Paternal deprivation during infancy results in dendrite- and time-specific changes of dendritic development and spine formation in the orbitofrontal cortex of the biparental rodent Octodon degus

Father's Absence in the Mongolian gerbil (Meriones unguiculatus) is associated with alterations in paternal behavior, T, cort, presence of ERα, and AR in mPOA/ BNST

Testosterone (T), estrogen receptor alpha (ERα), and androgen receptor (AR) play a significant role in the regulation of paternal behavior. We determined the effects of deprivation of paternal care on alterations in paternal behavior, T concentrations in plasma, and the presence of ERα and AR in the medial preoptic area (mPOA), bed nucleus of the stria terminalis (BNST), medial amygdala (MeA), and olfactory bulb (OB), as well as the corticosterone (CORT) concentrations in plasma caused by deprivation of paternal care in the Mongolian gerbil (Meriones unguiculatus). Twenty pairs of gerbils were formed; the pups were deprived of paternal care (DPC) in 10 pairs. In another 10 pairs, the pups received paternal care (PC). Ten males raised in DPC condition and 10 males raised in PC conditions were mated with virgin females. When they became fathers, each DPC male and PC male was subjected to tests of paternal behavior on day three postpartum. Blood samples were obtained to quantify T and CORT concentrations, and the brains were removed for ERα and AR immunohistochemistry analyses. DPC males gave less care to their pups than PC males, and they had significantly lower T concentrations and levels of ERα and AR in the mPOA and BNST than PC males. DPC males also had higher CORT concentrations than PC males. These results suggest that in the Mongolian gerbil father's absence causes a decrease in paternal care in the offspring, which is associated with alterations in the neuroendocrine mechanisms that regulate it.

Sex-specific behavioral and physiological changes during single parenting in a biparental species, Columba livia

Many species exhibit biparental care to maximize fitness. When a partner is lost, the surviving partner may alter their behavior to compensate offspring. Whether both sexes use the same physiological mechanisms to manifest their change in behavior remains elusive. We investigated behaviors and mechanisms associated with the alteration of parental care post-partner removal in a biparental avian species, the rock dove (Columba livia). We hypothesized that rock dove single parents experience sex-biased changes in neural genomic transcription and reproductive behaviors, and these changes are related to chick development. We manipulated parental partner presence and measured parental attendance, offspring growth, gene expression of glucocorticoid receptors (GR) and mineralocorticoid receptors (MR) in the pituitary, and GR, MR, and estrogen receptor beta (ER-β) in the hypothalamus. We also measured circulating plasma concentrations of the stress-associated hormone corticosterone and the parental care-associated hormone prolactin. We also quantified prolactin gene (PRL) expression changes in the pituitary, as well as prolactin receptor (PRLR) expression in the hypothalamus and pituitary. We found that single mothers and fathers maintained similar provisioning levels as paired parents, but spent less cumulative time brooding chicks. Chicks of single parents were smaller than paired-parented chicks after three days post-hatch. Mothers in both treatment groups experienced higher expression of hypothalamic GR as compared to fathers. Single parents experienced lower PRL gene expression in the pituitary as compared to paired parents. No significant differences were found for the circulating hormones or other genes listed.

Paternal deprivation induces vigilance-avoidant behavior and accompanies sex-specific alterations in stress reactivity and central proinflammatory cytokine response in California mice (Peromyscus californicus)

RATIONALE

Early-life stress (ELS) can increase anxiety, reduce prosocial behaviors, and impair brain regions that facilitate emotional and social development. This knowledge greatly stems from assessing disrupted mother-child relationships, while studies investigating the long-term effects of father-child relationships on behavioral development in children are scarce. However, available evidence suggests that fathers may uniquely influence a child's behavioral development in a sex-specific manner. Rodent models examining mother-offspring interaction demonstrate relationships among ELS, neuroinflammatory mediators, and behavioral development; yet, the role paternal care may play in neuroimmune functioning remains unreported.

OBJECTIVES

Using the biparental California mouse (Peromyscus californicus), we examined to what extent paternal deprivation impairs social and anxiety-like behaviors, augments peripheral corticosterone (CORT) response, and alters central proinflammatory cytokine production following an acute stressor in adulthood.

METHODS

Biparentally reared and paternally deprived (permanent removal of the sire 24 h post-birth) adult mice were assessed for sociability, preference for social novelty, social vigilance, and social avoidance behaviors, followed by novelty-suppressed feeding (NSF) testing for general anxiety-like behavior. Following an acute stressor, circulating CORT concentrations and region-specific proinflammatory cytokine concentrations were determined via radioimmunoassay and Luminex multianalyte analysis, respectively.

RESULTS

In response to a novel same-sex conspecific, social vigilance behavior was associated with reduced sociability and increased avoidance in paternally deprived mice-an effect not observed in biparentally reared counterparts. Yet, in response to a familiar same-sex conspecific, social vigilance persisted but only in paternally deprived females. The latency to consume during NSF testing was not significantly altered by paternal deprivation. In response to an acute physical stressor, lower circulating CORT concentrations were observed in paternally deprived females. Compared to control-reared males, paternal deprivation increased hypothalamic interleukin-1β, but decreased hippocampal IL-6 protein concentration.

CONCLUSION

Greater social vigilance behavior was demonstrated in paternally deprived mice while they avoided social interaction with a novel same-sex conspecific; however, in response to a familiar same-sex conspecific, paternal deprivation increased social vigilance behavior but only in females. It is possible that different neurobiological mechanisms underlie these observed behavioral outcomes as sex-specific central proinflammatory cytokine and stress responsivity were observed in paternally deprived offspring.

Associations of maternal emotion regulation with child white matter connectivity in Black American mother-child dyads

Parental emotion regulation plays a major role in parent-child interactions, and in turn, neural plasticity in children, particularly during sensitive developmental periods. However, little is known about how parental emotion dysregulation is associated with variation in children's brain structure, which was the goal of this study. Forty-five Black American mother-child dyads were recruited from an intergenerational trauma study; emotion regulation in mothers and their children (age 8-13 years) was assessed. Diffusion-weighted images were collected in children; deterministic tractography was used to reconstruct pathways of relevance to emotion regulation. Metrics of white matter connectivity [fractional anisotropy (FA), mean diffusivity (MD)] were extracted for pathways. Socio-economic variables were also included in statistical models. Maternal emotion dysregulation was the strongest predictor of child fornix MD (r = .35, p = .001), indicating that more severe emotion dysregulation in mothers corresponded with lower fornix connectivity in children. Maternal impulsivity was a strong predictor of child fornix MD (r = .51, p < .001). Maternal emotion dysregulation may adversely influence connectivity of the child.s fornix, a hippocampal-striatal pathway implicated in reward processes; these associations remained even after accounting for other socio-environmental factors. Dysregulated maternal emotions may uniquely impact children's adaptation to trauma/stress by affecting networks that support appetitive processing.

Behavioral and electrophysiological indices of inhibitory control in maltreated adolescents and nonmaltreated adolescents

Early adverse experiences are believed to have a profound effect on inhibitory control and the underlying neural regions. In the current study, behavioral and event-related potential (ERP) data were collected during a go/no-go task from adolescents who were involved with the child welfare system due to child maltreatment (n = 129) and low-income, nonmaltreated adolescents (n = 102). The nonmaltreated adolescents were more accurate than the maltreated adolescents on the go/no-go task, particularly on the no-go trials. Paralleling the results with typically developing populations, the nonmaltreated adolescents displayed a more pronounced amplitude of the N2 during the no-go trials than during the go trials. However, the maltreated adolescents demonstrated a more pronounced amplitude of the N2 during the go trials than during the no-go trials. Furthermore, while the groups did not differ during the go trials, the nonmaltreated adolescents displayed a more negative amplitude of the N2 than the maltreated adolescents during no-go trials. In contrast, there was not a significant group difference in amplitude of the P3. Taken together, these results provide evidence that the early adverse experiences encountered by maltreated populations impact inhibitory control and the underlying neural activity in early adolescence.

Disorganized attachment behaviors in infancy as predictors of brain morphology and peer rejection in late childhood

Studies show robust links between disorganized attachment in infancy and socioemotional maladjustment in childhood. Little is known, however, about the links between disorganized attachment and brain development, and whether attachment-related differences in brain morphology translate into meaningful variations in child socioemotional functioning. This study examined the links between infants' disorganized attachment behaviors toward their mothers, whole-brain regional grey matter volume and thickness, and peer rejection in late childhood. Thirty-three children and their mothers took part in this study. The Strange Situation Procedure was used to assess mother-infant attachment when infants were 18 months old. Magnetic resonance imaging was performed when they were 10 years old to assess cortical thickness and grey matter volumes. Children and teachers reported on peer rejection 1 year later, as an indicator of socioemotional maladjustment. Results indicated that disorganized attachment was not associated with grey matter volumes. However, children who exhibited more disorganized attachment behaviors in infancy had significantly thicker cortices in bilateral middle and superior frontal gyri, and extending to the inferior frontal gyrus, as well as the orbitofrontal and insular cortices in the right hemisphere in late childhood. Moreover, children with thicker cortices in these regions experienced greater peer rejection, as rated by themselves and their teachers. Although preliminary, these results are the first to indicate that disorganized attachment may play a role in cortical thickness development and that changes in cortical thickness are associated with differences in child socioemotional functioning.

Differential Role of Sex and Age in the Synaptic Transmission of Degus (Octodon degus)

Octodon degus are a diurnal long-lived social animal widely used to perform longitudinal studies and complex cognitive tasks to test for physiological conditions with similitude in human behavior. They show a complex social organization feasible to be studied under different conditions and ages. Several aspects in degus physiology demonstrated that these animals are susceptible to environmental conditions, such as stress, fear, feeding quality, and isolation. However, the relevance of these factors in life of this animal depends on sex and age. Despite its significance, there are few studies with the intent to characterize neurological parameters that include these two parameters. To determine the basal neurophysiological status, we analyzed basic electrophysiological parameters generated during basal activity or synaptic plasticity in the brain slices of young and aged female and male degus. We studied the hippocampal circuit of animals kept in social ambient in captivity under controlled conditions. The study of basal synaptic activity in young animals (12–24 months old) was similar between sexes, but female degus showed more efficient synaptic transmission than male degus. We found the opposite in aged animals (60–84 months old), where male degus had a more efficient basal transmission and facilitation index than female degus. Furthermore, female and male degus develop significant but not different long-term synaptic plasticity (LTP). However, aged female degus need to recruit twice as many axons to evoke the same postsynaptic activity as male degus and four times more when compared to young female degus. These data suggest that, unlike male degus, the neural status of aged female degus change, showing less number or functional axons available at advanced ages. Our data represent the first approach to incorporate the effect of sex along with age progression in basal neural status.

Maternal Separation Modifies the Activity of Social Processing Brain Nuclei Upon Social Novelty Exposure

Maternal separation has been shown to disrupt proper brain development and maturation, having profound consequences on the neuroendocrine systems in charge of the stress response, and has been shown to induce behavioral and cognitive abnormalities. At the behavioral level, maternal separation has been shown to increase offensive play-fighting in juvenile individuals and reduce social interest in adulthood. Since most of the studies that have evaluated the consequences of maternal separation on social behavior have focused on behavioral analysis, there is a need for a further understanding of the neuronal mechanisms underlying the changes in social behavior induced by maternal separation. Therefore, the aim of the present research was to assess the long-term effects of maternal separation on social interaction behavior and to assess the activity of several brain regions involved in the processing of social cues and reward upon social novelty exposure, using c-Fos immunohistochemistry as a marker of neuronal activity. Male Wistar rats were subjected to 4 h maternal separation during the neonatal period, 9:00 h-13:00 h from postnatal day 1 to 21, and exposed to social novelty during adulthood. After social novelty exposure, brains were fixed and coronal sections of the medial amygdala, lateral septum (LS), paraventricular nucleus of the hypothalamus, nucleus accumbens, and medial prefrontal cortex were obtained for c-Fos immunohistochemistry. Maternally separated rats spent less time investigating the novel peer, suggesting that maternal separation reduces social approach motivation. Furthermore, maternal separation reduced the number of c-Fos positive cells of the medial amygdala, paraventricular nucleus of the hypothalamus, LS, nucleus accumbens, and medial prefrontal cortex upon social novelty exposure. These findings suggest that maternal separation can reduce the plastic capacity of several brain nuclei, which constitute a physiological basis for the emergence of behavioral disorders presented later in life reported to be linked to early life adversity.

Involvement of the dopamine system in paternal behavior induced by repeated pup exposure in virgin male ICR mice

Like mothers, fathers play a vital role in the development of the brain and behavior of offspring in mammals with biparental care. Unlike mothers, fathers do not experience the physiological processes of pregnancy, parturition, or lactation before their first contact with offspring. Whether pup exposure can induce the onset of paternal behavior and the underlying neural mechanisms remains unclear. By using Slc:ICR male mice exhibiting maternal-like parental care, the present study found that repeated exposure to pups for six days significantly increased the total duration of paternal behavior and shortened the latency to retrieve and care for pups. Repeated pup exposure increased c-Fos-positive neurons and the levels of dopamine- and TH-positive neurons in the nucleus accumbens (NAc). In addition, inhibition of dopamine projections from the ventral tegmental area to the NAc using chemogenetic methods reduced paternal care induced by repeated pup exposure. In conclusion, paternal behavior in virgin male ICR mice can be initiated by repeated pup exposure via sensitization, and the dopamine system may be involved in this process.

Compositional variation in early-life parenting structures alters oxytocin and vasopressin 1a receptor development in prairie voles (Microtus ochrogaster)

Paternal absence can significantly alter bio-behavioural development in many biparental species. This effect has generally been demonstrated by comparing the development of offspring reared under biparental care with those reared by a single mother. However, studies employing this design conflate two significant modifications to early-life experience: removal of father-specific qualities and the general reduction of offspring-directed care. In the socially monogamous prairie vole (Microtus ochrogaster), the experience of paternal absence without substitution during development inhibits partner preference formation in adulthood, a hallmark of social monogamy, in females and males. Employing alloparents as substitutes for fathers, our previous work demonstrated that paternal absence affects pair-bond formation in female offspring via reduced quantity of care, although it affects pair-bond formation in male offspring by means of a missing paternal quality (or qualities). Here, we present evidence that paternal absence (with and without alloparental substitution) may alter the ontogeny of neural oxytocin receptor (OXTR) and/or vasopressin 1a receptor (AVPR1a) distribution in male and female prairie voles. Compared to biparentally reared controls (BPC), male offspring reared in mother only (MON) and maternal-plus-alloparental (MPA) conditions show lower densities of OXTR in the central amygdala; and MPA males show lower densities of OXTR in the caudate putamen and nucleus accumbens. Early-life experience was not associated with differences in AVPR1a density in males. However, MON and MPA females show greater densities of AVPR1a in the medial amygdala than BPC; and MPA females show greater densities of AVPR1a in the ventromedial nucleus of the hypothalamus. We also demonstrate with corticosterone concentrations that MON and MPA offspring are not differentially susceptible to a stressor (ie, social isolation) than BPC offspring. These findings suggest that paternal absence, although likely not a salient early-life stressor, has neuroendocrine consequences for offspring, some of which may affect partner preference formation.

The stressed orbitofrontal cortex

Stressor exposure causes dendritic remodeling on excitatory neurons in multiple regions of the brain, including the orbitofrontal cortex (OFC). Additionally, stressor and exogenous stress hormone exposure impair cognitive functions that are dependent on the OFC. For this Special Issue on the OFC, we summarize current literature regarding how stress-prenatal, postnatal, and even inter-generational-affects OFC neuron structure in rodents. We discuss dendrite structure, dendritic spines, and gene expression. We aim to provide a focused resource for those interested in how stressors impact this heterogeneous brain region. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

How stress physically re-shapes the brain: Impact on brain cell shapes, numbers and connections in psychiatric disorders

Severe stress is among the most robust risk factors for the development of psychiatric disorders. Imaging studies indicate that life stress is integral to shaping the human brain, especially regions involved in processing the stress response. Although this is likely underpinned by changes to the cytoarchitecture of cellular networks in the brain, we are yet to clearly understand how these define a role for stress in human psychopathology. In this review, we consolidate evidence of macro-structural morphometric changes and the cellular mechanisms that likely underlie them. Focusing on stress-sensitive regions of the brain, we illustrate how stress throughout life may lead to persistent remodelling of the both neurons and glia in cellular networks and how these may lead to psychopathology. We support that greater translation of cellular alterations to human cohorts will support parsing the psychological sequalae of severe stress and improve our understanding of how stress shapes the human brain. This will remain a critical step for improving treatment interventions and prevention outcomes.

Octodon degus: a natural model of multimorbidity for ageing research

Integrating the multifactorial processes co-occurring in both physiological and pathological human conditions still remains one of the main challenges in translational investigation. Moreover, the impact of age-associated disorders has increased, which underlines the urgent need to find a feasible model that could help in the development of successful therapies. In this sense, the Octodon degus has been indicated as a 'natural' model in many biomedical areas, especially in ageing. This rodent shows complex social interactions and high sensitiveness to early-stressful events, which have been used to investigate neurodevelopmental processes. Interestingly, a high genetic similarity with some key proteins implicated in human diseases, such as apolipoprotein-E, β-amyloid or insulin, has been demonstrated. On the other hand, the fact that this animal is diurnal has provided important contribution in the field of circadian biology. Concerning age-related diseases, this rodent could be a good model of multimorbidity since it naturally develops cognitive decline, neurodegenerative histopathological hallmarks, visual degeneration, type II diabetes, endocrinological and metabolic dysfunctions, neoplasias and kidneys alterations. In this review we have collected and summarized the studies performed on the Octodon degus through the years that support its use as a model for biomedical research, with a special focus on ageing.

Severe childhood and adulthood stress associates with neocortical layer-specific reductions of mature spines in psychiatric disorders

Severe stress exposure causes the loss of dendritic spines on cortical pyramidal neurons and induces psychiatric-like symptoms in rodent models. These effects are strongest following early-life stress and are most persistent on apical dendrites. However, the long-term impacts and temporal effects of stress exposure on the human brain remain poorly understood. Using a novel postmortem cohort of psychiatric cases with severe stress experienced in childhood, adulthood, or no severe stress, and matched controls, we aimed to determine the impact of stress timing on pyramidal neuron structure in the human orbitofrontal cortex (OFC). We performed Golgi Cox staining and manually measured the morphology and density of over 22,000 dendritic spines on layer-specific pyramidal neuron apical dendrites. We also quantified glucocorticoid receptor mRNA and protein as a marker of stress dysregulation. Both childhood and adulthood stress were associated with large reductions in mature mushroom spine density (up to 56% loss) in both the superficial (II/III) and deeper layers (V) of the OFC. However, childhood stress caused more substantial reductions to both total and mature mushroom spines. No difference in glucocorticoid receptor mRNA and protein were seen between groups, although both negatively correlated with total spine density within the whole cohort. These findings indicate that severe stress, especially when experienced during childhood, persistently affects the fine morphological properties of neurons in the human OFC. This may impact on cell connectivity in this brain area, and at least partly explain the social and emotional symptoms that originate in the OFC in psychiatric disorders.

Morphological Responses of Excitatory Prelimbic and Orbitofrontal Cortical Neurons to Excess Corticosterone in Adolescence and Acute Stress in Adulthood

Considerable evidence indicates that chronic stress and excess glucocorticoids induce neuronal remodeling in prefrontal cortical (PFC) regions. Adolescence is also characterized by a structural reorganization of PFC neurons, yet interactions between stress- and age-related structural plasticity are still being determined. We quantified dendritic spine densities on apical dendrites of excitatory neurons in the medial prefrontal cortex, prelimbic subregion (PL). Densities decreased across adolescent development, as expected, and spine volume increased. Unexpectedly, exposure to excess corticosterone (CORT) throughout adolescence did not cause additional dendritic spine loss detectable in adulthood. As a positive control dendrite population expected to be sensitive to CORT, we imaged neurons in the orbitofrontal cortex (OFC), confirming CORT-induced dendritic spine attrition on basal arbors of layer V neurons. We next assessed the effects of acute, mild stress in adulthood: On PL neurons, an acute stressor increased the density of mature, mushroom-shaped spines. Meanwhile, on OFC neurons, dendritic spine volumes and lengths were lower in mice exposed to both CORT and an acute stressor (also referred to as a "double hit"). In sum, prolonged exposure to excess glucocorticoids during adolescence can have morphological and also metaplastic consequences, but they are not global. Anatomical considerations are discussed.

Paternal Deprivation and Female Biparental Family Rearing Induce Dendritic and Synaptic Changes in Octodon degus: I. Medial Prefrontal Cortex

In most mammalian species parent-offspring interactions during early life periods primarily comprise social contacts with the mother, whereas the role of males in parental care is one of the most overlooked and understudied topics. The present study addressed the hypothesis that the complete deprivation of paternal care delays or permanently retards synaptic connectivity in the brain, particularly in the medial prefrontal cortex (mPFC) of the offspring in a sex-specific manner. Another aim of this study was to address the question whether and in which way replacing the father with a female caregiver (in our experiments the “aunt”) can “buffer” the detrimental effects of paternal deprivation on neuronal development. The comparison of: (a) single mother rearing; (b) biparental rearing by father and mother; and (c) biparental rearing by two female caregivers revealed that: (i) paternal care represents a critical environmental factor for synaptic and dendritic development of pyramidal neurons in the vmPFC of their offspring; (ii) a second female caregiver (“aunt”) does not “buffer” the neuronal consequences of paternal deprivation; and that (iii) neuronal development in the vmPFC is differentially affected in male and female offspring in response to different family constellations.

The neural mechanisms and consequences of paternal caregiving

In recent decades, human sociocultural changes have increased the numbers of fathers that are involved in direct caregiving in Western societies. This trend has led to a resurgence of interest in understanding the mechanisms and effects of paternal care. Across the animal kingdom, paternal caregiving has been found to be a highly malleable phenomenon, presenting with great variability among and within species. The emergence of paternal behaviour in a male animal has been shown to be accompanied by substantial neural plasticity and to be shaped by previous and current caregiving experiences, maternal and infant stimuli and ecological conditions. Recent research has allowed us to gain a better understanding of the neural basis of mammalian paternal care, the genomic and circuit-level mechanisms underlying paternal behaviour and the ways in which the subcortical structures that support maternal caregiving have evolved into a global network of parental care. In addition, the behavioural, neural and molecular consequences of paternal caregiving for offspring are becoming increasingly apparent. Future cross-species research on the effects of absence of the father and the transmission of paternal influences across generations may allow research on the neuroscience of fatherhood to impact society at large in a number of important ways.

Glucocorticoid-sensitive ventral hippocampal-orbitofrontal cortical connections support goal-directed action - Curt Richter Award Paper 2019

In an ever-changing and often ambiguous environment, organisms must use previously learned associations between antecedents and outcomes to predict future associations and make optimal choices. Chronic stress can impair one's ability to flexibly adjust behaviors when environmental contingencies change, particularly in cases of early-life stress. In mice, exposure to elevated levels of the primary stress hormone, corticosterone (CORT), during early adolescence is sufficient to impair response-outcome decision making later in life, biasing response strategies towards inflexible habits. Nevertheless, neurobiological mechanisms are still being defined. Here, we report that exposure to excess CORT in adolescence causes a loss of dendritic spines on excitatory pyramidal neurons in the lateral, but not medial, orbital prefrontal cortex (loPFC) of mice, and spine loss correlates with the severity of habit biases in adulthood. Excess CORT also reduces the presence of ventral hippocampal (vHC) axon terminals in the loPFC. To identify functional consequences, we inactivated vHC→loPFC projections in typical healthy mice during a period when mice must update response-outcome expectations to optimally acquire food reinforcers. Inactivation impaired the animals' subsequent ability to sustainably choose actions based on likely outcomes, causing them to defer to habit-based response strategies. Thus, vHC→loPFC projections are necessary for response-outcome expectancy updating and a target of excess glucocorticoids during early-life development. Their degradation is likely involved in long-term biases towards habit-based behaviors following glucocorticoid excess in adolescence.

Effects of parent-child interaction training on children who are excessively exposed to digital devices: A pilot study

Objective

In the last decade, the use of digital devices among children has increased. This study examines the effects of parent–child interaction training on the amount of time children use digital devices, conflict and closeness in parent–child relationships, executive functions, and the electroencephalogram absolute power in children who excessively use the digital devices.

Method

The sample group consisted of 12 children (24 to 47 months) who spent more than half of their waking hours using digital devices. Parents were trained to intensive interaction with the child for two months. Electroencephalogram absolute power, parent–child interaction, the amount of time children use digital devices, and children’s executive function skills were assessed.

Results

Parent–child intensive interaction reduces the use of digital devices; decrease the conflicts and increase the closeness in parent–child relationships; decrease executive functioning problems; and increase the absolute power of alpha and alpha 2 (F3), beta 1 (F3), and beta and beta 2 (F3, Fp2).

Conclusion

These findings provide evidence of the negative effects of the excessive use of digital devices in children, the importance of parent–child interaction, and its positive impacts on cognitive and brain functions in children. It might contribute to better understand the importance of parent–child interaction in the early years.

With a little help from her friends (and family) part II: Non-maternal caregiving behavior and physiology in mammals

The diversity of competing frameworks for explaining the evolution of non-maternal care in mammals (Part I, this issue) reflects the vast range of behaviors and associated outcomes these theories attempt to subsume. Caretaking comprises a wide variety of behavioral domains, and is mediated by an equally large range of physiological systems. In Part II, we provide an overview of how non-maternal care in mammals is expressed, the ways in which it is regulated, and the many effects such care has on both recipients and caretakers. We also discuss the two primary ways in which closer integration of ultimate and proximate levels of explanation can be useful when addressing questions about non-maternal caretaking. Specifically, proximate mechanisms provide important functional clues, and are key to testing theory concerning evolutionary tradeoffs. Finally, we highlight a number of methodological and publication biases that currently shape the literature, which provide opportunities for knowledge advancement in this domain going forward. In this conclusion to our two-part introduction, we provide a broad survey of the behavior and physiology that the contributions to this special issue represent.

Sensitive Fathering Buffers the Effects of Chronic Maternal Depression on Child Psychopathology

Maternal depression across the first years of life carries long-term negative consequences for children's well-being; yet, few studies focused on fathers as potential source of resilience in the context of chronic maternal depression. Utilizing an extreme-case design, a community birth cohort of married/cohabitating mothers (N = 1983) with no comorbid risk was repeatedly tested for maternal depression across the first year and again at 6 years, leading to two matched cohorts; 46 mothers with chronic depression and 103 non-depressed controls. At 6 years, mother and child underwent psychiatric diagnosis and mother-child and father-child interactions observed. Partners of depressed mothers exhibited reduced sensitivity, lower reciprocity, and higher tension during interactions, particularly among children with psychopathology. Maternal depression increased child propensity to display Axis-I disorder upon school-entry by fourfold. Sensitive fathering reduced this risk by half. Findings underscore the father's resilience-promoting role in cases of maternal depression and emphasize the need for father-focused interventions.

Rapid Infant Prefrontal Cortex Development and Sensitivity to Early Environmental Experience

Over the last fifteen years, the emerging field of developmental cognitive neuroscience has described the relatively late development of prefrontal cortex in children and the relation between gradual structural changes and children's protracted development of prefrontal-dependent skills. Widespread recognition by the broader scientific community of the extended development of prefrontal cortex has led to the overwhelming perception of prefrontal cortex as a "late developing" region of the brain. However, despite its supposedly protracted development, multiple lines of research have converged to suggest that prefrontal cortex development may be particularly susceptible to individual differences in children's early environments. Recent studies demonstrate that the impacts of early adverse environments on prefrontal cortex are present very early in development: within the first year of life. This review provides a comprehensive overview of new neuroimaging evidence demonstrating that prefrontal cortex should be characterized as a "rapidly developing" region of the brain, discusses the converging impacts of early adversity on prefrontal circuits, and presents potential mechanisms via which adverse environments shape both concurrent and long-term measures of prefrontal cortex development. Given that environmentally-induced disparities are present in prefrontal cortex development within the first year of life, translational work in intervention and/or prevention science should focus on intervening early in development to take advantages of this early period of rapid prefrontal development and heightened plasticity.

Enduring Effects of Paternal Deprivation in California Mice (Peromyscus californicus): Behavioral Dysfunction and Sex-Dependent Alterations in Hippocampal New Cell Survival

Early-life experiences with caregivers can significantly affect offspring development in human and non-human animals. While much of our knowledge of parent-offspring relationships stem from mother-offspring interactions, increasing evidence suggests interactions with the father are equally as important and can prevent social, behavioral, and neurological impairments that may appear early in life and have enduring consequences in adulthood. In the present study, we utilized the monogamous and biparental California mouse (Peromyscus californicus). California mouse fathers provide extensive offspring care and are essential for offspring survival. Non-sibling virgin male and female mice were randomly assigned to one of two experimental groups following the birth of their first litter: (1) biparental care: mate pairs remained with their offspring until weaning; or (2) paternal deprivation (PD): paternal males were permanently removed from their home cage on postnatal day (PND) 1. We assessed neonatal mortality rates, body weight, survival of adult born cells in the dentate gyrus of the hippocampus, and anxiety-like and passive stress-coping behaviors in male and female young adult offspring. While all biparentally-reared mice survived to weaning, PD resulted in a ~35% reduction in survival of offspring. Despite this reduction in survival to weaning, biparentally-reared and PD mice did not differ in body weight at weaning or into young adulthood. A sex-dependent effect of PD was observed on new cell survival in the dentate gyrus of the hippocampus, such that PD reduced cell survival in female, but not male, mice. While PD did not alter classic measures of anxiety-like behavior during the elevated plus maze task, exploratory behavior was reduced in PD mice. This observation was irrespective of sex. Additionally, PD increased some passive stress-coping behaviors (i.e., percent time spent immobile) during the forced swim task—an effect that was also not sex-dependent. Together, these findings demonstrate that, in a species where paternal care is not only important for offspring survival, PD can also contribute to altered structural and functional neuroplasticity of the hippocampus. The mechanisms contributing to the observed sex-dependent alterations in new cell survival in the dentate gyrus should be further investigated.

Paternal deprivation affects social behaviors and neurochemical systems in the offspring of socially monogamous prairie voles

Early life experiences, particularly the experience with parents, are crucial to phenotypic outcomes in both humans and animals. Although the effects of maternal deprivation on offspring well-being have been studied, paternal deprivation (PD) has received little attention despite documented associations between father absence and children health problems in humans. In the present study, we utilized the socially monogamous prairie vole (Microtus ochrogaster), which displays male-female pair bonding and bi-parental care, to examine the effects of PD on adult behaviors and neurochemical expression in the hippocampus. Male and female subjects were randomly assigned into one of two experimental groups that grew up with both the mother and father (MF) or with the mother-only (MO, to generate PD experience). Our data show that MO subjects received less parental licking/grooming and carrying and were left alone in the nest more frequently than MF subjects. At adulthood (∼75days of age), MO subjects displayed increased social affiliation (SOA) toward a conspecific compared to MF subjects, but the two groups did not differ in social recognition (SOR) and anxiety-like behavior. Interestingly, MO subjects showed consistent increases in both gene and protein expression of the brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB) as well as the levels of total histone 3 and histone 3 acetylation in the hippocampus compared to MF subjects. Further, PD experience increased glucocorticoid receptor beta (GRβ) protein expression in the hippocampus of females as well as increased corticotrophin receptor 2 (CRHR2) protein expression in the hippocampus of males, but decreased CRHR2 mRNA in both sexes. Together, our data suggest that PD has a long-lasting, behavior-specific effect on SOA and alters hippocampal neurochemical systems in the vole brain. The functional role of such altered neurochemical systems in social behaviors and the potential involvement of epigenetic events should be further studied.

Paradise Lost: The Neurobiological and Clinical Consequences of Child Abuse and Neglect

In the past two decades, much evidence has accumulated unequivocally demonstrating that child abuse and neglect is associated with a marked increase in risk for major psychiatric disorders (major depression, bipolar disorder, post-traumatic stress disorder [PTSD], substance and alcohol abuse, and others) and medical disorders (cardiovascular disease, diabetes, irritable bowel syndrome, asthma, and others). Moreover, the course of psychiatric disorders in individuals exposed to childhood maltreatment is more severe. Recently, the biological substrates underlying this diathesis to medical and psychiatric morbidity have been studied. This Review summarizes many of the persistent biological alterations associated with childhood maltreatment including changes in neuroendocrine and neurotransmitter systems and pro-inflammatory cytokines in addition to specific alterations in brain areas associated with mood regulation. Finally, I discuss several candidate gene polymorphisms that interact with childhood maltreatment to modulate vulnerability to major depression and PTSD and epigenetic mechanisms thought to transduce environmental stressors into disease vulnerability.

Multilevel developmental approaches to understanding the effects of child maltreatment: Recent advances and future challenges

Recent research in the field of child maltreatment has begun to shed new light on the emergence of health problems in children by emphasizing the responsiveness of developmental processes to children's environmental and biological contexts. Here, I highlight recent trends in the field with an emphasis on the effects of early life stress across multiple levels of developmental domains.

Preconception paternal stress in rats alters dendritic morphology and connectivity in the brain of developing male and female offspring

The goal of this research was to examine the effect of preconception paternal stress (PPS) on the subsequent neurodevelopment and behavior of male and female offspring. Prenatal (gestational) stress has been shown to alter brain morphology in the developing brain, and is presumed to be a factor in the development of some adult psychopathologies. Our hypothesis was that paternal stress in the preconception period could impact brain development in the offspring, leading to behavioral abnormalities later in life. The purpose of this study was to examine the effect of preconception paternal stress on developing male and female offspring brain morphology in five brain areas; medial prefrontal cortex (mPFC), orbitofrontal cortex (OFC), parietal cortex (Par1), hippocampus (CA1) and nucleus accumbens (NAc). Alterations in dendritic measures and spine density were observed in each brain area examined in paternal stress offspring. Our two main findings reveal; (1) PPS alters brain morphology and organization and these effects are different than the effects of stress observed at other ages; and, (2) the observed dendritic changes were sexually dimorphic. This study provides direct evidence that PPS modifies brain architecture in developing offspring, including dendritic length, cell complexity, and spine density. Alterations observed may contribute to the later development of psychopathologies and maladaptive behaviors in the offspring.

Plasticity in the prefrontal cortex of adult rats

We review the plastic changes of the prefrontal cortex of the rat in response to a wide range of experiences including sensory and motor experience, gonadal hormones, psychoactive drugs, learning tasks, stress, social experience, metaplastic experiences, and brain injury. Our focus is on synaptic changes (dendritic morphology and spine density) in pyramidal neurons and the relationship to behavioral changes. The most general conclusion we can reach is that the prefrontal cortex is extremely plastic and that the medial and orbital prefrontal regions frequently respond very differently to the same experience in the same brain and the rules that govern prefrontal plasticity appear to differ for those of other cortical regions.

Brain development, experience, and behavior

Brain development progresses through a series of stages beginning with neurogenesis and progressing to neural migration, maturation, synaptogenesis, pruning, and myelin formation. This review examines the literature on how early experiences alter brain development, including environmental events such as sensory stimuli, early stress, psychoactive drugs, parent-child relationships, peer relationships, intestinal flora, diet, and radiation. This sensitivity of the brain to early experiences has important implications for understanding neurodevelopmental disorders as well as the effect of medical interventions in children.

Paternal influences on offspring development: behavioural and epigenetic pathways

Although mammalian parent-offspring interactions during early life are primarily through the mother, there is increasing evidence for the impact of fathers on offspring development. A critical issue concerns the pathways through which this paternal influence is achieved. In the present review, we highlight the literature suggesting several of these routes of paternal effects in mammals. First, similar to mothers, fathers can influence offspring development through the direct care of offspring, as has been observed in biparental species. Second, there is growing evidence that, even in the absence of contact with offspring, fathers can transmit environmentally-induced effects (i.e. behavioural, neurobiological and metabolic phenotypes induced by stress, nutrition and toxins) to offspring and it has been speculated that these effects are achieved through inherited epigenetic variation within the patriline. Third, fathers may also impact the quality of mother-infant interactions and thus achieve an indirect influence on offspring. Importantly, these pathways of paternal influence are not mutually exclusive but rather serve as an illustration of the complex mechanisms through which parental influence is achieved. These influences may serve to transmit traits across generations, thus leading to a transgenerational transmission of neurobiological and behavioural phenotypes.

Quantitative investigations of axonal and dendritic arbors: development, structure, function, and pathology

The branching structures of neurons are a long-standing focus of neuroscience. Axonal and dendritic morphology affect synaptic signaling, integration, and connectivity, and their diversity reflects the computational specialization of neural circuits. Altered neuronal morphology accompanies functional changes during development, experience, aging, and disease. Technological improvements continuously accelerate high-throughput tissue processing, image acquisition, and morphological reconstruction. Digital reconstructions of neuronal morphologies allow for complex quantitative analyses that are unattainable from raw images or two-dimensional tracings. Furthermore, digitized morphologies enable computational modeling of biophysically realistic neuronal dynamics. Additionally, reconstructions generated to address specific scientific questions have the potential for continued investigations beyond the original reason for their acquisition. Facilitating multiple reuse are repositories like NeuroMorpho.Org, which ease the sharing of reconstructions. Here, we review selected scientific literature reporting the reconstruction of axonal or dendritic morphology with diverse goals including establishment of neuronal identity, examination of physiological properties, and quantification of developmental or pathological changes. These reconstructions, deposited in NeuroMorpho.Org, have since been used by other investigators in additional research, of which we highlight representative examples. This cycle of data generation, analysis, sharing, and reuse reveals the vast potential of digital reconstructions in quantitative investigations of neuronal morphology.

Seasonal variations of basal cortisol and high stress response to captivity in Octodon degus, a mammalian model species

Across vertebrates, the hypothalamic-pituitary-adrenal axis is a conserved neuroendocrine network that responds to changing environments and involves the release of glucocorticoids into the blood. Few studies have been carried out concerning mammalian adrenal regulation in wild species either in the laboratory or field, and even fewer have been able to determine true glucocorticoid baselines. We studied the South-American caviomorph rodent Octodon degus, a diurnal and social mammal that has become an important species in the biological research. First, we determined the plasma cortisol baseline and the acute stress concentrations during the non-reproductive and mating seasons in free-living individuals. Second, using the same protocol we assessed the impact of long-term captivity on the adrenal function in wild-caught degus and degus born in laboratory. Third, we examined laboratory groups formed with degus taken from two distant natural populations; one of them originally occurs at the Andes Mountains in high altitude conditions. The data revealed seasonal modulation of basal cortisol in the wild associated with mating. In laboratory, degus presented higher cortisol stress responses, with greater magnitudes shown in degus born and reared in captivity. No differences between populations were found. The results suggest differential regulatory mechanisms between basal and stress-induced cortisol levels, and context dependence of cortisol modulation in a mammalian species.

Father absence in the monogamous california mouse impairs social behavior and modifies dopamine and glutamate synapses in the medial prefrontal cortex

The role of the father in psycho-affective development is indispensable. Yet, the neurobehavioral effects of paternal deprivation (PD) are poorly understood. Here, we examined the behavioral consequences of PD in the California mouse, a species displaying monogamous bonding and biparental care, and assessed its impact on dopamine (DA), serotonin (5-HT), and glutamate (GLU) transmission in the medial prefrontal cortex (mPFC). In adult males, deficits in social interaction were observed, when a father-deprived (PD) mouse was matched with a PD partner. In adult females, deficits were observed when matching a PD animal with a non-PD control, and when matching 2 PD animals. PD also increased aggression in females. Behavioral abnormalities in PD females were associated with a sensitized response to the locomotor-activating effect of amphetamine. Following immunocytochemical demonstration of DA, 5-HT, and GLU innervations in the mPFC, we employed in vivo electrophysiology and microiontophoresis, and found that PD attenuated the basal activity of low-spiking pyramidal neurons in females. PD decreased pyramidal responses to DA in females, while enhancing responses to NMDA in both sexes. We thus demonstrate that, during critical neurodevelopmental periods, PD leads to sex-dependent abnormalities in social and reward-related behaviors that are associated with disturbances in cortical DA and GLU neurotransmission.

Patterns of brain activation in foster children and nonmaltreated children during an inhibitory control task

Children in foster care have often encountered a range of adverse experiences, including neglectful and/or abusive care and multiple caregiver transitions. Prior research findings suggest that such experiences negatively affect inhibitory control and the underlying neural circuitry. In the current study, event-related functional magnetic resonance imaging was employed during a go/no go task that assesses inhibitory control to compare the behavioral performance and brain activation of foster children and nonmaltreated children. The sample included two groups of 9- to 12-year-old children: 11 maltreated foster children and 11 nonmaltreated children living with their biological parents. There were no significant group differences on behavioral performance on the task. In contrast, patterns of brain activation differed by group. The nonmaltreated children demonstrated stronger activation than did the foster children across several regions, including the right anterior cingulate cortex, the middle frontal gyrus, and the right lingual gyrus, during correct no go trials, whereas the foster children displayed stronger activation than the nonmaltreated children in the left inferior parietal lobule and the right superior occipital cortex, including the lingual gyrus and cuneus, during incorrect no go trials. These results provide preliminary evidence that the early adversity experienced by foster children impacts the neural substrates of inhibitory control.

Early neglect is associated with alterations in white matter integrity and cognitive functioning

Cognitive deficits have been reported in children who experienced early neglect, especially children raised in institutionalized settings. Previous research suggests that early neglect may differentially affect the directional organization of white matter in the prefrontal cortex (PFC). This may be one mechanism to explain cognitive deficits associated with neglect. To test this idea, properties of white matter and neurocognitive performance were assessed in children who suffered early neglect and those raised in typical environments (n = 63, Mage  = 11.75 years). As predicted, prefrontal white matter microstructure was affected, consistent with more diffuse organization, in children that suffered early neglect and this was related to neurocognitive deficits. Such findings underscore how early adversity may affect the PFC and explain cognitive deficits associated with neglect.

Three-dimensional reconstruction of brain structures of the rodent Octodon degus: a brain atlas constructed by combining histological and magnetic resonance images

Degus (Octodon degus) are rodents that are becoming more widely used in the neuroscience field. Degus display several more complex behaviors than rats and mice, including complicated social behaviors, vocal communications, and tool usage with superb manual dexterity. However, relatively little information is known about the anatomy of degu brains. Therefore, for these complex behaviors to be correlated with specific brain regions, a contemporary atlas of the degu brain is required. This manuscript describes the construction of a three-dimensional (3D) volume rendered model of the degu brain that combines histological and magnetic resonance images. This atlas provides several advantages, including the ability to visualize the surface of the brain from any angle. The atlas also permits virtual cutting of brain sections in any plane and provides stereotaxic coordinates for all sections, to be beneficial for both experimental surgeries and radiological studies. The reconstructed 3D atlas is freely available online at: http://brainatlas.brain.riken.jp/degu/modules/xoonips/listitem.php?index_id=24 .

Paternal deprivation affects the functional maturation of corticotropin-releasing hormone (CRH)- and calbindin-D28k-expressing neurons in the bed nucleus of the stria terminalis (BNST) of the biparental Octodon degus

While the critical role of maternal care on the development of brain and behavior of the offspring has been extensively studied, our knowledge about the importance of paternal care for brain development of his offspring is still comparatively scarce. The aim of this study in the biparental caviomorph rodent Octodon degus was to analyze the impact of paternal care on the development of corticotropin-releasing hormone (CRH)-expressing neurons in the bed nucleus of the stria terminalis (BNST) and hypothalamic paraventricular nucleus (PVN). Both brain areas are key players in neuronal circuits that regulate hypothalamic–pituitary–adrenal axis (HPA) activity. At the age of postnatal day (PND) 21, we found that paternal deprivation resulted in a decreased density of CRH-containing neurons in the medial, but not in the lateral BNST, whereas no changes were observed in the PVN. These deprivation-induced changes were still prominent in adulthood. At PND 21, the density of Ca-binding protein calbindin D28K (CaBP-D28K)-expressing neurons was specifically increased in the medial, but not lateral BNST of father-deprived animals. In contrast, adult father-deprived animals show significantly decreased density of CaBP-D28K-expressing neurons in the lateral, but not medial BNST. Taken together, these results may have important implications for our understanding of the experience-driven development of neural circuits that regulate HPA activity mediating acute responses to stress and chronic anxiety.

Octodon degus: a model for the cognitive impairment associated with Alzheimer's disease

Octodon degus (O. degus) is a diurnal rodent that spontaneously develops several physiopathological conditions, analogous in many cases to those experienced by humans. In light of this, O. degus has recently been identified as a very valuable animal model for research in several medical fields, especially those concerned with neurodegenerative diseases in which risk is associated with aging. Octodon degus spontaneously develops β-amyloid deposits analogous to those observed in some cases of Alzheimer's disease (AD). Moreover, these deposits are thought to be the key feature for AD diagnosis, and one of the suggested causes of cell loss and cognitive deficit. This review aims to bring together information to support O. degus as a valuable model for the study of AD.

Non-genomic transmission of paternal behaviour between fathers and sons in the monogamous and biparental California mouse

Maternal behaviour has profound, long-lasting implications for the health and well-being of developing offspring. In the monogamous California mouse (Peromyscus californicus), care by both parents is critical for offspring survival. We tested the hypothesis that similar to maternal care in rodents, paternal huddling and grooming (HG) behaviour can be transmitted to future generations via behavioural mechanisms. In California mice, testosterone maintains paternal HG behaviour. In the present study, we randomly assigned a group of male California mice to castration or sham-operated conditions and allowed them to raise their offspring normally. Adult sons of these males were paired with a female, and they were observed interacting with their own offspring. We found that like their fathers, the sons of castrated males huddled and groomed their young at lower levels than the sons of sham-operated fathers. The sons of castrates also retrieved pups more frequently. When both parents were present, the sons of castrates also showed a trend towards engaging in less exploratory behaviour. These data support the hypothesis that paternal behaviour, like maternal behaviour, can be transferred to future generations via epigenetic mechanisms and suggest that in a biparental species both parents contribute to offspring behavioural development.

Paternal stress prior to conception alters DNA methylation and behaviour of developing rat offspring

Although there has been an abundance of research focused on offspring outcomes associated with maternal experiences, there has been limited examination of the relationship between paternal experiences and offspring brain development. As spermatogenesis is a continuous process, experiences that have the ability to alter epigenetic regulation in fathers may actually change developmental trajectories of offspring. The purpose of this study was to examine the effects of paternal stress prior to conception on behaviour and the epigenome of both male and female developing rat offspring. Male Long-Evans rats were stressed for 27 consecutive days and then mated with control female rats. Early behaviour was tested in offspring using the negative geotaxis task and the open field. At P21 offspring were sacrificed and global DNA methylation levels in the hippocampus and frontal cortex were analysed. Paternal stress prior to conception altered behaviour of all offspring on the negative geotaxis task, delaying acquisition of the task. In addition, male offspring demonstrated a reduction in stress reactivity in the open field paradigm spending more time than expected in the centre of the open field. Paternal stress also altered DNA methylation patterns in offspring at P21, global methylation was reduced in the frontal cortex of female offspring, but increased in the hippocampus of both male and female offspring. The results from this study clearly demonstrate that paternal stress during spermatogenesis can influence offspring behaviour and DNA methylation patterns, and these affects occur in a sex-dependent manner. Development takes place in the centre of a complex interaction between maternal, paternal, and environmental influences, which combine to produce the various phenotypes and individual differences that we perceive.