Sensitive and critical periods during neurotypical and aberrant neurodevelopment: A framework for neurodevelopmental disorders

Contributions of dysfunctional plasticity mechanisms to the development of atypical perceptual processing

Experimental studies of sensory plasticity during development in birds and mammals have highlighted the importance of sensory experiences for the construction and refinement of functional neural circuits. We discuss how dysregulation of experience-dependent brain plasticity can lead to abnormal perceptual representations that may contribute to heterogeneous deficits symptomatic of several neurodevelopmental disorders. We focus on alterations of somatosensory processing and the dynamic reorganization of cortical synaptic networks that occurs during early perceptual development. We also discuss the idea that the heterogeneity of strengths and weaknesses observed in children with neurodevelopmental disorders may be a direct consequence of altered plasticity mechanisms during early development. Treating the heterogeneity of perceptual developmental trajectories as a phenomenon worthy of study rather than as an experimental confound that should be overcome may be key to developing interventions that better account for the complex developmental trajectories experienced by modern humans.

Novel pharmacological targets for GABAergic dysfunction in ADHD

Attention deficit/hyperactivity disorder (ADHD) is a neurodevelopment disorder that affects approximately 5% of the population. The disorder is characterized by impulsivity, hyperactivity, and deficits in attention and cognition, although symptoms vary across patients due to the heterogenous and polygenic nature of the disorder. Stimulant medications are the standard of care treatment for ADHD patients, and their effectiveness has led to the dopaminergic hypothesis of ADHD in which deficits in dopaminergic signaling, especially in cortical brain regions, mechanistically underly ADHD pathophysiology. Despite their effectiveness in many individuals, almost one-third of patients do not respond to stimulant treatments and the long-term negative side effects of these medications remain unclear. Emerging clinical evidence is beginning to highlight an important role of dysregulated excitatory/inhibitory (E/I) balance in ADHD. These deficits in E/I balance are related to functional abnormalities in glutamate and Gamma-Aminobutyric Acid (GABA) signaling in the brain, with increasing emphasis placed on GABAergic interneurons driving specific aspects of ADHD pathophysiology. Recent genome-wide association studies (GWAS) have also highlighted how genes associated with GABA function are mutated in human populations with ADHD, resulting in the generation of several new genetic mouse models of ADHD. This review will discuss how GABAergic dysfunction underlies ADHD pathophysiology, and how specific receptors/proteins related to GABAergic interneuron dysfunction may be pharmacologically targeted to treat ADHD in subpopulations with specific comorbidities and symptom domains. This article is part of the Special Issue on "PFC circuit function in psychiatric disease and relevant models".

Characterizing ambulatory function in children with PPP2R5D-related neurodevelopmental disorder

BACKGROUND

Individuals with PPP2R5D-related neurodevelopmental disorder have an atypical gait pattern characterized by ataxia and incoordination. Structured, quantitative assessments are needed to further understand the impact of these impairments on function.

RESEARCH QUESTION

How do gait parameters and ambulatory function of individuals with PPP2R5D-related neurodevelopmental disorder compare to age and sex matched healthy norms?

METHODS

Twenty-six individuals with PPP2R5D pathogenic genetic variants participated in this observational, single visit study. Participants completed at least one of the following gait assessments: quantitative gait analysis at three different speeds (preferred pace walking (PPW), fast paced walking (FPW) and running, six-minute walk test (6MWT), 10-meter walk run (10MWR), and timed up and go (TUG). Descriptive statistics were used to summarize gait variables. Percent of predicted values were calculated using published norms. Paired t-tests and regression analyses were used to compare gait variables.

RESULTS

The median age of the participants was 8 years (range 4-27) and eighteen (69.2 %) were female. Individuals with PPP2R5D-related neurodevelopmental disorder walked slower and with a wider base of support than predicted for their age and sex. Stride velocity ranged from 48.9 % to 70.1 % and stride distance from 58.5 % to 81.9 % of predicted during PPW. Percent of predicted distance walked on the 6MWT ranged from 30.6 % to 71.1 % representing varied walking impairment. Increases in stride distance, not cadence, were associated with changes in stride velocity in FPW (R2 = 0.675, p =< 0.001) and running conditions (R2 = 0.918, p =< 0.001).

SIGNIFICANCE

We quantitatively assessed the abnormal gait in individuals with PPP2R5D-related neurodevelopmental disorder. These impairments may affect ability to adapt to environmental changes and participation in daily life. Rehabilitative interventions targeting gait speed and balance may improve function and safety for individuals with PPP2R5D-related neurodevelopmental disorder.

Childhood adversities characterize the heterogeneity in the brain pattern of individuals during neurodevelopment

BACKGROUND

Several factors shape the neurodevelopmental trajectory. A key area of focus in neurodevelopmental research is to estimate the factors that have maximal influence on the brain and can tip the balance from typical to atypical development.

METHODS

Utilizing a dissimilarity maximization algorithm on the dynamic mode decomposition (DMD) of the resting state functional MRI data, we classified subjects from the cVEDA neurodevelopmental cohort (n = 987, aged 6-23 years) into homogeneously patterned DMD (representing typical development in 809 subjects) and heterogeneously patterned DMD (indicative of atypical development in 178 subjects).

RESULTS

Significant DMD differences were primarily identified in the default mode network (DMN) regions across these groups (p < 0.05, Bonferroni corrected). While the groups were comparable in cognitive performance, the atypical group had more frequent exposure to adversities and faced higher abuses (p < 0.05, Bonferroni corrected). Upon evaluating brain-behavior correlations, we found that correlation patterns between adversity and DMN dynamic modes exhibited age-dependent variations for atypical subjects, hinting at differential utilization of the DMN due to chronic adversities.

CONCLUSION

Adversities (particularly abuse) maximally influence the DMN during neurodevelopment and lead to the failure in the development of a coherent DMN system. While DMN's integrity is preserved in typical development, the age-dependent variability in atypically developing individuals is contrasting. The flexibility of DMN might be a compensatory mechanism to protect an individual in an abusive environment. However, such adaptability might deprive the neural system of the faculties of normal functioning and may incur long-term effects on the psyche.

Altered brain serotonin 5-HT1A receptor expression and function in juvenile Fmr1 knockout mice

There are no approved pharmacotherapies for fragile X syndrome (FXS), a rare neurodevelopmental disorder caused by a mutation in the FMR1 promoter region that leads to various symptoms, including intellectual disability and auditory hypersensitivity. The gene that encodes inhibitory serotonin 1A receptors (5-HT1ARs) is differentially expressed in embryonic brain tissue from individuals with FXS, and 5-HT1ARs are highly expressed in neural systems that are disordered in FXS, providing a rationale to focus on 5-HT1ARs as targets to treat symptoms of FXS. We examined agonist-labeled 5-HT1AR densities in male and female Fmr1 knockout mice and found no differences in whole-brain 5-HT1AR expression in adult control compared to Fmr1 knockout mice. However, juvenile Fmr1 knockout mice had lower whole-brain 5-HT1AR expression than age-matched controls. Consistent with these results, juvenile Fmr1 knockout mice showed reduced behavioral responses elicited by the 5-HT1AR agonist (R)-8-OH-DPAT, effects blocked by the selective 5-HT1AR antagonist, WAY-100635. Also, treatment with the selective 5-HT1AR agonist, NLX-112, dose-dependently prevented audiogenic seizures (AGS) in juvenile Fmr1 knockout mice, an effect reversed by WAY-100635. Suggestive of a potential role for 5-HT1ARs in regulating AGS, compared to males, female Fmr1 knockout mice had a lower prevalence of AGS and higher expression of antagonist-labeled 5-HT1ARs in the inferior colliculus and auditory cortex. These results provide preclinical support that 5-HT1AR agonists may be therapeutic for young individuals with FXS hypersensitive to auditory stimuli.

Association between prenatal exposure to rare earth elements and the neurodevelopment of children at 24-months of age: A prospective cohort study

The increasing consumption of rare earth elements (REEs) has resulted in a considerable risk of environmental exposure. However, the adverse effects of prenatal REEs exposure on children's neurodevelopment are not yet fully recognized. Therefore, we investigated the individual and joint effects of prenatal exposure to 13 REEs on children's neurocognitive development based on 809 mother-child pairs from a large birth cohort in Wuhan, China. Maternal urinary concentrations of 13 REEs were repeatedly measured by inductively coupled plasma mass spectrometry. Children's neurodevelopment [e.g., mental and psychomotor development index (MDI/PDI)] at 24-months was assessed using Bayley Scales of Infant Development of Chinese Revision. GEE and BKMR models were applied to estimate the individual and joint effects of prenatal REE exposure on child neurodevelopment level. After controlling for typical confounders, we observed that exposure to 9 REEs during the first trimester were significantly associated with decreased MDI scores [βs and 95% confidence intervals (CIs) ranging from -2.24 (-3.86 ∼ -0.63) to -1.44 (-2.26∼ -0.26)], and 7 REEs during third trimester were significantly associated decreased PDI scores [β and 95% CIs ranging from -1.95 (-3.19 ∼ -0.71) to -1.25 (-2.34 ∼ -0.16)]. Higher quantiles of REE mixture in first and third trimester were associated with decreased MDI and PDI score. Thulium, erbium in the first trimester and cerium, lanthanum in the third trimester accounted most importance to joint effects on MDI and PDI, respectively. In conclusion, prenatal exposure to higher concentrations of REEs during the first and third trimester were negative associated with children's neurodevelopment.

Interdisciplinary fetal-neonatal neurology training applies neural exposome perspectives to neurology principles and practice

An interdisciplinary fetal-neonatal neurology (FNN) program over the first 1,000 days teaches perspectives of the neural exposome that are applicable across the life span. This curriculum strengthens neonatal neurocritical care, pediatric, and adult neurology training objectives. Teaching at maternal-pediatric hospital centers optimally merges reproductive, pregnancy, and pediatric approaches to healthcare. Phenotype-genotype expressions of health or disease pathways represent a dynamic neural exposome over developmental time. The science of uncertainty applied to FNN training re-enforces the importance of shared clinical decisions that minimize bias and reduce cognitive errors. Trainees select mentoring committee participants that will maximize their learning experiences. Standardized questions and oral presentations monitor educational progress. Master or doctoral defense preparation and competitive research funding can be goals for specific individuals. FNN principles applied to practice offer an understanding of gene-environment interactions that recognizes the effects of reproductive health on the maternal-placental-fetal triad, neonate, child, and adult. Pre-conception and prenatal adversities potentially diminish life-course brain health. Endogenous and exogenous toxic stressor interplay (TSI) alters the neural exposome through maladaptive developmental neuroplasticity. Developmental disorders and epilepsy are primarily expressed during the first 1,000 days. Communicable and noncommunicable illnesses continue to interact with the neural exposome to express diverse neurologic disorders across the lifespan, particularly during the critical/sensitive time periods of adolescence and reproductive senescence. Anomalous or destructive fetal neuropathologic lesions change clinical expressions across this developmental-aging continuum. An integrated understanding of reproductive, pregnancy, placental, neonatal, childhood, and adult exposome effects offers a life-course perspective of the neural exposome. Exosome research promises improved disease monitoring and drug delivery starting during pregnancy. Developmental origins of health and disease principles applied to FNN practice anticipate neurologic diagnoses with interventions that can benefit successive generations. Addressing health care disparities in the Global South and high-income country medical deserts require constructive dialogue among stakeholders to achieve medical equity. Population health policies require a brain capital strategy that reduces the global burden of neurologic diseases by applying FNN principles and practice. This integrative neurologic care approach will prolong survival with an improved quality of life for persons across the lifespan confronted with neurological disorders.

Anaesthesia-induced Changes in Genomic Expression Leading to Neurodegeneration

General anaesthetics (GA) have been in continuous clinical use for more than 170 years, with millions of young and elderly populations exposed to GA to relieve perioperative discomfort and carry out invasive examinations. Preclinical studies have shown that neonatal rodents with acute and chronic exposure to GA suffer from memory and learning deficits, likely due to an imbalance between excitatory and inhibitory neurotransmitters, which has been linked to neurodevelopmental disorders. However, the mechanisms behind anaesthesia-induced alterations in late postnatal mice have yet to be established. In this narrative review, we present the current state of knowledge on early life anaesthesia exposure-mediated alterations of genetic expression, focusing on insights gathered on propofol, ketamine, and isoflurane, as well as the relationship between network effects and subsequent biochemical changes that lead to long-term neurocognitive abnormalities. Our review provides strong evidence and a clear picture of anaesthetic agents' pathological events and associated transcriptional changes, which will provide new insights for researchers to elucidate the core ideas and gain an in-depth understanding of molecular and genetic mechanisms. These findings are also helpful in generating more evidence for understanding the exacerbated neuropathology, impaired cognition, and LTP due to acute and chronic exposure to anaesthetics, which will be beneficial for the prevention and treatment of many diseases, such as Alzheimer's disease. Given the many procedures in medical practice that require continuous or multiple exposures to anaesthetics, our review will provide great insight into the possible adverse impact of these substances on the human brain and cognition.

Impact of Prenatal Acetaminophen Exposure for Hippocampal Development Disorder on Mice

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used as analgesic agents. They have been detected in various environmental matrices. The degradation of environmental contaminants and the long-term adverse effects have become a major public concern. Prenatal exposure to acetaminophen can cause damage to the developing hippocampus. However, the molecular mechanisms behind hippocampal damage following prenatal acetaminophen exposure (PAcE) remain unclear. The present study shows an increased risk of adverse neurodevelopmental outcomes in offspring following exposure to acetaminophen during pregnancy on mice. The results revealed that different doses, timings, and duration of exposure to acetaminophen during pregnancy were associated with dose-dependent changes in the hippocampus of the offspring. Furthermore, exposure to high doses, multiple-treatment courses, and late pregnancy induced pathological changes, such as wrinkling and vacuolation, inhibited hippocampal proliferation and increased apoptosis. In addition, PAcE significantly decreased the expression of genes related to synaptic development in fetal hippocampal neurons and hippocampal astrocyte and microglia were also damaged to varying degrees. The significant reduction either in SOX2, an essential gene in regulating neural progenitor cell proliferation, and reduction of genes related to the SOX2/Notch pathway may suggest that the role of SOX2/Notch pathway in impaired hippocampal development in the offspring due to PAcE. In general, PAcE at high doses, multiple-treatment courses, and mid- and late gestation were associated with neurodevelopmental toxicity to the offspring.

Neurodevelopmental Outcomes Among Offspring Exposed to Corticosteroid and B2-Adrenergic Agonists In Utero

Importance

Corticosteroids and β2-adrenergic agonists are commonly used during pregnancy to treat asthma. However, offspring neurodevelopmental outcomes following in utero exposure to these medications remain unclear.

Objective

To investigate the association between timing of in utero exposure to corticosteroids and β2-adrenergic agonists and offspring neurodevelopmental milestones during the first 3 years of life.

Design, Setting, and Participants

This cohort study obtained data from the Japan Environment and Children's Study, an ongoing birth cohort study conducted in collaboration with 15 Regional Centers across Japan. Participants were mother-offspring pairs who were recruited between January 1, 2011, and March 31, 2014. Data were analyzed between January and February 2023.

Exposure

Corticosteroids and β2-adrenergic agonists were the exposure of interest. Timing of corticosteroid and β2-adrenergic agonist exposure included early pregnancy (weeks 0-12), mid- to late pregnancy (weeks >12), and both stages of pregnancy.

Main Outcomes and Measures

Offspring neurodevelopmental milestones (communication, gross motor, fine motor, problem-solving, and personal-social skills) were assessed using the Japanese version of the Ages and Stages Questionnaires, 3rd edition, at 6, 12, 18, 24, 30, and 36 months.

Results

In total, 91 460 mother-offspring pairs were analyzed. Among mothers, the mean (SD) age at delivery was 31.20 (5.05) years. Among offspring, 46 596 (50.9%) were males and 44 864 (49.1%) were females, of whom 66.4% had a gestational age of 39 to 41 weeks. During early, mid- to late, and both stages of pregnancy, 401 (0.4%), 935 (1.0%), and 568 (0.6%) offspring, respectively, were exposed to corticosteroids, whereas 170 (0.2%), 394 (0.4%), and 184 (0.2%), respectively, were exposed to β2-adrenergic agonists. No association of corticosteroid exposure during early, mid- to late, and both stages of pregnancy with all 5 neurodevelopmental milestones was found. Similarly, no association between β2-adrenergic agonist use during early pregnancy and all 5 neurodevelopmental milestones was observed. An association was found between β2-adrenergic agonist exposure during mid- to late pregnancy and delayed personal-social skills (adjusted odds ratio, 1.48; 95% CI, 1.01-2.32; P = .045).

Conclusions and Relevance

Results of this study found no association between in utero corticosteroid and β2-adrenergic agonist exposure and offspring neurodevelopmental outcomes, regardless of the timing of exposure. Despite the limitations and low power of the study, the findings suggest that corticosteroids and β2-adrenergic agonists are safe for pregnant individuals with asthma and the neurodevelopment of their offspring.

To speak may draw on epigenetic writing and reading: Unravelling the complexity of speech and language outcomes across chromatin-related neurodevelopmental disorders

Speech and language development are complex neurodevelopmental processes that are incompletely understood, yet current evidence suggests that speech and language disorders are prominent in those with disorders of chromatin regulation. This review aimed to unravel what is known about speech and language outcomes for individuals with chromatin-related neurodevelopmental disorders. A systematic literature search following PRISMA guidelines was conducted on 70 chromatin genes, to identify reports of speech/language outcomes across studies, including clinical reports, formal subjective measures, and standardised/objective measures. 3932 studies were identified and screened and 112 were systematically reviewed. Communication impairment was core across chromatin disorders, and specifically, chromatin writers and readers appear to play an important role in motor speech development. Identification of these relationships is important because chromatin disorders show promise as therapeutic targets due to the capacity for epigenetic modification. Further research is required using standardised and formal assessments to understand the nuanced speech/language profiles associated with variants in each gene, and the influence of chromatin dysregulation on the neurobiology of speech and language development.

Developmental delays in cortical auditory temporal processing in a mouse model of Fragile X syndrome

BACKGROUND

Autism spectrum disorders (ASD) encompass a wide array of debilitating symptoms, including sensory dysfunction and delayed language development. Auditory temporal processing is crucial for speech perception and language development. Abnormal development of temporal processing may account for the language impairments associated with ASD. Very little is known about the development of temporal processing in any animal model of ASD.

METHODS

In the current study, we quantify auditory temporal processing throughout development in the Fmr1 knock-out (KO) mouse model of Fragile X Syndrome (FXS), a leading genetic cause of intellectual disability and ASD-associated behaviors. Using epidural electrodes in awake and freely moving wildtype (WT) and KO mice, we recorded auditory event related potentials (ERP) and auditory temporal processing with a gap-in-noise auditory steady state response (gap-ASSR) paradigm. Mice were recorded at three different ages in a cross sectional design: postnatal (p)21, p30 and p60. Recordings were obtained from both auditory and frontal cortices. The gap-ASSR requires underlying neural generators to synchronize responses to gaps of different widths embedded in noise, providing an objective measure of temporal processing across genotypes and age groups.

RESULTS

We present evidence that the frontal, but not auditory, cortex shows significant temporal processing deficits at p21 and p30, with poor ability to phase lock to rapid gaps in noise. Temporal processing was similar in both genotypes in adult mice. ERP amplitudes were larger in Fmr1 KO mice in both auditory and frontal cortex, consistent with ERP data in humans with FXS.

CONCLUSIONS

These data indicate cortical region-specific delays in temporal processing development in Fmr1 KO mice. Developmental delays in the ability of frontal cortex to follow rapid changes in sounds may shape language delays in FXS, and more broadly in ASD.

Delaying the GABA Shift Indirectly Affects Membrane Properties in the Developing Hippocampus

During the first two postnatal weeks, intraneuronal chloride concentrations in rodents gradually decrease, causing a shift from depolarizing to hyperpolarizing GABA responses. The postnatal GABA shift is delayed in rodent models for neurodevelopmental disorders and in human patients, but the impact of a delayed GABA shift on the developing brain remains obscure. Here we examine the direct and indirect consequences of a delayed postnatal GABA shift on network development in organotypic hippocampal cultures made from 6- to 7-d-old mice by treating the cultures for 1 week with VU0463271, a specific inhibitor of the chloride exporter KCC2. We verified that VU treatment delayed the GABA shift and kept GABA signaling depolarizing until DIV9. We found that the structural and functional development of excitatory and inhibitory synapses at DIV9 was not affected after VU treatment. In line with previous studies, we observed that GABA signaling was already inhibitory in control and VU-treated postnatal slices. Surprisingly, 14 d after the VU treatment had ended (DIV21), we observed an increased frequency of spontaneous inhibitory postsynaptic currents in CA1 pyramidal cells, while excitatory currents were not changed. Synapse numbers and release probability were unaffected. We found that dendrite-targeting interneurons in the stratum radiatum had an elevated resting membrane potential, while pyramidal cells were less excitable compared with control slices. Our results show that depolarizing GABA signaling does not promote synapse formation after P7, and suggest that postnatal intracellular chloride levels indirectly affect membrane properties in a cell-specific manner.SIGNIFICANCE STATEMENT During brain development, the action of neurotransmitter GABA shifts from depolarizing to hyperpolarizing. This shift is a thought to play a critical role in synapse formation. A delayed shift is common in rodent models for neurodevelopmental disorders and in human patients, but its consequences for synaptic development remain obscure. Here, we delayed the GABA shift by 1 week in organotypic hippocampal cultures and carefully examined the consequences for circuit development. We find that delaying the shift has no direct effects on synaptic development, but instead leads to indirect, cell type-specific changes in membrane properties. Our data call for careful assessment of alterations in cellular excitability in neurodevelopmental disorders.

Expert consensus on neurodevelopmental outcomes in pregnancy pharmacovigilance studies

Background: Exposure in utero to certain medications can disrupt processes of fetal development, including brain development, leading to a continuum of neurodevelopmental difficulties. Recognizing the deficiency of neurodevelopmental investigations within pregnancy pharmacovigilance, an international Neurodevelopmental Expert Working Group was convened to achieve consensus regarding the core neurodevelopmental outcomes, optimization of methodological approaches and barriers to conducting pregnancy pharmacovigilance studies with neurodevelopmental outcomes. Methods: A modified Delphi study was undertaken based on stakeholder and expert input. Stakeholders (patient, pharmaceutical, academic and regulatory) were invited to define topics, pertaining to neurodevelopmental investigations in medication-exposed pregnancies. Experts were identified for their experience regarding neurodevelopmental outcomes following medicinal, substances of misuse or environmental exposures in utero. Two questionnaire rounds and a virtual discussion meeting were used to explore expert opinion on the topics identified by the stakeholders. Results: Twenty-five experts, from 13 countries and professionally diverse backgrounds took part in the development of 11 recommendations. The recommendations focus on the importance of neurodevelopment as a core feature of pregnancy pharmacovigilance, the timing of study initiation and a core set of distinct but interrelated neurodevelopmental skills or diagnoses which require investigation. Studies should start in infancy with an extended period of investigation into adolescence, with more frequent sampling during rapid periods of development. Additionally, recommendations are made regarding optimal approach to neurodevelopmental outcome measurement, comparator groups, exposure factors, a core set of confounding and mediating variables, attrition, reporting of results and the required improvements in funding for potential later emerging effects. Different study designs will be required depending on the specific neurodevelopmental outcome type under investigation and whether the medicine in question is newly approved or already in widespread use. Conclusion: An improved focus on neurodevelopmental outcomes is required within pregnancy pharmacovigilance. These expert recommendations should be met across a complementary set of studies which converge to form a comprehensive set of evidence regarding neurodevelopmental outcomes in pregnancy pharmacovigilance.

Critical periods and Autism Spectrum Disorders, a role for sleep

Brain development relies on both experience and genetically defined programs. Time windows where certain brain circuits are particularly receptive to external stimuli, resulting in heightened plasticity, are referred to as "critical periods". Sleep is thought to be essential for normal brain development. Importantly, studies have shown that sleep enhances critical period plasticity and promotes experience-dependent synaptic pruning in the developing mammalian brain. Therefore, normal plasticity during critical periods depends on sleep. Problems falling and staying asleep occur at a higher rate in Autism Spectrum Disorder (ASD) relative to typical development. In this review, we explore the potential link between sleep, critical period plasticity, and ASD. First, we review the importance of critical period plasticity in typical development and the role of sleep in this process. Next, we summarize the evidence linking ASD with deficits in synaptic plasticity in rodent models of high-confidence ASD gene candidates. We then show that the high-confidence rodent models of ASD that show sleep deficits also display plasticity deficits. Given how important sleep is for critical period plasticity, it is essential to understand the connections between synaptic plasticity, sleep, and brain development in ASD. However, studies investigating sleep or plasticity during critical periods in ASD mouse models are lacking. Therefore, we highlight an urgent need to consider developmental trajectory in studies of sleep and plasticity in neurodevelopmental disorders.

Early 7,8-Dihydroxyflavone Administration Ameliorates Synaptic and Behavioral Deficits in the Young FXS Animal Model by Acting on BDNF-TrkB Pathway

Fragile X syndrome (FXS) is the leading inherited form of intellectual disability and the most common cause of autism spectrum disorders. FXS patients exhibit severe syndromic features and behavioral alterations, including anxiety, hyperactivity, impulsivity, and aggression, in addition to cognitive impairment and seizures. At present, there are no effective treatments or cures for FXS. Previously, we have found the divergence of BDNF-TrkB signaling trajectories is associated with spine defects in early postnatal developmental stages of Fmr1 KO mice. Here, young fragile X mice were intraperitoneal injection with 7,8-Dihydroxyflavone (7,8-DHF), a high affinity tropomyosin receptor kinase B (TrkB) agonist. 7,8-DHF ameliorated morphological abnormities in dendritic spine and synaptic structure and rescued synaptic and hippocampus-dependent cognitive dysfunction. These observed improvements of 7,8-DHF involved decreased protein levels of BDNF, p-TrkB^Y816, p-PLCγ, and p-CaMKII in the hippocampus. In addition, 7,8-DHF intervention in primary hippocampal neurons increased p-TrkB^Y816 and activated the PLCγ1-CaMKII signaling pathway, leading to improvement of neuronal morphology. This study is the first to account for early life synaptic impairments, neuronal morphological, and cognitive delays in FXS in response to the abnormal BDNF-TrkB pathway. Present studies provide novel evidences about the effective early intervention in FXS mice at developmental stages and a strategy to produce powerful impacts on neural development, synaptic plasticity, and behaviors.

Sexual Dimorphism in the Closure of the Hippocampal Postnatal Critical Period of Synaptic Plasticity after Intrauterine Growth Restriction: Link to Oligodendrocyte and Glial Dysregulation

Intrauterine growth restriction (IUGR) resulting from hypertensive disease of pregnancy (HDP) leads to sexually dimorphic hippocampal-dependent cognitive and memory impairment in humans. In our translationally relevant mouse model of IUGR incited by HDP, we have previously shown that the synaptic development in the dorsal hippocampus including GABAergic development, NPTX2+ excitatory synaptic formation, axonal myelination, and perineural net (PNN) formation were perturbed by IUGR at adolescent equivalence in humans (P40). The persistence of these disturbances through early adulthood and the potential upstream mechanisms are currently unknown. Thus, we hypothesized that NPTX2+ expression, PNN formation, axonal myelination, all events closing synaptic development in the hippocampus, will be persistently perturbed, particularly affecting IUGR female mice through P60 given the fact that they had worse short-term recognition memory in this model. We additionally hypothesized that such sexual dimorphism is linked to persistent glial dysregulation. We induced IUGR by a micro-osmotic pump infusion of a potent vasoconstrictor U-46619, a thromboxane A2-analog, in the last week of the C57BL/6 mouse gestation to precipitate HDP. Sham-operated mice were used as controls. At P60, we assessed hippocampal and hemispheric volumes, NPTX2 expression, PNN formation, as well as myelin basic protein (MBP), Olig2, APC/CC1, and M-NF expression. We also evaluated P60 astrocytic (GFAP) reactivity and microglial (Iba1 and TMEM119) activation using immunofluorescent-immunohistochemistry and Imaris morphological analysis plus cytokine profiling using Meso Scale Discovery platform. IUGR offspring continued to have smaller hippocampal volumes at P60 not related to changes in hemisphere volume. NPTX2+ puncta counts and volumes were decreased in IUGR hippocampal CA subregions of female mice compared to sex-matched shams. Intriguingly, NPTX2+ counts and volumes were concurrently increased in the dentate gyrus (DG) subregion. PNN volumes were smaller in CA1 and CA3 of IUGR female mice along with PNN intensity in CA3 but they had larger volumes in the CA3 of IUGR male mice. The myelinated axon (MBP+) areas, volumes, and lengths were all decreased in the CA1 of IUGR female mice compared to sex-matched shams, which correlated with a decrease in Olig2 nuclear expression. No decrease in the number of APC/CC1+ mature oligodendrocytes was identified. We noted an increase in M-NF expression in the mossy fibers connecting DG to CA3 only in IUGR female mice. Reactive astrocytes denoted by GFAP areas, volumes, lengths, and numbers of branching were increased in IUGR female CA1 but not in IUGR male CA3 compared to sex-matched shams. Lastly, activated microglia were only detected in IUGR female CA1 and CA3 subregions. We detected no difference in the cytokine profile between sham and IUGR adult mice of either sex. Collectively, our data support a sexually dimorphic impaired closure of postnatal critical period of synaptic plasticity in the hippocampus of young adult IUGR mice with greater effects on females. A potential mechanism supporting such dimorphism may include oligodendrocyte dysfunction in IUGR females limiting myelination, allowing axonal overgrowth followed by a reactive glial-mediated synaptic pruning.

Effects of intrauterine growth restriction on embryonic hippocampal dentate gyrus neurogenesis and postnatal critical period of synaptic plasticity that govern learning and memory function

Intrauterine growth restriction (IUGR) complicates up to 10% of human pregnancies and is the second leading cause of perinatal morbidity and mortality after prematurity. The most common etiology of IUGR in developed countries is uteroplacental insufficiency (UPI). For survivors of IUGR pregnancies, long-term studies consistently show a fivefold increased risk for impaired cognition including learning and memory deficits. Among these, only a few human studies have highlighted sex differences with males and females having differing susceptibilities to different impairments. Moreover, it is well established from brain magnetic resonance imaging that IUGR affects both white and gray matter. The hippocampus, composed of the dentate gyrus (DG) and cornu ammonis (CA) subregions, is an important gray matter structure critical to learning and memory, and is particularly vulnerable to the chronic hypoxic-ischemic effects of UPI. Decreased hippocampal volume is a strong predictor for learning and memory deficits. Decreased neuron number and attenuated dendritic and axonal morphologies in both the DG and CA are additionally seen in animal models. What is largely unexplored is the prenatal changes that predispose an IUGR offspring to postnatal learning and memory deficits. This lack of knowledge will continue to hinder the design of future therapy to improve learning and memory. In this review, we will first present the clinical susceptibilities and human epidemiology data regarding the neurological sequelae after IUGR. We will follow with data generated using our laboratory’s mouse model of IUGR, that mimics the human IUGR phenotype, to dissect at the cellular and molecular alterations in embryonic hippocampal DG neurogenesis. We will lastly present a newer topic of postnatal neuron development, namely the critical period of synaptic plasticity that is crucial in achieving an excitatory/inhibitory balance in the developing brain. To our knowledge, these findings are the first to describe the prenatal changes that lead to an alteration in postnatal hippocampal excitatory/inhibitory imbalance, a mechanism that is now recognized to be a cause of neurocognitive/neuropsychiatric disorders in at-risk individuals. Studies are ongoing in our laboratory to elucidate additional mechanisms that underlie IUGR-induced learning and memory impairment and to design therapy aimed at ameliorating such impairment.

From circuits to behavior: Amygdala dysfunction in fragile X syndrome

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by a repeat expansion mutation in the promotor region of the FMR1 gene resulting in transcriptional silencing and loss of function of fragile X messenger ribonucleoprotein 1 protein (FMRP). FMRP has a well-defined role in the early development of the brain. Thus, loss of the FMRP has well-known consequences for normal cellular and synaptic development leading to a variety of neuropsychiatric disorders including an increased prevalence of amygdala-based disorders. Despite our detailed understanding of the pathophysiology of FXS, the precise cellular and circuit-level underpinnings of amygdala-based disorders is incompletely understood. In this review, we discuss the development of the amygdala, the role of neuromodulation in the critical period plasticity, and recent advances in our understanding of how synaptic and circuit-level changes in the basolateral amygdala contribute to the behavioral manifestations seen in FXS.

Association between screen time and developmental and behavioral problems among children in the United States: evidence from 2018 to 2020 NSCH

Excessive digital media use has become the common phenomenon among children's lifestyle, and its influences on the plausible accompanying psychological and behavioral problems are gradually investigated. This study aimed to examine the association between screen time and developmental and behavioral problems of children in the United States (US). A secondary analysis based on the data from the 2018 to 2020 National Survey of Children's Health (NSCH) was conducted. Seven types of developmental and behavioral problems and screen time on weekdays of children were collected through parents/caregivers' recall. Logistic regression models were constructed to determine the associations. Overall, 101,350 children aged between 0 and 17 years old were included in this study and 70.3% of preschoolers aged 0-5 years old and 80.2% of children and adolescents aged 6-17 years old had excessive screen time. Excessive screen time was positively associated with behavioral and conduct problem, developmental delay, speech disorder, learning disability, autism spectrum disorders (ASD), and attention deficit hyperactivity disorder (ADHD) and there were significant dose-response relationships. The association between excessive screen time and developmental and behavioral problems was stronger among preschoolers than among children and adolescents. Boys with excessive screen time showed high odds of most types of developmental and behavioral problems. It can be concluded that children with excessive screen time are at high odds of developmental and behavioral problems, especially for preschoolers and boys. Early intervention of digital media use is urgent and essential for children in the US.

NRXN1 depletion in the medial prefrontal cortex induces anxiety-like behaviors and abnormal social phenotypes along with impaired neurite outgrowth in rat

BACKGROUND

Neurodevelopmental disorders (NDDs) are a group of disorders induced by abnormal brain developmental processes. The prefrontal cortex (PFC) plays an essential role in executive function, and its role in NDDs has been reported. NDDs are associated with high-risk gene mutations and share partially overlapping genetic abnormalities.

METHODS

Neurexins (NRXNs) are related to autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). NRXN1, an essential susceptibility gene for NDDs, has been reported to be associated with NDDs. However, little is known about its key role in NDDs.

RESULTS

NRXN1 downregulation in the medial PFC induced anxiety-like behaviors and abnormal social phenotypes with impaired neurite outgrowth in Sh-NRXN1 in prefrontal neurons. Moreover, tandem mass tag (TMT)-based proteomic analysis of rat brain samples showed that NRXN1 downregulation led to significant proteome alterations, including pathways related to the extracellular matrix, cell membrane, and morphologic change. Furthermore, full-automatic immunoblotting analysis verified the differently expressed proteins related to cell morphology and membrane structure.

CONCLUSIONS

Our results confirmed the association of NRXN1 with abnormal behaviors in NDDs and provided richer insights into specific prefrontal knockdown in adolescence, potentially expanding the NRXN1 interactome and contributing to human health.

Impact of prenatal amoxicillin exposure on hippocampal development deficiency

BACKGROUND

Amoxicillin has been widely used to treat infectious diseases during pregnancy. Current studies suggest that amoxicillin exposure during pregnancy could lead to developmental disorders in the offspring and increase the incidence of long-term complications such as asthma and kidney damage in adulthood. However, the adverse effects of prenatal amoxicillin exposure (PAmE) including administration stage, doses and courses on fetal hippocampal neurodevelopment and its function in the offspring have not been elucidated. In this study, we intend to investigate the effects of PAmE on fetal hippocampal development and its possible mechanisms.

METHOD

Pregnant Kunming mice were given intragastric administration with amoxicillin at different administration stage, doses and courses, and GD (gestational day) 18 offspring hippocampus was collected for morphological and development-related functional assays, and the molecular mechanisms were explored.

RESULTS

PAmE induced hippocampal hypoplasia in the offspring with suppressed hippocampal neuronal cell proliferation and impaired neuronal synaptic plasticity comparatively; hippocampal astrocyte and microglia were damaged to varying degrees. The developmental toxicity of PAmE in fetal mices varies by time, dose, and course of treatment. The most severe damage was observed in the late gestation, high dose, and multi-course dosing groups. The significant reduction either in SOX2, an essential gene in regulating neural progenitor cell proliferation, and reduction of genes related to the Wnt/β-catenin pathway may suggest that the key role of SOX2/Wnt/β-catenin pathway in impaired hippocampal development in the offspring due to PAmE.

CONCLUSION

In this study, PAmE was found to be developmentally toxic to the hippocampus thus to induce developmental damage to various hippocampal cells; Even with current clinically safe doses, potential hippocampal damage to offspring may still present; This study provides a theoretical and experimental basis for guiding the rational usage of drugs during pregnancy and giving effectively assessment of the risk on fetal hippocampal developmental toxicity.

Mother and sibling interactions during the preweaning period influence myelination and impulse propagation of the sensory sural nerve in the adult rat

To investigate whether mother and sibling interactions during the preweaning period influence the histological and electrophysiological characteristics of the sensory sural nerve (SUn) in the adult rat, litters composed of 1, 3, 6, 9, and 12 male pups (P) were formed and the pups routinely weighed until postnatal day 60 (PND60). At PND9, 3P and 6P litters showed greater body weight than pups without siblings or from 9P or 12P litters, and such differences in weight were maintained until adulthood. Analysis of maternal licking at PND8 and 9 showed that pups from large litters received fewer licks than pups from small size litters. At PND60, SUn of rats from 6P and 9P litters had greater compound action potential (CAP) amplitude and a higher proportion of axons with large myelin thickness than nerves from rats of 1P, 3P, or 12P litters. SUn of heaviest rats from 9P and 12P litters had greater CAP area and myelination than the lightest rats from the same litters. We propose that a complex interplay of sensory, social, and nutritional factors arising from mother and littermate interactions during the preweaning period influence myelination and the propagation of action potentials in the SUn of adult rats.

Palmitoylethanolamide attenuates neurodevelopmental delay and early hippocampal damage following perinatal asphyxia in rats

Impaired gas exchange close to labor causes perinatal asphyxia (PA), a neurodevelopmental impairment factor. Palmitoylethanolamide (PEA) proved neuroprotective in experimental brain injury and neurodegeneration models. This study aimed to evaluate PEA effects on the immature-brain, i.e., early neuroprotection by PEA in an experimental PA paradigm. Newborn rats were placed in a 37°C water bath for 19 min to induce PA. PEA 10 mg/kg, s.c., was administered within the first hour of life. Neurobehavioral responses were assessed from postnatal day 1 (P1) to postnatal day 21 (P21), recording the day of appearance of several reflexes and neurological signs. Hippocampal CA1 area ultrastructure was examined using electron microscopy. Microtubule-associated protein 2 (MAP-2), phosphorylated high and medium molecular weight neurofilaments (pNF H/M), and glial fibrillary acidic protein (GFAP) were assessed using immunohistochemistry and Western blot at P21. Over the first 3 weeks of life, PA rats showed late gait, negative geotaxis and eye-opening onset, and delayed appearance of air-righting, auditory startle, sensory eyelid, forelimb placing, and grasp reflexes. On P21, the hippocampal CA1 area showed signs of neuronal degeneration and MAP-2 deficit. PEA treatment reduced PA-induced hippocampal damage and normalized the time of appearance of gait, air-righting, placing, and grasp reflexes. The outcome of this study might prove useful in designing intervention strategies to reduce early neurodevelopmental delay following PA.

Oxytocin-based therapies for treatment of Prader-Willi and Schaaf-Yang syndromes: evidence, disappointments, and future research strategies

The prosocial neuropeptide oxytocin is being developed as a potential treatment for various neuropsychiatric disorders including autism spectrum disorder (ASD). Early studies using intranasal oxytocin in patients with ASD yielded encouraging results and for some time, scientists and affected families placed high hopes on the use of intranasal oxytocin for behavioral therapy in ASD. However, a recent Phase III trial obtained negative results using intranasal oxytocin for the treatment of behavioral symptoms in children with ASD. Given the frequently observed autism-like behavioral phenotypes in Prader-Willi and Schaaf-Yang syndromes, it is unclear whether oxytocin treatment represents a viable option to treat behavioral symptoms in these diseases. Here we review the latest findings on intranasal OT treatment, Prader-Willi and Schaaf-Yang syndromes, and propose novel research strategies for tailored oxytocin-based therapies for affected individuals. Finally, we propose the critical period theory, which could explain why oxytocin-based treatment seems to be most efficient in infants, but not adolescents.

Repeated ketamine anesthesia during neurodevelopment upregulates hippocampal activity and enhances drug reward in male mice

Early exposures to anesthetics can cause long-lasting changes in excitatory/inhibitory synaptic transmission (E/I imbalance), an important mechanism for neurodevelopmental disorders. Since E/I imbalance is also involved with addiction, we further investigated possible changes in addiction-related behaviors after multiple ketamine anesthesia in late postnatal mice. Postnatal day (PND) 16 mice received multiple ketamine anesthesia (35 mg kg^-1, 5 days), and behavioral changes were evaluated at PND28 and PND56. Although mice exposed to early anesthesia displayed normal behavioral sensitization, we found significant increases in conditioned place preference to both low-dose ketamine (20 mg kg^-1) and nicotine (0.5 mg kg^-1). By performing transcriptome analysis and whole-cell recordings in the hippocampus, a brain region involved with CPP, we also discovered enhanced neuronal excitability and E/I imbalance in CA1 pyramidal neurons. Interestingly, these changes were not found in female mice. Our results suggest that repeated ketamine anesthesia during neurodevelopment may influence drug reward behavior later in life.

The association of prenatal and childhood pyrethroid pesticide exposure with school-age ADHD traits

BACKGROUND

Pyrethroid insecticides are commonly used in residential settings, and their use has increased rapidly. Although research has been scarce, they have been reported to be associated with impaired neurodevelopment. Moreover, susceptible exposure windows and the long-term effects of pyrethroids have not been investigated. We examined the association between pyrethroid exposure and attention-deficit/hyperactivity disorder (ADHD) symptoms over time, with exposure windows spanning from the prenatal period to school-age.

METHODS

Using 524 mother-child pairs, we measured urinary concentrations of 3-phenoxybenzoic acid (3-PBA), a major pyrethroid metabolite, and asked parents to fill-out the ADHD Rating Scale IV (ARS). We used Poisson regression to identify the susceptible periods of pyrethroid exposure, by correlating various 3-PBA exposure windows (prenatal, ages 2, 4, 6 and 8) with ADHD symptoms at ages 6 and 8.

RESULTS

Doubling of prenatal and age 2 3-PBA concentrations was associated with increased ADHD symptoms at age 6 (2.7% change, 95% confidence interval [CI]: 0.3, 5.2; 5.2% change [95% CI: 0.5, 10.2], respectively). The 3-PBA concentrations at age 4 and age 6 were linked with ADHD symptoms at age 8 (2.7% change [95% CI: 0.3, 5.3]; 3.3% change [95% CI: 0.2, 6.4], respectively). There were no clear sex-specific patterns in association.

DISCUSSION

Both prenatal and early-childhood exposure to 3-PBA were found to be associated with ADHD symptoms. Exposure during pregnancy, and at ages 2 to 6 were found to be susceptible periods for pyrethroid neurotoxicity at ages 6 and 8.

Osteopathic Care as (En)active Inference: A Theoretical Framework for Developing an Integrative Hypothesis in Osteopathy

Osteopathy is a person-centred healthcare discipline that emphasizes the body’s structure-function interrelationship—and its self-regulatory mechanisms—to inform a whole-person approach to health and wellbeing. This paper aims to provide a theoretical framework for developing an integrative hypothesis in osteopathy, which is based on the enactivist and active inference accounts. We propose that osteopathic care can be reconceptualised under (En)active inference as a unifying framework. Active inference suggests that action-perception cycles operate to minimize uncertainty and optimize an individual’s internal model of the lived world and, crucially, the consequences of their behaviour. We argue that (En)active inference offers an integrative framework for osteopathy, which can evince the mechanisms underlying dyadic and triadic (e.g., in paediatric care) exchanges and osteopathic care outcomes. We propose that this theoretical framework can underpin osteopathic care across the lifespan, from preterm infants to the elderly and those with persistent pain and other physical symptoms. In situations of chronicity, as an ecological niche, the patient-practitioner dyad provides the osteopath and the patient with a set of affordances, i.e., possibilities for action provided by the environment, that through shared intentionally, can promote adaptations and restoration of productive agency. Through a dyadic therapeutic relationship, as they engage with their ecological niche’s affordances—a structured set of affordances shared by agents—osteopath and patient actively construct a shared sense-making narrative and realise a shared generative model of their relation to the niche. In general, touch plays a critical role in developing a robust therapeutic alliance, mental state alignment, and biobehavioural synchrony between patient and practitioner. However, its role is particularly crucial in the fields of neonatology and paediatrics, where it becomes central in regulating allostasis and restoring homeostasis. We argue that from an active inference standpoint, the dyadic shared ecological niche underwrites a robust therapeutic alliance, which is crucial to the effectiveness of osteopathic care. Considerations and implications of this model—to clinical practice and research, both within- and outside osteopathy—are critically discussed.

Analysis of gait synchrony and balance in neurodevelopmental disorders using computer vision techniques

Gait tasks are commonly administered during motor assessments of children with neurodevelopmental disorders (NDDs). Gait analyses are often conducted in laboratory settings using costly and cumbersome experiments. In this paper, we propose a computational pipeline using computer vision techniques as an ecological and precise method to quantify gait in children with NDDs with challenging behaviors. We analyzed videos of 15 probands (PB) and 12 typically developing (TD) siblings, engaged in a preferred-pace walking task, using pose estimation software to track points of interest on their bodies over time. Analyzing the extracted information revealed that PB children had significantly less whole-body gait synchrony and poorer balance compared to their TD siblings. Our work offers a cost-effective method while preserving the validity of its results. This remote approach increases access to more diverse and distant cohorts and thus lowers barriers to research participation, further enriching our understanding of motor outcomes in NDDs.

Intrauterine Growth Restriction Disrupts the Postnatal Critical Period of Synaptic Plasticity in the Mouse Dorsal Hippocampus in a Model of Hypertensive Disease of Pregnancy

INTRODUCTION

Intrauterine growth restriction (IUGR) from hypertensive disease of pregnancy complicates up to 10% of all pregnancies. Significant hippocampal-dependent cognitive and memory impairments as well as neuropsychiatric disorders have been linked to IUGR. Because disturbance of the hippocampal critical period (CPd) of synaptic plasticity leads to impairments similar to those described in IUGR human offspring, we hypothesized that IUGR would perturb the CPd of synaptic plasticity in the mouse hippocampus in our model.

METHODS

IUGR was produced by a micro-osmotic pump infusion of the potent vasoconstrictor U-46619, a thromboxane A2-agonist, at embryonic day 12.5 in C57BL/6J mouse dams to precipitate hypertensive disease of pregnancy and IUGR. Sham-operated mice acted as controls. At P10, P18, and P40, we assessed astrogliosis using GFAP-IHC. In dorsal CA1 and CA3 subfields, we assessed the immunoreactivities (IR) (IF-IHC) to (i) parvalbumin (PV) and glutamate decarboxylase (GAD) 65/67, involved in CPd onset; (ii) PSA-NCAM that antagonizes CPd onset; (iii) NPTX2, necessary for excitatory synapse formation and engagement of CPd; and (iv) MBP and WFA, staining perineural nets (PNNs), marking CPd closure. ImageJ/Fiji and IMARIS were used for image processing and SPSS v24 for statistical analysis.

RESULTS

Although PV+ interneuron numbers and IR intensity were unchanged, development of GAD65/67+ synaptic boutons was accelerated at P18 IUGR mice and inversely correlated with decreased expression of PSA-NCAM in the CA of P18 IUGR mice at P18. NPTX2+ puncta and total volume were persistently decreased in the CA3 pyramidal and radiatum layers of IUGR mice from P18 to P40. At P40, axonal myelination (MBP+) in CA3 of IUGR mice was decreased and correlated with NPTX2 deficits. Lastly, the volume and integrity of the PNNs in the dorsal CA was disrupted in IUGR mice at P40.

DISCUSSION/CONCLUSION

IUGR disrupts the molecular and structural initiation, consolidation, and closure of the CPd of synaptic plasticity in the mouse hippocampus in our model, which may explain the learning and memory deficits observed in juvenile IUGR mice and the cognitive disorders seen in human IUGR offspring. The mechanistic links warrant further investigation, to identify therapeutic targets to prevent neurodevelopmental deficits in patients affected by IUGR.

Late-Onset Behavioral and Synaptic Consequences of L-Type Ca2+ Channel Activation in the Basolateral Amygdala of Developing Rats

Postnatal CNS development is fine-tuned to drive the functional needs of succeeding life stages; accordingly, the emergence of sensory and motor functions, behavioral patterns and cognitive abilities relies on a complex interplay of signaling pathways. Strictly regulated Ca²⁺ signaling mediated by L-type channels (LTCCs) is crucial in neural circuit development and aberrant increases in neuronal LTCC activity are linked to neurodevelopmental and psychiatric disorders. In the amygdala, a brain region that integrates signals associated with aversive and rewarding stimuli, LTCCs contribute to NMDA-independent long-term potentiation (LTP) and are required for the consolidation and extinction of fear memory. In vitro studies have elucidated distinct electrophysiological and synaptic properties characterizing the transition from immature to functionally mature basolateral subdivision of the amygdala (BLA) principal neurons. Further, acute increase of LTCC activity selectively regulates excitability and spontaneous synaptic activity in immature BLA neurons, suggesting an age-dependent regulation of BLA circuitry by LTCCs. This study aimed to elucidate whether early life alterations in LTCC activity subsequently affect synaptic strength and amygdala-dependent behaviors in early adulthood. In vivo intra-amygdala injection of an LTCC agonist at a critical period of postnatal neurodevelopment in male rat pups was used to examine synaptic plasticity of BLA excitatory inputs, expression of immediate early genes (IEGs) and glutamate receptors, as well as anxiety and social affiliation behaviors at a juvenile age. Results indicate that enhanced LTCC activity in immature BLA principal neurons trigger persistent changes in the developmental trajectory to modify membrane properties and synaptic LTP at later stages, concomitant with alterations in amygdala-related behavioral patterns.

Heterosynaptic Plasticity and the Experience-Dependent Refinement of Developing Neuronal Circuits

Neurons remodel the structure and strength of their synapses during critical periods of development in order to optimize both perception and cognition. Many of these developmental synaptic changes are thought to occur through synapse-specific homosynaptic forms of experience-dependent plasticity. However, homosynaptic plasticity can also induce or contribute to the plasticity of neighboring synapses through heterosynaptic interactions. Decades of research in vitro have uncovered many of the molecular mechanisms of heterosynaptic plasticity that mediate local compensation for homosynaptic plasticity, facilitation of further bouts of plasticity in nearby synapses, and cooperative induction of plasticity by neighboring synapses acting in concert. These discoveries greatly benefited from new tools and technologies that permitted single synapse imaging and manipulation of structure, function, and protein dynamics in living neurons. With the recent advent and application of similar tools for in vivo research, it is now feasible to explore how heterosynaptic plasticity contribute to critical periods and the development of neuronal circuits. In this review, we will first define the forms heterosynaptic plasticity can take and describe our current understanding of their molecular mechanisms. Then, we will outline how heterosynaptic plasticity may lead to meaningful refinement of neuronal responses and observations that suggest such mechanisms are indeed at work in vivo. Finally, we will use a well-studied model of cortical plasticity—ocular dominance plasticity during a critical period of visual cortex development—to highlight the molecular overlap between heterosynaptic and developmental forms of plasticity, and suggest potential avenues of future research.

The evolutionary significance of human brown adipose tissue: Integrating the timescales of adaptation

While human adaptability is regarded as a classical topic in anthropology, recent work provides new insight into metabolic adaptations to cold climates and the role of phenotypic plasticity in human evolution. A growing body of literature demonstrates that adults retain brown adipose tissue (BAT) which may play a role in non-shivering thermogenesis. In this narrative review, we apply the timescales of adaptation framework in order to explore the adaptive significance of human BAT. Human variation in BAT is shaped by multiple adaptive modes (i.e., allostasis, acclimatization, developmental adaptation, epigenetic inheritance, and genetic adaptation), and together the adaptive modes act as an integrated system. We hypothesize that plasticity in BAT facilitated the successful expansion of human populations into circumpolar regions, allowing for selection of genetic adaptations to cold climates to take place. Future research rooted in human energetics and biocultural perspectives is essential for understanding BAT's adaptive and health significance.

Association of phthalate exposure with autistic traits in children

BACKGROUND

Phthalates are synthetic chemicals with endocrine-disrupting properties. They are reportedly associated with various neurotoxic outcomes. Studies on exposure to phthalates and children's autistic traits have shown inconsistent results with respect to sex and susceptible time periods. We investigated the association of phthalate exposure during the prenatal period and childhood with autistic traits over time using a birth cohort in South Korea.

METHODS

Five phthalate metabolites were measured during mid-term pregnancy and children's follow-up at ages of 4, 6, and 8 years among a total of 547 mother-child pairs. The social communication questionnaire (SCQ) was used to assess autistic traits of children at each time point. The relationship between phthalate metabolites and SCQ scores were analyzed by exposure windows and sex.

RESULTS

A 2.7 fold increase in di-(2-ethylhexyl) phthalate metabolite levels, mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) during pregnancy was associated with increased SCQ scores at 4 years by 8.5% (95% confidence intervals [CI]: 1.9%, 15.5%) and 7.4% (95% CI: 0.3%, 15.0%), respectively, but not at the age of 6 or 8 years. Moreover, MEHHP levels at ages of 4 and 8 years were associated with increased SCQ scores at 8 years by 9.9% (95% CI: 1.8%, 18.6%) and 9.6% (95% CI: 1.3%, 18.6%), respectively. Boys showed stronger associations between phthalate exposure and SCQ scores than girls.

CONCLUSION

The study suggested different susceptible time windows of phthalate exposure: exposure during pregnancy is associated with autistic traits in young children, whereas exposure during early childhood years leads to autistic traits in school-aged children, particularly boys.

Environment in Children's Health: A New Challenge for Risk Assessment

In the last few years, many studies have focused on the effects of environmental contaminant exposure during the prenatal period or infancy as predictors of health outcomes in the future. In these time windows, due to their rapid growth, and physiologic and metabolic development, we can observe a higher vulnerability to the effects of environment, with respect to adulthood. The evidence of possible influences, partly mediated by epigenetic mechanisms, involve neurobehavioral responses and immune, endocrine, and respiratory systems, acting directly on the child or indirectly when mediated by placental transfer or breast feeding. In particular, due to a greater intake of air, food, and fluids relative to body weight, crawling behaviors and short stature, the risk of excessive exposure is greater in children. However, data on the long-term implications of early exposures are scarce. Additionally, so that physicians and institutions for child care and assistance of pregnant women can take actions to counteract the effects of chemical pollution (i.e., by educational opportunities), a risk assessment perspective that responds to the biocomplexity of the human being is needed. The present paper provides an overview of physiologic and behavioral characteristics during the perinatal period and in childhood, suggesting in a more integrated way, the need of a new risk-assessment approach to managing chronic disease in pediatric patients.

Anticipating the long-term neurodevelopmental impact of the COVID-19 pandemic on newborns and infants: A call for research and preventive policy

It is estimated that 116 million children were born worldwide in the first nine months of the COVID-19 pandemic. Given the critical importance of early life for neurodevelopment, and evidence suggesting that prenatal maternal stress and early childhood adversity negatively impact neurodevelopment, it is alarming that many pregnant women and new mothers are experiencing high levels of pandemic-related stress. Research and proactive mental health policy is needed to minimize the impact of the COVID-19 pandemic on the future mental health of a global cohort of newborns and infants.

Viral model of maternal immune activation alters placental AMPK and mTORC1 signaling in rats

INTRODUCTION

Maternal immune activation (MIA) is associated with neurodevelopmental disorders in offspring. We previously demonstrated that poly(I:C)-mediated MIA alters placental and fetal brain amino acid transporter expression in rats, which could potentially play a role in altered neurodevelopment; however, the mechanism(s) underlying these changes in amino acid transporter expression remain unknown. The objective of the current study was to investigate the mechanism(s) underlying poly(I:C)-mediated changes in the expression of the amino acid transporters in the placenta.

METHODS

Pregnant rats received poly(I:C) on gestational day 14 and placentas were collected 6 h later. Mass spectrometry-based proteomics of placentas was performed followed by pathway enrichment analysis. Activation of mTORC1 and its upstream regulator, AMPK, was investigated using immunoblotting. Finally, the role of mTORC1 and AMPK in regulating the expression and localization of the amino acid transporters EAAT2 and ASCT1 was investigated in the human choriocarcinoma cell line JAR.

RESULTS

The impact of poly(I:C) on the placental proteome was highly sexually dimorphic. While proteomics-based pathway enrichment analysis indicated enrichment of mTOR signaling in male placentas only, further investigation revealed inhibition of mTORC1 in both male and female placentas in addition to activation of AMPK. In vitro, activation of AMPK and inhibition of mTORC1 decreased membrane localization of EAAT2 and ASCT1.

DISCUSSION

Poly(I:C)-mediated MIA activates AMPK and inhibits mTORC1 in rat placenta, both of which decrease expression and membrane localization of EAAT2 and ASCT1 in vitro. Thus, AMPK/mTORC1 signaling could be a novel treatment target for alleviating MIA-mediated changes in placental amino acid transport.

Human IPSC-Derived Model to Study Myelin Disruption

Myelin is of vital importance to the central nervous system and its disruption is related to a large number of both neurodevelopmental and neurodegenerative diseases. The differences observed between human and rodent oligodendrocytes make animals inadequate for modeling these diseases. Although developing human in vitro models for oligodendrocytes and myelinated axons has been a great challenge, 3D cell cultures derived from iPSC are now available and able to partially reproduce the myelination process. We have previously developed a human iPSC-derived 3D brain organoid model (also called BrainSpheres) that contains a high percentage of myelinated axons and is highly reproducible. Here, we have further refined this technology by applying multiple readouts to study myelination disruption. Myelin was assessed by quantifying immunostaining/confocal microscopy of co-localized myelin basic protein (MBP) with neurofilament proteins as well as proteolipid protein 1 (PLP1). Levels of PLP1 were also assessed by Western blot. We identified compounds capable of inducing developmental neurotoxicity by disrupting myelin in a systematic review to evaluate the relevance of our BrainSphere model for the study of the myelination/demyelination processes. Results demonstrated that the positive reference compound (cuprizone) and two of the three potential myelin disruptors tested (Bisphenol A, Tris(1,3-dichloro-2-propyl) phosphate, but not methyl mercury) decreased myelination, while ibuprofen (negative control) had no effect. Here, we define a methodology that allows quantification of myelin disruption and provides reference compounds for chemical-induced myelin disruption.

Human Oligodendrocytes and Myelin In Vitro to Evaluate Developmental Neurotoxicity

Neurodevelopment is uniquely sensitive to toxic insults and there are concerns that environmental chemicals are contributing to widespread subclinical developmental neurotoxicity (DNT). Increased DNT evaluation is needed due to the lack of such information for most chemicals in common use, but in vivo studies recommended in regulatory guidelines are not practical for the large-scale screening of potential DNT chemicals. It is widely acknowledged that developmental neurotoxicity is a consequence of disruptions to basic processes in neurodevelopment and that testing strategies using human cell-based in vitro systems that mimic these processes could aid in prioritizing chemicals with DNT potential. Myelination is a fundamental process in neurodevelopment that should be included in a DNT testing strategy, but there are very few in vitro models of myelination. Thus, there is a need to establish an in vitro myelination assay for DNT. Here, we summarize the routes of myelin toxicity and the known models to study this particular endpoint.

Astrocytes close the mouse critical period for visual plasticity

Brain postnatal development is characterized by critical periods of experience-dependent remodeling of neuronal circuits. Failure to end these periods results in neurodevelopmental disorders. The cellular processes defining critical-period timing remain unclear. Here, we show that in the mouse visual cortex, astrocytes control critical-period closure. We uncover the underlying pathway, which involves astrocytic regulation of the extracellular matrix, allowing interneuron maturation. Unconventional astrocyte connexin signaling hinders expression of extracellular matrix-degrading enzyme matrix metalloproteinase 9 (MMP9) through RhoA-guanosine triphosphatase activation. Thus, astrocytes not only influence the activity of single synapses but also are key elements in the experience-dependent wiring of brain circuits.

A white paper on a neurodevelopmental framework for drug discovery in autism and other neurodevelopmental disorders

In the last decade there has been a revolution in terms of genetic findings in neurodevelopmental disorders (NDDs), with many discoveries critical for understanding their aetiology and pathophysiology. Clinical trials in single-gene disorders such as fragile X syndrome highlight the challenges of investigating new drug targets in NDDs. Incorporating a developmental perspective into the process of drug development for NDDs could help to overcome some of the current difficulties in identifying and testing new treatments. This paper provides a summary of the proceedings of the 'New Frontiers Meeting' on neurodevelopmental disorders organised by the European College of Neuropsychopharmacology in conjunction with the Innovative Medicines Initiative-sponsored AIMS-2-TRIALS consortium. It brought together experts in developmental genetics, autism, NDDs, and clinical trials from academia and industry, regulators, patient and family associations, and other stakeholders. The meeting sought to provide a platform for focused communication on scientific insights, challenges, and methodologies that might be applicable to the development of CNS treatments from a neurodevelopmental perspective. Multidisciplinary translational consortia to develop basic and clinical research in parallel could be pivotal to advance knowledge in the field. Although implementation of clinical trials for NDDs in paediatric populations is widely acknowledged as essential, safety concerns should guide each aspect of their design. Industry and academia should join forces to improve knowledge of the biology of brain development, identify the optimal timing of interventions, and translate these findings into new drugs, allowing for the needs of users and families, with support from regulatory agencies.

Effect of Neonatal Treatment With the NMDA Receptor Antagonist, MK-801, During Different Temporal Windows of Postnatal Period in Adult Prefrontal Cortical and Hippocampal Function

The neonatal MK-801 model of schizophrenia has been developed based on the neurodevelopmental and NMDA receptor hypofunction hypotheses of schizophrenia. This animal model is generated with the use of the NMDA receptor antagonist, MK-801, during different temporal windows of postnatal life of rodents leading to behavioral defects in adulthood. However, no studies have examined the role of specific postnatal time periods in the neonatal MK-801 (nMK-801) rodent model and the resulting behavioral and neurobiological effects. Thus, the goal of this study is to systematically investigate the role of NMDA hypofunction, during specific temporal windows in postnatal life on different cognitive and social behavioral paradigms, as well as various neurobiological effects during adulthood. Both female and male mice were injected intraperitoneally (i.p.) with MK-801 during postnatal days 7-14 (p7-14) or 11-15 (p11-15). Control mice were injected with saline during the respective time period. In adulthood, mice were tested in various cognitive and social behavioral tasks. Mice nMK-801-treated on p7-14 show impaired performance in the novel object, object-to-place, and temporal order object recognition (TOR) tasks, the sociability test, and contextual fear extinction. Mice nMK-801-treated on p11-15 only affects performance in the TOR task, the social memory test, and contextual fear extinction. No differences were identified in the expression of NMDA receptor subunits, the synapsin or PSD-95 proteins, either in the prefrontal cortex (PFC) or the hippocampus (HPC), brain regions significantly affected in schizophrenia. The number of parvalbumin (PV)-expressing cells is significantly reduced in the PFC, but not in the HPC, of nMK-801-treated mice on p7-14 compared to their controls. No differences in PV-expressing cells (PFC or HPC) were identified in nMK-801-treated mice on p11-15. We further examined PFC function by recording spontaneous activity in a solution that allows up state generation. We find that the frequency of up states is significantly reduced in both nMK-801-treated mice on p7-14 and p11-15 compared to saline-treated mice. Furthermore, we find adaptations in the gamma and high gamma activity in nMK-801-treated mice. In conclusion, our results show that MK-801 treatment during specific postnatal temporal windows has differential effects on cognitive and social behaviors, as well as on underlying neurobiological substrates.

Fmrp regulates oligodendrocyte lineage cell specification and differentiation

Neurodevelopment requires the precise integration of a wide variety of neuronal and glial cell types. During early embryonic development, motor neurons and then oligodendrocyte precursor cells (OPCs) are specified from neural progenitors residing in the periventricular pMN progenitor domain of the spinal cord. Following gliogenesis, OPCs can differentiate as oligodendrocytes (OLs)-the myelinating glial cells of the central nervous system-or remain as OPCs. To generate unique cell types capable of highly divergent functions, these specification and differentiation events require specialized gene expression programs. RNA binding proteins (RBPs) regulate mRNA localization and translation in the developing nervous system and are linked to many neurodevelopmental disorders. One example is Fragile X syndrome (FXS), caused by the loss of the RBP fragile X mental retardation protein (FMRP). Importantly, infants with FXS have reduced white matter and we previously showed that zebrafish Fmrp is autonomously required in OLs to promote myelin sheath growth. We now find that Fmrp regulates cell specification in pMN progenitor cells such that fmr1 mutant zebrafish generate fewer motor neurons and excess OPCs. Fmrp subsequently promotes differentiation of OPCs, leading to fewer differentiating OLs in the developing spinal cord of fmr1 larvae. Although the early patterning of spinal progenitor domains appears largely normal in fmr1 mutants during early embryogenesis, Shh signaling is greatly diminished. Taken together, these results suggest cell stage-specific requirements for Fmrp in the specification and differentiation of oligodendrocyte lineage cells.

Neuroplasticity and non-invasive brain stimulation in the developing brain

The brain is a dynamic organ whose growth and organization varies according to each subject's life experiences. Through adaptations in gene expression and the release of neurotrophins and neurotransmitters, these experiences induce a process of cellular realignment and neural network reorganization, which consolidate what is called neuroplasticity. However, despite the brain's resilience and dynamism, neuroplasticity is maximized during the first years of life, when the developing brain is more sensitive to structural reorganization and the repair of damaged neurons. This review presents an overview of non-invasive brain stimulation (NIBS) techniques that have increasingly been a focus for experimental research and the development of therapeutic methods involving neuroplasticity, especially Transcranial Magnetic Stimulation (TMS) and Transcranial Direct Current Stimulation (tDCS). Due to its safety risk profile and extensive tolerability, several trials have demonstrated the benefits of NIBS as a feasible experimental alternative for the treatment of brain and mind disorders in children and adolescents. However, little is known about the late impact of neuroplasticity-inducing tools on the developing brain, and there are concerns about aberrant plasticity. There are also ethical considerations when performing interventions in the pediatric population. This article will therefore review these aspects and also obstacles related to the premature application of NIBS, given the limited evidence available concerning the extent to which these methods interfere with the developing brain.

Genetic and activity dependent-mechanisms wiring the cortex: Two sides of the same coin

The cerebral cortex is responsible for the higher-order functions of the brain such as planning, cognition, or social behaviour. It provides us with the capacity to interact with and transform our world. The substrates of cortical functions are complex neural circuits that arise during development from the dynamic remodelling and progressive specialization of immature undefined networks. Here, we review the genetic and activity-dependent mechanisms of cortical wiring focussing on the importance of their interaction. Cortical circuits emerge from an initial set of neuronal types that engage in sequential forms of embryonic and postnatal activity. Such activities further complement the cells' genetic programs, increasing neuronal diversity and modifying the electrical properties while promoting selective connectivity. After a temporal window of enhanced plasticity, the main features of mature circuits are established. Failures in these processes can lead to neurodevelopmental disorders whose treatment remains elusive. However, a deeper dissection of cortical wiring will pave the way for innovative therapies.

Evidence for a sensitive period of plasticity in brown adipose tissue during early childhood among indigenous Siberians

OBJECTIVES

Evolutionary theorists have debated the adaptive significance of developmental plasticity in organisms with long lifespans such as humans. This debate in part stems from uncertainty regarding the timing of sensitive periods. Does sensitivity to environmental signals fluctuate across development or does it steadily decline? We investigated developmental plasticity in brown adipose tissue (BAT) among indigenous Siberians in order to explore the timing of phenotypic sensitivity to cold stress.

METHODS

BAT thermogenesis was quantified using infrared thermal imaging in 78 adults (25 men; 33 women). Cold exposure during gestation, infancy, early childhood, middle childhood, and adolescence was quantified using: (1) the average ambient temperature across each period; (2) the number of times daily temperature dropped below -40°F during each period. We also assessed past cold exposure with a retrospective survey of participation in outdoor activities.

RESULTS

Adult BAT thermogenesis was significantly associated with the average temperature (p = 0.021), the number of times it was below -40°F (p = 0.026), and participation in winter outdoor activities (p = 0.037) during early childhood.

CONCLUSIONS

Our results suggest that early childhood represents an important stage for developmental plasticity, and that culture may play a critical role in shaping the timing of environmental signals. The findings highlight a new pathway through which the local consequences of global climate change may influence human biology, and they suggest that ambient temperature may represent an understudied component of the developmental origins of health and disease.

A study on visual preference for social stimuli in typical Ecuadorian preschoolers as a contribution to the identification of autism risk factors

The goal of this study was to examine the visual preference towards socially salient stimuli, using a low-cost eye-tracking device in a group of typically developing (TD) Ecuadorian preschoolers aged 11 to 60 months, from rural and urban areas, and from families with low to high socioeconomic status (SES). Series of original stimuli inspired by those used in Western experiments on the early detection of Autism Spectrum Disorder (ASD) were proposed in two eye-tracking tasks. Two types of movements (human vs. object) were presented in task 1, and dynamic speaking faces in task 2. Parental perceptions of the adaptability of the low-cost eye-tracking device used here were also investigated through a questionnaire. The analyses of mean fixation times showed a visual preference for human movements compared to moving objects whatever age, residency location or SES. In task 2, visual preference for the mouth's area compared to the eyes' area was observed in specific conditions, modulated by residency location and SES but not by age. The analyses of the parental perception indicated that the eye-tracking technique is well accepted. The findings suggest that these stimuli, along with the experimental procedure and low-cost eye-tracking device used in the present study may be a relevant tool that can be used in clinical settings as a contribution to the early identification of at-risk factors of ASD in low- and middle-income contexts.