Synchronized maternal-infant elevations of primate CSF CRF concentrations in response to variable foraging demand

Lifelong reductions of PKMζ in ventral hippocampus of nonhuman primates exposed to early-life adversity due to unpredictable maternal care

Protein kinase Mζ (PKMζ) maintains long-term potentiation (LTP) and long-term memory through persistent increases in kinase expression. Early-life adversity is a precursor to adult mood and anxiety disorders, in part, through persistent disruption of emotional memory throughout life. Here we subjected 10- to 16-wk-old male bonnet macaques to adversity by a maternal variable-foraging demand paradigm. We then examined PKMζ expression in their ventral hippocampi as 7- to 12-yr-old adults. Quantitative immunohistochemistry reveals decreased PKMζ in dentate gyrus, CA1, and subiculum of subjects who had experienced early-life adversity due to the unpredictability of maternal care. Adult animals with persistent decrements of PKMζ in ventral hippocampus express timid rather than confrontational responses to a human intruder. Persistent down-regulation of PKMζ in the ventral hippocampus might reduce the capacity for emotional memory maintenance and contribute to the long-lasting emotional effects of early-life adversity.

Developmental Antecedents of Adult Macaque Neurogenesis: Early-Life Adversity, 5-HTTLPR Polymorphisms, and Adolescent Hippocampal Volume

INTRODUCTION

Attenuated adult hippocampal neurogenesis may manifest in affective symptomatology and/or resistance to antidepressant treatment. While early-life adversity and the short variant ('s') of the serotonin transporter gene's long polymorphic region (5-HTTLPR) are suggested as interacting risk factors for affective disorders, no studies have examined whether their superposed risk effectuates neurogenic changes into adulthood. Similarly, it is not established whether reduced hippocampal volume in adolescence, variously identified as a marker and antecedent of affective disorders, anticipates diminished adult neurogenesis. We investigate these potential developmental precursors of neurogenic alterations using a bonnet macaque model.

METHODS

Twenty-five male infant bonnet macaques were randomized to stressed [variable foraging demand (VFD)] or normative [low foraging demand (LFD)] rearing protocols and genotyped for 5-HTTLPR polymorphisms. Adolescent MRI brain scans (mean age 4.2y) were available for 14 subjects. Adult-born neurons were detected post-mortem (mean age 8.6y) via immunohistochemistry targeting the microtubule protein doublecortin (DCX). Models were adjusted for age and weight.

RESULTS

A putative vulnerability group (VG) of VFD-reared 's'-carriers (all 's/l') exhibited reduced neurogenesis compared to non-VG subjects. Neurogenesis levels were positively predicted by ipsilateral hippocampal volume normalized for total brain volume, but not by contralateral or raw hippocampal volume.

LIMITATIONS

No 's'-carriers were identified in LFD-reared subjects, precluding a 2×2 factorial analysis.

CONCLUSION

The 's' allele (with adverse rearing) and low adolescent hippocampal volume portend a neurogenic deficit in adult macaques, suggesting persistent alterations in hippocampal plasticity may contribute to these developmental factors' affective risk in humans.

Cortisol and socioeconomic status in early childhood: A multidimensional assessment

The hypothalamic-pituitary-adrenal (HPA) axis is sensitive to early life stress, with enduring consequences for biological stress vulnerability and health (Gunnar & Talge, 2008). Low socioeconomic status (SES) is associated with dysregulation of the stress hormone cortisol in early childhood. However, a mechanistic understanding of this association is lacking. Multidimensional assessment of both SES and cortisol is needed to characterize the intricate relations between SES and cortisol function in early childhood. We assessed parent-reported family income, parent education, occupational prestige, neighborhood risk, food insecurity, and household chaos for 12-month-old infants (N = 90) and 3.5-year-old children (N = 91). Hair cortisol concentration (HCC) was obtained from parent and child, indexing chronic biological stress, and diurnal salivary cortisol was measured in the children. Controlling for parent HCC, parent education uniquely predicted infant and child HCC and, in addition, neighborhood risk uniquely predicted infant HCC. Household chaos predicted bedtime salivary cortisol concentration (SCC) for both infants and children, and infant daily cortisol output. Food insecurity was associated with flattened cortisol slope in 3.5-year-old children. Parental sensitivity did not mediate relations between SES and cortisol. Results highlight the utility of SES measures that index unpredictable and unsafe contexts, such as neighborhood risk, food insecurity, and household chaos.

Social Allostasis and Social Allostatic Load: A New Model for Research in Social Dynamics, Stress, and Health

Theories such as social baseline theory have argued that social groups serve a regulatory function but have not explored whether this regulatory process carries costs for the group. Allostatic load, the wear and tear on regulatory systems caused by chronic or frequent stress, is marked by diminished stress system flexibility and compromised recovery. We argue that allostatic load may develop within social groups as well and provide a model for how relationship dysfunction operates. Social allostatic load may be characterized by processes such as groups becoming locked into static patterns of interaction and may ultimately lead to up-regulation or down-regulation of a group's set point, or the optimal range of arousal or affect around which the group tends to converge. Many studies of emotional and physiological linkage within groups have reported that highly correlated states of arousal, which may reflect failure to maintain a group-level regulatory baseline, occur in the context of stress, conflict, and relationship distress. Relationship strain may also place greater demands on neurocognitive regulatory processes. Just as allostatic load may be detrimental to individual health, social allostatic load may corrode relationship quality.

Maternal Cerebrospinal Fluid Glutamate in Response to Variable Foraging Demand: Relationship to Cerebrospinal Fluid Serotonin Metabolites in Grown Offspring

Background

Maternal response to allostatic overload during infant rearing may alter neurobiological measures in grown offspring, potentially increasing susceptibility to mood and anxiety disorders. We examined maternal cerebrospinal fluid (CSF) glutamate response during exposure to variable foraging demand (VFD), a bonnet macaque model of allostatic overload, testing whether activation relative to baseline predicted concomitant CSF elevations of the stress neuropeptide, corticotropin-releasing factor. We investigated whether VFD-induced activation of maternal CSF glutamate affects maternal–infant attachment patterns and offspring CSF 5-hydroxyindoleacetic acid concentrations.

Methods

Mother–infant dyads were exposed to the “VFD stressor,” a paradigm in which mothers experience 16 weeks of foraging uncertainty while rearing their infant offspring. Through staggering the infant age of VFD onset, both a cross-sectional design and a longitudinal design were used. Maternal CSF glutamate and glutamine concentrations post-VFD exposure were cross-sectionally compared to maternal VFD naive controls. Proportional change in concentrations of maternal glutamate (and glutamine), a longitudinal measure, was evaluated in relation to VFD-induced elevations of CSF corticotropin-releasing factor. The former measure was related to maternal–infant proximity scores obtained during the final phases of VFD exposure. Maternal glutamatergic response to VFD exposure was used as a predictor variable for young adolescent offspring CSF metabolites of serotonin, dopamine, and norepinephrine.

Results

Following VFD exposure, maternal CSF glutamate concentrations correlated positively with maternal CSF CRF concentrations. Activation relative to baseline of maternal CSF glutamate concentrations following VFD exposure correlated directly with a) increased maternal-infant proximity during the final phases of VFD and b) offspring CSF concentrations of monoamine metabolites including 5-hydroxyindoleacetic acid, which was elevated relative to controls.

Conclusions

Activation of maternal CSF glutamate in response to VFD-induced allostasis is directly associated with elevations of maternal CSF corticotropin-releasing factor. Maternal CSF glutamate alterations induced by VFD potentially compromise serotonin neurotransmission in grown offspring, conceivably modeling human vulnerability to treatment-resistant mood and anxiety disorders.

Early Life Stress Associated With Increased Striatal N-Acetyl-Aspartate: Cerebrospinal Fluid Corticotropin-Releasing Factor Concentrations, Hippocampal Volume, Body Mass and Behavioral Correlates

Introduction

Using proton magnetic resonance spectroscopy imaging, the effects of early life stress on nonhuman primate striatal neuronal integrity were examined as reflected by N-acetyl aspartate (NAA) concentrations. NAA measures were interrogated through examining their relationship to previously documented early life stress markers—cerebrospinal fluid corticotropin-releasing factor concentrations, hippocampal volume, body mass, and behavioral timidity. Rodent models of depression exhibit increases in neurotrophic effects in the nucleus accumbens. We hypothesized that rearing under conditions of early life stress (variable foraging demand, VFD) would produce persistent elevations of NAA concentrations (in absolute or ratio form) in ventral striatum/caudate nucleus (VS/CN) with altered correlation to early life stress markers.

Methods

Eleven bonnet macaque males reared under VFD conditions and seven age-matched control subjects underwent proton magnetic resonance spectroscopy imaging during young adulthood. Voxels were placed over VS/CN to capture nucleus accumbens. Cisternal cerebrospinal fluid corticotropin-releasing factor concentrations, hippocampal volume, body mass, and response to a human intruder had been previously determined.

Results

VFD-reared monkeys exhibited significantly increased NAA/creatine concentrations in right VS/CN in comparison to normally reared controls, controlling for multiple comparisons. In comparison to controls, VFD cerebrospinal fluid corticotropin-releasing factor concentrations were directly associated with right VS/CN absolute NAA. Left hippocampal volume was inversely associated with left VS/CN NAA/creatine in VFD reared but not in controls. Disruption of a normative inverse correlation between left VS/CN NAA and body mass was noted in VFD. Only non-VFD subjects exhibited a direct relationship between timidity response to an intruder and right VS/CN NAA.

Conclusion

Early life stress produced persistent increases in VS/CN NAA, which demonstrated specific patterns of association (or lack thereof) to early life stress markers in comparison to non-VFD subjects. The data are broadly consistent with a stable nonhuman primate phenotype of anxiety and mood disorder vulnerability whereby in vivo indicators of neuronal integrity, although reduced in hippocampus, are increased in striatum. The findings may provide a catalyst for further studies in humans and other species regarding a reciprocal hippocampal/nucleus accumbens relationship in affective disorders.

Maternal hypothalamic-pituitary-adrenal axis response to foraging uncertainty: A model of individual vs. social allostasis and the "Superorganism Hypothesis"

INTRODUCTION

Food insecurity is a major global contributor to developmental origins of adult disease. The allostatic load of maternal food uncertainty from variable foraging demand (VFD) activates corticotropin-releasing factor (CRF) without eliciting hypothalamic-pituitary-adrenal (HPA) activation measured on a group level. Individual homeostatic adaptations of the HPA axis may subserve second-order homeostasis, a process we provisionally term "social allostasis." We postulate that maternal food insecurity induces a "superorganism" state through coordination of individual HPA axis response.

METHODS

Twenty-four socially-housed bonnet macaque maternal-infant dyads were exposed to 16 weeks of alternating two-week epochs of low or high foraging demand shown to compromise normative maternal-infant rearing. Cerebrospinal fluid (CSF) CRF concentrations and plasma cortisol were measured pre- and post-VFD. Dyadic distance was measured, and blinded observers performed pre-VFD social ranking assessments.

RESULTS

Despite marked individual cortisol responses (mean change = 20%) there was an absence of maternal HPA axis group mean response to VFD (0%). Whereas individual CSF CRF concentrations change = 56%, group mean did increase 25% (p = 0.002). Our "dyadic vulnerability" index (low infant weight, low maternal weight, subordinate maternal social status and reduced dyadic distance) predicted maternal cortisol decreases (p < 0.0001) whereas relatively "advantaged" dyads exhibited maternal cortisol increases in response to VFD exposure.

COMMENT

In response to a chronic stressor, relative dyadic vulnerability plays a significant role in determining the directionality and magnitude of individual maternal HPA axis responses in the service of maintaining a "superorganism" version of HPA axis homeostasis, provisionally termed "social allostasis."

Consequences of early adverse rearing experience(EARE) on development: insights from non-human primate studies

Early rearing experiences are important in one's whole life, whereas early adverse rearing experience(EARE) is usually related to various physical and mental disorders in later life. Although there were many studies on human and animals, regarding the effect of EARE on brain development, neuroendocrine systems, as well as the consequential mental disorders and behavioral abnormalities, the underlying mechanisms remain unclear. Due to the close genetic relationship and similarity in social organizations with humans, non-human primate(NHP) studies were performed for over 60 years. Various EARE models were developed to disrupt the early normal interactions between infants and mothers or peers. Those studies provided important insights of EARE induced effects on the physiological and behavioral systems of NHPs across life span, such as social behaviors(including disturbance behavior, social deficiency, sexual behavior, etc), learning and memory ability, brain structural and functional developments(including influences on neurons and glia cells, neuroendocrine systems, e.g., hypothalamic-pituitary-adrenal(HPA) axis, etc). In this review, the effects of EARE and the underlying epigenetic mechanisms were comprehensively summarized and the possibility of rehabilitation was discussed.

Reduced left ventricular dimension and function following early life stress: A thrifty phenotype hypothesis engendering risk for mood and anxiety disorders

Background

Early life stress (ELS) in macaques in the form of insecure maternal attachment putatively induces epigenetic adaptations resulting in a "thrifty phenotype" throughout the life cycle. For instance, ELS induces persistent increases in insulin resistance, hippocampal and corpus callosum atrophy and reduced "behavioral plasticity", which, taken together, engenders an increased risk for mood and anxiety disorders in humans but also a putative sparing of calories. Herein, we test the hypothesis whether a thrifty phenotype induced by ELS is peripherally evident as hypotrophy of cardiac structure and function, raising the possibility that certain mood disorders may represent maladaptive physiological and central thrift adaptations.

Methods

14 adult bonnet macaques (6 males) exposed to the maternal variable foraging demand (VFD) model of ELS were compared to 20 non-VFD adult subjects (6 males). Left ventricle end-diastolic dimension (LVEDD), Left ventricle end-systolic dimension (LVESD) and stroke volume (SV) were calculated using echocardiography. Blood pressure and heart rate were measured only in females. Previously obtained neurobehavioral correlates available only in males were analyzed in the context of cardiac parameters.

Results

Reduced LVESD (p < 0.05) was observed when controlled for age, sex, body weight and crown-rump length whereas ejection fraction (EF) (p = 0.037) was greater in VFD-reared versus non-VFD subjects. Pulse pressure was lower in VFD versus non-VFD females (p < 0.05). Male timidity in response to a human intruder was associated with reduced LVEDD (p < 0.05).

Conclusions

ELS is associated with both structural and functional reductions of left ventricular measures, potentially implying a body-wide thrifty phenotype. Parallel "thrift" adaptations may occur in key brain areas following ELS and may play an unexplored role in mood and anxiety disorder susceptibility.

Patterns of anterior versus posterior white matter fractional anistotropy concordance in adult nonhuman primates: Effects of early life stress

INTRODUCTION

Functional neuroimaging studies report global prefrontal dysconnectivity in mood disorders, supporting the notion of widespread disruptions in brain networks. Microscopic alterations in white matter (WM) tracts - which possess neuroplastic properties and play a central role in brain connectivity - are interrogated herein in the context of brain dysconnectivity. Early life stress (ELS), an antecedent to human mood disorders, induces WM alterations in volumetrics and integrity. We hypothesized that nonhuman primate infants exposed to ELS would exhibit persistent impairments in both frontal and posterior concordance of WM integrity, therefore contributing to global brain dysconnectivity.

METHODS

Using a 3T MRI, diffusion tensor imaging (DTI) was performed on 21 adult male Bonnet macaques, 12 of whom had been raised under variable foraging demand (VFD) conditions and nine of whom had been raised under normative conditions (Non-VFD). As representative of anterior regions, fractional anisotropy (FA) concordance between anterior corpus callosum (ACorpusC) and anterior limb of the internal capsule (ALIC) was examined. For posterior regions, FA concordance between posterior corpus callosum (PCorpusC) and posterior limb of the internal capsule (PLICA) and between PCorpusC and occipital WM was examined. Examination of posterior FA was explored in the context of frontal markers of neuroplasticity.

RESULTS

A concordant relationship for FA between left ALIC and ACorpusC was evident in Non-VFD-reared subjects, but significantly absent in VFD-reared subjects. For left posterior regions, FA concordance between PLICA and PCorpusC and occipital WM and PCorpusC was evident in VFD-reared and not Non-VFD-reared subjects. The posterior concordance in VFD was significantly distinguishable from the deficit in anterior concordance FA in VFD.

CONCLUSIONS

The findings support the view that disrupted emotional integrity of the maternal-infant attachment process affects normative synchronous development of frontal white matter tracts but creates errant posterior concordance and also disrupts an inverse relationship between posterior white matter tracts and markers of neuroplasticity. We provide preliminary evidence that a concordant relationship between capsular-callosal FA may become discordant, providing a putative mechanism for prefrontal functional brain dysconnectivity.

Influence of maternal care on the developing brain: Mechanisms, temporal dynamics and sensitive periods

Variation in maternal care can lead to divergent developmental trajectories in offspring with implications for neuroendocrine function and behavioral phenotypes. Study of the long-term outcomes associated with mother-infant interactions suggests complex mechanisms linking the experience of variation in maternal care and these neurobiological consequences. Through integration of genetic, molecular, cellular, neuroanatomical, and neuroendocrine approaches, significant advances in our understanding of these complex pathways have been achieved. In this review, we will consider the impact of maternal care on male and female offspring development with a particular focus on the issues of timing and mechanism. Identifying the period of sensitivity to maternal care and the temporal dynamics of the molecular and neuroendocrine changes that are a consequence of maternal care represents a critical step in the study of mechanism.

The lasting impact of early-life adversity on individuals and their descendants: potential mechanisms and hope for intervention

The adverse effects of early-life stress are pervasive, with well-established mental and physical health consequences for exposed individuals. The impact of early adverse experiences is also highly persistent, with documented increases in risk for mental illness across the life span that are accompanied by stable alterations in neural function and hormonal responses to stress. Here, we review some of these 'stress phenotypes', with a focus on intermediary factors that may signal risk for long-term mental health outcomes, such as altered development of the fear regulation system. Intriguingly, recent research suggests that such stress phenotypes may persist even beyond the life span of the individuals, with consequences for their offspring and grand-offspring. Phenotypic characteristics may be transmitted to future generations via either the matriline or the patriline, a phenomenon that has been demonstrated in both human and animal studies. In this review, we highlight behavioral and epigenetic factors that may contribute to this multigenerational transmission and discuss the potential of various treatment approaches that may halt the cycle of stress phenotypes.

Early-life experience, epigenetics, and the developing brain

Development is a dynamic process that involves interplay between genes and the environment. In mammals, the quality of the postnatal environment is shaped by parent-offspring interactions that promote growth and survival and can lead to divergent developmental trajectories with implications for later-life neurobiological and behavioral characteristics. Emerging evidence suggests that epigenetic factors (ie, DNA methylation, posttranslational histone modifications, and small non-coding RNAs) may have a critical role in these parental care effects. Although this evidence is drawn primarily from rodent studies, there is increasing support for these effects in humans. Through these molecular mechanisms, variation in risk of psychopathology may emerge, particularly as a consequence of early-life neglect and abuse. Here we will highlight evidence of dynamic epigenetic changes in the developing brain in response to variation in the quality of postnatal parent-offspring interactions. The recruitment of epigenetic pathways for the biological embedding of early-life experience may also have transgenerational consequences and we will describe and contrast two routes through which this transmission can occur: experience dependent vs germline inheritance. Finally, we will speculate regarding the future directions of epigenetic research and how it can help us gain a better understanding of the developmental origins of psychiatric dysfunction.

Neurobiology of Maternal Stress: Role of Social Rank and Central Oxytocin in Hypothalamic-Pituitary Adrenal Axis Modulation

BACKGROUND

Chronic stress may conceivably require plasticity of maternal physiology and behavior to cope with the conflicting primary demands of infant rearing and foraging for food. In addition, social rank may play a pivotal role in mandating divergent homeostatic adaptations in cohesive social groups. We examined cerebrospinal fluid (CSF) oxytocin (OT) levels and hypothalamic-pituitary adrenal (HPA) axis regulation in the context of maternal social stress and assessed the contribution of social rank to dyadic distance as reflective of distraction from normative maternal-infant interaction.

METHODS

Twelve socially housed mother-infant bonnet macaque dyads were studied after variable foraging demand (VFD) exposure compared to 11 unstressed dyads. Dyadic distance was determined by behavioral observation. Social ranking was performed blindly by two observers. Post-VFD maternal plasma cortisol and CSF OT were compared to corresponding measures in non-VFD-exposed mothers.

RESULTS

High-social rank was associated with increased dyadic distance only in VFD-exposed dyads and not in control dyads. In mothers unexposed to VFD, social rank was not related to maternal cortisol levels, whereas VFD-exposed dominant versus subordinate mothers exhibited increased plasma cortisol. Maternal CSF OT directly predicted maternal cortisol only in VFD-exposed mothers. CSF OT was higher in dominant versus subordinate mothers. VFD-exposed mothers with "high" cortisol specifically exhibited CSF OT elevations in comparison to control groups.

CONCLUSION

Pairing of maternal social rank to dyadic distance in VFD presumably reduces maternal contingent responsivity, with ensuing long-term sequelae. VFD-exposure dichotomizes maternal HPA-axis response as a function of social rank with relatively reduced cortisol in subordinates. OT may serve as a homeostatic buffer during maternal stress exposure.

Glucagon-like peptide-1 as predictor of body mass index and dentate gyrus neurogenesis: neuroplasticity and the metabolic milieu

Glucagon-like peptide-1 (GLP-1) regulates carbohydrate metabolism and promotes neurogenesis. We reported an inverse correlation between adult body mass and neurogenesis in nonhuman primates. Here we examine relationships between physiological levels of the neurotrophic incretin, plasma GLP-1 (pGLP-1), and body mass index (BMI) in adolescence to adult neurogenesis and associations with a diabesity diathesis and infant stress. Morphometry, fasting pGLP-1, insulin resistance, and lipid profiles were measured in early adolescence in 10 stressed and 4 unstressed male bonnet macaques. As adults, dentate gyrus neurogenesis was assessed by doublecortin staining. High pGLP-1, low body weight, and low central adiposity, yet peripheral insulin resistance and high plasma lipids, during adolescence were associated with relatively high adult neurogenesis rates. High pGLP-1 also predicted low body weight with, paradoxically, insulin resistance and high plasma lipids. No rearing effects for neurogenesis rates were observed. We replicated an inverse relationship between BMI and neurogenesis. Adolescent pGLP-1 directly predicted adult neurogenesis. Two divergent processes relevant to human diabesity emerge—high BMI, low pGLP-1, and low neurogenesis and low BMI, high pGLP-1, high neurogenesis, insulin resistance, and lipid elevations. Diabesity markers putatively reflect high nutrient levels necessary for neurogenesis at the expense of peripheral tissues.

Early life stress and macaque amygdala hypertrophy: preliminary evidence for a role for the serotonin transporter gene

Background: Children exposed to early life stress (ELS) exhibit enlarged amygdala volume in comparison to controls. The primary goal of this study was to examine amygdala volumes in bonnet macaques subjected to maternal variable foraging demand (VFD) rearing, a well-established model of ELS. Preliminary analyses examined the interaction of ELS and the serotonin transporter gene on amygdala volume. Secondary analyses were conducted to examine the association between amygdala volume and other stress-related variables previously found to distinguish VFD and non-VFD reared animals.

Methods: Twelve VFD-reared and nine normally reared monkeys completed MRI scans on a 3T system (mean age = 5.2 years).

Results: Left amygdala volume was larger in VFD vs. control macaques. Larger amygdala volume was associated with: “high” cerebrospinal fluid concentrations of corticotropin releasing-factor (CRF) determined when the animals were in adolescence (mean age = 2.7 years); reduced fractional anisotropy (FA) of the anterior limb of the internal capsule (ALIC) during young adulthood (mean age = 5.2 years) and timid anxiety-like responses to an intruder during full adulthood (mean age = 8.4 years). Right amygdala volume varied inversely with left hippocampal neurogenesis assessed in late adulthood (mean age = 8.7 years). Exploratory analyses also showed a gene-by-environment effect, with VFD-reared macaques with a single short allele of the serotonin transporter gene exhibiting larger amygdala volume compared to VFD-reared subjects with only the long allele and normally reared controls.

Conclusion: These data suggest that the left amygdala exhibits hypertrophy after ELS, particularly in association with the serotonin transporter gene, and that amygdala volume variation occurs in concert with other key stress-related behavioral and neurobiological parameters observed across the lifecycle. Future research is required to understand the mechanisms underlying these diverse and persistent changes associated with ELS and amygdala volume.

Impact of childhood stress on psychopathology

OBJECTIVE

Advances in our knowledge of mental disorder (MD) genetics have contributed to a better understanding of their pathophysiology. Nonetheless, several questions and doubts persist. Recent studies have focused on environmental influences in the development of MDs, and the advent of neuroscientific methodologies has provided new perspectives. Early life events, such as childhood stress, may affect neurodevelopment through mechanisms such as gene-environment interactions and epigenetic regulation, thus leading to diseases in adulthood. The aim of this paper is to review the evidence regarding the role of the environment, particularly childhood stress, in the pathophysiology of MD.

METHODOLOGY

We reviewed articles that evaluated environmental influences, with a particular focus on childhood trauma, brain morphology, cognitive functions, and the development of psychopathology and MD.

RESULTS AND CONCLUSION

MRI studies have shown that exposure to trauma at an early age can result in several neurostructural changes, such as the reduction of the hippocampus and corpus callosum. Cognitive performance and functioning are also altered in this population. Finally, childhood stress is related to an increased risk of developing MD such as depression, bipolar disorder, schizophrenia and substance abuse. We conclude that there is robust evidence of the role of the environment, specifically adverse childhood experiences, in various aspects of MD.

Food insecurity and chronic disease

Household food insecurity has been previously hypothesized to promote dependence on inexpensive, highly palatable foods that are energy dense. Such dependence, and the cyclical nature of having enough food in the beginning of the month followed by food scarcity at the end of the month, could lead to weight gain over a short period of time. Such dependence on energy-dense foods and weight gain may play a direct role in the development of chronic conditions. Other compounding factors that result from exposure to household food insecurity have been well described, including pathways by which stress promotes visceral fat accumulation and chronic disease. This symposium review paper summarizes the literature on the link between food insecurity and the following: 1) diet, 2) weight gain, and 3) chronic disease, especially among women. This paper also proposes a framework for considering how the lived experience of household food insecurity may potentiate the development of chronic disease by activating the stress response among individuals at critical developmental periods in a food-impoverished environment.

Early-life stress, corpus callosum development, hippocampal volumetrics, and anxious behavior in male nonhuman primates

Male bonnet monkeys (Macaca radiata) were subjected to the variable foraging demand (VFD) early stress paradigm as infants, MRI scans were completed an average of 4 years later, and behavioral assessments of anxiety and ex-vivo corpus callosum (CC) measurements were made when animals were fully matured. VFD rearing was associated with smaller CC size, CC measurements were found to correlate with fearful behavior in adulthood, and ex-vivo CC assessments showed high consistency with earlier MRI measures. Region of interest (ROI) hippocampus and whole brain voxel-based morphometry assessments were also completed and VFD rearing was associated with reduced hippocampus and inferior and middle temporal gyri volumes. The animals were also characterized according to serotonin transporter genotype (5-HTTLPR), and the effect of genotype on imaging parameters was explored. The current findings highlight the importance of future research to better understand the effects of stress on brain development in multiple regions, including the corpus callosum, hippocampus, and other regions involved in emotion processing. Nonhuman primates provide a powerful model to unravel the mechanisms by which early stress and genetic makeup interact to produce long-term changes in brain development, stress reactivity, and risk for psychiatric disorders.

Early-life stress, corticotropin-releasing factor, and serotonin transporter gene: a pilot study

Recent studies have indicated a gene-by-environment interaction between serotonin transporter gene (5-HTTLPR) polymorphism and childhood abuse on depressive symptoms. In addition, persistent elevation of cerebrospinal fluid (CSF) corticotropin-releasing factor (CRF) concentrations following early-life adversity has been posited to underlie the subsequent development of major depression. This pilot study tested the hypothesis that elevations of juvenile CSF CRF concentrations are, in part, determined by an interaction between polymorphisms of the 5-HTTLPR and early-life stress. Nine juvenile male bonnet macaques (Macaca radiata) had been raised under variable foraging demand (VFD) conditions, a nonhuman primate model of early-life stress, whereas nine subjects were normatively raised under LFD (low foraging demand) conditions. Genotyping revealed that four (44.4%) of the VFD-reared monkeys possessed at least one "s" allele whereas five VFD monkeys were of the l/l genotype. Of the nine LFD subjects, two (22%) had the s/l genotype and seven had the l/l genotype. A "juvenile" CSF sample was obtained at approximately 3 years of age. CSF CRF concentrations were elevated specifically in the VFD "s/s" and "s/l" allele group in comparison to each of the remaining three groups, indicating a gene-by-environment (G×E) interaction.

Gene-environment interaction of child temperament

OBJECTIVE

The aims of this study were to review studies on the molecular genetics of child temperament and prospectively analyze infant temperament as a function of the interaction between infant and mother: 5-HTT, DRD4, and MAO-A functional polymorphisms and the mother's emotional state.

METHOD

A prospective study of 317 newborns and their mothers was performed. Infant temperament and the mother's anxiety and confidence in caregiving were evaluated at 8 and 32 weeks after childbirth using the Mother and Baby Scale. The mother's emotional state was evaluated using the Edinburgh Postpartum Depression Scale and the State-Trait Anxiety Inventory. These variables were correlated with 5-HTTLPR and Stin2 variants in the 5-HTT gene and the DRD4 variable number tandem repeats Exon 3 and MAO-A variable number tandem repeats genotypes of both the infants and their mothers.

RESULTS

The irritability scores of infants with the 5-HTTLPR s allele showed a linear relationship with their mothers' anxiety of caregiving at 8 (p = .011) and 32 weeks (p = .001), whereas the irritability of infants carrying the HTTLPR ll genotype was independent of their mothers' anxiety.

CONCLUSIONS

The review of the literature in this field and the results of this study support that the 5-HTTLPR polymorphism moderates the influence of the mother's anxiety on infant irritability.

Early-life stress and neurometabolites of the hippocampus

We tested the hypothesis that early life stress would persistently compromise neuronal viability of the hippocampus of the grown nonhuman primate. Neuronal viability was assessed through ascertainment of N-acetyl aspartate (NAA)-an amino acid considered reflective of neuronal density/functional integrity-using in vivo proton magnetic resonance spectroscopic imaging (MRSI). The subjects reported herein represent a re-analysis of a sample of nineteen adult male bonnet macaques that had been reared in infancy under induced stress by maternal variable foraging demand (VFD) (N=10) or control rearing conditions (N=9). The MRSI spectral readings were recorded using a GE 1.5 Tesla machine under anesthesia. Relative NAA values were derived using NAA as numerator and both choline (Cho) or creatine (Cr) as denominators. Left medial temporal lobe (MTL) NAA/Cho but not NAA/Cr was decreased in VFD subjects versus controls. An MTL NAA/Cho ratio deficit remained significant when controlling for multiple confounding variables. Regression analyses suggested that the NAA/Choline finding was due to independently low left NAA and high left choline. Right MTL showed no rearing effects for NAA, but right NAA was positively related to body mass, irrespective of denominator. The current data indicate that decreased left MTL NAA/Cho may reflect low neuronal viability of the hippocampus following early life stress in VFD-reared versus normally-reared subjects. Given the importance of the hippocampus in stress-mediated toxicity, validation of these data using absolute quantification is suggested and correlative neurohistological studies of hippocampus are warranted.

The role of early life stress in development of the anterior limb of the internal capsule in nonhuman primates

Deep brain stimulation (DBS) of the anterior limb of the internal capsule (ALIC) may be effective in treating depression. Parental verbal abuse has been linked to decreased fractional anisotropy (FA) of white matter and reduced FA correlated with depression and anxiety scores. Utilizing a nonhuman primate model of mood and anxiety disorders following disrupted mother-infant attachment, we examined whether adverse rearing conditions lead to white matter impairment of the ALIC. We examined white matter integrity using Diffusion Tensor Imaging (DTI) on a 3T-MRI. Twenty-one adult male Bonnet macaques participated in this study: 12 were reared under adverse [variable foraging demand (VFD)] conditions whereas 9 were reared under normative conditions. We examined ALIC, posterior limb of the internal capsule (PLIC) and occipital white matter. VFD rearing was associated with significant reductions in FA in the ALIC with no changes evident in the PLIC or occipital cortex white matter. Adverse rearing in monkeys persistently impaired frontal white matter tract integrity, a novel substrate for understanding affective susceptibility.

Risk and resilience: early manipulation of macaque social experience and persistent behavioral and neurophysiological outcomes

OBJECTIVE

To review the contributions of research on nonhuman primates, specifically macaque monkeys, to the understanding of early social stress and its effects on behavior and neurophysiology.

METHOD

Review and synthesis of two bodies of work on macaque monkeys and early social manipulation: peer rearing and variable foraging demands. The literature was searched with Medline using key terms macaque, variable foraging, and peer rearing. The reference lists of these articles were also used to generate potential studies for review.

RESULTS

Nonhuman primate macaques show similarities to humans in their social development and functioning. Peer rearing of young macaques and rearing of young macaques with mothers experiencing variable foraging conditions both result in increased anxious, impulsive, and aggressive temperament and behavior; more reactive stress physiology; altered neurotransmitter functioning; and immune and metabolic changes. Functional variants of specific genes that code for neuromodulators are mediators of these effects.

CONCLUSIONS

Disrupted social relations during macaque rearing contribute to the risk for developing emotional and neurophysiological disturbance. In the face of such disruption, certain genotypes contribute to resilience. This can be alternately stated that, for animals of high-risk genotypes, resilience is conferred by quality relationships during rearing. This interaction of genetics with early social environment also applies to child mental health, implicating biological mediators identified in macaques as contributing to more complex outcomes in humans.

Epigenetic mechanisms mediating the long-term effects of maternal care on development

The long-term consequences of early environmental experiences for development have been explored extensively in animal models to better understand the mechanisms mediating risk of psychopathology in individuals exposed to childhood adversity. One common feature of these models is disruption of the mother-infant relationship which is associated with impairments in stress responsivity and maternal behavior in adult offspring. These behavioral and physiological characteristics are associated with stable changes in gene expression which emerge in infancy and are sustained into adulthood. Recent evidence suggests that these long-term effects may be mediated by epigenetic modification to the promoter regions of steroid receptor genes. In particular, DNA methylation may be critical to maternal effects on gene expression and thus generate phenotypic differentiation of offspring and, through effects on maternal behavior of offspring, mediate the transmission of these effects across generations. In this review we explore evidence for the influence of mother-infant interactions on the epigenome and consider evidence for and the implications of such epigenetic effects for human mental health.

Neurodevelopmental sequelae of postnatal maternal care in rodents: clinical and research implications of molecular insights

Parental care plays an important role in the emotional and cognitive development of the offspring. Children who have been exposed to abuse or neglect are more likely to develop numerous psychopathologies, while good parent-infant bonding is associated with improved resiliency to stress. Similar observations have also been reported in non-human primates and rodents, suggesting that at least some neurodevelopmental aspects of parent-offspring interactions are conserved among mammals and could therefore be studied in animals. We present data to suggest that frequency of licking and grooming provided by the dam during a critical period in development plays an important role in modifying neurodevelopment. These findings are examined in the broader context in which exposure to other sensory modalities such as vision or hearing during a specific period in development shapes brain development with functional consequences that persist into adulthood. We also discuss recent rodent work showing that increased frequency of licking and grooming provided by the dam during the first week of life is associated with changes in DNA methylation of promoter elements that control expression of these genes and behavior. The stability of DNA methylation in postmitotic cells provides a possible molecular scaffold by which changes in gene expression and behavioral traits induced by postnatal maternal care are maintained throughout life. Finally, the relevance of findings reported in rodents to those noted in non-human primates and humans are assessed and the research and clinical implications of these observations for future work are explored.

Collective consciousness and its pathologies: understanding the failure of AIDS control and treatment in the United States

We address themes of distributed cognition by extending recent formal developments in the theory of individual consciousness. While single minds appear biologically limited to one dynamic structure of linked cognitive submodules instantiating consciousness, organizations, by contrast, can support several, sometimes many, such constructs simultaneously, although these usually operate relatively slowly. System behavior remains, however, constrained not only by culture, but by a developmental path dependence generated by organizational history, in the context of market selection pressures. Such highly parallel multitasking – essentially an institutional collective consciousness – while capable of reducing inattentional blindness and the consequences of failures within individual workspaces, does not eliminate them, and introduces new characteristic malfunctions involving the distortion of information sent between workspaces and the possibility of pathological resilience – dysfunctional institutional lock-in. Consequently, organizations remain subject to canonical and idiosyncratic failures analogous to, but more complicated than, those afflicting individuals. Remediation is made difficult by the manner in which pathological externalities can write images of themselves onto both institutional function and corrective intervention. The perspective is applied to the failure of AIDS control and treatment in the United States.

Psychological stressors as a model of maternal adversity: diurnal modulation of corticosterone responses and changes in maternal behavior

Maternal adversity is associated with long-lasting consequences on cognitive development, behavior and physiological responses in rat offspring. Few studies have examined whether repeated maternal stress produces repeated activation of the hypothalamus-pituitary-adrenal (HPA) axis in mothers and whether it modifies maternal behavior. Here, we tested a novel model of perinatal stress using repeated exposure to "purely" psychological stressors throughout the gestation and lactation periods in rats. We first tested the diurnal influences of repeated 1-h strobe light exposure on maternal corticosterone secretion. Despite the hyporesponsiveness to stress documented in late pregnant and lactating mothers, we observed an enhanced response to strobe light in the afternoon compared to the morning in stressed mothers during lactation. Next, dams were exposed to 24-h forced foraging followed by 10-h wet bedding during the diurnal peak of corticosterone secretion. Although no corticosterone responses to forced foraging and wet bedding were observed, the combination of both stressors had a significant effect on maternal behavior. Mother-pup interactions were significantly altered during the first 8 days of lactation. Taken together, these findings suggest that lactating mothers maintain responsiveness to specific and repeated psychological stressors, in particular at the time of the diurnal peak in corticosterone secretion. Depending on the stressor applied, either neuroendocrine activation or changes in maternal behavior might be important determinants of the long-term consequences in the offspring. The combination of forced foraging, wet bedding and strobe light might represent a novel model of mild maternal adversity using "purely" psychological stressors.

Food insecurity and the risks of depression and anxiety in mothers and behavior problems in their preschool-aged children

OBJECTIVES

We sought to determine if the prevalence of depression and anxiety in mothers and the prevalence of behavior problems in preschool-aged children are more common when mothers report being food insecure.

METHODS

A cross-sectional survey of 2870 mothers of 3-year-old children was conducted in 2001-2003 in 18 large US cities. On the basis of the adult food-security scale calculated from the US Household Food Security Survey Module, mothers were categorized into 3 levels: fully food secure, marginally food secure, and food insecure. The 12-month prevalence in mothers of a major depressive episode and generalized anxiety disorder was assessed by the Composite International Diagnostic Interview-Short Form. A child behavior problem in > or = 1 of 3 domains (aggressive, anxious/depressed, or inattention/hyperactivity) was based on the Child Behavior Checklist.

RESULTS

Seventy-one percent of the respondents were fully food secure, 17% were marginally food secure, and 12% were food insecure. After adjustment for sociodemographic factors plus maternal physical health, alcohol use, drug use, prenatal smoking, and prenatal physical domestic violence, the percentage of mothers with either major depressive episode or generalized anxiety disorder increased with increasing food insecurity: 16.9%, 21.0%, and 30.3% across the 3 levels. Among children, after further adjustment for maternal major depressive episode and generalized anxiety disorder, the percentage with a behavior problem also increased with increasing food insecurity: 22.7%, 31.1%, and 36.7%.

CONCLUSIONS

Mental health problems in mothers and children are more common when mothers are food insecure, a stressor that can potentially be addressed by social policy.

Maternal-Infant Response to Variable Foraging Demand in Nonhuman Primates: Effects of Timing of Stressor on Cerebrospinal Fluid Corticotropin-Releasing Factor and Circulating Glucocorticoid Concentrations

The maternal stress response may vary as a function of infant developmental phase. Using a median split, 13 bonnet macaque (M. radiata) mother-infant dyads were exposed to early initiation of variable foraging demand (VFD), a prolonged stressor, whereas 11 dyads were exposed to late VFD onset. Cerebrospinal fluid (CSF) and plasma samples were obtained from mothers and infants prior to and following VFD. Increases in maternal CSF corticotropin-releasing factor (CRF) concentrations were evident in response to late, but not early, VFD. Mothers exhibited either increased or decreased cortisol concentrations in response to VFD. However, absolute cortisol change was greater in early versus late VFD. Timing of the VFD stressor differentially affects maternal neuroendocrine response, with potential implications for the offspring's developmental trajectory.

A Global Workspace perspective on mental disorders

Background

Recent developments in Global Workspace theory suggest that human consciousness can suffer interpenetrating dysfunctions of mutual and reciprocal interaction with embedding environments which will have early onset and often insidious staged developmental progression, possibly according to a cancer model, in which a set of long-evolved control strategies progressively fails.

Methods and results

A rate distortion argument implies that, if an external information source carries a damaging 'message', then sufficient exposure to it, particularly during critical developmental periods, is sure to write a sufficiently accurate image of it on mind and body in a punctuated manner so as to initiate or promote similarly progressively punctuated developmental disorder, in essence either a staged failure affecting large-scale brain connectivity, which is the sine qua non of human consciousness, or else damaging the ability of embedding goal contexts to contain conscious dynamics.

Conclusion

The key intervention, at the population level, is clearly to limit exposure to factors triggering developmental disorders, a question of proper environmental sanitation, in a large sense, primarily a matter of social justice which has long been known to be determined almost entirely by the interactions of cultural trajectory, group power relations, and economic structure, with public policy. Intervention at the individual level appears limited to triggering or extending periods of remission, representing reestablishment of an extensive, but largely unexplored, spectrum of evolved control strategies, in contrast with the far better-understood case of cancer.