Altered development of hippocampus-dependent associative learning following early-life adversity

Transient impairment in microglial function causes sex-specific deficits in synaptic maturity and hippocampal function in mice exposed to early adversity

Abnormal development and function of the hippocampus are two of the most consistent findings in humans and rodents exposed to early-life adversity (ELA), with males often being more affected than females. Using the limited bedding (LB) paradigm as a rodent model of ELA, we found that male adolescent mice that had been exposed to LB exhibit significant deficits in contextual fear conditioning and synaptic connectivity in the hippocampus, which are not observed in females. This is linked to altered developmental refinement of connectivity, with LB severely impairing microglial-mediated synaptic pruning in the hippocampus of male and female pups on postnatal day 17 (P17), but not in adolescent P33 mice when levels of synaptic engulfment by microglia are substantially lower. Since the rodent hippocampus undergoes intense synaptic pruning during the second and third weeks of life, we investigated whether microglia are required for the synaptic and behavioral aberrations observed in adolescent LB mice. Indeed, transient ablation of microglia from P13-21 in normally developing mice caused sex-specific behavioral and synaptic abnormalities similar to those observed in adolescent LB mice. Furthermore, chemogenetic activation of microglia during the same period reversed the microglial-mediated phagocytic deficits at P17 and restored normal contextual fear conditioning and synaptic connectivity in adolescent LB male mice. Our data support an additional contribution of astrocytes in the sex-specific effects of LB, with increased expression of the membrane receptor MEGF10 and enhanced synaptic engulfment in hippocampal astrocytes of 17-day-old LB females, but not in LB male littermates. These findings suggest a potential compensatory mechanism that may explain the relative resilience of LB females. Collectively, our study highlights a novel role for glial cells in mediating sex-specific hippocampal deficits in a mouse model of ELA.

Cross-species analysis uncovers the mitochondrial stress response in the hippocampus as a shared mechanism in mouse early life stress and human depression

Depression, or major depressive disorder, poses a significant burden for both individuals and society, affecting approximately 10.8% of the general population. This psychiatric disorder leads to approximately 800,000 deaths per year. A combination of genetic and environmental factors such as early life stress (ELS) increase the risk for development of depression in humans, and a clear role for the hippocampus in the pathophysiology of depression has been shown. Nevertheless, the underlying mechanisms of depression remain poorly understood, resulting in a lack of effective treatments. To better understand the core mechanisms underlying the development of depression, we used a cross-species design to investigate shared hippocampal pathophysiological mechanisms in mouse ELS and human depression. Mice were subjected to ELS by a maternal separation paradigm, followed by RNA sequencing analysis of the adult hippocampal tissue. This identified persistent transcriptional changes linked to mitochondrial stress response pathways, with oxidative phosphorylation and protein folding emerging as the main mechanisms affected by maternal separation. Remarkably, there was a significant overlap between the pathways involved in mitochondrial stress response we observed and publicly available RNAseq data from hippocampal tissue of depressive patients. This cross-species conservation of changes in gene expression of mitochondria-related genes suggests that mitochondrial stress may play a pivotal role in the development of depression. Our findings highlight the potential significance of the hippocampal mitochondrial stress response as a core mechanism underlying the development of depression. Further experimental investigations are required to expand our understanding of these mechanisms.

Early adversity causes sex-specific deficits in perforant pathway connectivity and contextual memory in adolescent mice

BACKGROUND

Early life adversity impairs hippocampal development and function across diverse species. While initial evidence indicated potential variations between males and females, further research is required to validate these observations and better understand the underlying mechanisms contributing to these sex differences. Furthermore, most of the preclinical work in rodents was performed in adult males, with only few studies examining sex differences during adolescence when such differences appear more pronounced. To address these concerns, we investigated the impact of limited bedding (LB), a mouse model of early adversity, on hippocampal development in prepubescent and adolescent male and female mice.

METHODS

RNA sequencing, confocal microscopy, and electron microscopy were used to evaluate the impact of LB and sex on hippocampal development in prepubescent postnatal day 17 (P17) mice. Additional studies were conducted on adolescent mice aged P29-36, which included contextual fear conditioning, retrograde tracing, and ex vivo diffusion magnetic resonance imaging (dMRI).

RESULTS

More severe deficits in axonal innervation and myelination were found in the perforant pathway of prepubescent and adolescent LB males compared to LB female littermates. These sex differences were due to a failure of reelin-positive neurons located in the lateral entorhinal cortex (LEC) to innervate the dorsal hippocampus via the perforant pathway in males, but not LB females, and were strongly correlated with deficits in contextual fear conditioning.

CONCLUSIONS

LB impairs the capacity of reelin-positive cells located in the LEC to project and innervate the dorsal hippocampus in LB males but not female LB littermates. Given the critical role that these projections play in supporting normal hippocampal function, a failure to establish proper connectivity between the LEC and the dorsal hippocampus provides a compelling and novel mechanism to explain the more severe deficits in myelination and contextual freezing found in adolescent LB males.

A retrospective cohort study analyzing the changes in early childhood development during the COVID-19 pandemic

OBJECTIVE

To investigate early childhood development (ECD) outcomes in different subgroups before and during the COVID-19 pandemic.

STUDY DESIGN

A retrospective cohort study of children 3-58 months of age whose caregivers completed a Survey of Well-being of Young Children (SWYC) as part of a well child visit (WCC). The data were divided into two phases: pre-pandemic (September 2018 - February 2020), and during pandemic (September 2020 - February 2022). The difference in the proportion of forms with Meets Expectations interpreted scores on the SWYC Developmental Milestones pre-pandemic versus during the pandemic timeframe overall and among subgroups were reported. Hypotheses were tested using logistic regression with repeated measures.

RESULTS

14,550 patients were included in the sample for analysis with 52,558 SWYC form observations. There was no difference in the odds of a Meets Expectations interpreted score before and after the pandemic for the entire sample, OR 0.99 (95 % CI: 0.94-1.04). There was evidence of decreased odds of an interpreted score of Meets Expectations for the following subgroups: male, Hispanic/Latino ethnicity, ages of 24, 30 or 36 months at WCC, Medicaid insurance, 2nd HOUSES Quartile, requiring interpreter, single parent household, young maternal age, maternal substance abuse, and race identified as Native Hawaiian/Pacific Islander, American Indian/Native Alaskan or Other.

CONCLUSION

Decreased odds of meeting developmental milestones during the pandemic were evident in certain high risk sub-groups revealing unequal distribution of suboptimal developmental outcomes within our population during the pandemic that may be exacerbating existing inequities impacting development in children.

Transient Impairment in Microglial Function Causes Sex-Specific Deficits in Synaptic and Hippocampal Function in Mice Exposed to Early Adversity

Abnormal development and function of the hippocampus are two of the most consistent findings in humans and rodents exposed to early life adversity, with males often being more affected than females. Using the limited bedding (LB) paradigm as a rodent model of early life adversity, we found that male adolescent mice that had been exposed to LB exhibit significant deficits in contextual fear conditioning and synaptic connectivity in the hippocampus, which are not observed in females. This is linked to altered developmental refinement of connectivity, with LB severely impairing microglial-mediated synaptic pruning in the hippocampus of male and female pups on postnatal day 17 (P17), but not in adolescent P33 mice when levels of synaptic engulfment by microglia are substantially lower. Since the hippocampus undergoes intense synaptic pruning during the second and third weeks of life, we investigated whether microglia are required for the synaptic and behavioral aberrations observed in adolescent LB mice. Indeed, transient ablation of microglia from P13-21, in normally developing mice caused sex-specific behavioral and synaptic abnormalities similar to those observed in adolescent LB mice. Furthermore, chemogenetic activation of microglia during the same period reversed the microglial-mediated phagocytic deficits at P17 and restored normal contextual fear conditioning and synaptic connectivity in adolescent LB male mice. Our data support an additional contribution of astrocytes in the sex-specific effects of LB, with increased expression of the membrane receptor MEGF10 and enhanced synaptic engulfment in hippocampal astrocytes of 17-day-old LB females, but not in LB male littermates. This finding suggests a potential compensatory mechanism that may explain the relative resilience of LB females. Collectively, these studies highlight a novel role for glial cells in mediating sex-specific hippocampal deficits in a mouse model of early-life adversity.

Adverse Life Experiences and Brain Function: A Meta-Analysis of Functional Magnetic Resonance Imaging Findings

Importance

Adverse life experiences have been proposed to contribute to diverse mental health problems through an association with corticolimbic functioning. Despite compelling evidence from animal models, findings from studies in humans have been mixed; activation likelihood estimation (ALE) meta-analyses have failed to identify a consistent association of adverse events with brain function.

Objective

To investigate the association of adversity exposure with altered brain reactivity using multilevel kernel density analyses (MKDA), a meta-analytic approach considered more robust than ALE to small sample sizes and methodological differences between studies.

Data Sources

Searches were conducted using PsycInfo, Medline, EMBASE, and Web of Science from inception through May 4, 2022. The following search term combinations were used for each database: trauma, posttraumatic stress disorder (PTSD), abuse, maltreatment, poverty, adversity, or stress; and functional magnetic resonance imaging (fMRI) or neuroimaging; and emotion, emotion regulation, memory, memory processing, inhibitory control, executive functioning, reward, or reward processing.

Study Selection

Task-based fMRI studies within 4 domains (emotion processing, memory processing, inhibitory control, and reward processing) that included a measure of adverse life experiences and whole-brain coordinate results reported in Talairach or Montreal Neurological Institute space were included. Conference abstracts, books, reviews, meta-analyses, opinions, animal studies, articles not in English, and studies with fewer than 5 participants were excluded.

Data Extraction and Synthesis

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses reporting guideline, 2 independent reviewers assessed abstracts and full-text articles for entry criteria. A third reviewer resolved conflicts and errors in data extraction. Data were pooled using a random-effects model and data analysis occurred from August to November 2022.

Main Outcomes and Measures

Peak activation x-axis (left-right), y-axis (posterior-anterior), and z-axis (inferior-superior) coordinates were extracted from all studies and submitted to MKDA meta-analyses.

Results

A total of 83 fMRI studies were included in the meta-analysis, yielding a combined sample of 5242 participants and 801 coordinates. Adversity exposure was associated with higher amygdala reactivity (familywise error rate corrected at P < .001; x-axis = 22; y-axis = -4; z-axis = -17) and lower prefrontal cortical reactivity (familywise error rate corrected at P < .001; x-axis = 10; y-axis = 60; z-axis = 10) across a range of task domains. These altered responses were only observed in studies that used adult participants and were clearest among those who had been exposed to severe threat and trauma.

Conclusions and Relevance

In this meta-analysis of fMRI studies of adversity exposure and brain function, prior adversity exposure was associated with altered adult brain reactivity to diverse challenges. These results might better identify how adversity diminishes the ability to cope with later stressors and produces enduring susceptibility to mental health problems.

A proof-of-concept study of vicarious extinction learning and autonomic synchrony in parent-child dyads and posttraumatic stress disorder

Though threat-extinction models continue to inform scientific study of traumatic stress, knowledge of learning and extinction as mechanisms linking exposure to psychopathology remains critically limited among youth. This proof-of-concept study advances the study of threat-extinction in youth by determining feasibility of electrodermal stimulation (EDS), vicarious extinction learning via their parent, and social threat learning in pediatric PTSD (pPTSD). Typically developing (TD) and PTSD-diagnosed youth in 45 mother-child dyads completed an extinction learning paradigm. The use of EDS was first investigated in a cohort of TD youth (n = 20) using a 2-day paradigm without vicarious extinction, while direct (for TD and pPTSD) and vicarious (for pPTSD) extinction were investigated in a 3-day paradigm (n = 25). Threat acquisition and extinction were monitored using skin-conductance response (SCR) and behavioral expectations of EDS. Using Bayesian modeling to accommodate this pilot sample, our results demonstrate: (1) EDS-conditioning to be highly feasible and well-tolerated across TD and trauma-exposed youth, (2) Successful direct and vicarious extinction learning in trauma-exposed youth, and (3) PTSD-associated patterns in extinction learning and physiological synchrony between parent-child dyads. In summary, these novel approaches have the potential to advance translational studies in the mechanistic understanding of parent-child transmission of risk and youth psychopathology.

Behavioural clusters characteristic of cardiovascular reactivity profiles relate to poorer health outcomes

OBJECTIVES

Blunted cardiovascular reactivity is associated with a distinct behavioural profile of greater exposure to early life adversity, coupled with higher levels of behavioural disengagement and symptoms of depression. The present study sought to extend on this work by investigating if behavioural clusters with distinct patterns of reactivity were related to health and behavioural outcomes at baseline and at a 4-year follow-up.

METHODS

Hierarchical cluster analyses were conducted using longitudinal data drawn from the Midlife Development in the United States (MIDUS 2) Biomarker Project and the MIDUS 3 follow-up 4 years later. During MIDUS, 2 participants (N = 513) underwent a standardized stress testing protocol and had their blood pressure and heart rate monitored throughout. In addition, hierarchical cluster analyses were conducted on responses from measures of early life adversity, behavioural disengagement and depression. Binary logistic regressions were conducted to determine whether cluster membership was related to health and behavioural outcomes which were taken at both time points.

RESULTS

Three behavioural clusters emerged with statistically different blood pressure reactivity patterns. The cluster characterized by greater exposure to early life adversity, higher levels of behavioural disengagement and depressive symptoms, had relatively lower blood pressure reactivity patterns compared with both the exaggerated reactivity cluster and the cluster similar to the sample mean. In fully adjusted models, this cluster was associated with hypertension (p = .050) and depressed affect (p = .033), while Cluster 1 characteristic of an exaggerated blood pressure reactivity profile was associated with depressed affect (p < .001). Cluster membership did not significantly predict future health status.

CONCLUSION

This study extends research on behavioural clusters characteristic of reactivity profiles to demonstrate how they relate to health and behavioural outcomes during MIDUS 2.

Association between Childhood Maltreatment and Depressive and Anxiety Symptoms among Men Who Have Sex with Men in Los Angeles

Adverse childhood experiences (ACEs) have been associated with poor mental health outcomes in adulthood. Childhood maltreatment is related to both depressive and anxiety symptoms. Our objective was to investigate these associations among low-income, mostly Black and Latino men who have sex with men (MSM), as these may be a particularly vulnerable population group. Data come from a longitudinal study of MSM with varied substance use behaviors (n = 321) collected between August 2014 and April 2022. Cumulative, childhood maltreatment ACEs, and the single ACE of childhood sexual abuse were investigated as potential predictors of self-reported depressive and anxiety symptoms in mixed-effects logistic and ordinal regression models. There was no evidence of a dose-response relationship between the number of ACEs and the predicted probability of depressive and anxiety symptoms. Compared to MSM reporting fewer than five ACEs, those with five or more ACEs had approximately double the odds ratio of reporting depressive (OR = 1.93; 95% CI: 1.04-3.60) and anxiety symptoms (OR = 2.21; 95% CI: 1.05-4.68). The dimension of childhood maltreatment had a more robust prediction of depressive symptoms than the dimension of household dysfunction across all models. The association between childhood sexual abuse history and depressive symptoms remained after adjustment for the other nine ACEs (OR = 2.27; 95% CI: 1.11-4.68). The ordinal logistic model suggested that cumulative ACEs more than triple the odds of being in a higher anxiety category (OR = 3.12; 95% CI: 1.58-6.14), with associations reported for childhood maltreatment ACEs (OR = 1.31; 95% CI: 1.06-1.66) and childhood sexual abuse (OR = 1.93; 95% CI: 0.89-4.21). Childhood maltreatment ACEs, particularly childhood sexual abuse, are salient predictors of depressive and anxiety symptoms among adult urban MSM. Mitigating the impact of childhood maltreatment requires understanding the additional burden of social distress often faced by MSM throughout the life course.

Childhood trauma and brain structure in children and adolescents

The dimensional model of adversity proposes that experiences of threat and deprivation have distinct neurodevelopmental consequences. We examined these dimensions, separately and jointly, with brain structure in a sample of 149 youth aged 8-17-half recruited based on exposure to threat-related experiences. We predicted that greater threat would be uniquely associated with reduced cortical thickness and surface area in brain regions associated with salience processing including ventromedial prefrontal cortex (vmPFC), anterior cingulate cortex (ACC), and insula, and that deprivation experiences would be uniquely associated with reductions in cortical thickness and surface area in frontoparietal areas associated with cognitive control. As predicted, greater threat was associated with thinner cortex in a network including areas involved in salience processing (anterior insula, vmPFC), and smaller amygdala volume (particularly in younger participants), after controlling for deprivation. Contrary to our hypotheses, threat was also associated with thinning in the frontoparietal control network. However, these associations were reduced following control for deprivation. No associations were found between deprivation and brain structure. This examination of deprivation and threat concurrently in the same sample provided further evidence that threat-related experiences influence the structure of the developing brain independent of deprivation.

The effects of early life adversity on children's mental health and cognitive functioning

Emerging evidence suggests that partially distinct mechanisms may underlie the association between different dimensions of early life adversity (ELA) and psychopathology in children and adolescents. While there is minimal evidence that different types of ELA are associated with specific psychopathology outcomes, there are partially unique cognitive and socioemotional consequences of specific dimensions of ELA that increase transdiagnostic risk of mental health problems across the internalizing and externalizing spectra. The current review provides an overview of recent findings examining the cognitive (e.g., language, executive function), socioemotional (e.g., attention bias, emotion regulation), and mental health correlates of ELA along the dimensions of threat/harshness, deprivation, and unpredictability. We underscore similarities and differences in the mechanisms connecting different dimensions of ELA to particular mental health outcomes, and identify gaps and future directions that may help to clarify inconsistencies in the literature. This review focuses on childhood and adolescence, periods of exquisite neurobiological change and sensitivity to the environment. The utility of dimensional models of ELA in better understanding the mechanistic pathways towards the expression of psychopathology is discussed, with the review supporting the value of such models in better understanding the developmental sequelae associated with ELA. Integration of dimensional models of ELA with existing models focused on psychiatric classification and biobehavioral mechanisms may advance our understanding of the etiology, phenomenology, and treatment of mental health difficulties in children and youth.

Dysregulation of adult hippocampal neuroplasticity in major depression: pathogenesis and therapeutic implications

Major depressive disorder (MDD) was previously hypothesized to be a disease of monoamine deficiency in which low levels of monoamines in the synaptic cleft were believed to underlie depressive symptoms. More recently, however, there has been a paradigm shift toward a neuroplasticity hypothesis of depression in which downstream effects of antidepressants, such as increased neurogenesis, contribute to improvements in cognition and mood. This review takes a top-down approach to assess how changes in behavior and hippocampal-dependent circuits may be attributed to abnormalities at the molecular, structural, and synaptic level. We conclude with a discussion of how antidepressant treatments share a common effect in modulating neuroplasticity and consider outstanding questions and future perspectives.

Cluster analysis reveals distinct patterns of childhood adversity, behavioral disengagement, and depression that predict blunted heart rate reactivity to acute psychological stress

BACKGROUND

There is considerable evidence documenting associations between early life adversity, behavioral disengagement, and depression with blunted cardiovascular reactivity to acute psychological stress. However, while often examined as independent predictors, it is also likely that a combination of these factors uniquely relate to cardiovascular reactivity.

PURPOSE

The present study employed multivariate cluster analysis to examine if distinct combinations of these outcomes relate to cardiovascular stress reactivity.

METHODS

Participants (N = 467) were predominantly female (60.6%) with a mean age of 19.30 years (SD = 0.82). Measures of early life adversity, behavioral disengagement, and depression were completed; in addition, participants had their blood pressure and heart rate monitored throughout a standardized stress testing session. Cardiovascular reactivity was calculated as the difference between mean stress and mean baseline cardiovascular values.

RESULTS

Analyses revealed two clusters with distinct patterns of exposure to early life adversity, levels of behavioral disengagement and depression, uniquely related to cardiovascular reactivity. In unadjusted models, Cluster 1 that was characterized by greater exposure to early life adversity, higher levels of behavioral disengagement and depression, was associated with lower systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) reactivity. Cluster 2 was characterized by reactivity values similar to the sample means. In fully adjusted models, Cluster 1 predicted heart rate reactivity to stress.

CONCLUSIONS

The present study identifies a behavioral cluster that is characteristic of a blunted heart rate reactivity profile, significantly extending the research in this area.

A meta-analysis of the relation between hippocampal volume and memory ability in typically developing children and adolescents

Memory is supported by a network of brain regions, with the hippocampus serving a critical role in this cognitive process. Previous meta-analyses on the association between hippocampal structure and memory have largely focused on adults. Multiple studies have since suggested that hippocampal volume is related to memory performance in children and adolescents; however, the strength and direction of this relation varies across reports, and thus, remains unclear. To further understand this brain-behavior relation, we conducted a meta-analysis to investigate the association between hippocampal volume (assessed as total volume) and memory during typical development. Across 25 studies and 61 memory outcomes with 1357 participants, results showed a small, but significant, positive association between total hippocampal volume and memory performance. Estimates of the variability across studies in the relation between total volume and memory were not explained by differences in memory task type (delayed vs. immediate; relational vs. nonrelational), participant age range, or the method of normalization of hippocampal volumes. Overall, findings suggest that larger total hippocampal volume relates to better memory performance in children and adolescents and that this relation is similar across the memory types and age ranges assessed. To facilitate enhanced generalization across studies in the future, we discuss considerations for the field moving forward.

Emotional maltreatment and neglect impact neural activation upon exclusion in early and mid-adolescence: An event-related fMRI study

Child maltreatment gives rise to atypical patterns of social functioning with peers which might be particularly pronounced in early adolescence when peer influence typically peaks. Yet, few neuroimaging studies in adolescents use peer interaction paradigms to parse neural correlates of distinct maltreatment exposures. This fMRI study examines effects of abuse, neglect, and emotional maltreatment (EM) among 98 youth (n = 58 maltreated; n = 40 matched controls) using an event-related Cyberball paradigm affording assessment of both social exclusion and inclusion across early and mid-adolescence (≤13.5 years, n = 50; >13.5 years, n = 48). Younger adolescents showed increased activation to social exclusion versus inclusion in regions implicated in mentalizing (e.g., superior temporal gyrus). Individual exposure-specific analyses suggested that neglect and EM coincided with less reduction of activation to social exclusion relative to inclusion in the dorsal anterior cingulate cortex/pre-supplementary motor area (dACC/pre-SMA) among younger versus older adolescents. Integrative follow-up analyses showed that EM accounted for this dACC/pre-SMA activation pattern over and above other exposures. Moreover, age-independent results within respective exposure groups revealed that greater magnitude of neglect predicted blunted exclusion-related activity in the parahippocampal gyrus, while EM predicted increased activation to social exclusion in the precuneus/posterior cingulate cortex.

Longitudinal hippocampal circuit change differentiates persistence and remission of pediatric posttraumatic stress disorder

BACKGROUND

Previous studies have identified functional brain abnormalities in pediatric posttraumatic stress disorder (pPTSD) suggesting altered frontoparietal-subcortical function during emotion processing. However, little is known about how the brain functionally changes over time in recovery versus the persistence of pPTSD.

METHODS

This longitudinal study recruited 23 youth with PTSD and 28 typically developing (TD) youth (ages: 8.07-17.99). Within the PTSD group, nine remitted by the 1-year follow-up (Remit) while the remaining 14 persisted (PTSD). At each visit, youth completed an emotional processing task in which they viewed threat and neutral images during functional magnetic resonance imaging (fMRI). Voxelwise activation analyses using linear mixed-effects regression were conducted using a group (TD, Remit, PTSD) by time (baseline, follow-up) by valence (threat, neutral) design. Based on activation findings, a subsequent analysis of hippocampal functional connectivity was performed using a similar model.

RESULTS

PTSD youth showed significantly increasing hippocampal activation to threatening images compared to TD youth, while the Remit group showed more similar patterns to TD youth. Subsequent hippocampal functional connectivity analyses reveal the Remit group showed increasing functional connectivity between the hippocampus and visual cortex (V4) while viewing threat stimuli.

CONCLUSIONS

These findings represent one of the first preliminary reports of functional brain substrates of persistence and remission in pPTSD. Notably, increased hippocampal activation to threat and decreased connectivity in the hippocampal-V4 network over time may contribute to persistence in pPTSD. These findings suggest potential biomarkers that could be utilized to advance the treatment of pediatric PTSD.

Sex-specific effects of social isolation stress and ketamine on hippocampal plasticity

Chronic social isolation stress (SIS) induces lasting negative effects on the brain, including memory deficits, cognitive impairments, and mood alterations such as depression and anxiety. All these symptoms, at least in part, reflect reduced hippocampal function. In both clinical and preclinical studies, subanesthetic doses of the NMDA receptor antagonist, ketamine (KET), was shown to have rapid and lasting antidepressant effects. Animal studies have shown that biological sex and levels of gonadal hormones alter the behavioral effects of KET, with ovarian hormones increasing sensitivity to the antidepressant-like effects of KET. Since the hippocampus plays a key role in mediating some of the effects of SIS, and considering that KET at low doses has been shown to rescue some of the behavioral deficits of isolation rearing this study aimed to assess the effects of isolation stress on pre- and post-synaptic hippocampal functions in male and female rats reared in SIS, as well as determine whether some of the physiological deficits can be rescued with a single injection of sub-anesthetic doses of KET. To do this, Sprague-Dawley rats were raised from weaning in either social isolation or with same-sex cage mate for 5 to 7 weeks. Male and female rats in either diestrus of proestrus received a single injection of KET (0, 2.5, or 5.0 mg/kg) three hours prior to termination and collection of acute hippocampal slices for ex vivo electrophysiological field potential recordings. Long-term potentiation (LTP) and paired pulse facilitation (PPF) outputs were assessed in a canonical CA3-CA1 dorsal hippocampal circuit. Our data show that SIS inhibits hippocampal LTP without affecting PPF in male rats, an effect that was rescued by KET. In female rats, isolation stress did not alter LTP, but did reduce PPF - especially when females were tested in diestrus-, an effect that was rescued by KET at the highest dose. Our data thus suggest sex differences in the contribution of pre-and postsynaptic hippocampal compartments in response to stress and KET.

Glia-Driven Brain Circuit Refinement Is Altered by Early-Life Adversity: Behavioral Outcomes

Early-life adversity (ELA), often clinically referred to as "adverse childhood experiences (ACE)," is the exposure to stress-inducing events in childhood that can result in poor health outcomes. ELA negatively affects neurodevelopment in children and adolescents resulting in several behavioral deficits and increasing the risk of developing a myriad of neuropsychiatric disorders later in life. The neurobiological mechanisms by which ELA alters neurodevelopment in childhood have been the focus of numerous reviews. However, a comprehensive review of the mechanisms affecting adolescent neurodevelopment (i.e., synaptic pruning and myelination) is lacking. Synaptic pruning and myelination are glia-driven processes that are imperative for brain circuit refinement during the transition from adolescence to adulthood. Failure to optimize brain circuitry between key brain structures involved in learning and memory, such as the hippocampus and prefrontal cortex, leads to the emergence of maladaptive behaviors including increased anxiety or reduced executive function. As such, we review preclinical and clinical literature to explore the immediate and lasting effects of ELA on brain circuit development and refinement. Finally, we describe a number of therapeutic interventions best-suited to support adolescent neurodevelopment in children with a history of ELA.

COVID-19 in Early Life: Infants and Children Are Affected Too

Compared with adults, children are less likely infected with SARS-CoV-2 and are often asymptomatic when infected. However, infection in children can lead to severe disease. The pandemic affects the lives of all children, especially those with lower socioeconomic status. This review highlights the physiological impacts of COVID-19 in early life.

Early Life Adversity and Polygenic Risk for High Fasting Insulin Are Associated With Childhood Impulsivity

While the co-morbidity between metabolic and psychiatric behaviors is well-established, the mechanisms are poorly understood, and exposure to early life adversity (ELA) is a common developmental risk factor. ELA is associated with altered insulin sensitivity and poor behavioral inhibition throughout life, which seems to contribute to the development of metabolic and psychiatric disturbances in the long term. We hypothesize that a genetic background associated with higher fasting insulin interacts with ELA to influence the development of executive functions (e.g., impulsivity in young children). We calculated the polygenic risk scores (PRSs) from the genome-wide association study (GWAS) of fasting insulin at different thresholds and identified the subset of single nucleotide polymorphisms (SNPs) that best predicted peripheral insulin levels in children from the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort [N = 467; p_{t– initial} = 0.24 (10,296 SNPs), p_{t– refined} = 0.05 (57 SNPs)]. We then calculated the refined PRS (rPRS) for fasting insulin at this specific threshold in the children from the Maternal Adversity, Vulnerability and Neurodevelopment (MAVAN) cohort and investigated its interaction effect with adversity on an impulsivity task applied at 36 months. We found a significant effect of interaction between fasting insulin rPRS and adversity exposure predicting impulsivity measured by the Snack Delay Task at 36 months [β = −0.329, p = 0.024], such that higher PRS [β = −0.551, p = 0.009] was linked to more impulsivity in individuals exposed to more adversity. Enrichment analysis (MetaCore^TM) of the SNPs that compose the fasting insulin rPRS at this threshold was significant for certain nervous system development processes including dopamine D2 receptor signaling. Additional enrichment analysis (FUMA) of the genes mapped from the SNPs in the fasting insulin rPRS showed enrichment with the accelerated cognitive decline GWAS. Therefore, the genetic background associated with risk for adult higher fasting insulin moderates the impact of early adversity on childhood impulsivity.

The potential impact of the COVID-19 pandemic on child growth and development: a systematic review

OBJECTIVE

This was a systematic review of studies that examined the impact of epidemics or social restriction on mental and developmental health in parents and children/adolescents.

SOURCE OF DATA

The PubMed, WHO COVID-19, and SciELO databases were searched on March 15, 2020, and on April 25, 2020, filtering for children (0-18 years) and humans.

SYNTHESIS OF DATA

The tools used to mitigate the threat of a pandemic such as COVID-19 may very well threaten child growth and development. These tools - such as social restrictions, shutdowns, and school closures - contribute to stress in parents and children and can become risk factors that threaten child growth and development and may compromise the Sustainable Development Goals. The studies reviewed suggest that epidemics can lead to high levels of stress in parents and children, which begin with concerns about children becoming infected. These studies describe several potential mental and emotional consequences of epidemics such as COVID-19, H1N1, AIDS, and Ebola: severe anxiety or depression among parents and acute stress disorder, post-traumatic stress, anxiety disorders, and depression among children. These data can be related to adverse childhood experiences and elevated risk of toxic stress. The more adverse experiences, the greater the risk of developmental delays and health problems in adulthood, such as cognitive impairment, substance abuse, depression, and non-communicable diseases.

CONCLUSION

Information about the impact of epidemics on parents and children is relevant to policy makers to aid them in developing strategies to help families cope with epidemic/pandemic-driven adversity and ensure their children's healthy development.

Deficits in hippocampal-dependent memory across different rodent models of early life stress: systematic review and meta-analysis

Exposure to early life stress (ELS) causes abnormal hippocampal development and functional deficits in rodents and humans, but no meta-analysis has been used yet to quantify the effects of different rodent models of ELS on hippocampal-dependent memory. We searched PubMed and Web of Science for publications that assessed the effects of handling, maternal separation (MS), and limited bedding and nesting (LBN) on performance in the Morris water maze (MWM), novel object recognition (NOR), and contextual fear conditioning (CFC). Forty-five studies met inclusion criteria (n = 451-763 rodents per test) and were used to calculate standardized mean differences (Hedge's g) and to assess heterogeneity, publication bias, and the moderating effects of sex and species (rats vs. mice). We found significantly lower heterogeneity in LBN compared to handling and MS with no consistent effects of sex or species across the three paradigms. LBN and MS caused similar cognitive deficits in tasks that rely heavily on the dorsal hippocampus, such as MWM and NOR, and were significantly different compared to the improved performance seen in rodents exposed to handling. In the CFC task, which relies more on the ventral hippocampus, all three paradigms showed reduced freezing with moderate effect sizes that were not statistically different. These findings demonstrate the utility of using meta-analysis to quantify outcomes in a large number of inconsistent preclinical studies and highlight the need to further investigate the possibility that handling causes different alterations in the dorsal hippocampus but similar outcomes in the ventral hippocampus when compared to MS and LBN.

Pediatric obstructive sleep apnea revisited: Perioperative considerations for the pediatric Anesthesiologist

Pediatric obstructive sleep apnea presents in up to 7% of children and represents a constellation from nasal turbulence to cessation in gas exchange. There are numerous end organ sequelae including neurocognitive morbidity associated with persistent OSA. Adenotonsillectomy (AT), the first line therapy for pediatric OSA, has not been demonstrated to reduce all end organ morbidity, specifically neurological and behavioral morbidity. Furthermore, certain at-risk populations are at higher risk from neurocognitive morbidity. Precise knowledge and perioperative planning is required to ensure optimal evidence-based practices in children with OSA. This comprehensive review covers the seminal perioperative implications of OSA, including preoperative polysomnography, pharmacotherapeutics, and postoperative risk stratification.

Childhood Adversity and Neural Development: A Systematic Review

An extensive literature on childhood adversity and neurodevelopment has emerged over the past decade. We evaluate two conceptual models of adversity and neurodevelopment-the dimensional model of adversity and stress acceleration model-in a systematic review of 109 studies using MRI-based measures of neural structure and function in children and adolescents. Consistent with the dimensional model, children exposed to threat had reduced amygdala, medial prefrontal cortex (mPFC), and hippocampal volume and heightened amygdala activation to threat in a majority of studies; these patterns were not observed consistently in children exposed to deprivation. In contrast, reduced volume and altered function in frontoparietal regions were observed consistently in children exposed to deprivation but not children exposed to threat. Evidence for accelerated development in amygdala-mPFC circuits was limited but emerged in other metrics of neurodevelopment. Progress in charting neurodevelopmental consequences of adversity requires larger samples, longitudinal designs, and more precise assessments of adversity.

Distinct aspects of the early environment contribute to associative memory, cued attention, and memory-guided attention: Implications for academic achievement

Childhood socioeconomic status (SES) is associated with numerous aspects of cognitive development and disparities in academic achievement. The specific environmental factors that contribute to these disparities remain poorly understood. We used observational methods to characterize three aspects of the early environment that may contribute to SES-related differences in cognitive development: violence exposure, cognitive stimulation, and quality of the physical environment. We evaluated the associations of these environmental characteristics with associative memory, cued attention, and memory-guided attention in a sample of 101 children aged 60-75 months. We further investigated whether these specific cognitive abilities mediated the association between SES and academic achievement 18 months later. Violence exposure was specifically associated with poor associative memory, but not cued attention or memory-guided attention. Cognitive stimulation and higher quality physical environment were positively associated with cued attention accuracy, but not after adjusting for all other environmental variables. The quality of the physical environment was associated with memory-guided attention accuracy. Of the cognitive abilities examined, only memory-guided attention contributed to SES-related differences in academic achievement. These findings suggest specificity in how particular aspects of early environmental experience scaffold different types of attention and memory subserved by distinct neural circuits and shed light on a novel cognitive-developmental mechanism underlying SES-related disparities in academic achievement.

Impaired hippocampus-dependent associative learning as a mechanism underlying PTSD: A meta-analysis

Smaller hippocampal volume is associated with increased risk for PTSD following trauma, but the hippocampal functions involved remain unknown. We propose a conceptual model that identifies broad impairment in hippocampus-dependent associative learning as a vulnerability factor for PTSD. Associative learning of foreground cues and background context is required to form an integrated representation of an event. People with poor associative learning may have difficulty remembering who or what was present during a trauma, where the trauma occurred, or the sequence of events, which may contribute to PTSD symptoms. We argue that associative learning difficulties in PTSD exist for cues and context, regardless of the emotional nature of the information. This contrasts with PTSD models that focus exclusively on threat-processing or contextual-processing. In a meta-analysis, people with PTSD exhibited poor associative learning of multiple information types compared to those without PTSD. Differences were of medium effect size and similar magnitude for neutral and negative/trauma-related stimuli. We provide evidence for associative learning difficulties as a neurocognitive pathway that may contribute to PTSD.