Neuroplasticity in the maternal hippocampus: Relation to cognition and effects of repeated stress

Racial Differences in Psychosocial Resources and Mental and Physical Health Outcomes during Pregnancy: A structural equation modeling approach

Objectives

Poor prenatal health is of particular concern among minoritized individuals who may experience adverse social determinants of health contributing to the intergenerational transmission of health disparities. The purpose of this study was to investigate associations between psychosocial resources, and mental and physical health among a prenatal sample, and to explore if these relationships vary by race.

Methods

English-speaking pregnant individuals living in the United States were recruited using Centiment (n=340). Participants completed a 121-item cross-sectional survey. We conducted a single- and multi-group structural equation model to test hypothesized relationships, and then investigated differences by pregnant White individuals versus Black, Indigenous, and People of Color (BIPOC).

Results

Our final single-group model exhibited good model fit (χ2 (43) = 99.07, p<.01, CFI = 0.97, SRMR = 0.04, and RMSEA = 0. 06 (0.05 - 0.08)). After controlling for demographic characteristics and social determinants of health, higher levels of mindfulness were statistically significantly related to lower anxiety and depression scores (both p<.01). Higher levels of social supports were statistically significantly related to lower anxiety scores. Scale measurement invariance was confirmed for the multi-group model and the structural model was statistically significantly different between pregnant White individuals and BIPOC in this sample (Δ χ2 (27) = 116.71, p <.01).

Conclusions

Identification of core components of psychosocial resource interventions, consideration of upstream structural determinants, mindfulness and valued-living (MVL)-based strategies, cultural adaptation, and an emphasis on resilience rather than psychopathology may result in improved prenatal health among pregnant individuals traditionally underrepresented in research.

Enduring maternal brain changes and their role in mediating motherhood's impact on well-being

Parenthood, particularly motherhood, is known to impact the structure and function of the brain in the short term, but the long-term effects of parenthood and their impacts on well-being are still poorly understood. This study explores the potential longer-term associations between parenthood and the brain, parenthood and well-being, and the potential role of brain modifications in influencing mothers' well-being. Using data from the UK Biobank, which includes brain imaging information from individuals aged 45-82 at the MRI scanning, we discovered differences in brain structure between mothers and non-mothers, with mothers exhibiting widely distributed higher gray matter density, particularly strong in frontal and occipital regions. No brain changes were observed in fathers. Parents reported a higher sense of life's meaning compared to their childless counterparts. Gray matter changes did not mediate the relationship between motherhood and well-being. This suggests that the alterations in gray matter associated with motherhood do not play a deterministic role in shaping long-term changes in well-being.

Parental status and markers of brain and cellular age: A 3D convolutional network and classification study

Recent research shows prominent effects of pregnancy and the parenthood transition on structural brain characteristics in humans. Here, we present a comprehensive study of how parental status and number of children born/fathered links to markers of brain and cellular ageing in 36,323 UK Biobank participants (age range 44.57-82.06 years; 52% female). To assess global effects of parenting on the brain, we trained a 3D convolutional neural network on T1-weighted magnetic resonance images, and estimated brain age in a held-out test set. To investigate regional specificity, we extracted cortical and subcortical volumes using FreeSurfer, and ran hierarchical clustering to group regional volumes based on covariance. Leukocyte telomere length (LTL) derived from DNA was used as a marker of cellular ageing. We employed linear regression models to assess relationships between number of children, brain age, regional brain volumes, and LTL, and included interaction terms to probe sex differences in associations. Lastly, we used the brain measures and LTL as features in binary classification models, to determine if markers of brain and cellular ageing could predict parental status. The results showed associations between a greater number of children born/fathered and younger brain age in both females and males, with stronger effects observed in females. Volume-based analyses showed maternal effects in striatal and limbic regions, which were not evident in fathers. We found no evidence for associations between number of children and LTL. Classification of parental status showed an Area under the ROC Curve (AUC) of 0.57 for the brain age model, while the models using regional brain volumes and LTL as predictors showed AUCs of 0.52. Our findings align with previous population-based studies of middle- and older-aged parents, revealing subtle but significant associations between parental experience and neuroimaging-based surrogate markers of brain health. The findings further corroborate results from longitudinal cohort studies following parents across pregnancy and postpartum, potentially indicating that the parenthood transition is associated with long-term influences on brain health.

Environmental enrichment attenuates depressive-like behavior in maternal rats by inhibiting neuroinflammation and apoptosis and promoting neuroplasticity

Gestational stress can exacerbate postpartum depression (PPD), for which treatment options remain limited. Environmental enrichment (EE) may be a therapeutic intervention for neuropsychiatric disorders, including depression, but the specific mechanisms by which EE might impact PPD remain unknown. Here we examined the behavioral, molecular, and cellular impact of EE in a stable PPD model in rats developed through maternal separation (MS). Maternal rats subjected to MS developed depression-like behavior and cognitive dysfunction together with evidence of significant neuroinflammation including microglia activation, neuronal apoptosis, and impaired synaptic plasticity. Expanding the duration of EE to throughout pregnancy and lactation, we observed an EE-associated reversal of MS-induced depressive phenotypes, inhibition of neuroinflammation and neuronal apoptosis, and improvement in synaptic plasticity in maternal rats. Thus, EE effectively alleviates neuroinflammation, neuronal apoptosis, damage to synaptic plasticity, and consequent depression-like behavior in mother rats experiencing MS-induced PPD, paving the way for new preventive and therapeutic strategies for PPD.

Investigating female versus male differences in white matter neuroplasticity associated with complex visuo-motor learning

Magnetic resonance imaging (MRI) has increasingly been used to characterize structure-function relationships during white matter neuroplasticity. Biological sex differences may be an important factor that affects patterns of neuroplasticity, and therefore impacts learning and rehabilitation. The current study examined a participant cohort before and after visuo-motor training to characterize sex differences in microstructural measures. The participants (N = 27) completed a 10-session (4 week) complex visuo-motor training task with their non-dominant hand. All participants significantly improved movement speed and their movement speed variability over the training period. White matter neuroplasticity in females and males was examined using fractional anisotropy (FA) and myelin water fraction (MWF) along the cortico-spinal tract (CST) and the corpus callosum (CC). FA values showed significant differences in the middle portion of the CST tract (nodes 38-51) across the training period. MWF showed a similar cluster in the inferior portion of the tract (nodes 18-29) but did not reach significance. Additionally, at baseline, males showed significantly higher levels of MWF measures in the middle body of the CC. Combining data from females and males would have resulted in reduced sensitivity, making it harder to detect differences in neuroplasticity. These findings offer initial insights into possible female versus male differences in white matter neuroplasticity during motor learning. This warrants investigations into specific patterns of white matter neuroplasticity for females versus males across the lifespan. Understanding biological sex-specific differences in white matter neuroplasticity may have significant implications for the interpretation of change associated with learning or rehabilitation.

Impact of glyphosate-based herbicide exposure through maternal milk on offspring's antioxidant status, neurodevelopment, and behavior

Glyphosate-based Herbicide (GBH) is a widely used pesticide that functions as a broad-spectrum, non-selective herbicide. Despite advanced research to describe the neurotoxic potential of GBH, the harmful effects on maternal behavior and neurodevelopment of offspring remain unclear. This study was conducted to highlight the effects of GBH on the antioxidant system, anxiety traits, social interaction, and cognitive and sensorimotor functions in pups exposed to 25 or 50 mg/l daily via their mother's milk. Concerning the biochemical biomarkers, GBH administered during the early stages of development negatively affected the status of antioxidant enzymes and lipid peroxidation in the brain structures of the pups. Furthermore, our results showed a significant decrease in acetylcholinesterase (AChE) specific activity within the brains of treated pups. The results of the behavioral tests indicated that the treated offspring developed anxiety, memory, and sociability disorders, as evidenced by the Open Field, Y-maze, object recognition task, and social interaction tests. Through neurodevelopmental testing, we also showed sensorimotor impairment (righting reflex and negative geotaxis) and abnormal maternal behavior. Altogether, our study clearly demonstrates that the developing brain is sensitive to GBH.

Mitochondrial might: powering the peripartum for risk and resilience

The peripartum period, characterized by dynamic hormonal shifts and physiological adaptations, has been recognized as a potentially vulnerable period for the development of mood disorders such as postpartum depression (PPD). Stress is a well-established risk factor for developing PPD and is known to modulate mitochondrial function. While primarily known for their role in energy production, mitochondria also influence processes such as stress regulation, steroid hormone synthesis, glucocorticoid response, GABA metabolism, and immune modulation - all of which are crucial for healthy pregnancy and relevant to PPD pathology. While mitochondrial function has been implicated in other psychiatric illnesses, its role in peripartum stress and mental health remains largely unexplored, especially in relation to the brain. In this review, we first provide an overview of mitochondrial involvement in processes implicated in peripartum mood disorders, underscoring their potential role in mediating pathology. We then discuss clinical and preclinical studies of mitochondria in the context of peripartum stress and mental health, emphasizing the need for better understanding of this relationship. Finally, we propose mitochondria as biological mediators of resilience to peripartum mood disorders.

Recalibration of the stress response system over adult development: Is there a perinatal recalibration period?

During early life-sensitive periods (i.e., fetal, infancy), the developing stress response system adaptively calibrates to match environmental conditions, whether harsh or supportive. Recent evidence suggests that puberty is another window when the stress system is open to recalibration if environmental conditions have shifted significantly. Whether additional periods of recalibration exist in adulthood remains to be established. The present paper draws parallels between childhood (re)calibration periods and the perinatal period to hypothesize that this phase may be an additional window of stress recalibration in adult life. Specifically, the perinatal period (defined here to include pregnancy, lactation, and early parenthood) is also a developmental switch point characterized by heightened neural plasticity and marked changes in stress system function. After discussing these similarities, lines of empirical evidence needed to substantiate the perinatal stress recalibration hypothesis are proposed, and existing research support is reviewed. Complexities and challenges related to delineating the boundaries of perinatal stress recalibration and empirically testing this hypothesis are discussed, as well as possibilities for future multidisciplinary research. In the theme of this special issue, perinatal stress recalibration may be a mechanism of multilevel, multisystem risk, and resilience, both intra-individually and intergenerationally, with implications for optimizing interventions.

Gestational stress decreases postpartum mitochondrial respiration in the prefrontal cortex of female rats

Postpartum depression (PPD) is a major psychiatric complication of childbirth, affecting up to 20% of mothers, yet remains understudied. Mitochondria, dynamic organelles crucial for cell homeostasis and energy production, share links with many of the proposed mechanisms underlying PPD pathology. Brain mitochondrial function is affected by stress, a major risk factor for development of PPD, and is linked to anxiety-like and social behaviors. Considering the importance of mitochondria in regulating brain function and behavior, we hypothesized that mitochondrial dysfunction is associated with behavioral alterations in a chronic stress-induced rat model of PPD. Using a validated and translationally relevant chronic mild unpredictable stress paradigm during late gestation, we induced PPD-relevant behaviors in adult postpartum Wistar rats. In the mid-postpartum, we measured mitochondrial function in the prefrontal cortex (PFC) and nucleus accumbens (NAc) using high-resolution respirometry. We then measured protein expression of mitochondrial complex proteins and 4-hydroxynonenal (a marker of oxidative stress), and Th1/Th2 cytokine levels in PFC and plasma. We report novel findings that gestational stress decreased mitochondrial function in the PFC, but not the NAc of postpartum dams. However, in groups controlling for the effects of either stress or parity alone, no differences in mitochondrial respiration measured in either brain regions were observed compared to nulliparous controls. This decrease in PFC mitochondrial function in stressed dams was accompanied by negative behavioral consequences in the postpartum, complex-I specific deficits in protein expression, and increased Tumor Necrosis Factor alpha cytokine levels in plasma and PFC. Overall, we report an association between PFC mitochondrial respiration, PPD-relevant behaviors, and inflammation following gestational stress, highlighting a potential role for mitochondrial function in postpartum health.

The Impact of Mild Chronic Stress and Maternal Experience in the Fmr1 Mouse Model of Fragile X Syndrome

Fragile X syndrome (FXS) is a pervasive developmental disorder and the most common monogenic cause of autism spectrum disorder (ASD). Female heterozygous (HET) carriers play a major role in the transmission of the pathology and present several FXS- and ASD-like behavioral alterations. Despite their clear genetic origins, FXS symptoms are known to be modulated by environmental factors, e.g., exposure to chronic stress, especially during critical life periods, such as pregnancy. Pregnancy, together with pups' care, constitutes maternal experience, i.e., another powerful environmental factor affecting several neurobehavioral functions in females. Here we investigated the impact of maternal experience on the long-term effects of stress in Fmr1-HET female mice. Our findings demonstrated that the behavioral abnormalities of HET females, i.e., hyperactivity and memory deficits, were unaffected by stress or maternal experience. In contrast, stress, independently of maternal experience, induced the appearance of cognitive deficits in WT mice. Maternal experience increased anxiety levels in all mice and enhanced their corticosterone levels, concomitantly promoting the effects of stress on social communication and adrenal glands. In translational terms, these results advance our understanding of the environmental modulation of the behavioral alterations observed in FXS female carriers and highlight the long-term impact of maternal experience and its interactions with chronic stress.

Parental experience is linked with lower vasopressin receptor 1a binding and decreased postpartum androgens in titi monkeys

Parenting induces many neurological and behavioral changes that enable parents to rear offspring. Vasopressin plays an important role in this process via its effects on cognition, affect, and neuroplasticity, and in some cases, via interactions with decreased parental androgens. Thus far, the role of these hormones has been primarily studied in rodents. To address this gap, we explored vasopressin receptors and androgens in titi monkeys, a pair-bonding and biparental primate species. In Studies 1 and 2, we used receptor autoradiography to correlate arginine vasopressin receptor 1a (AVPR1a) binding in the hippocampus (Study 1, n = 10) and the rest of the forebrain (Study 2, n = 23) with parental status, parental experience, parity, infant carrying, and pair affiliation. We found that parents exhibited lower AVPR1a binding than non-parents throughout most brain regions assessed, with especially strong effects in the hippocampus (β = -.61), superior colliculus (β = -.88), lateral septum (β = -.35), and medial preoptic area (β = -.29). The other measures of parental experience also tended to be negatively associated with AVPR1a binding across different brain regions. In Study 3 (n = 44), we compared pre- and postpartum urinary androgen levels in parents and non-parents and found that mothers exhibited a sustained androgen decrease across 3-4 months postpartum (relative to 3 months prepartum; β ranged from -.72 to -.62 for different comparisons). For males, we found that multiparous fathers exhibited decreased androgen levels at 1-2 weeks postpartum (β = -.25) and at 3-4 months postpartum (β = -.40) compared to the prepartum, indicating both immediate and long-term reductions with subsequent paternal experience. Together, the results of this study suggest that decreases in AVPR1a binding and circulating androgens are associated with parental behavior and physiology in titi monkeys.

Postpartum depression: aetiology, pathogenesis and the role of nutrients and dietary supplements in prevention and management

Postpartum depression (PPD) is a challenging psychological disorder faced by 10-30% of mothers across the globe. In India, it occurs among 22% of mothers. Its aetiology and pathophysiology aren't fully understood as of today but multiple theories on the interplay of hormones, neurotransmitters, genetics, epigenetics, nutrients, socio-environmental factors, etc. exist. Nutrients are not only essential for the synthesis of neurotransmitters, but they may also indirectly influence genomic pathways that methylate DNA, and there is evidence for molecular associations between nutritional quality and psychological well-being. Increased behavioural disorders have been attributed to macro- and micronutrient deficiencies, and dietary supplementation has been effective in treating several neuropsychiatric illnesses. Nutritional deficiencies occur frequently in women, especially during pregnancy and breastfeeding. The aim of this study was to perform a comprehensive literature review of evidence-based research in order to identify, gather and summarize existing knowledge on PPD's aetiology, pathophysiology, and the role of nutrients in its prevention as well as management. The possible mechanisms of action of nutrients are also presented here. Study findings show that the risk of depression increases when omega-3 fatty acid levels are low. Both fish oil and folic acid supplements have been used to effectively treat depression. Antidepressant efficacy is lowered by folate insufficiency. Folate, vitamin B12, iron, etc. deficiencies are more prevalent in depressed people than in non-depressed people. Serum cholesterol levels and plasma tryptophan levels are found to be inversely correlated with PPD. Serum vitamin D levels were associated inversely with perinatal depression. These findings highlight the importance of adequate nutrition in the antepartum period. Given that nutritional therapies can be affordable, safe, simple to use, and are typically well-accepted by patients, more focus should be placed on dietary variables in PPD.

Lactation attenuates pro-oxidant reactions in the maternal brain

Reactive oxygen species (ROS) are intimately linked to bioenergetics and redox biology, contributing to cellular functioning and physiological signaling, but also acting as toxic agents during oxidative stress. Hence, the balance between pro-oxidant reactions and the activity of antioxidant defenses sustains a basal oxidative status, controls the increase of redox signaling, and mediates potential pathological events during oxidative stress. Maternal experience, especially during nursing, requires high energetic demands and expenditure to ensure the well-being of the offspring. The mother must adapt from satisfying her own needs to additionally fulfilling those of her descendants. Oxidative stress has been proposed as one of the reproductive trade-off hallmarks. However, the oxidative shielding hypothesis has also been proposed in the context of reproduction. The reproductive experience induces a wide range of well-documented changes in the female brain, which potentially lead to protection against the enhanced oxidative activity. To date, the metabolic and cellular mechanisms that underlie lactation-induced neuroprotection against oxidants are unknown. The neuroendocrine changes in the brain of the lactating dam promote diminished propensity to excitotoxic brain injury and stress, as well as enhanced neuroprotection and plasticity. In addition to review studies on the oxidant balance due to motherhood, we included new data from our laboratory, addressing the importance of measuring pro-oxidant reactions in separated brain regions. The hippocampus of lactating rats exhibits lower levels of pro-oxidant reactions than that of virgin rats, supporting the oxidative shielding hypothesis in lactation.

The Role of Oxytocin in Domestic Animal’s Maternal Care: Parturition, Bonding, and Lactation

Oxytocin (OXT) is one of the essential hormones in the birth process; however, estradiol, prolactin, cortisol, relaxin, connexin, and prostaglandin are also present. In addition to parturition, the functions in which OXT is also involved in mammals include the induction of maternal behavior, including imprinting and maternal care, social cognition, and affiliative behavior, which can affect allo-parental care. The present article aimed to analyze the role of OXT and the neurophysiologic regulation of this hormone during parturition, how it can promote or impair maternal behavior and bonding, and its importance in lactation in domestic animals.

Matrescence: lifetime impact of motherhood on cognition and the brain

Profound environmental, hormonal, and neurobiological changes mark the transition to motherhood as a major biosocial life event. Despite the ubiquity of motherhood, the enduring impact of caregiving on cognition and the brain across the lifespan is not well characterized and represents a unique window of opportunity to investigate human neural and cognitive development. By integrating insights from the human and animal maternal brain literatures with theories of cognitive ageing, we outline a framework for understanding maternal neural and cognitive changes across the lifespan. We suggest that the increased cognitive load of motherhood provides an initial challenge during the peripartum period, requiring continuous adaptation; yet when these demands are sustained across the lifespan, they result in increased late-life cognitive reserve.

Potential mechanisms and modulators of food intake during pregnancy

Dietary choice during pregnancy is crucial not only for fetal development, but also for long-term health outcomes of both mother and child. During pregnancy, dramatic changes in endocrine, cognitive, and reward systems have been shown to take place. Interestingly, in different contexts, many of these mechanisms play a key role in guiding food intake. Here, we review how food intake may be impacted as a function of pregnancy-induced changes across species. We first summarize changes in endocrine and metabolic signaling in the course of pregnancy. Then, we show how these may be related to cognitive function and reward processing in humans. Finally, we link these to potential drivers of change in eating behavior throughout the course of pregnancy.

Mapping the effects of pregnancy on resting state brain activity, white matter microstructure, neural metabolite concentrations and grey matter architecture

While animal studies have demonstrated a unique reproduction-related neuroplasticity, little is known on the effects of pregnancy on the human brain. Here we investigated whether pregnancy is associated with changes to resting state brain activity, white matter microstructure, neural metabolite concentrations and grey matter architecture using a comprehensive pre-conception cohort study. We show that pregnancy leads to selective and robust changes in neural architecture and neural network organization, which are most pronounced in the Default Mode Network. These neural changes correlated with pregnancy hormones, primarily third-trimester estradiol, while no associations were found with other factors such as osmotic effects, stress and sleep. Furthermore, the changes related to measures of maternal-fetal bonding, nesting behavior and the physiological responsiveness to infant cues, and predicted measures of mother-infant bonding and bonding impairments. These findings suggest there are selective pregnancy-related modifications in brain structure and function that may facilitate peripartum maternal processes of key relevance to the mother-infant dyad.

Hippocampal volume changes in a pharmacological sex-hormone manipulation risk model for depression in women

Hormone transition phases may trigger depression in some women, yet the underlying mechanisms remain elusive. In a pharmacological sex-hormone manipulation model, we previously reported that estradiol reductions, induced with a gonadotropin-releasing hormone agonist (GnRHa), provoked subclinical depressive symptoms in healthy women, especially if neocortical serotonin transporter (SERT) binding also increased. Within this model, we here evaluated if GnRHa, compared to placebo, reduced hippocampal volume, in a manner that depended on the magnitude of the estradiol decrease and SERT binding, and if this decrease translated to the emergence of subclinical depressive symptoms. Sixty-three healthy, naturally cycling women were included in a randomized, double-blind, placebo-controlled GnRHa-intervention study. We quantified the change from baseline to follow-up (n = 60) in serum estradiol (ΔEstradiol), neocortical SERT binding ([¹¹C] DASB positron emission tomography; ΔSERT), subclinical depressive symptoms (Hamilton depression rating scale; ΔHAMD-17), and hippocampal volume (magnetic resonance imaging data analyzed in Freesurfer 7.1, ΔHippocampus). Group differences in ΔHippocampus were evaluated in a t-test. Within the GnRHa group, associations between ΔEstradiol, ΔHippocampus, and ΔHAMD-17, in addition to ΔSERT-by-ΔEstradiol interaction effects on ΔHippocampus, were evaluated with linear regression models. Mean ΔHippocampus was not significantly different between the GnRHa and placebo group. Within the GnRHa group, hippocampal volume reductions were associated with the magnitude of estradiol decrease (p = 0.04, Cohen's f² = 0.18), controlled for baseline SERT binding, but not subclinical depressive symptoms. There was no ΔSERT-by-ΔEstradiol interaction effects on ΔHippocampus. If replicated, our data highlight a possible association between estradiol fluctuations and hippocampal plasticity, adjusted for serotonergic contributions.

Toxic Effects of Glyphosate on the Nervous System: A Systematic Review

Glyphosate, a non-selective systemic biocide with broad-spectrum activity, is the most widely used herbicide in the world. It can persist in the environment for days or months, and its intensive and large-scale use can constitute a major environmental and health problem. In this systematic review, we investigate the current state of our knowledge related to the effects of this pesticide on the nervous system of various animal species and humans. The information provided indicates that exposure to glyphosate or its commercial formulations induces several neurotoxic effects. It has been shown that exposure to this pesticide during the early stages of life can seriously affect normal cell development by deregulating some of the signaling pathways involved in this process, leading to alterations in differentiation, neuronal growth, and myelination. Glyphosate also seems to exert a significant toxic effect on neurotransmission and to induce oxidative stress, neuroinflammation and mitochondrial dysfunction, processes that lead to neuronal death due to autophagy, necrosis, or apoptosis, as well as the appearance of behavioral and motor disorders. The doses of glyphosate that produce these neurotoxic effects vary widely but are lower than the limits set by regulatory agencies. Although there are important discrepancies between the analyzed findings, it is unequivocal that exposure to glyphosate produces important alterations in the structure and function of the nervous system of humans, rodents, fish, and invertebrates.

Experience-Regulated Neuronal Signaling in Maternal Behavior

Maternal behavior is shaped and challenged by the changing developmental needs of offspring and a broad range of environmental factors, with evidence indicating that the maternal brain exhibits a high degree of plasticity. This plasticity is displayed within cellular and molecular systems, including both intra- and intercellular signaling processes as well as transcriptional profiles. This experience-associated plasticity may have significant overlap with the mechanisms controlling memory processes, in particular those that are activity-dependent. While a significant body of work has identified various molecules and intracellular processes regulating maternal care, the role of activity- and experience-dependent processes remains unclear. We discuss recent progress in studying activity-dependent changes occurring at the synapse, in the nucleus, and during the transport between these two structures in relation to maternal behavior. Several pre- and postsynaptic molecules as well as transcription factors have been found to be critical in these processes. This role reflects the principal importance of the molecular and cellular mechanisms of memory formation to maternal and other behavioral adaptations.

Less can be more: Fine tuning the maternal brain

PAWLUSKI, J.L., Hoekzema, E., Leuner, B., and Lonstein, J.S. Less can be more: Fine tuning the maternal brain. NEUROSCI BIOBEHAV REV (129) XXX-XXX, 2022. Plasticity in the female brain across the lifespan has recently become a growing field of scientific inquiry. This has led to the understanding that the transition to motherhood is marked by some of the most significant changes in brain plasticity in the adult female brain. Perhaps unexpectedly, plasticity occurring in the maternal brain often involves a decrease in brain volume, neurogenesis and glial cell density that presumably optimizes caregiving and other postpartum behaviors. This review summarizes what we know of the 'fine-tuning' of the female brain that accompanies motherhood and highlights the implications of these changes for maternal neurobehavioral health. The first part of the review summarizes structural and functional brain changes in humans during pregnancy and postpartum period with the remainder of the review focusing on neural and glial plasticity during the peripartum period in animal models. The aim of this review is to provide a clear understanding of when 'less is more' in maternal brain plasticity and where future research can focus to improve our understanding of the unique brain plasticity occurring during matrescence.

Recent Neuroscience Advances in Human Parenting

The transition to parenthood entails brain adaptations to the demands of caring for a newborn. This chapter reviews recent neuroscience findings on human parenting, focusing on neuroimaging studies. First, we describe the brain circuits underlying human maternal behavior, which comprise ancient subcortical circuits and more sophisticated cortical regions. Then, we present the short-term and long-term functional and structural brain adaptations that characterize the transition to motherhood, discuss the long-term effects of parenthood on the brain, and propose several underlying neural mechanisms. We also review neuroimaging findings in biological fathers and alloparents (such as other relatives or adoptive parents), who engage in parenting without directly experiencing pregnancy or childbirth. Finally, we describe perinatal mental illnesses and discuss the neural responses associated with such disorders. To date, studies indicate that parenthood is a period of enhanced brain plasticity within brain areas critical for cognitive and social processing and that both parenting experience and gestational-related factors can prime such plasticity.

Is Brain-Derived Neurotropic Factor Methylation Involved in the Association Between Prenatal Stress and Maternal Postnatal Anxiety During the COVID-19 Pandemic?

BACKGROUND

The COVID-19 pandemic is a collective trauma that may expose susceptible individuals to high levels of stress. Pregnant women represent a high-risk population, considering that pregnancy is a period of heightened neuroplasticity and susceptibility to stress through epigenetic mechanisms. Previous studies showed that the methylation status of the BDNF gene is linked with prenatal stress exposure. The goals of this study were (a) to assess the association between pandemic-related stress and postnatal anxiety and (b) to investigate the potential role of maternal BDNF methylation as a significant mediator of this association.

METHODS

In the present study, we report data on the association among pandemic-related stress during pregnancy, maternal BDNF methylation, and postnatal anxiety symptoms. Pandemic-related stress and postnatal anxiety were assessed through self-report instruments. BDNF methylation was estimated in 11 CpG sites in DNA from mothers' buccal cells. Complete data were available from 108 mothers.

RESULTS

Results showed that pandemic-related stress was associated with an increased risk of postnatal anxiety, r = 0.20, p < 0.05. CpG-specific BDNF methylation was significantly associated with both prenatal pandemic-related stress, r = 0.21, p < 0.05, and postnatal maternal anxious symptoms, r = 0.25, p = 0.01. Moreover, a complete mediation by the BDNF CpG6 methylation emerged between pandemic-related stress during pregnancy and postnatal maternal anxiety, ACME = 0.66, p < 0.05.

CONCLUSION

These findings suggest that BDNF epigenetic regulation by pandemic-related stress might contribute to increase the risk of anxiety in mothers. Policymakers should prioritize the promotion of health and wellbeing in pregnant women and mothers during the present healthcare emergency.

A history of previous childbirths is linked to women's white matter brain age in midlife and older age

Maternal brain adaptations occur in response to pregnancy, but little is known about how parity impacts white matter and white matter ageing trajectories later in life. Utilising global and regional brain age prediction based on multi-shell diffusion-weighted imaging data, we investigated the association between previous childbirths and white matter brain age in 8,895 women in the UK Biobank cohort (age range = 54-81 years). The results showed that number of previous childbirths was negatively associated with white matter brain age, potentially indicating a protective effect of parity on white matter later in life. Both global white matter and grey matter brain age estimates showed unique contributions to the association with previous childbirths, suggesting partly independent processes. Corpus callosum contributed uniquely to the global white matter association with previous childbirths, and showed a stronger relationship relative to several other tracts. While our findings demonstrate a link between reproductive history and brain white matter characteristics later in life, longitudinal studies are required to establish causality and determine how parity may influence women's white matter trajectories across the lifespan.

Melatonin: From Neurobiology to Treatment

Melatonin, the major regulator of the sleep/wake cycle, also plays important physiological and pharmacological roles in the control of neuronal plasticity and neuroprotection. Accordingly, the secretion of this hormone reaches the maximal extent during brain development (childhood-adolescence) while it is greatly reduced during aging, a condition associated to altered sleep pattern and reduced neuronal plasticity. Altogether, these properties of melatonin have allowed us to demonstrate in both experimental models and clinical studies the great chronobiotic efficacy and sleep promoting effects of exogenous melatonin. Thus, the prolonged release formulation of melatonin, present as a drug in the pharmaceutical market, has been recently recommended for the treatment of insomnia in over 55 years old subjects.

Interactive effects of compounding multidimensional stressors on maternal and male and female rat offspring outcomes

Exposure to adverse childhood experiences (ACEs) is a risk factor for the development of psychiatric disorders in addition to cardiovascular associated diseases. This risk is elevated when the cumulative burden of ACEs is increased. Laboratory animals can be used to model the changes (as well as the underlying mechanisms) that result in response to adverse events. In this study, using male and female Sprague Dawley rats, we examined the impact of increasing stress burden, utilizing both two adverse early life experiences (parental/offspring high fat diet + limited bedding exposure) and three adverse early life experiences (parental/offspring high fat diet + limited bedding exposure + neonatal inflammation), on maternal care quality and offspring behavior. Additionally, we measured hormones and hippocampal gene expression related to stress. We found that the adverse perinatal environment led to a compensatory increase in maternal care. Moreover, these dams had reduced maternal expression of oxytocin receptor, compared to standard housed dams, in response to acute stress on postnatal day (P)22. In offspring, the two-hit and three-hit models resulted in a hyperlocomotor phenotype and increased body weights. Plasma leptin and hippocampal gene expression of corticotropin releasing hormone (Chrh)1 and Crhr2 were elevated (males) while expression of oxytocin was reduced (females) following acute stress. On some measures (e.g., hyperlocomotion, leptin), the magnitude of change was lower in the three-hit compared to the two-hit model. This suggests that multiple early adverse events can have interactive, and often unpredictable, impacts, highlighting the importance of modeling complex interactions amongst stressors during development.

The birthing brain: A lacuna in neuroscience

During pregnancy, maternal brain neuroplasticity indicates vast neurofunctional and neuroanatomical changes. Recent findings documented a similarly massive readjustment after pregnancy. Currently, these brain changes are interpreted as preparation for and adjustment of the maternal brain to motherhood. Yet, this perspective leaves many questions unsolved. Neuroscientific studies have not yet been conducted to determine the brain areas that function during natural childbirth even though physiological birth is the natural process of women who have reproduced successfully throughout two million years of evolution of the genus Homo. It is rational to believe that the female brain is an active and crucial actor during birth and that birth, itself, is a process that requires brain neuroplasticity. Lack of studies of the birthing brain and brain preparation for birth is a significant lacuna in neuroscience research. I demonstrate theoretically that a new hypothesis for complementary interpretation of maternal brain neuroplasticity is reasonable: Certain maternal brain changes during pregnancy can be interpreted asbrain preparation for birth and certain maternal brain changes after birth can be interpreted asbrain recovery after the tremendous event of birth. This essay can be a starting point for new directions in neuroscience studies.

How stress can influence brain adaptations to motherhood

Research shows that a woman's brain and body undergo drastic changes to support her transition to parenthood during the perinatal period. The presence of this plasticity suggests that mothers' brains may be changed by their experiences. Exposure to severe stress may disrupt adaptive changes in the maternal brain and further impact the neural circuits of stress regulation and maternal motivation. Emerging literature of human mothers provides evidence that stressful experience, whether from the past or present environment, is associated with altered responses to infant cues in brain circuits that support maternal motivation, emotion regulation, and empathy. Interventions that reduce stress levels in mothers may reverse the negative impact of stress exposure on the maternal brain. Finally, outstanding questions regarding the timing, chronicity, types, and severity of stress exposure, as well as study design to identify the causal impact of stress, and the role of race/ethnicity are discussed.

Prolactin enhances hippocampal synaptic plasticity in female mice of reproductive age

Dynamic signaling between the endocrine system (ES) and the nervous system (NS) is essential for brain and body homeostasis. In particular, reciprocal interaction occurs during pregnancy and motherhood that may involve changes in some brain plasticity processes. Prolactin (PRL), a hormone with pleiotropic effects on the NS, promotes maternal behavior and has been linked to modifications in brain circuits during motherhood; however, it is unclear whether PRL may regulate synaptic plasticity. Therefore, the main aim of the present work was to determine the cellular and molecular mechanisms triggered by PRL that regulate synaptic plasticity in the hippocampus. By analyzing extracellular recordings in CA3‐CA1 synapses of hippocampal slices, we report that PRL modifies short and long‐term synaptic plasticity in female mice of reproductive age, but not in sexually immature females or adult males. This effect is carried out through mechanisms that include participation of GABA_A receptors and activation of the JAK2‐mediated signaling pathway. These findings show for the first time how PRL enhances the synaptic strength in hippocampal circuits and that this effect is sexually dimorphic, which would influence complex brain processes in physiological conditions like pregnancy and lactation.

Gestational exposure to excessive levels of dexamethasone impairs maternal care and impacts on the offspring's survival in rats

Administration of dexamethasone (DEX) during late gestation is a model to study growth restriction in rodents, but the pup's mortality index can be high, depending on DEX dosage, and little is known about the effects of DEX on maternal care (MC). Considering that an inadequate MC can also contribute to pup's mortality in this model, we evaluated the effects of DEX on dams' behavior and its consequences on offspring survival. We also investigated whether the cross-fostering of pups from dams treated or not with DEX could improve pup's survival. Wistar rats were treated with DEX (14th to 19th day of gestation -0.2 mg/kg, B.W, in the drinking water). Nest building, MC and responses in the elevated plus-maze, forced swimming and object recognition tests were evaluated. DEX reduced gestational weight gain and impaired neonatal development, reducing pup's survival to 0% by the 3rd postnatal day. DEX-treated dams reduced the expression of typical MC and increased anxiety-like behaviors. After cross-fostering, DEX-treated mothers behaved similarly to controls, indicating that a healthy offspring is crucial to induce adequate MC. Cross-fostering increased the survival index from zero to 25% in the DEX offspring. Postnatal development of the DEX offspring was comparable to controls after cross-fostering. We concluded that exposure to DEX during late gestation causes behavioral changes that compromise the maternal emotional state, disrupting the expression of MC. Although it does not seem to be the main cause of pup's mortality, our data indicate that an adequate MC improves pup's survival in this model.

Oxytocin receptor binding in the titi monkey hippocampal formation is associated with parental status and partner affiliation

Social cognition is facilitated by oxytocin receptors (OXTR) in the hippocampus, a brain region that changes dynamically with pregnancy, parturition, and parenting experience. We investigated the impact of parenthood on hippocampal OXTR in male and female titi monkeys, a pair-bonding primate species that exhibits biparental care of offspring. We hypothesized that in postmortem brain tissue, OXTR binding in the hippocampal formation would differ between parents and non-parents, and that OXTR density would correlate with frequencies of observed parenting and affiliative behaviors between partners. Subjects were 10 adult titi monkeys. OXTR binding in the hippocampus (CA1, CA2/3, CA4, dentate gyrus, subiculum) and presubiculum layers (PSB1, PSB3) was determined using receptor autoradiography. The average frequency of partner affiliation (Proximity, Contact, and Tail Twining) and infant carrying were determined from longitudinal observations (5-6 per day). Analyses showed that parents exhibited higher OXTR binding than non-parents in PSB1 (t₍₈₎ = - 2.33, p = 0.048), and that OXTR binding in the total presubiculm correlated negatively with Proximity (r = - 0.88) and Contact (r = - 0.91), but not Tail Twining or infant carrying. These results suggest that OXTR binding in the presubiculum supports pair bonding and parenting behavior, potentially by mediating changes in hippocampal plasticity.

Associations between stress exposure and new mothers' brain responses to infant cry sounds

Exposure to severe stress has been linked to negative postpartum outcomes among new mothers including mood disorders and harsh parenting. Non-human animal studies show that stress exposure disrupts the normative adaptation of the maternal brain, thus identifying a neurobiological mechanism by which stress can lead to negative maternal outcomes. However, little is known about the impact of stress exposure on the maternal brain response to infant cues in human mothers. We examined the association of stress exposure with brain response to infant cries and maternal behaviors, in a socioeconomically diverse (low- and middle-income) sample of first-time mothers (N=53). Exposure to stress across socioeconomic, environmental, and psychosocial domains was associated with reduced brain response to infant cry sounds in several regions, including the right insula/inferior frontal gyrus and superior temporal gyrus. Reduced activation in these regions was further associated with lower maternal sensitivity observed during a mother-infant interaction. The findings demonstrate that higher levels of stress exposure may be associated with reduced brain response to an infant’s cry in regions that are important for emotional and social information processing, and that reduced brain responses may further be associated with increased difficulties in developing positive mother-infant relationships.

Towards an understanding of women's brain aging: the immunology of pregnancy and menopause

Women are at significantly greater risk of developing Alzheimer's disease and show higher prevalence of autoimmune conditions relative to men. Women's brain health is historically understudied, and little is therefore known about the mechanisms underlying epidemiological sex differences in neurodegenerative diseases, and how female-specific factors may influence women's brain health across the lifespan. In this review, we summarize recent studies on the immunology of pregnancy and menopause, emphasizing that these major immunoendocrine transition phases may play a critical part in women's brain aging trajectories.

Postpartum environmental challenges alter maternal responsiveness and offspring development

Because many threats exist in an animal's natural habitat, it is important to understand the impact of environmental challenges on maternal-offspring interactions and outcomes. In the current study, a rodent model incorporating the presence of restricted resources and an environmental threat (e.g. predator-related odors and sounds) was investigated. Specifically, pregnant females were assigned to one of four treatments: standard resources, without threat (SR; n = 7); standard resources plus threat (SR-T; n = 8); restricted resources, without threat (RR; n = 7); and restricted resources plus threat (RR-T; n = 6). Maternal rats were moved into the assigned conditions on postnatal day 2 and remained until pups were weaned. Following a standard pup retrieval task on postnatal days 2 and 6, maternal rats were exposed to a retrieval challenge task on postnatal day 8 in which each rat had to traverse a novel barrier to retrieve pups. For neurobiological measures of stress/resilience responsiveness, fecal samples were collected for detection of corticosterone and DHEA metabolites; additionally, immunohistochemistry was conducted on the maternal brains to indicate the presence of Neuropeptide Y (NPY) and Brain Derived Neurotrophic Factor (BDNF) immunoreactivity in the hippocampus, amygdala and hypothalamus. Pup development measures, including body weight and tail length, were also collected. Results suggest that maternal rats with restricted resources exhibited diminished maternal responsiveness that resulted in altered pup development measures; further, restricted resource rats exhibited endocrine markers of compromised emotional resilience (lower DHEA) and decreased neural markers of neuroplasticity (BDNF) and emotional resilience (NPY). Interestingly, predator threat affected various aspects of maternal-pup interactions but had no effect on neurobiological variables, suggesting that restricted resources had a more negative impact on maternal-related outcomes than the presence of predator threat.

Acupuncture in Obstetrics and Gynecology

Importance

Acupuncture is a key component of therapy in traditional Chinese medicine. Only in the last few decades has acupuncture become popular in the United States. The mechanism behind acupuncture's effects on the body and brain has not been completely elucidated, but there is evidence that acupuncture has effects on the endocrine, immune, and sympathetic and parasympathetic nervous systems. It may also act through electrical and mechanical signaling through the connective tissue and fascia. Despite this uncertainty, the positive effects of acupuncture have been well established.

Objective

In this review, we discuss the basic concepts of traditional Chinese medicine and acupuncture and examine the evidence regarding the use of acupuncture in obstetrics and gynecology.

Evidence Acquisition

We conducted a literature review of acupuncture in obstetrics and gynecology using PubMed.

Results

The available data demonstrate that acupuncture is beneficial in the treatment of labor pain, back pain in pregnancy, and dysmenorrhea. It is unclear if acupuncture is effective for hyperemesis, chemotherapy-induced nausea and vomiting, and menopausal hot flushes, or if moxibustion is effective in correcting breech presentation. There are limited but positive data regarding menopause-related sleep disturbances, depression in pregnancy, and overactive bladder. Acupuncture is not beneficial for improving outcomes in in vitro fertilization.

Conclusions and Relevance

Acupuncture is an increasingly popular therapy with many potential applications in obstetrics and gynecology. A general understanding of the basic principles of acupuncture and the safety and efficacy of its practice is necessary for the general obstetrician and gynecologist to make informed recommendations to patients.

Effect of sertraline on central serotonin and hippocampal plasticity in pregnant and non-pregnant rats

One of the most frequently prescribed selective serotonin reuptake inhibitor medications (SSRIs) for peripartum mood and anxiety disorders is sertraline (Zoloft®). Sertraline can help alleviate mood and anxiety symptoms in many women but it is not known how sertraline, or SSRIs in general, affect the neurobiology of the brain particularly when pregnant. The aim of this study was to investigate how sertraline affects plasticity in the hippocampus, a brain area integral in depression and SSRI efficacy (particularly in males), during late pregnancy and whether these effects differ from the effects of sertraline in non-pregnant females. To do this pregnant and age-matched non-pregnant female Sprague-Dawley rats were used. For the last half of pregnancy (10 days), and at matched points in non-pregnant females, rats were given sertraline (2.5 mg/kg/day or 10 mg/kg/day) or vehicle (0 mg/kg/day). Brains were used to investigate effects on the serotonergic system in the hippocampus and prefrontal cortex and measures of neuroplasticity in the hippocampus. Results show that pregnant females have significantly higher serum levels of sertraline compared to non-pregnant females but that rates of serotonin turnover in the hippocampus and PFC are similar between pregnant and non-pregnant females. Sertraline increased synaptophysin density in the dentate gyrus and CA3 and was associated with a decrease in cell proliferation in the dentate gyrus of non-pregnant, but not pregnant, females. During late pregnancy the hippocampus showed significant reductions in neurogenesis and increases in synaptophysin density. This research highlights the need to consider the unique effect of reproductive state on the neuropharmacology of SSRIs.

Neurophysiological and cognitive changes in pregnancy

The hormonal fluctuations in pregnancy drive a wide range of adaptive changes in the maternal brain. These range from specific neurophysiological changes in the patterns of activity of individual neuronal populations, through to complete modification of circuit characteristics leading to fundamental changes in behavior. From a neurologic perspective, the key hormone changes are those of the sex steroids, estradiol and progesterone, secreted first from the ovary and then from the placenta, the adrenal glucocorticoid cortisol, as well as the anterior pituitary peptide hormone prolactin and its pregnancy-specific homolog placental lactogen. All of these hormones are markedly elevated during pregnancy and cross the blood-brain barrier to exert actions on neuronal populations through receptors expressed in specific regions. Many of the hormone-induced changes are in autonomic or homeostatic systems. For example, patterns of oxytocin and prolactin secretion are dramatically altered to support novel physiological functions. Appetite is increased and feedback responses to metabolic hormones such as leptin and insulin are suppressed to promote a positive energy balance. Fundamental physiological systems such as glucose homeostasis and thermoregulation are modified to optimize conditions for fetal development. In addition to these largely autonomic changes, there are also changes in mood, behavior, and higher processes such as cognition. This chapter summarizes the hormonal changes associated with pregnancy and reviews how these changes impact on brain function, drawing on examples from animal research, as well as available information about human pregnancy.

Neurobiology of maternal mental illness

This chapter provides an overview of current research discoveries beginning to uncover the neurobiology of maternal mental illness. Results are described according to standard diagnostic categories (specifically, perinatal depression, perinatal anxiety and OCD, postpartum psychosis and bipolar disorder, and trauma and posttraumatic stress disorder), yet we aim to put this approach in context with the introduction of a classification model for psychiatric research, the research domain criteria, gaining traction in basic and clinical translational fields. We first review a new area of study, the neuroplasticity of the pregnant and postpartum brain, as work here has relevance for understanding the pathophysiology of mental disorders and may provide clues to changes in brain functioning that are related to compromised parenting in the context of postpartum depression. We next provide background information on neuroendocrine and immune changes during pregnancy and, to a lesser extent, the postpartum period, as alterations in these systems are significantly implicated in underlying neurobiology of mental illness for peripartum women. Our discussion of the major mental illnesses for pregnant and postpartum women includes neuroendocrine changes, neuroinflammation, and neurotransmitter alterations, as well as circuit dysfunction. Overall, remarkable progress has been made in identifying variations in neurobiology (and related systems) involved in maternal mental illness; yet, it is clear that, as classified with standard diagnostic systems, these are heterogeneous disorders and there is individual variability in the alterations in neurobiology for the same illness.

Population-based neuroimaging reveals traces of childbirth in the maternal brain

Maternal brain adaptations have been found across pregnancy and postpartum, but little is known about the long-term effects of parity on the maternal brain. Using neuroimaging and machine learning, we investigated structural brain characteristics in 12,021 middle-aged women from the UK Biobank, demonstrating that parous women showed less evidence of brain aging compared to their nulliparous peers. The relationship between childbirths and a "younger-looking" brain could not be explained by common genetic variation or relevant confounders. Although prospective longitudinal studies are needed, the results suggest that parity may involve neural changes that could influence women's brain aging later in life.

Fatherhood diminishes the hippocampal damaging action of excitotoxic lesioning in mice

Parental experience imposes neuroplasticity in the hippocampus of females and males. In lactating rat dams, the hippocampus is protected against excitotoxic damage by kainic acid lesioning, although it is still unknown whether paternity can provide such protection to male rodents. To evaluate the protective effects of fatherhood against excitotoxic lesions, we paired male mice with females and co-housed them until the day of parturition (PPD0), when we randomly assigned them to two groups: (i) the pregnancy group (males housed individually overnight and injected i.c.v. with 100 ng per 1 μL of kainic acid or vehicle on PPD1) and (ii) the sire group (males housed with the dam and pups until PPD8, when injected i.c.v. after evaluation of parental behaviour). Individually housed virgin adult male mice formed the control group. Markers of neurodegeneration (NeuN, Fluoro-Jade C) and astrogliosis (glial fibrillary acidic protein) were evaluated in fixed cerebral tissue containing the dorsal CA1, CA3 and CA4 hippocampal subfields. The CA1 subfield did not suffer damage in any of the experimental groups. The sire group exhibited less neurodegeneration and astrogliosis in the CA3 and CA4 subfields compared to their respective controls, independently of the expression of parental behaviour. Western blot analysis was conducted for prolactin (PRL), PRL receptor and related intracellular pathways. Monomeric PRL was lower in the hippocampus of sires in the first week postpartum with a parallel rise of a 48-kDa dimerised isoform compared to virgin controls. The long isoform of PRL receptor did not change, and signal transducer and activator of transcription 5 (STAT5) was not detected in the hippocampus. However, a sustained rise in pAkt, a signalling molecule that participates in cell survival, was observed in the sire group. These results indicate that the hippocampus of sires housed with the dam and pups is less sensitive to neurotoxic injury, which might not be primarily regulated by PRL-STAT5-modulated mechanisms.

Experience of Adversity during a First Lactation Modifies Prefrontal Cortex Morphology in Primiparous Female Rats: Lack of Long Term Effects on a Subsequent Lactation

Reproductive experience is associated with morphological and functional plasticity in brain areas important for cognitive and emotional responses, including the infralimbic (IL) medial prefrontal cortex (mPFC). Here we examined whether suboptimal conditions during a first lactation could modify lactation-induced morphological IL mPFC changes, leading to alterations in stress responses and attention and whether any observed effects would persist into a second lactation. Reduced availability of bedding and nesting material (LB) was used to induce unfavorable conditions in primiparous (P) mothers. In normal bedding (NB) conditions, P mothers exhibited high spine number and density on postpartum day (PPD)10, which greatly decreased 2 weeks after weaning of their pups. In contrast, P-LB mothers had a lower spine number and density on PPD10, which markedly increased after weaning. LB exposure did not modify stress responsiveness to a ferret odor on PPD5 in primiparous or in multiparous (M) females. Number of errors and trials to criterion in the attention set shifting task were not modified by a history of adversity in multiparous females, although this group tended to exhibit higher attentional abilities than M-NB females. These results suggest that adversity acutely reduces morphological plasticity in the maternal mPFC during lactation, an effect that is not associated with significant changes in stress responses and/or glucocorticoid production. Medial PFC morphological changes induced by LB subside during a subsequent lactation as does the effect of maternity itself.

Glyphosate and glyphosate-based herbicide exposure during the peripartum period affects maternal brain plasticity, maternal behaviour and microbiome

Glyphosate is found in a large array of non-selective herbicides such as Roundup® (Monsanto, Creve Coeur, MO, USA) and is by far the most widely used herbicide. Recent work in rodent models suggests that glyphosate-based herbicides during development can affect neuronal communication and result in altered behaviours, albeit through undefined mechanisms of action. To our knowledge, no study has investigated the effects glyphosate or its formulation in herbicide on maternal behaviour and physiology. In the present study, relatively low doses of glyphosate (5 mg kg-1  d-1 ), Roundup® (5 mg kg-1  d-1 glyphosate equivalent), or vehicle were administered by ingestion to Sprague-Dawley rats from gestational day (GD) 10 to postpartum day (PD)22. The treatments significantly altered licking behaviour toward pups between PD2 and PD6. We also show in the dams at PD22 that Roundup exposure affected the maturation of doublecortin-immunoreactive new neurones in the dorsal dentate gyrus of the hippocampus of the mother. In addition, the expression of synaptophysin was up-regulated by glyphosate in the dorsal and ventral dentate gyrus and CA3 regions of the hippocampus, and down-regulated in the cingulate gyrus. Although a direct effect of glyphosate alone or its formulation on the central nervous system is currently not clear, we show that gut microbiota is significantly altered by the exposure to the pesticides, with significant alteration of the phyla Bacteroidetes and Firmicutes. This is the first study to provide evidence that glyphosate alone or in formulation (Roundup) differentially affects maternal behaviour and modulates neuroplasticity and gut microbiota in the mother.

Multiparity Dampened the Neurobehavioral Consequences of Mother-Pup Separation Stress in Dams

Reproductive experience in mammals produces significant neuroendocrine and behavioral changes that are necessary to ensure the survival of the mother and the young. Exposure to stress during postpartum may affect the proper development of maternal behaviors. The present study examined whether previous reproductive experience affects neurobehavioral responses in females exposed to mother-infant separation stress during the postpartum period (4.5 h/day for 3 weeks). Anxiety-like behavior and spatial learning were evaluated in nulliparous (NP), primiparous (PRI) and multiparous (MULT). In maternal animals (PRI and MULT), maternal behavior was also assessed. Cell survival and proliferation in the dentate gyrus, as well as BDNF expression in the hippocampus, were evaluated by immunohistochemistry as possible candidates for mediating brain plasticity in response to reproductive experience and stress. Anxiety-like behavior as measured on the open field test showed an increase in NP and PRI-stressed, while neither stressed nor unstressed MULT expressed this behavior. Maternal unstressed animals both PRI and MULT exhibited enhanced memory task performance in the Barnes maze. Multiparity increased cell proliferation and cell survival in female rats and these changes occurred independently of pup exposure. The expression of BDNF was higher in the CA1 area in MULT rats. Although multiparity protects the mother against some of the effects of maternal separation stress, promoting behaviors directed to the pups during the early postpartum, preventing anxiety-like behaviors and mitigating memory deterioration after weaning, the data showed that disrupting natural dam-pup interaction produced neurobiological consequences on the mother even with multiple reproductive experience.

Mothers, Fathers, and Others: Neural Substrates of Parental Care

Parental care is essential for the survival of offspring in altricial mammalian species. However, in most mammals, virgin females tend to avoid or attack infants. Moreover, most males demonstrate avoidance and aggression toward infants, and have little to no involvement in parental care. What mechanisms suppress avoidance, and support approach towards pups, to promote maternal care? In biparental and cooperatively breeding species, what mechanisms allow nonmothers (i.e., fathers and alloparents) to demonstrate parental care? In this review we consider the mechanisms that subserve parental care in mothers, fathers, and others (i.e., alloparents). We emphasize recent discoveries and research trends with particular emphasis on neuroendocrinology, neuroplasticity, transcriptomics, and epigenetics. Finally, we consider outstanding questions and outline opportunities for future research.

The parental brain and behavior: A target for endocrine disruption

During pregnancy, the sequential release of progesterone, 17β-estradiol, prolactin, oxytocin and placental lactogens reorganize the female brain. Brain structures such as the medial preoptic area, the bed nucleus of the stria terminalis and the motivation network including the ventral tegmental area and the nucleus accumbens are reorganized by this specific hormonal schedule such that the future mother will be ready to provide appropriate care for her offspring right at parturition. Any disruption to this hormone pattern, notably by exposures to endocrine disrupting chemicals (EDC), is therefore likely to affect the maternal brain and result in maladaptive maternal behavior. Development effects of EDCs have been the focus of intense study, but relatively little is known about how the maternal brain and behavior are affected by EDCs. We encourage further research to better understand how the physiological hormone sequence prepares the mother's brain and how EDC exposure could disturb this reorganization.

Neural correlates of emotion processing comparing antidepressants and exogenous oxytocin in postpartum depressed women: An exploratory study

Despite common use of antidepressants to treat postpartum depression, little is known about the impact of antidepressant use on postpartum brain activity. Additionally, although oxytocin has been investigated as a potential treatment for postpartum depression, the interaction between antidepressants and exogenous oxytocin on brain activity is unknown. We explored postpartum depressed women's neural activation in areas identified as important to emotion and reward processing and potentially, antidepressant response: the amygdala, nucleus accumbens and ventral tegmental area. We conducted a secondary analysis of a functional imaging study of response to sexual, crying infant and smiling infant images in 23 postpartum depressed women with infants under six months (11 women taking antidepressants, 12 unmedicated). Participants were randomized to receive a single dose of oxytocin or placebo nasal spray. There was significantly higher amygdala activation to sexual stimuli than either neutral or infant-related stimuli among women taking antidepressants or receiving oxytocin nasal spray. Among unmedicated women receiving placebo, amygdala activation was similar across stimuli types. There were no significant effects of antidepressants nor oxytocin nasal spray on reward area processing (i.e., in the nucleus accumbens or ventral tegmental area). Among postpartum women who remain depressed, there may be significant interactions between the effects of antidepressant use and exogenous oxytocin on neural activity associated with processing emotional information. Observed effect sizes were moderate to large, strongly suggesting the need for further replication with a larger sample.

Limbic-visual attenuation to crying faces underlies neglectful mothering

Neglectful mothering is one of the most common forms of childhood maltreatment, involving a severe disregard of the child's needs, yet little is known about its neural substrate. A child's needs are usually conveyed by signals of distress revealed by crying faces. We tested whether infant and adult crying faces are processed differently in two sociodemographically similar groups of Neglectful (NM) and non-neglectful Control Mothers (CM). We used functional brain imaging to analyze the BOLD response from 43 mothers (23 neglectful and 20 control) while viewing faces from infants and adults (crying and neutral). In NM as compared to CM, the BOLD responses to both infant and adult crying faces were significantly reduced in the cerebellum, lingual, fusiform, amygdala, hippocampus, parahippocampus, and inferior frontal gyrus. The reduced BOLD was also modulated by comorbid psychiatric symptoms. In the CM, frontal activation to infant versus adult crying faces was enhanced, whereas in the NM activation in the anterior cingulate cortex to infant crying was reduced compared to adult crying. The altered neural response to crying faces in NM, showing generic face and infant-specific face processing deficits, could underlie their characteristic poor social abilities as well as their poor response to infant needs, both affecting the caregiving role.