OUP accepted manuscript

Amygdala volumes and associations with socio-emotional competencies in preterm youth: cross-sectional and longitudinal data

BACKGROUND

Socio-emotional difficulties often result from very preterm (VPT) birth. The amygdala's developmental trajectory, including its nuclei, has been recognized as a significant factor in observed difficulties. This study aims to assess the relationship between amygdala volume and socio-emotional competencies in VPT children and adolescents.

METHODS

Socio-emotional competencies were assessed, and amygdala volumes, including subnuclei, were extracted automatically from structural scans in a cross-sectional cohort of VPT (n = 75) and full-term (FT, n = 41) aged 6-14 years. Group differences in amygdala volumes were assessed using ANCOVA, and associations with socio-emotional competencies were studied using partial least squares correlation (PLSC). In a VPT subgroup, additional longitudinal data with amygdala volumes at term-equivalent age (TEA) were manually extracted, growth rates calculated, and associations with school-age socio-emotional competencies investigated using PLSC.

RESULTS

Using cross-sectional data at school-age, amygdala volumes displayed comparable developmental patterns between the VPT and the FT groups. Greater volumes were associated with more emotional regulation difficulties in VPT and lower affect recognition competencies in FT. In the longitudinal VPT subgroup, no significant associations were found between amygdala volume trajectory and socio-emotional competencies.

CONCLUSION

Although our findings suggest typical amygdala development after VPT birth, further research is necessary to elucidate the developmental trajectory of amygdala and the role of resilience factors.

IMPACT

In our cohort, amygdala volumes, including subnuclei, displayed comparable developmental trajectories between the very preterm and the full-term groups. Higher amygdala volumes at school-age were associated with higher emotional regulation difficulties in the very-preterm born group, and with lower affect recognition abilities in full-term born children and adolescents. In a subgroup of very-preterm children and adolescents followed from birth to school-age, no significant associations were found between amygdala volumes at term-equivalent age and socio-emotional competencies at school-age.

Amygdala structure and function and its associations with social-emotional outcomes in a low-risk preterm sample

Amygdala atypical volume development and functional connectivity (FC) at small gestational ages (GA) have been found across childhood. This adult-oriented study assesses whether altered amygdala structure and function is present following low-risk preterm birth. T1-weighted and resting-state functional MRI images of 33 low-risk preterm (30-36 weeks' GA) and 29 full-term (37-42 weeks' GA) young adults of both sexes, aged between 20 and 32 years old, were analyzed using FreeSurfer (v6.0.0) and Coon Toolbox (v21.a). The social-emotional assessment included Happé's Strange Stories Test, the Moral Judgment Test, Delay-Discounting Test, Adult Self Report, and Emotion Regulation Questionnaire. No differences were found in social-emotional outcomes or amygdala volumes between the groups. Low-risk preterm young adults showed increased FC between the left amygdala, right amygdala and medial frontal cortex (MedFC) (F = 9.89, p-FWE = 0.009) at cluster level compared to their full-term peers. However, significant results at connection level were not observed between left and right amygdala. Lastly, increased FC at cluster level between the right amygdala and MedFC, and left amygdala and MedFC, was related to better social-emotional outcomes only in low-risk preterm young adults (F = 6.60, p-FWE = 0.036) at cluster level. At connection level, in contrast, only right amygdala-MedFC increased FC was significantly associated with better social-emotional outcomes. This study reveals that low-risk prematurity does not have an effect on social-emotional outcomes or structural amygdala volumes during young adulthood. However, individuals who were considered to be at a lower risk of exhibiting neurodevelopmental alterations following preterm birth demonstrated increased FC between the left and right amygdala and MedFC.

Prenatal exposure to maternal disadvantage-related inflammatory biomarkers: associations with neonatal white matter microstructure

Prenatal exposure to heightened maternal inflammation has been associated with adverse neurodevelopmental outcomes, including atypical brain maturation and psychiatric illness. In mothers experiencing socioeconomic disadvantage, immune activation can be a product of the chronic stress inherent to such environmental hardship. While growing preclinical and clinical evidence has shown links between altered neonatal brain development and increased inflammatory states in utero, the potential mechanism by which socioeconomic disadvantage differentially impacts neural-immune crosstalk remains unclear. In the current study, we investigated associations between socioeconomic disadvantage, gestational inflammation, and neonatal white matter microstructure in 320 mother-infant dyads over-sampled for poverty. We analyzed maternal serum levels of four cytokines (IL-6, IL-8, IL-10, TNF-α) over the course of pregnancy in relation to offspring white matter microstructure and socioeconomic disadvantage. Higher average maternal IL-6 was associated with very low socioeconomic status (SES; INR < 200% poverty line) and lower neonatal corticospinal fractional anisotropy (FA) and lower uncinate axial diffusivity (AD). No other cytokine was associated with SES. Higher average maternal IL-10 was associated with lower FA and higher radial diffusivity (RD) in corpus callosum and corticospinal tracts, higher optic radiation RD, lower uncinate AD, and lower FA in inferior fronto-occipital fasciculus and anterior limb of internal capsule tracts. SES moderated the relationship between average maternal TNF-α levels during gestation and neonatal white matter diffusivity. When these interactions were decomposed, the patterns indicated that this association was significant and positive among very low SES neonates, whereby TNF-α was inversely and significantly associated with inferior cingulum AD. By contrast, among the more advantaged neonates (lower-to-higher SES [INR ≥ 200% poverty line]), TNF-α was positively and significantly associated with superior cingulum AD. Taken together, these findings suggest that the relationship between prenatal cytokine exposure and white matter microstructure differs as a function of SES. These patterns are consistent with a scenario where gestational inflammation's effects on white matter development diverge depending on the availability of foundational resources in utero.

Distinct Neurodevelopmental Trajectories in Groups of Very Preterm Children Screening Positively for Autism Spectrum Conditions

Very preterm (VPT; < 33 weeks' gestation) toddlers screening positively for autism spectrum conditions (ASC) may display heterogenous neurodevelopmental trajectories. Here we studied neonatal brain volumes and childhood ASC traits evaluated with the Social Responsiveness Scale (SRS-2) in VPT-born toddlers (N = 371; median age 20.17 months) sub-divided into three groups based on their Modified-Checklist for Autism in Toddlers scores. These were: those screening positively failing at least 2 critical items (critical-positive); failing any 3 items, but less than 2 critical items (non-critical-positive); and screening negatively. Critical-positive scorers had smaller neonatal cerebellar volumes compared to non-critical-positive and negative scorers. However, both positive screening groups exhibited higher childhood ASC traits compared to the negative screening group, suggesting distinct aetiological trajectories associated with ASC outcomes.

Associations between infant amygdala functional connectivity and social engagement following a stressor: A preliminary investigation

Functional architecture of the infant brain, especially functional connectivity (FC) within the amygdala network and between the amygdala and other networks (i.e., default-mode [DMN] and salience [SAL] networks), provides a neural basis for infant socioemotional functioning. Yet, little is known about the extent to which early within- and between-network amygdala FC are related to infant stress recovery across the first year of life. In this study, we examined associations between amygdala FC (i.e., within-network amygdala connectivity, and between-network amygdala connectivity with the DMN and SAL) at 3 months and infant recovery from a mild social stressor at 3, 6 and 9 months. At 3 months, thirty-five infants (13 girls) underwent resting-state functional magnetic resonance imaging during natural sleep. Infants and their mothers completed the still-face paradigm at 3, 6, and 9 months, and infant stress recovery was assessed at each time point as the proportion of infant social engagement during the reunion episode. Bivariate correlations indicated that greater positive within-network amygdala FC and greater positive amygdala-SAL FC, but not amygdala-DMN FC, at 3 months predicted lower levels of stress recovery at 3 and 6 months, but were nonsignificant at 9 months. These findings provide preliminary evidence that early functional synchronization within the amygdala network, as well as segregation between the amygdala and the SAL, may contribute to infant stress recovery in the context of infant-mother interaction.

Longitudinal neonatal brain development and socio-demographic correlates of infant outcomes following preterm birth

Preterm birth results in premature exposure of the brain to the extrauterine environment during a critical period of neurodevelopment. Consequently, infants born preterm are at a heightened risk of adverse behavioural outcomes in later life. We characterise longitudinal development of neonatal regional brain volume and functional connectivity in the first weeks following preterm birth, sociodemographic factors, and their respective relationships to psychomotor outcomes and psychopathology in toddlerhood. We study 121 infants born preterm who underwent magnetic resonance imaging shortly after birth, at term-equivalent age, or both. Longitudinal regional brain volume and functional connectivity were modelled as a function of psychopathology and psychomotor outcomes at 18 months. Better psychomotor functioning in toddlerhood was associated with greater relative right cerebellar volume and a more rapid decrease over time of sensorimotor degree centrality in the neonatal period. In contrast, increased 18-month psychopathology was associated with a more rapid decrease in relative regional subcortical volume. Furthermore, while socio-economic deprivation was related to both psychopathology and psychomotor outcomes, cognitively stimulating parenting predicted psychopathology only. Our study highlights the importance of longitudinal imaging to better predict toddler outcomes following preterm birth, as well as disparate environmental influences on separable facets of behavioural development in this population.

Prenatal Stress and the Developing Brain: Postnatal Environments Promoting Resilience

Heightened maternal stress during pregnancy is associated with atypical brain development and an elevated risk for psychopathology in offspring. Supportive environments during early postnatal life may promote brain development and reverse atypical developmental trajectories induced by prenatal stress. We reviewed studies focused on the role of key early environmental factors in moderating associations between prenatal stress exposure and infant brain and neurocognitive outcomes. Specifically, we focused on the associations between parental caregiving quality, environmental enrichment, social support, and socioeconomic status with infant brain and neurocognitive outcomes. We examined the evidence that these factors may moderate the effects of prenatal stress on the developing brain. Complementing findings from translational models, human research suggests that high-quality early postnatal environments are associated with indices of infant neurodevelopment that have also been associated with prenatal stress, such as hippocampal volume and frontolimbic connectivity. Human studies also suggest that maternal sensitivity and higher socioeconomic status may attenuate the effects of prenatal stress on established neurocognitive and neuroendocrine mediators of risk for psychopathology, such as hypothalamic-pituitary-adrenal axis functioning. Biological pathways that may underlie the effects of positive early environments on the infant brain, including the epigenome, oxytocin, and inflammation, are also discussed. Future research in humans should examine resilience-promoting processes in relation to infant brain development using large sample sizes and longitudinal designs. The findings from this review could be incorporated into clinical models of risk and resilience during the perinatal period and used to design more effective early programs that reduce risk for psychopathology.

The Role of Oxytocin in Abnormal Brain Development: Effect on Glial Cells and Neuroinflammation

The neonatal period is critical for brain development and determinant for long-term brain trajectory. Yet, this time concurs with a sensitivity and risk for numerous brain injuries following perinatal complications such as preterm birth. Brain injury in premature infants leads to a complex amalgam of primary destructive diseases and secondary maturational and trophic disturbances and, as a consequence, to long-term neurocognitive and behavioral problems. Neuroinflammation is an important common factor in these complications, which contributes to the adverse effects on brain development. Mediating this inflammatory response forms a key therapeutic target in protecting the vulnerable developing brain when complications arise. The neuropeptide oxytocin (OT) plays an important role in the perinatal period, and its importance for lactation and social bonding in early life are well-recognized. Yet, novel functions of OT for the developing brain are increasingly emerging. In particular, OT seems able to modulate glial activity in neuroinflammatory states, but the exact mechanisms underlying this connection are largely unknown. The current review provides an overview of the oxytocinergic system and its early life development across rodent and human. Moreover, we cover the most up-to-date understanding of the role of OT in neonatal brain development and the potential neuroprotective effects it holds when adverse neural events arise in association with neuroinflammation. A detailed assessment of the underlying mechanisms between OT treatment and astrocyte and microglia reactivity is given, as well as a focus on the amygdala, a brain region of crucial importance for socio-emotional behavior, particularly in infants born preterm.

Large-scale brain network dynamics in very preterm children and relationship with socio-emotional outcomes: an exploratory study

BACKGROUND

Children born very preterm (VPT; <32 weeks' gestation) are at high risk of neurodevelopmental and behavioural difficulties associated with atypical brain maturation, including socio-emotional difficulties. The analysis of large-scale brain network dynamics during rest allows us to investigate brain functional connectivity and its association with behavioural outcomes.

METHODS

Dynamic functional connectivity was extracted by using the innovation-driven co-activation patterns framework in VPT and full-term children aged 6-9 to explore changes in spatial organisation, laterality and temporal dynamics of spontaneous large-scale brain activity (VPT, n = 28; full-term, n = 12). Multivariate analysis was used to explore potential biomarkers for socio-emotional difficulties in VPT children.

RESULTS

The spatial organisation of the 13 retrieved functional networks was comparable across groups. Dynamic features and lateralisation of network brain activity were also comparable for all brain networks. Multivariate analysis unveiled group differences in associations between dynamical functional connectivity parameters with socio-emotional abilities.

CONCLUSION

In this exploratory study, the group differences observed might reflect reduced degrees of maturation of functional architecture in the VPT group in regard to socio-emotional abilities. Dynamic features of functional connectivity could represent relevant neuroimaging markers and inform on potential mechanisms through which preterm birth leads to neurodevelopmental and behavioural disorders.

IMPACT

Spatial organisation of the retrieved resting-state networks was comparable between school-aged very preterm and full-term children. Dynamic features and lateralisation of network brain activity were also comparable across groups. Multivariate pattern analysis revealed different patterns of association between dynamical functional connectivity parameters and socio-emotional abilities in the very preterm and full-term groups. Findings suggest a reduced degree of maturation of the functional architecture in the very preterm group in association with socio-emotional abilities.

The critical importance of follow-up to school age: Contributions of the NICHD Neonatal Research Network

Follow-up studies are essential for understanding outcomes and informing the care of infants with high risk for medical and developmental consequences because of extreme prematurity or perinatal illness. Studies that extend to school age often identify sequelae that go unrecognized in neonatal or short-term follow-up studies. Many critical neurocognitive, behavioral, functional, and health outcomes are best assessed beginning at school age. The Eunice Kennedy Shriver National Institute of Child Health and Development Neonatal Research Network (NRN) has performed comprehensive school age evaluations of several key trial cohorts. This manuscript summarizes the important contributions of school age follow-up studies in the NRN, both historically and in ongoing research. We describe in detail the clinical questions that have been answered by the completed studies and new questions about the outcomes of high-risk infants that must be addressed by ongoing and future studies.

Amygdala subnuclei volumes, functional connectivity, and social–emotional outcomes in children born very preterm

Children born very preterm can demonstrate social-cognitive impairments, which may result from limbic system dysfunction. Altered development of the subnuclei of the amygdala, stress-sensitive regions involved in emotional processing, may be key predictors of social-skill development. In a prospective cohort study, 7-year-old children born very preterm underwent neurodevelopmental testing and brain MRI. The Child Behavioral Checklist was used to assess social–emotional outcomes. Subnuclei volumes were extracted automatically from structural scans (n = 69) and functional connectivity (n = 66) was examined. General Linear Models were employed to examine the relationships between amygdala subnuclei volumes and functional connectivity values and social–emotional outcomes. Sex was a significant predictor of all social–emotional outcomes (P < 0.05), with boys having poorer social–emotional outcomes. Smaller right basal nuclei volumes (B = -0.043, P = 0.014), smaller right cortical volumes (B = -0.242, P = 0.02) and larger right central nuclei volumes (B = 0.85, P = 0.049) were associated with increased social problems. Decreased connectivity strength between thalamic and amygdala networks and smaller right basal volumes were significant predictors of greater social problems (both, P < 0.05), effects which were stronger in girls (P = 0.025). Dysregulated maturation of the amygdala subnuclei, along with altered connectivity strength in stress-sensitive regions, may reflect stress-induced dysfunction and can be predictive of social–emotional outcomes.

Emotion Recognition in Preterm and Full-Term School-Age Children

Children born preterm (<37 weeks’ gestation) show a specific vulnerability for socio-emotional difficulties, which may lead to an increased likelihood of developing behavioral and psychiatric problems in adolescence and adulthood. The accurate decoding of emotional signals from faces represents a fundamental prerequisite for early social interactions, allowing children to derive information about others’ feelings and intentions. The present study aims to explore possible differences between preterm and full-term children in the ability to detect emotional expressions, as well as possible relationships between this ability and socio-emotional skills and problem behaviors during everyday activities. We assessed 55 school-age children (n = 34 preterm and n = 21 full-term) with a cognitive battery that ensured comparable cognitive abilities between the two groups. Moreover, children were asked to identify emotional expressions from pictures of peers’ faces (Emotion Recognition Task). Finally, children’s emotional, social and behavioral outcomes were assessed with parent-reported questionnaires. The results revealed that preterm children were less accurate than full-term children in detecting positive emotional expressions and they showed poorer social and behavioral outcomes. Notably, correlational analyses showed a relationship between the ability to recognize emotional expressions and socio-emotional functioning. The present study highlights that early difficulties in decoding emotional signals from faces may be critically linked to emotional and behavioral regulation problems, with important implications for the development of social skills and effective interpersonal interactions.

Early Childhood Temperamental Trajectories following Very Preterm Birth and Their Association with Parenting Style

Childhood temperament is an early characteristic shaping later life adjustment. However, little is currently known about the stability of early temperament and its susceptibility to the environment in children born very preterm (VPT; <33 weeks’ gestation). Here, we investigated infant-to-childhood temperamental trajectories, and their interaction with parental practices, in VPT children. Maternal reports of infant temperament were collected in 190 infants (mean age: 11.27 months; range 9−18 months) enrolled in the longitudinal Evaluation of Preterm Imaging (ePrime; Eudra: CT 2009-011602-42) study, using the ePrime questionnaire on infant temperament. At 4−7 years of age, further assessments of child temperament (Children’s Behavior Questionnaire—Very Short Form) and parenting style (Arnold’s Parenting Scale) were conducted. Results showed that more difficult temperament in infancy was associated with increased Negative Affectivity in childhood, regardless of parenting practices. This lends support to the stability of early temperamental traits reflecting negative emotionality. In contrast, a lax parenting style moderated the relationship between easy infant temperament and Negative Affectivity at 4−7 years, such that an easier infant temperament was increasingly associated with higher childhood Negative Affectivity scores as parental laxness increased. These results highlight a potential vulnerability of VPT infants considered by their mothers to be easy to handle, as they may be more susceptible to the effects of suboptimal parenting in childhood.