Early Caregiving and Human Biobehavioral Development: A Comparative Physiology Approach

Effects of early life adversity and adolescent basolateral amygdala activity on corticolimbic connectivity and anxiety behaviors

Early postnatal development of corticolimbic circuitry is shaped by the environment and is vulnerable to early life challenges. Prior work has shown that early life adversity (ELA) leads to hyperinnervation of glutamatergic basolateral amygdala (BLA) projections to the prefrontal cortex (PFC) in adolescence. While hyperinnervation is associated with later-life anxiety behaviors, the physiological changes underpinning corticolimbic and behavioral impacts of ELA are not understood. We tested whether postsynaptic BLA-driven PFC activity is enhanced in ELA-exposed animals, using the maternal separation (MS) model of ELA. PFC local-field potential following BLA stimulation was facilitated in MS-exposed adolescents. Since ELA increases activity of the early-developing BLA, while the PFC exhibits protracted development, we further examined impacts of glutamatergic BLA activity during early adolescence on later-life PFC innervation and heightened anxiety. In early adolescence, MS-exposed animals exhibited decreased anxiety-like behavior, and acute adolescent BLA inhibition induced behaviors that resembled those of MS animals. To examine long-lasting impacts of adolescent BLA activity on innervation, BLA-originating axonal boutons in the PFC were quantified in late adolescence after early adolescent BLA inhibition. We further tested whether late adolescent BLA-PFC changes were associated with anxious reactivity expressed as heightened acoustic startle responses. MS rearing increased BLA-PFC innervation and threat reactivity in late adolescence, however early adolescent BLA inhibition was insufficient to prevent MS effects, suggesting that earlier BLA activity or post-synaptic receptor rearrangement in the PFC drives altered innervation. Taken together, these findings highlight both pre- and postsynaptic changes in the adolescent BLA-PFC circuit following ELA.

Neurodevelopmental origins of substance use disorders: Evidence from animal models of early-life adversity and addiction

Addiction is a chronic relapsing disorder with devastating personal, societal, and economic consequences. In humans, early-life adversity (ELA) such as trauma, neglect, and resource scarcity are linked with increased risk of later-life addiction, but the brain mechanisms underlying this link are still poorly understood. Here, we focus on data from rodent models of ELA and addiction, in which causal effects of ELA on later-life responses to drugs and the neurodevelopmental mechanisms by which ELA increases vulnerability to addiction can be determined. We first summarize evidence for a link between ELA and addiction in humans, then describe how ELA is commonly modeled in rodents. Since addiction is a heterogeneous disease with many individually varying behavioral aspects that may be impacted by ELA, we next discuss common rodent assays of addiction-like behaviors. We then summarize the specific addiction-relevant behavioral phenotypes caused by ELA in male and female rodents and discuss some of the underlying changes in brain reward and stress circuits that are likely responsible. By better understanding the behavioral and neural mechanisms by which ELA promotes addiction vulnerability, we hope to facilitate development of new approaches for preventing or treating addiction in those with a history of ELA.

Neighborhood poverty, allostatic load, and changes in cellular aging in African American young adults: the moderating role of attachment

Attachment experiences are thought to contribute to physical health across the lifespan. Evidence suggests that attachment style may serve as a protective factor for individuals' physical health by mitigating the negative effects of social and environmental risk factors. In the present study, we evaluated how attachment styles may moderate the link between African American adolescents' exposure to neighborhood poverty and accelerated cellular aging in young adulthood. Analyses revealed that allostatic load at age 19 mediated the association between neighborhood poverty in adolescence and changes in cellular aging from age 20 to 27. Notably, attachment avoidance (but not attachment anxiety) moderated this association, such that allostatic load was only associated with faster cellular aging for individuals who were high in avoidance. These findings suggest that allostatic load may give rise to faster cellular aging, but these detrimental effects of allostatic load can be offset by young adults' effective use of attachment figures.

The Welch Emotional Connection Screen: Adapting observational methods to pediatric primary care via resident training

The Welch Emotional Connection Screen (WECS) is a novel instrument that is a brief, practicable, evidenced-based observational screening tool for assessing relationship health between parent and child. The WECS requires observing 2-3 min of face-to-face interactions between parent and child, without toys, prompts, paradigms or technology. Here, we describe a translational project from the coding lab to the primary care provider via a residency training program conducted with 50 residents during a 30-day developmental and behavioral pediatrics medical resident education rotation. The aims of this study were to evaluate the efficacy of WECS pediatric resident training: 1) to improve residents' accuracy in recognizing the dyadic behaviors of emotional connection (EC) via WECS training; and 2) to improve residents' attitudes, self-efficacy, and perceived professional norms (ASPPN) pertaining to Early Relational Health in Pediatrics. Results indicate that using a rapid prototyping approach to training, residents improved in their identification of dyads showing low to midrange levels of emotional connection. As well, resident attitudes about the importance of relationship health in pediatrics and their self-efficacy in identifying emotional connection improved significantly after this brief resident training.

Frontal EEG asymmetry in infants observing separation and comforting events: The role of infants' attachment relationship

The development of social-cognitive abilities in infancy is subject to an intricate interaction between maturation of neural systems and environmental input. We investigated the role of infants’ attachment relationship quality in shaping infants’ neural responses to observed social interactions. One-hundred thirty 10-month-old infants participated in an EEG session while they watched animations involving a distressing separation event that ended with either comforting or ignoring behavior. Frontal asymmetry (FA) in the alpha range - which is indicative of approach-withdrawal tendencies - was measured with EEG. Attachment quality was assessed using the Strange Situation procedure at 12 months. Overall, infants with disorganized attachment showed a lack of right-sided – withdrawal related – FA compared to secure and insecure infants. Furthermore, only avoidant infants exhibited reduced right-sided FA responses following the separation. Contrary to our expectations, the type of response (comforting vs. ignoring) did not elicit differences in FA patterns, and attachment quality did not moderate the effects of the type of response on frontal asymmetry. Implications for research on attachment-related biases in social information processing and on the neural underpinnings of prosocial behaviors are discussed.

The Developmental Origins of Opioid Use Disorder and Its Comorbidities

Opioid use disorder (OUD) rarely presents as a unitary psychiatric condition, and the comorbid symptoms likely depend upon the diverse risk factors and mechanisms by which OUD can arise. These factors are heterogeneous and include genetic predisposition, exposure to prescription opioids, and environmental risks. Crucially, one key environmental risk factor for OUD is early life adversity (ELA). OUD and other substance use disorders are widely considered to derive in part from abnormal reward circuit function, which is likely also implicated in comorbid mental illnesses such as depression, bipolar disorder, and schizophrenia. ELA may disrupt reward circuit development and function in a manner predisposing to these disorders. Here, we describe new findings addressing the effects of ELA on reward circuitry that lead to OUD and comorbid disorders, potentially via shared neural mechanisms. We discuss some of these OUD-related problems in both humans and animals. We also highlight the increasingly apparent, crucial contribution of biological sex in mediating the range of ELA-induced disruptions of reward circuitry which may confer risk for the development of OUD and comorbid neuropsychiatric disorders.

Altered corticolimbic connectivity reveals sex-specific adolescent outcomes in a rat model of early life adversity

Exposure to early-life adversity (ELA) increases the risk for psychopathologies associated with amygdala-prefrontal cortex (PFC) circuits. While sex differences in vulnerability have been identified with a clear need for individualized intervention strategies, the neurobiological substrates of ELA-attributable differences remain unknown due to a paucity of translational investigations taking both development and sex into account. Male and female rats exposed to maternal separation ELA were analyzed with anterograde tracing from basolateral amygdala (BLA) to PFC to identify sex-specific innervation trajectories through juvenility (PD28) and adolescence (PD38;PD48). Resting-state functional connectivity (rsFC) was assessed longitudinally (PD28;PD48) in a separate cohort. All measures were related to anxiety-like behavior. ELA-exposed rats showed precocial maturation of BLA-PFC innervation, with females affected earlier than males. ELA also disrupted maturation of female rsFC, with enduring relationships between rsFC and anxiety-like behavior. This study is the first providing both anatomical and functional evidence for sex- and experience-dependent corticolimbic development.

Having a traumatic childhood increases the risk a person will develop anxiety disorders later in life. Early life adversity affects men and women differently, but scientists do not yet know why. Learning more could help scientists develop better ways to prevent or treat anxiety disorders in men and women who experienced childhood trauma.

Anxiety occurs when threat-detecting brain circuits turn on. These circuits begin working in infancy, and during childhood and adolescence, experiences shape the brain to hone the body’s responses to perceived threats. Two areas of the brain that are important hubs for anxiety-related brain circuits include the basolateral amygdala (BLA) and the prefrontal cortex (PFC).

Now, Honeycutt et al. show that rats that experience early life adversity develop stronger connections between the BLA and PFC, and these changes occur earlier in female rats. In the experiments, one group of rats was repeatedly separated from their mothers and littermates (an early life trauma), while a second group was not. Honeycutt et al. examined the connections between the BLA and PFC in the two groups at three different time periods during their development: the juvenile stage, early adolescence, and late adolescence.

The experiments showed stronger connections between the BLA and PFC begin to appear earlier in juvenile traumatized female rats. But these changes did not appear in their male counterparts until adolescence. Lastly, the rats that developed these strengthened BLA-PFC connections also behaved more anxiously later in life. This may mean that the ideal timing for interventions may be different for males and females. More work is needed to see if these results translate to humans and then to find the best times and methods to help people who experienced childhood trauma.

Browne J, Austin J, M. Myers M, Welch MG. The Welch Emotional Connection Screen: validation of a brief mother-infant relational health screen

AIM

The Welch Emotional Connection Screen (WECS), assesses mother-infant Emotional Connection in clinical settings. It includes: Attraction, Vocal Communication, Facial Communication, Sensitivity/Reciprocity and clinical decision of Emotional Connection (yes/no). We tested concurrent and construct validity of the WECS and associations with behavioural and physiological measures in preterm infants.

METHODS

Videos from 76 mothers-infants (gestational age 36 weeks) during an in-NICU caregiving paradigm were coded for maternal caregiving behaviour. Videos of mothers-infants were also obtained at 4 months during 10 minutes of face-to-face play (coded with WECS and for maternal positivity and infant social engagement) and the still-face paradigm (coded for infant behavioural approach towards mother; infant electrocardiogram acquired in vivo).

RESULTS

WECS maternal scores were positively associated with maternal sensitivity and quality of vocal contact at 36 weeks (caregiving) and maternal positivity at 4 months (face-to-face). WECS infant scores positively correlated with infant social engagement and maternal positivity during face-to-face interactions at 4 months. Infants from emotionally not connected dyads (vs. emotionally connected dyads) displayed autonomic dysregulation and less approach-seeking behaviour towards mother during interactive/play sessions of the still-face paradigm.

CONCLUSION

This preliminary evidence supports the WECS as a valid screen for rating mother-preterm infant emotional connection associated with healthier infant biobehavioural stress responding.

Neurohormones and temperament interact during infant development

The infant's psycho-physiological regulatory system begins to develop prenatally and continues to mature during the postnatal period. Temperament is a construct comprising tonic individual differences in dispositional physiological and behavioural reactions as well as an evolving ability to regulate to environmental conditions. Theoretical models and research have shown that neurohormonal and -physiological factors contribute to individual development and impact infant behaviours as well as the developing regulatory system. Moreover, prenatal maternal risks such as stress and depression are thought to programme fetal regulatory tendencies and that influences neural and behavioural functioning in infancy. The purpose of this review is to examine the theories and research that link infant temperament to neurohormonal and -physiological development in typically developing infants and in those exposed to environmental risk. Research has demonstrated associations between individual variation in physiological stress responses and regulation (measured with cortisol). Moreover, studies have noted an association with physiological regulation and socio-emotional interaction (as measured by the touch-oxytocin link) that may buffer emotional dysregulation. The interaction between individual differences in temperamental tendencies, neurohormonal and -physiological patterns will be discussed by presenting data from studies that have shown that infant neurohormonal and -physiological functioning sets an important trajectory for the development of the individual.This article is part of the theme issue 'Diverse perspectives on diversity: multi-disciplinary approaches to taxonomies of individual differences'.

Early life trauma increases threat response of peri-weaning rats, reduction of axo-somatic synapses formed by parvalbumin cells and perineuronal net in the basolateral nucleus of amygdala

Early life trauma is a risk factor for life-long disorders related to emotional processing, but knowledge underlying its enduring effect is incomplete. This study was motivated by the hypothesis that early life trauma increases amygdala-dependent threat responses via reduction in inhibition by parvalbumin (PV) interneurons and perineuronal nets (PNN) supporting PV cells, thus increasing excitability of the basolateral amygdala (BLA). From postnatal day (PN) 8-12, rat pups of both sexes were reared under normal bedding or under insufficient nest-building materials to induce maternal-to-infant maltreatment trauma (Scarcity-Adversity Model, SAM). At weaning age of PN23, the SAM group exhibited increased threat responses to predator odor. The SAM-induced increase in threat response was recapitulated in normally reared PN22-23 rats that were unilaterally depleted of PNN in the BLA by the enzymes, chondroitinase-ABC plus hyaluronidase at PN19-20. Light and electron microscopic analysis of the BLA revealed that anterior-to-mid levels of SAM group's BLAs exhibited decreased PNN intensity and decreased axo-somatic synapses between PV-to-principal pyramidal-like neurons and PV-to-PV. PV and PNN densities (cells/mm² ) in the BLA of both control (CON) and SAM groups were still low at PN12 and SAM delayed the ontogenetic rise of PV intensity and PNN density. Moreover, PV cell density in the anterior-to-mid BLA correlated negatively with threat response of CON animals, but not for SAM animals. Thus, reduction of PNN-supported, PV-mediated somatic inhibition of pyramidal cells provides a mechanistic support for the enduring effect of early life maltreatment manifested as increasing innate threat response at weaning.