This systematic review further supports a link between specific structural brain abnormalities and BD. Future studies should investigate cortical thickness with respect to at-risk populations to determine whether these neuropathologies develop before or after the onset of BD.

The extent to which neural networks underlying emotional behavior in infancy serve as precursors of later behavioral and emotional problems is unclear. Even less is known about caregiving influences on these early brain-behavior relationships. To study brain-emotional behavior relationships in infants, we examined resting-state functional network metrics and infant emotional behavior in the context of early maternal caregiving. We assessed 46 3-month-old infants and their mothers from a community sample. Infants underwent functional MRI during sleep. Resting-state data were processed using graph theory techniques to examine specific nodal metrics as indicators of network functionality. Infant positive and negative emotional behaviors, and positive, negative and mental-state talk (MST) indices of maternal caregiving were coded independently from filmed interactions. Regression analyses tested associations among nodal metrics and infant emotionality, and the moderating effects of maternal behavior on these relationships. All results were FDR corrected at alpha = 0.05. While relationships between infant emotional behavior or maternal caregiving, and nodal metrics were weak, higher levels of maternal MST strengthened associations between infant positive emotionality and nodal metrics within prefrontal (p < 0.0001), and occipital (p < 0.0001) cortices more generally. Positive and negative aspects of maternal caregiving had little effect. Our findings suggest that maternal MST may play an important role in strengthening links between emotion regulation neural circuitry and early infant positive behavior. They also provide objective neural markers that could inform and monitor caregiving-based interventions designed to improve the health and well-being of vulnerable infants at-risk for behavioral and emotional problems.

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Bipolar disorder (BD) is a serious psychiatric illness with demonstrated abnormalities in reward processing circuitry. Examining this circuitry in youth at familial risk for BD may provide further insight into the underlying mechanisms of BD development. In this study, we compared offspring of bipolar parents (OBP, n = 32), offspring of comparison parents with non-BD psychopathology (OCP, n = 36), and offspring of healthy parents (OHP, n = 39) during a functional magnetic resonance imaging reward processing task. Elastic net regression analyses identified 26 activity, functional connectivity (FC), and demographic variables that explained 34.24% of the variance in group (λ = 0.224). ANOVA and post-hoc analyses revealed that OBP had significantly lower right ventral striatum-left caudal anterior cingulate FC to loss (OBP versus OCP: p = 0.028, OBP versus OHP: p = 0.015) and greater right pars orbitalis-left (OBP versus OCP: p = 0.003, OBP versus OHP: p = 0.036) and-right (OBP versus OCP: p = 0.001, OBP versus OHP: p = 0.038) orbitofrontal cortex FC to reward versus OCP and OHP, respectively. These findings were not affected by non-BD psychopathology, psychotropic medication use, or symptomatology. There were no changes in, or relationships between, neuroimaging or symptom measures at follow-up (mean(SD) = 2.70(1.22) year inter-scan interval) in a subset of youth with followup data (OBP, n = 14; OCP, n = 8; OHP, n = 19). These findings suggest that lower right ventral striatum-left caudal anterior cingulate FC to loss and greater right pars orbitalis-orbitofrontal cortex FC to reward may be trait-level neural markers that may reflect risk for BD in at-risk youth. These findings comprise important steps toward identifying neural markers of BD risk, which may enhance early identification and guide interventions for youth at familial risk for BD.

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