Gene-Environment Interactions and the Neurobiology of Social Conflict

Neurobiology of Parental Regulation of the Infant and Its Disruption by Trauma Within Attachment

The complex process of regulating physiological functions and homeostasis during external and internal disruptions develops slowly in altricial species, with parental care functioning as a co-regulator of infant physiological and emotional homeostasis. Here, we review our current understanding of the infant's use of parental behaviors for neurobehavioral regulation and its disruption with harsh parental care. Taking a cross-species view, we briefly review the human developmental literature that highlights the importance of the caregiver in scaffolding the child's physiological and emotional regulation, especially under threat and stress. We then use emerging corresponding animal literature within the phylogenetically preserved attachment system to help define neural systems supporting caregiver regulation and its supporting causal mechanism to provide translational bridges to inform causation and mechanisms impossible to define in children. Next, we briefly review animal research highlighting the impact of specific sensory stimuli imbedded in parental care as important for infant physiological and emotion regulation. We then highlight the importance of parental sensory stimuli gaining hedonic value to go beyond simple sensory stimuli to further impact neurobehavioral regulation, with poor quality of care compromising the infant's ability to use these cues for regulation. Clinically, parental regulation of the infant is correlated with later-life neurobehavioral outcome and quality of life. We suggest an understanding of this parental regulation of the infant's immediate neurobehavioral functioning within the context of attachment quality, that may provide insights into the complex processes during early life, initiating the pathway to pathology.

Infant Attachment and Social Modification of Stress Neurobiology

Decades of research have informed our understanding of how stress impacts the brain to perturb behavior. However, stress during development has received specific attention as this occurs during a sensitive period for scaffolding lifelong socio-emotional behavior. In this review, we focus the developmental neurobiology of stress-related pathology during infancy and focus on one of the many important variables that can switch outcomes from adaptive to maladaptive outcome: caregiver presence during infants' exposure to chronic stress. While this review relies heavily on rodent neuroscience research, we frequently connect this work with the human behavioral and brain literature to facilitate translation. Bowlby's Attachment Theory is used as a guiding framework in order to understand how early care quality impacts caregiver regulation of the infant to produce lasting outcomes on mental health.

Timing is critical: Gene, environment and timing interactions in genetics of suicide in children and adolescents

Suicidal behavior runs in families and is prevalent in adolescence. Case-control and family-based studies in this age group failed to find a genetic association that survived replications. Gene environment approach gave new hope for possible associations especially with the short allele of the serotonin transporter promoter polymorphism (5-HTTLPR). However, a recent meta-analysis raised doubts about the consistency of these findings. Some new structural and functional imaging data may shade light on the age-related and gender-related development of the brain. This review suggests a new approach to gene by environment and timing interaction to understand the interplay that leads to suicidality in adolescents and young adults.

Neurobiology of maternal regulation of infant fear: the role of mesolimbic dopamine and its disruption by maltreatment

Child development research highlights caregiver regulation of infant physiology and behavior as a key feature of early life attachment, although mechanisms for maternal control of infant neural circuits remain elusive. Here we explored the neurobiology of maternal regulation of infant fear using neural network and molecular levels of analysis in a rodent model. Previous research has shown maternal suppression of amygdala-dependent fear learning during a sensitive period. Here we characterize changes in neural networks engaged during maternal regulation and the transition to infant self-regulation. Metabolic mapping of 2-deoxyglucose uptake during odor-shock conditioning in postnatal day (PN)14 rat pups showed that maternal presence blocked fear learning, disengaged mesolimbic circuitry, basolateral amygdala (BLA), and plasticity-related AMPA receptor subunit trafficking. At PN18, when maternal presence only socially buffers threat learning (similar to social modulation in adults), maternal presence failed to disengage the mesolimbic dopaminergic system, and failed to disengage both the BLA and plasticity-related AMPA receptor subunit trafficking. Further, maternal presence failed to block threat learning at PN14 pups following abuse, and mesolimbic dopamine engagement and AMPA were not significantly altered by maternal presence-analogous to compromised maternal regulation of children in abusive relationships. Our results highlight three key features of maternal regulation: (1) maternal presence blocks fear learning and amygdala plasticity through age-dependent suppression of amygdala AMPA receptor subunit trafficking, (2) maternal presence suppresses engagement of brain regions within the mesolimbic dopamine circuit, and (3) early-life abuse compromises network and molecular biomarkers of maternal regulation, suggesting reduced social scaffolding of the brain.

Unique infant neurobiology produces distinctive trauma processing

Trauma experienced in early life has unique neurobehavioral outcomes related to later life psychiatric sequelae. Recent evidence has further highlighted the context of infant trauma as critical, with trauma experienced within species-atypical aberrations in caregiving quality as particularly detrimental. Using data from primarily rodent models, we review the literature on the interaction between trauma and attachment in early life, which highlights the role of the caregiver's presence in engagement of attachment brain circuitry and suppressing threat processing by the amygdala. Together these data suggest that infant trauma processing and its enduring effects are impacted by both the immaturity of brain areas for processing trauma and the unique functioning of the early-life brain, which is biased towards forming robust attachments regardless of the quality of care. Understanding the critical role of the caregiver in further altering early life brain processing of trauma is important for developing age-relevant treatment and interventions.

Personality disorders as disorganisation of attachment and affect regulation

If personality disorder is no longer to be a diagnosis of exclusion it needs a conceptual framework that fits both the symptoms of the illness and the behavioural problems that constitute its current diagnostic criteria. In this article, we suggest that personality disorder is best understood as disorganisation of the capacity for affect regulation, mediated by early attachments. We present evidence for this argument based on both developmental and neurobiological research.

The neurobiology of safety and threat learning in infancy

What an animal needs to learn to survive is altered dramatically as they change from dependence on the parent for protection to independence and reliance on self-defense. This transition occurs in most altricial animals, but our understanding of the behavioral neurobiology has mostly relied on the infant rat. The transformation from dependence to independence occurs over three weeks in pups and is accompanied by complex changes in responses to both natural and learned threats and the supporting neural circuitry. Overall, in early life, the threat system is quiescent and learning is biased towards acquiring attachment related behaviors to support attachment to the caregiver and proximity seeking. Caregiver-associated cues learned in infancy have the ability to provide a sense of safety throughout lifetime. This attachment/safety system is activated by learning involving presumably pleasurable stimuli (food, warmth) but also painful stimuli (tailpinch, moderate shock). At about the midway point to independence, pups begin to have access to the adult-like amygdala-dependent threat system and amygdala-dependent responses to natural dangers such as predator odors. However, pups have the ability to switch between the infant and adult-like system, which is controlled by maternal presence and modification of stress hormones. Specifically, if the pup is alone, it will learn fear but if with the mother it will learn attachment (10-15days of age). As pups begin to approach weaning, pups lose access to the attachment system and rely only on the amygdala-dependent threat system. However, pups learning system is complex and exhibits flexibility that enables the mother to override the control of the attachment circuit, since newborn pups may acquire threat responses from the mother expressing fear in their presence. Together, these data suggest that the development of pups' threat learning system is not only dependent upon maturation of the amygdala, but it is also exquisitely controlled by the environment. Most notably the mother can switch pup learning between attachment to threat learning in a moment's notice. This enables the mother to navigate pup's learning about the world and what is threatening and what is safe.

Early life adversity during the infant sensitive period for attachment: Programming of behavioral neurobiology of threat processing and social behavior

Animals, including humans, require a highly coordinated and flexible system of social behavior and threat evaluation. However, trauma can disrupt this system, with the amygdala implicated as a mediator of these impairments in behavior. Recent evidence has further highlighted the context of infant trauma as a critical variable in determining its immediate and enduring consequences, with trauma experienced from an attachment figure, such as occurs in cases of caregiver-child maltreatment, as particularly detrimental. This review focuses on the unique role of caregiver presence during early-life trauma in programming deficits in social behavior and threat processing. Using data primarily from rodent models, we describe the interaction between trauma and attachment during a sensitive period in early life, which highlights the role of the caregiver's presence in engagement of attachment brain circuitry and suppressing threat processing by the amygdala. These data suggest that trauma experienced directly from an abusive caregiver and trauma experienced in the presence of caregiver cues produce similar neurobehavioral deficits, which are unique from those resulting from trauma alone. We go on to integrate this information into social experience throughout the lifespan, including consequences for complex scenarios, such as dominance hierarchy formation and maintenance.

Attachment Figure's Regulation of Infant Brain and Behavior

Altricial infants (i.e., requiring parental care for survival), such as humans and rats, form an attachment to their caregiver and receive the nurturing and protections needed for survival. Learning has a strong role in attachment, as is illustrated by strong attachment formed to non-biological caregivers of either sex. Here we summarize and integrate results from animal and human infant attachment research that highlights the important role of social buffering (social presence) of the stress response by the attachment figure and its effect on infant processing of threat and fear through modulation of the amygdala. Indeed, this work suggests the caregiver switches off amygdala function in rodents, although recent human research suggests a similar process in humans and nonhuman primates. This cross-species analysis helps provide insight and unique understanding of attachment and its role in the neurobiology of infant behavior within attachment.

Early Predictors of Impaired Social Functioning in Male Rhesus Macaques (Macaca mulatta)

Autism spectrum disorder (ASD) is characterized by social cognition impairments but its basic disease mechanisms remain poorly understood. Progress has been impeded by the absence of animal models that manifest behavioral phenotypes relevant to ASD. Rhesus monkeys are an ideal model organism to address this barrier to progress. Like humans, rhesus monkeys are highly social, possess complex social cognition abilities, and exhibit pronounced individual differences in social functioning. Moreover, we have previously shown that Low-Social (LS) vs. High-Social (HS) adult male monkeys exhibit lower social motivation and poorer social skills. It is not known, however, when these social deficits first emerge. The goals of this study were to test whether juvenile LS and HS monkeys differed as infants in their ability to process social information, and whether infant social abilities predicted later social classification (i.e., LS vs. HS), in order to facilitate earlier identification of monkeys at risk for poor social outcomes. Social classification was determined for N = 25 LS and N = 25 HS male monkeys that were 1-4 years of age. As part of a colony-wide assessment, these monkeys had previously undergone, as infants, tests of face recognition memory and the ability to respond appropriately to conspecific social signals. Monkeys later identified as LS vs. HS showed impairments in recognizing familiar vs. novel faces and in the species-typical adaptive ability to gaze avert to scenes of conspecific aggression. Additionally, multivariate logistic regression using infant social ability measures perfectly predicted later social classification of all N = 50 monkeys. These findings suggest that an early capacity to process important social information may account for differences in rhesus monkeys' motivation and competence to establish and maintain social relationships later in life. Further development of this model will facilitate identification of novel biological targets for intervention to improve social outcomes in at-risk young monkeys.

Unique neurobiology during the sensitive period for attachment produces distinctive infant trauma processing

BACKGROUND

Trauma has neurobehavioral effects when experienced at any stage of development, but trauma experienced in early life has unique neurobehavioral outcomes related to later life psychiatric sequelae. Recent evidence has further highlighted the context of infant trauma as a critical variable in determining its immediate and enduring consequences. Trauma experienced from an attachment figure, such as occurs in cases of caregiver child maltreatment, is particularly detrimental.

METHODS

Using data primarily from rodent models, we review the literature on the interaction between trauma and attachment in early life, which highlights the role of the caregiver's presence in engagement of attachment brain circuitry and suppressing threat processing by the amygdala. We then consider how trauma with and without the caregiver produces long-term changes in emotionality and behavior, and suggest that these experiences initiate distinct pathways to pathology.

RESULTS

Together these data suggest that infant trauma processing and its enduring effects are impacted by both the immaturity of brain areas for processing trauma and the unique functioning of the early-life brain, which is biased toward processing information within the attachment circuitry.

CONCLUSION

An understanding of developmental differences in trauma processing as well as the critical role of the caregiver in further altering early life brain processing of trauma is important for developing age-relevant treatment and interventions.

Developmental neurobiology of the rat attachment system and its modulation by stress

Stress is a powerful modulator of brain structure and function. While stress is beneficial for survival, inappropriate stress dramatically increases the risk of physical and mental health problems, particularly when experienced during early developmental periods. Here we focus on the neurobiology of the infant rat's odor learning system that enables neonates to learn and approach the maternal odor and describe the unique role of the stress hormone corticosterone in modulating this odor approach learning across development. During the first nine postnatal days, this odor approach learning of infant rats is supported by a wide range of sensory stimuli and ensures attachment to the mother's odor, even when interactions with her are occasionally associated with pain. With maturation and the emergence of a stress- or pain-induced corticosterone response, this odor approach learning terminates and a more adult-like amygdala-dependent fear/avoidance learning emerges. Strikingly, the odor approach and attenuated fear learning of older pups can be re-established by the presence of the mother, due to her ability to suppress her pups' corticosterone release and amygdala activity. This suggests that developmental changes in stress responsiveness and the stimuli that produce a stress response might be critically involved in optimally adapting the pup's attachment system to its respective ecological niche.

Stress and the reproductive axis

There exists a reciprocal relationship between the hypothalamic-pituitary-adrenal (HPA) and the hypothalamic-pituitary-gonadal (HPG) axes, wherein the activation of one affects the function of the other and vice versa. For example, both testosterone and oestrogen modulate the response of the HPA axis, whereas activation of the stress axis, especially activation that is repeating or chronic, has an inhibitory effect upon oestrogen and testosterone secretion. Alterations in maternal care can produce significant effects on both HPG and HPA physiology, as well as behaviour in the offspring at adulthood. For example, changes in reproductive behaviour induced by altered maternal care may alter the expression of sex hormone receptors such as oestrogen receptor (ER)α that govern sexual behaviour, and may be particularly important in determining the sexual strategies utilised by females. Stress in adulthood continues to mediate HPG activity in females through activation of a sympathetic neural pathway originating in the hypothalamus and releasing norepinephrine into the ovary, which produces a noncyclic anovulatory ovary that develops cysts. In the opposite direction, sex differences and sex steroid hormones regulate the HPA axis. For example, although serotonin (5-HT) has a stimulatory effect on the HPA axis in humans and rodents that is mediated by the 5-HT1A receptor, only male rodents respond to 5-HT1A antagonism to show increased corticosterone responses to stress. Furthermore, oestrogen appears to decrease 5-HT1A receptor function at presynaptic sites, yet increases 5-HT1A receptor expression at postsynaptic sites. These mechanisms could explain the heightened stress HPA axis responses in females compared to males. Studies on female rhesus macaques show that chronic stress in socially subordinate female monkeys produces a distinct behavioural phenotype that is largely unaffected by oestrogen, a hyporesponsive HPA axis that is hypersensitive to the modulating effects of oestrogen, and changes in 5-HT1A receptor binding in the hippocampus and hypothalamus of social subordinate female monkeys that are restored or inverted by oestrogen replacement. This review summarises all of these studies, emphasising the profound effect that the interaction of the reproductive and stress axes may have on human reproductive health and emotional wellbeing.

The significance of attachment security for children's social competence with peers: a meta-analytic study

This meta-analytic review examines the association between attachment during the early life course and social competence with peers during childhood, and compares the strength of this association with those for externalizing and internalizing symptomatology. Based on 80 independent samples (N = 4441), the association between security and peer competence was significant (d = 0.39, CI 0.32; 0.47) and not moderated by the age at which peer competence was assessed. Avoidance (d = 0.17, CI 0.05; 0.30), resistance (d = 0.29, CI 0.09; 0.48), and disorganization (d = 0.25, CI 0.10; 0.40) were significantly associated with lower peer competence. Attachment security was significantly more strongly associated with peer competence than internalizing (but not externalizing) symptomatology. Discussion focuses on the significance of early attachment for the development of peer competence versus externalizing and internalizing psychopathology.

Neurobiological mechanisms for impulsive-aggression: the role of MAOA

Aggression may be present across a large part of the spectrum of psychopathology, and underlies costly criminal antisocial behaviors. Human aggression is a complex and underspecified construct, confounding scientific discovery. Nevertheless, some biologically tractable subtypes are apparent, and one in particular-impulsive (reactive) aggression-appears to account for many facets of aggression-related dysfunction in psychiatric illness. Impulsive-aggression is significantly heritable, suggesting genetic transmission. However, the specific neurobiological mechanisms that mediate genetic risk for impulsive-aggression remain unclear. Here, we review extant data on the genetics and neurobiology of individual differences in impulsive-aggression, with particular attention to the role of genetic variation in Monoamine Oxidase A (MAOA) and its impact on serotonergic signaling within corticolimbic circuitry.

Social subordination stress and serotonin transporter polymorphisms: associations with brain white matter tract integrity and behavior in juvenile female macaques

We examined the relationship between social rank and brain white matter (WM) microstructure, and socioemotional behavior, and its modulation by serotonin (5HT) transporter (5HTT) polymorphisms in prepubertal female macaques. Using diffusion tensor imaging and tract-based spatial statistics, social status differences were found in medial prefrontal cortex (mPFC) WM and cortico-thalamic tracts, with subordinates showing higher WM structural integrity (measured as fractional anisotropy, FA) than dominant animals. 5HTT genotype-related differences were detected in the posterior limb of the internal capsule, where s-variants had higher FA than l/l animals. Status by 5HTT interaction effects were found in (1) external capsule (middle longitudinal fasciculus), (2) parietal WM, and (3) short-range PFC tracts, with opposite effects in dominant and subordinate animals. In most regions showing FA differences, opposite differences were detected in radial diffusivity, but none in axial diffusivity, suggesting that differences in tract integrity likely involve differences in myelin. These findings highlight that differences in social rank are associated with differences in WM structural integrity in juveniles, particularly in tracts connecting prefrontal, sensory processing, motor and association regions, sometimes modulated by 5HTT genotype. Differences in these tracts were associated with increased emotional reactivity in subordinates, particularly with higher submissive and fear behaviors.

Age at adoption from institutional care as a window into the lasting effects of early experiences

One of the major questions of human development is how early experience impacts the course of development years later. Children adopted from institutional care experience varying levels of deprivation in their early life followed by qualitatively better care in an adoptive home, providing a unique opportunity to study the lasting effects of early deprivation and its timing. The effects of age at adoption from institutional care are discussed for multiple domains of social and behavioral development within the context of several prominent developmental hypotheses about the effects of early deprivation (cumulative effects, experience-expectant developmental programming, and experience-adaptive developmental programming). Age at adoption effects are detected in a majority of studies, particularly when children experienced global deprivation and were assessed in adolescence. For most outcomes, institutionalization beyond a certain age is associated with a step-like increase in risk for lasting social and behavioral problems, with the step occurring at an earlier age for children who experienced more severe levels of deprivation. Findings are discussed in terms of their concordance and discordance with our current hypotheses, and speculative explanations for the findings are offered.

Genes, cognition, and social behavior: next steps for foundations and researchers

Editor's note This well circulated but heretofore unpublished report is the summary statement of an interdisciplinary meeting of scholars convened by the National Science Foundation in Arlington, Virginia on June 28, 2010. The workshop, which was funded by the NSF's Political Science Program (Social, Behavioral & Economic Sciences Grant #1037831), was convened to answer two compelling questions: Are studies of social behavior that build from discoveries about genes and/or cognition of greater social and scientific value than studies of the same topics that ignore such factors? And, how can fundable research on genes, cognition, and politics generate transformative scientific practices, infrastructure, and findings of high social value? Assembled for the workshop were a group of scholars representing diverse yet increasingly connected research areas, including genetics, cognitive science and neuroscience, decision making and risk analysis, economics, political science, and sociology. The resulting report outlines the substantial challenges facing interdisciplinary research but also describes the considerable contributions to knowledge that could result from sustained collaborations between biologists, geneticists, and brain scientists on the one hand and social scientists on the other. Following this main report are three white papers by Jeremy Freese. Elizabeth Hammock, and Rose McDermott, which address importmant considerations related to the discussion. For a download of the full report, see http://www.isr.umich.edu.cps/workshop.Welcome.html.

The development and neurobiology of infant attachment and fear

Survival of altricial infants depends on attachment to the caregiver - a process that requires infants to identify, learn, remember, and approach their attachment figure. Here we review the neurobiology of attachment in infant rats where learning about the caregiver is supported by a specialized attachment neural circuitry to promote the infant-caregiver relationship. Specifically, the attachment circuit relies on infants acquiring learned preferences to the maternal odor, and this behavior is supported by the hyperfunctioning locus coeruleus and generous amounts of norepinephrine to produce experience-induced changes in the olfactory bulb and anterior piriform cortex. Infants also possess a reduced ability to acquire learned aversions or fear, and this behavior is facilitated through attenuated amygdala plasticity to block fear learning. Presumably, this attachment circuitry constrains the infant animal to express only learned preferences regardless of the quality of care received. As pups mature, and begin to travel in and out of the nest, the specialized attachment learning becomes contextually confined to when pups are with the mother. Thus, when outside the nest, these older pups show learning more typical of adult learning, presumably to prepare for independent life outside the nest. The quality of attachment can alter this circuitry, with early life stress prematurely terminating the pups' access to the attachment system through premature functional activation of the amygdala. Overall, the attachment circuit appears to have a dual function: to keep pups close to the caregiver but also to shape pups' behavior to match the environment and define long-term emotion and cognition.

Störungen des Sozialverhaltens

Dieser Beitrag diskutiert die prädiktive Validität der allgemeinen Diagnosekriterien von Störungen des Sozialverhaltens nach ICD-10 und DSM-IV-TR. Dabei wird Bezug genommen auf aktuelle Befunde, die eine Phänotypisierung früh beginnender Störungen des Sozialverhaltens auf der Basis neurobiologischer und persönlichkeitsspezifischer Faktoren nahelegen. Untersuchungsergebnisse, die auf defizitäre neurobiologische Mechanismen aggressiven Verhaltens in Bezug auf Prozesse der Emotionswahrnehmung und Emotionsregulation hinweisen, werden dargestellt, wobei auch die Bedeutung möglicher mediierender Einflüsse früher psychosozialer Erfahrungen auf neurobiologische Funktionen erörtert wird. Die klinischen Implikationen für die Klassifikation, den Verlauf und die Behandlung von Störungen des Sozialverhaltens werden abschließend diskutiert.

Intronic tandem repeat in the serotonin transporter gene in Old World monkeys: a new transcriptional regulator?

The serotonin transporter gene (SLC6A4) is heavily involved in the regulation of social behaviour of primates. Old World monkeys (e.g. macaques, baboons) have been used to study interactions between variation in the SLC6A4 gene and behaviour. Correlations of variation at one polymorphism located in the promoter region (known as 5HTTLPR) and variation at SLC6A4 expression levels, serotonin turnover and behaviour has been widely studied. In Old World monkeys, the third intron of the SLC6A4 gene also presents a tandem repeat, which sequence varies across species by a few point substitutions. We predict that in these species, this repeated region also acts as transcriptional regulatory domain and that sequence variation at this polymorphic locus might result in differential levels of expression in gene-environment interactions. For testing these hypotheses, the tandem repeat of Mandrillus sphinx and Cercopithecus aethiops from the third intron were cloned into a reporter gene vector and delivered to either primary cultures of rat neonate frontal cortex or the human cell line (JAr) to analyse their transcriptional activities. These repeated sequences supported significantly different levels of gene expression only when delivered into frontal cortex cultures. Furthermore, we tested in silico if such substitutions could have an effect on their binding profile to RNA- and DNA-binding proteins and on splicing. Taken together our results suggest that the tandem repeat in the third intron of the SLC6A4 gene of Old World monkeys could constitute a second transcriptional regulator as suggested for the 5HTTLPR and therefore contribute to diversification of serotonin-related behaviour in these primates.

When the serotonin transporter gene meets adversity: the contribution of animal models to understanding epigenetic mechanisms in affective disorders and resilience

Although converging epidemiological evidence links exposure to stressful life events with increased risk for affective spectrum disorders, there is extraordinary interindividual variability in vulnerability to adversity. The environmentally moderated penetrance of genetic variation is thought to play a major role in determining who will either develop disease or remain resilient. Research on genetic factors in the aetiology of disorders of emotion regulation has, nevertheless, been complicated by a mysterious discrepancy between high heritability estimates and a scarcity of replicable gene-disorder associations. One explanation for this incongruity is that at least some specific gene effects are conditional on environmental cues, i.e. gene-by-environment interaction (G × E) is present. For example, a remarkable number of studies reported an association of variation in the human serotonin (5-HT) transporter gene (SLC6A4, 5-HTT, SERT) with emotional and cognitive traits as well as increased risk for depression in interaction with psychosocial adversity. The results from investigations in non-human primate and mouse support the occurrence of G × E interaction by showing that variation of 5-HTT function is associated with a vulnerability to adversity across the lifespan leading to unfavourable outcomes resembling various neuropsychiatric disorders. The neural and molecular mechanisms by which environmental adversity in early life increases disease risk in adulthood are not known but may include epigenetic programming of gene expression during development. Epigenetic mechanisms, such as DNA methylation and chromatin modification, are dynamic and reversible and may also provide targets for intervention strategies (see Bountra et al., Curr Top Behav Neurosci, 2011). Animal models amenable to genetic manipulation are useful in the identification of molecular mechanisms underlying epigenetic programming by adverse environments and individual differences in resilience to stress. Therefore, deeper insight into the role of epigenetic regulation in the process of neurodevelopmental programmes is likely to result in early diagnosis of affective spectrum disorders and will contribute to the design of innovative treatments targeting neural pathways that foster resilience.

Transitions in sensitive period attachment learning in infancy: the role of corticosterone

Survival of altricial infants, including humans and rats, depends on attachment to the caregiver - a process that requires infants to recognize, learn, and remember their attachment figure. The demands of a dynamic environment combined with a maturing organism require frequent neurobehavioral reorganization. This restructuring of behavior and its supporting neural circuitry can be viewed through the unique lens of attachment learning in rats in which preference learning is enhanced and aversion learning is attenuated. Behavioral restructuring is well adapted to securing the crucial infant-caregiver relationship regardless of the quality of care. With maturation and the end of the infant-caregiver attachment learning period, the complex interplay of neural structures, hormones, and social behavior coordinates the developing rat's eventual transition to life outside of the nest. Nevertheless, early-life environmental and physiological stressors can alter the resilient nature of this system, particularly with respect to the amygdala, and these changes may provide important clues to understanding the lasting effects of early stress.

The evolutionary versus socio-economic view on grandparenthood: What are the grandparents' underlying motivations?

Coall & Hertwig (C&H) give an ambitious review about the broad range of grandparenting literature from the perspective of different disciplines. They aim to show, how evolutionary theory, sociology, and economics can mutually enrich each other. However, the differences between the evolutionary and the socio-economic perspective should be more clearly pointed out, because they usually deal with different research questions. Grandparents' well-being could be divided into its underlying components.

Animal violence demystified

Violence has been observed in humans and animals alike, indicating its evolutionary/biological significance. However, violence in animals has often been confounded with functional forms of aggressive behavior. Currently, violence in animals is identified primarily as either a quantitative behavior (an escalated, pathological and abnormal form of aggression characterized primarily by short attack latencies, and prolonged and frequent harm-oriented conflict behaviors) or a qualitative one (characterized by attack bites aimed at vulnerable parts of the opponent's body and context independent attacks regardless of the environment or the sex and type of the opponent). Identification of an operational definition for violence thus not only helps in understanding its potential differences from adaptive forms of aggression but also in the selection of appropriate animal models for both. We address this issue theoretically by drawing parallels from research on aggression and appeasement in humans and other animals. We also provide empirical evidences for violence in mice selected for high aggression by comparing our findings with other currently available potentially violent rodent models. The following violence-specific features namely (1) Display of low levels of pre-escalatory/ritualistic behaviors. (2) Immediate and escalated offense durations with low withdrawal rates despite the opponent's submissive supine and crouching/defeat postures. (3) Context independent indiscriminate attacks aimed at familiar/unfamiliar females, anaesthetized males and opponents and in neutral environments. (4) Orientation of attack-bites toward vulnerable body parts of the opponent resulting in severe wounding. (5) Low prefrontal serotonin (5-HT) levels upon repeated aggression. (6) Low basal heart rates and hyporesponsive hypothalamus-pituitary-adrenocortical (HPA) axis were identified uniquely in the short attack latency (SAL) mice suggesting a qualitative difference between violence and adaptive aggression in animals.

Social subordination and polymorphisms in the gene encoding the serotonin transporter enhance estradiol inhibition of luteinizing hormone secretion in female rhesus monkeys

Psychosocial factors, particularly social stress, may compromise reproduction. However, some individuals may be more susceptible to socially induced infertility. The present study used group-housed, adult, ovariectomized rhesus monkeys to test the hypothesis that exposure to psychosocial stress, imposed by social subordination, would enhance estradiol (E2)-negative feedback inhibition of LH. Because polymorphisms in the gene encoding the serotonin transporter (SLC6A4) may contribute to individual differences in response to adverse environments, we determined whether subordinate females with the short-promoter-length allele (s-variant) would show greater suppression of LH. Subordinate females, particularly those with the s-variant SLC6A4 genotype, received significantly higher rates of noncontact aggression from more dominant cage mates and had consistently lower body weights. Serum LH was not influenced by social status in the absence of E2. In contrast, subordinate females were hypersensitive to E2-negative feedback inhibition of LH. Furthermore, serum LH in subordinate females with s-variant SLC6A4 genotype was maximally suppressed by Day 4 of treatment, whereas nadir concentrations were not reached until later in treatment in other females. Finally, pharmacological elevation of serum cortisol potentiated E2-negative feedback inhibition in all females. The current data suggest that infertility induced by psychosocial stressors may be mediated by hypersensitivity to E2-negative feedback and that polymorphisms in the SLC6A4 gene may contribute to differences in reproductive compromise in response to chronic stress.

Association between the serotonin transporter promoter polymorphism (5-HTTLPR) and adult unresolved attachment

Research on antecedents of organized attachment has focused on the quality of caregiving received during childhood. In recent years, research has begun to examine the influence of genetic factors on quality of infant attachment. However, no published studies report on the association between specific genetic factors and adult attachment. This study examined the link between the 5-HTTLPR promoter polymorphism of the serotonin transporter gene and adult unresolved attachment assessed with the Adult Attachment Interview. Genetic material and information on attachment-related loss or trauma were available for 86 participants. Multivariate regression analyses showed an association between the short 5-HTTLPR allele and increased risk for unresolved attachment. Temperament traits and psychological symptoms did not affect the association between 5-HTTLPR and unresolved attachment. The authors hypothesize that the increased susceptibility to unresolved attachment among carriers of the short allele of 5-HTTLPR is consistent with the role of serotonin in modulation of frontal-amygdala circuitry. The findings challenge current thinking by demonstrating significant genetic influences on a phenomenon previously thought to be largely environmentally driven.

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.

How can the study of biological processes help design new interventions for children with severe antisocial behavior?

Children with severe antisocial behavior have an increased risk of showing violently aggressive and other forms of problem behavior in adolescence and adulthood. It is well established that both biological and social factors are involved in the development of antisocial behavior. The primary aim of this paper is to discuss the evidence that specific neurobiological systems are involved in the etiology of childhood-onset antisocial behavior. These factors are responsible for the severity of the behavioral problems observed in antisocial children, but they also play a role in their persistence, because they influence children's interactions with their environment. We will discuss the possible causes of disruptions in neurobiological systems in childhood antisocial behavior and point out the implications of these findings for theory and clinical practice. We will argue that familial factors (e.g., genetic influences, early childhood adversity) are linked to negative behavioral outcomes (e.g., antisocial behavior problems) through the mediating and transactional interplay with neurobiological deficits. An investigation of neurobiological functioning in antisocial children might not only indicate which children are most likely to persist in engaging in severe antisocial behavior, but also guide the development of new interventions.

Schools, Skills, and Synapses

This paper discusses (a) the role of cognitive and noncognitive ability in shaping adult outcomes, (b) the early emergence of differentials in abilities between children of advantaged families and children of disadvantaged families, (c) the role of families in creating these abilities, (d) adverse trends in American families, and (e) the effectiveness of early interventions in offsetting these trends. Practical issues in the design and implementation of early childhood programs are discussed.

Interaction of child and family psychopathology leading to suicidal behavior

According to the Centers for Disease Control and Prevention, suicide is the third leading cause of death in adolescence in the United States. Nonfatal forms of suicidal behavior are the most common reasons for the psychiatric hospitalization of adolescents in many countries. The risk for suicide attempt among offspring of suicide completers is multifactorial, challenging experts to develop a strategy that includes assessment and management that consider these factors. Although treatment of depression is necessary, antisuicide treatment strategies that solely target depression may not be sufficient to reduce suicidal risk. Other factors, such as impulsive aggression and parental history of sexual abuse, also contribute to suicidal risk.

Selective impairment of cognitive performance in the young monkey following recovery from iron deficiency

OBJECTIVE

While poor nutrition during development is an obvious concern, the magnitude and duration of the neural and cognitive deficits that occur after moderate iron deficiency in infancy have remained controversial. A nonhuman primate model of infancy anemia was refined to investigate the effects on cognitive performance.

METHODS

Young rhesus monkeys that experienced a delimited period of iron deficiency were tested on a series of cognitive tasks following normalization of their hematological status. Beginning at 8 to 9 months of age, 2 months after weaning from their mothers and consumption of solid food, the previously iron-deficient (ID) monkeys (n = 17) were compared to age- and gender-matched, iron-sufficient (IS) (n = 27) monkeys on a series of three tests of cognitive performance. Using the Wisconsin General Testing Apparatus, a Black/White Discrimination task was followed by acquisition of Black/White Reversal (BWR).

RESULTS

ID monkeys were significantly slower at mastering the BWR task (p < .04), which required reversing and inhibiting the previously learned response. In addition, ID infants were significantly less object oriented (p < .017) and more distractible (p < .018). However, on two subsequent tests, the Concurrent Object Discrimination and Delayed Non-Match-to-Sample, there were no differences in acquisition, performance, or behavioral reactivity.

CONCLUSIONS

The initial cognitive and behavioral deficits are similar to those seen in follow-up evaluations of anemic children, but the limited extent of the impairment after this moderate iron deficiency that involved a select nutrient deficiency is encouraging for the benefits attainable through early identification and iron supplementation.

Wheel-running activity increases with social stress in male DBA mice

Social affiliation-avoidance behaviors are essential indices of sociality. We examined changes in social affiliation-avoidance behaviors in an open-field apparatus while simultaneously measuring wheel-running activity. Recent studies suggest that mice increase wheel-running activity in stressful situations; thus, we hypothesized that wheel-running activity would reflect a state of social stress and avoidance. Mean duration of wheel-running increased significantly when mice were confronted with unfamiliar mice compared to cage mates. There were negative correlations between the amount of wheel-running and social affiliation indices. We also examined the effect of social defeat on wheel-running activity. Mice that had experienced social defeat significantly increased their wheel-running when an aggressor mouse was present. This social defeat-induced wheel-running activity was ameliorated by the administration of diazepam. Our results indicate that wheel-running activity is relevant to social affiliation-avoidance behaviors and may be a reliable index of anxiety induced by social stress.

Gene-environment interactions, not neonatal growth hormone deficiency, time puberty in female rhesus monkeys

The factors that influence the timing of puberty and the onset of adult fertility are poorly understood. While focus on the juvenile period has provided insights into how growth-related cues affect pubertal timing, growth velocity during infancy that is sustained into the juvenile period may be important. On the other hand, social factors, specifically exposure to psychosocial stressors, can delay sexual maturation, possibly by altering growth velocities during development. Using female rhesus monkeys, the present study used a prospective analysis to determine how neonatal growth hormone (GH) inhibition with a sandostatin analog or suppression of the pituitary-gonadal axis with a GnRH analog affected growth and sexual maturation. A separate retrospective analysis was done assessing the effects of social dominance status during development on pubertal timing. Because a specific polymorphism in the gene encoding the serotonin (5HT) reuptake transporter increases vulnerability to psychosocial stressors, females were also genotyped and were then classified as socially dominant, having both alleles for the long promoter variant or having at least one allele for the short promoter variant, or as socially subordinate, having the long variant or having the short variant. Neonatal treatments were not balanced for social status or genotype, so analyses were performed separately. Although the neonatal treatments reduced GH secretion postnatally and through the juvenile period, neither growth nor sexual maturation was affected. In contrast, the retrospective analysis showed sexual maturation was delayed significantly in subordinate females carrying at least one allele of the short promoter variant in the gene encoding the 5HT reuptake transporter, and this delay was associated with reduced GH and leptin secretion during the juvenile phase but not with differences in growth velocities from birth. These data suggest that decreased neonatal GH secretion does not adversely affect sexual maturation, but that polymorphisms in the gene encoding the 5HT transporter modulate the adverse consequences of social subordination on the timing of puberty in female rhesus monkeys.

Coping resources, coping processes, and mental health

Coping, defined as action-oriented and intrapsychic efforts to manage the demands created by stressful events, is coming to be recognized both for its significant impact on stress-related mental and physical health outcomes and for its intervention potential. We review coping resources that aid in this process, including individual differences in optimism, mastery, self-esteem, and social support, and examine appraisal and coping processes, especially those marked by approach or avoidance. We address the origins of coping resources and processes in genes, early life experience, and gene-environment interactions, and address neural underpinnings of coping that may shed light on evaluating coping interventions. We conclude by outlining possible intervention strategies for improving coping processes.

Case–control and within-family tests for association between 5HTTLPR and conduct problems in a longitudinal adolescent sample

BACKGROUND

Several recent studies have reported an association between the serotonin transporter 5HTTLPR (s-allele) and aggression; however, non-replications have also been reported. Inconsistencies may be explained by gene-environment interactions. Using a large general population sample, we sought to test for an association between 5HTTLPR and conduct problems, and to explore for a possible 5HTTLPR by maltreatment interaction.

METHODS

Using Caucasian adolescents from the genetic-pairs sample of the National Longitudinal Study of Adolescent Health (n=1,736), we tested for an association between 5HTTLPR and both a categorical and, separately, a continuous measure of conduct problems using regression analyses while controlling for sex, family effects, and age. We then tested for an association between 5HTTLPR and conduct problems using the within-family test Quantitative Transmission Disequilibrium Test. Analyses were repeated for a measure of adolescence-limited delinquency.

RESULTS

Results did not support an association between 5HTTLPR and conduct problems or delinquency. The Quantitative Transmission Disequilibrium Test analyses, which account for population stratification, were nonsignificant (F=0.17; P=0.68); introducing maltreatment as a covariate into the model did not affect this association (F=0.17; P=0.68). No association was seen between 5HTTLPR and a measure of adolescence-limited delinquency (F=0.54; P=0.46).

DISCUSSION

Using two methods in a large general population sample we did not find a significant association between 5HTTLPR and conduct problems. A gene by maltreatment interaction was not supported.

The interaction of psychosocial adversity and biological risk in childhood aggression

Childhood aggression has both biological and environmental underpinnings. However, the manner in which these factors interact to influence various types of aggression remains an important area of study. The current study examined the degree to which biological risk and psychosocial adversity, both alone and in combination, are associated with childhood aggression. Linear regression procedures were used to assess the extent to which biological risk status (low vs. high serotonergic responsivity, as measured by prolactin response to fenfluramine), magnitude of psychosocial risk, and the interaction of these factors predicted parent and teacher ratings of aggression and delinquency. After accounting for the independent contribution of biological and psychosocial risk, the interaction of biological and psychosocial risk was significantly associated with parent-rated aggression and marginally related to parent-rated delinquency. In contrast, no such interaction was observed for teacher-rated aggression. Findings suggest that individuals at biological risk for aggression may be particularly vulnerable to the impact of psychosocial adversity.

The importance of stress and genetic variation in human aggression

Both genetic and environmental factors have key roles in determining aggressive tendencies. In particular, reaction to stress appears to be an important factor in precipitating aggressive episodes and individuals may vary in their ability to cope with stressful environments depending on their genetic make up. Evidence from humans and primates indicates that adverse rearing conditions may interact with variants in stress and neurotransmitter pathway genes leading to antisocial and/or violent behaviour. Common alleles of some serotonin pathway genes, including those involved in its degradation (monoamine oxidase A, MAOA), or its re-uptake into pre-synaptic neurones (serotonin transporter, SERT) have been shown to confer functional variation. Examination of the interaction between the alleles of such polymorphisms (in particular those affecting MAOA) and environmental stressors suggest that they may provide protection against, or increase sensitivity to, abusive upbringing; an observation that may explain part of the variability in developmental outcomes associated with maltreatment.

Evo-devo and the evolution of social behavior

The integration of evolutionary biology with developmental genetics into the hybrid field of 'evo-devo' resulted in major advances in understanding multicellular development and morphological evolution. Here we show how insights from evo-devo can be applied to study the evolution of social behavior. We develop this idea by reviewing studies that suggest that molecular pathways controlling feeding behavior and reproduction in solitary insects are part of a 'genetic toolkit' underlying the evolution of a particularly complex form of social behavior, division of labor among workers in honeybee colonies. The evo-devo approach, coupled with advances in genomics for non-model genetic organisms, including the recent sequencing of the honeybee genome, promises to advance our understanding of the evolution of social behavior.

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.

Case-control and within-family tests for an association between conduct disorder and 5HTTLPR

Several lines of research have suggested that serotonin dysfunction is associated with aggression, impulsivity, and antisocial behavior. A functional polymorphism in the promoter region (s, short and l, long allele variant) of the serotonin transporter gene (SLC6A4) that results in decreased transcription of the serotonin transporter gene has been linked with such serotonin dysfunction. To test for an association between 5HTTLPR genotype and conduct disorder diagnosis/aggression. Analysis for association between 5HTTLPR and conduct disorder/aggression using a case-control design and the transmission disequilibrium test. Conduct-disordered adolescents, who were drawn from admissions to a program that treats adolescents with serious substance and behavior problems, and conduct-disordered siblings of these patients (n, 297) were compared with non-conduct-disordered control adolescents and non-conduct-disordered siblings of these controls (n, 93). Second, using patient families where parental DNA was available, transmission disequilibrium tests were conducted for two phenotypes: (1) conduct disorder (74 trios), and (2) conduct disorder with at least one aggressive symptom (57 trios). Case-control analyses suggested a strong association between the ss genotype and conduct disorder (chi2(2) = 14.3; P < 0.01). Within-family analyses for conduct disorder with at least one aggressive symptom significantly favored greater transmission of the s-allele to affected offspring (chi(tdt)(2) = 4.13; P = 0.04); for conduct disorder, without aggressive symptoms, however, results were non-significant (chi(tdt)(2) = 1.61; P = 0.20). These data suggest that the s-allele may confer some risk for aggressive behavior or may be in linkage disequilibrium with such an allele.

Translating research findings on early experience to prevention: animal and human evidence on early attachment relationships

Recent studies provide a wealth of findings on the mechanisms by which early stress exposure, particularly within the early child-parent attachment relationship, may influence long-term adaptation. Translating these findings to clinical practice and social policy is now underway. In this review, some key considerations in this translational task are examined, specifically, the conceptual bases underlying the research designs, the putative mechanisms involved, and the degree to which currently available findings might shape interventions. Although the primary focus is on depression, a broader range of phenotypes associated with poor early caregiving environments is also considered.

Mental representations of attachment in identical female twins with and without conduct problems

Insecure mental representations of attachment, a nearly invariant feature of cluster B personality disorders, have never previously been studied in twins. We conducted the Adult Attachment Interview (AAI) on 33 pairs of monozygotic (MZ) female twins reared together as an initial exploration of causal influences on mental representations of attachment. As predicted by attachment theory, we observed substantial twin-twin concordance for attachment security (odds ratio 13.8; P = 0.001), a similar level of concordance between twins and their non-twin siblings, and an inverse relationship between attachment security and current level of aggression (P = 0.01). These data indicate that there are minimal effects of non-shared environmental influences (or measurement error) on attachment classifications derived from the AAI. In this sample of twins with and without histories of Conduct Disorder, mental representations of attachment appear to be highly familial, i.e., strongly influenced by either shared environmental factors, genetic factors, or both.

Further evidence for an association of 5-HTTLPR with intensity dependence of auditory-evoked potentials

Intensity dependence of auditory-evoked potentials (IAEP) has been suggested as an indicator of central serotonergic neurotransmission. Two recent studies investigated a possible association of IAEP with a functional polymorphism in the transcriptional control region of the serotonin transporter gene (5-HTTLPR) that has a short (s) and a long (l) variant. Although both studies found an association between 5-HTTLPR and IAEP, Gallinat et al found l/l individuals to exhibit lower IAEP, whereas Strobel et al observed stronger IAEP in l/l individuals. These conflicting results require further evaluation and more attention needs to be paid to variables that are known to be confounded with the effects of IAEP and 5-HTTLPR. Using a paradigm comparable to Strobel et al, the present study analyzes the effect of 5-HTTLPR on IAEP in a healthy male student sample (N=91; age=23 years, SD=1.9) that was homogenous for most significant confounding variables. A stronger IAEP was shown in l/l individuals, irrespective of the method of IAEP parametrization. This also held at retest after 3 weeks in a subsample (N=18). Given the successful replication of Strobel et al, several possible reasons for conflicting results with regard to Gallinat et al are discussed. It is argued that the most significant difference between Gallinat et al on the one hand, and Strobel et al and this study on the other, is that different intensity ranges are used which impact IAEP. Therefore, this study encourages further analysis of dose dependence of results.