This is a significant finding that not only defined the connection between levels of bioenergetic activity and susceptibility to viral infection for the first time but also demonstrated that inhibiting glucose metabolism blocks HIV-1 replication in infected cells and promotes the elimination of virus by enhancing cell death of infected cells. Thus, the traditional paradigm of viewing host cell susceptibility to viral infection in terms of the availability of specific protein/carbohydrate receptors can now be expanded to also include the underlying metabolic behavior of target cells as another host determinant of virus tropism. Future studies are needed to examine the variable susceptibility of other metabolically plastic cells to viruses and to determine whether this metabolic Achilles heel might be manipulated pharmacologically or through diet to prevent or eliminate infection.Viruses are obligate intracellular pathogens that are highly adapted to productively infect certain cell types . Therefore, uncovering the host factors necessary for cell susceptibility is crucial for developing strategies to prevent viral infection. Investigating viral tropism for viruses that infect cells of the immune system is particularly challenging, because immune cells are highly plastic and able to differentiate temporally into a range of resting and active morphologies. Additionally, immune cells are further plastic in regard to their metabolic activity, as they adjust their metabolism to facilitate differentiation and effector function. Indeed, this phenomenon is the focus of a whole field of immunology dubbed “immunometabolism” , 7. Rece−/− and Irg1−/− neurons, which are more susceptible to viral infection than wild-type cells. Importantly, the authors did not see changes in the expression of interferon-stimulated genes in the sensitive Ripk3−/− ZIKV-infected cells or in mice, demonstrating that the antiviral response caused by itaconate was not due to an interferon response. Even more strikingly, exogenous itaconate injected intracranially in ZIKV-infected mice reduced brain viral burden, which has important implications for potential treatment of CNS infection. This study suggests that small molecule metabolites may have been repurposed during evolution in different cell types, depending on the unique vulnerabilities and roles of the cells. This is particularly significant for viruses like ZIKV, which can infect a range of cell types in different species, and can cause differential metabolic rewiring in human versus mosquito cells [In addition to generating a cellular landscape that promotes viral infection, cellular metabolism can also be modulated to create an antiviral state. There is much evidence connecting cellular metabolism and the antiviral interferon response . Howeverto cells . HoweverThe traditional way of envisioning metabolism is as a team of enzymes working in a linear pathway, in which each enzyme modifies a substrate and passes it on down the line for some specific metabolic goal. However, there is a growing appreciation for nonmetabolic roles of metabolic enzymes during infection, which can have major consequences to the life or death of the cell and to the immune response. It has been known that hexokinase (HK), the first enzyme in glycolysis, is predominantly physically associated with the outer surface of the mitochondrion. During HIV-1 infection of macrophages, this mitochondrial association is enhanced, and viral infection was observed to cause increased levels of mitochondria-bound HK . HoweverIt is now well established that viruses can drastically alter the metabolic behavior of the cells they infect, often promoting a cellular milieu that supports viral replication, and sometimes activating an antiviral state. When considering the larger process of viral pathogenesis, it is important to consider that all organisms, including those commonly used in research, have evolved specific metabolic programs that are tissue and species specific  and that


The human intestinal tract  is inhabited by over 100 trillion microorganisms; including over 1000 species of known bacteria. These organisms have co-evolved with humans over millennia to live together for mutual benefit. Though long overlooked in considerations of human health and disease treatment, gut microorganisms are highly involved in numerous metabolic reactions which influence normal host physiology. A variety of biologic, medical, and lifestyle factors appear to contribute to gut dysbiosis in late-life, and interventions specifically designed to target these factors may be useful in restoring microbial balance. Evidence from both clinical and preclinical studies suggests that gut dysbiosis is related to age-related inflammation as well as age-related conditions including frailty, Alzheimer’s disease, and perhaps even longevity. Crosstalk between the gut and multiple organ systems  may lead to the development of age-related diseases and loss of physiological function, although the signals are not well understood. In this symposium we address the broad topic of the Gut Microbiome and Aging by presenting evidence from multiple model systems  and provide a forum to discuss critical areas of research for moving forward.