The influence of motherhood on neural systems for reward processing in low income, minority, young women

Reduced postpartum hippocampal volume is associated with positive mother-infant caregiving behavior

BACKGROUND

Maternal caregiving is a complex set of behaviors that can be impacted by early life stress (ELS), yet human neurobiological mechanisms are not well understood.

METHODS

Young mothers (n=137) were enrolled into a neuroimaging substudy of the longitudinal Pittsburgh Girls Study (PGS). Using data collected annually while subjects were ages 8-16, ELS was calculated as a composite score of poverty, trauma, and difficult life circumstances. At 4 months postpartum, mothers underwent neuroimaging and filmed mother-infant interaction. Maternal caregiving was coded along 6 dimensions yielding "positive" and "negative" components of caregiving. Participants' MPRAGE images were subjected to preprocessing and voxel-based morphometry (VBM) to quantify vmPFC, amygdala and hippocampus gray matter (GM) volume. We used hierarchical linear regression to investigate the relationship between GM volume and maternal caregiving, covarying for ELS as well as maternal age, weeks postpartum, race and postpartum depression score.

RESULTS

Hippocampal GM volume was inversely associated with independent observations of positive maternal caregiving. Similar findings in the vmPFC did not remain significant after correction for multiple comparisons. ELS, particularly physical assault, was associated with reduced GM volumes but was unrelated to observed maternal caregiving.

LIMITATIONS

Our single-timepoint MRI-based GM volume method was not able to demonstrate time-related intra-individual perinatal neuroplasticity, nor could it resolve neural subregions involved in caregiving-related plasticity.

CONCLUSIONS

Our findings shed light on the putative plasticity of the human maternal extra-hypothalamic stress-circuitry underlying positive maternal caregiving behavior. Whether reduced hippocampal GM volume represents pruning or represents neural resilience in the face of ELS, remains to be studied.

A tumultuous transition to motherhood: Altered brain and hormonal responses in mothers with postpartum depression

Postpartum depression (PPD) is a common but complex condition that is poorly understood and multifactorial in aetiology. It is a condition that can compromise the mother's care for her infant, which may pose challenges to the formation of the mother-infant bond and the infant's overall development. Past research has looked at abnormalities in the brain circuitry and hormonal profiles of mothers with PPD compared to non-depressed mothers. However, abnormalities in PPD that may specifically affect the mother's care of her infant have not been clearly assessed. Thus, the present review aims to synthesise studies of altered brain and hormonal responses in mothers with PPD in relation to their care of their infant. First, we review maternal brain responses and their relation to PPD symptomatology, focusing on the salience/fear network, reward/attachment network and default mode network. Next, we discuss oxytocin and hypothalamic-pituitary-adrenal axis hormones in the context of maternal behaviour and PPD. Finally, we synthesise these findings and propose how future studies may benefit from the combined study of both neural and hormonal activity to better understand the underlying neurobiology of maternal care in PPD.

A Transactional Model of Infant Still-Face Response and Maternal Behavior During the First Year

The present study takes a transactional approach to extend understanding of temporal relations between parenting behaviors and infant response to the face‐to‐face still‐face, a widely used method assessing infants’ affective and behavioral response to a violation of social expectations. A low‐income, urban sample of 180 mothers and infants participated when infants were 4 and 6 months old. Directional relations between infants’ still‐face response (i.e., change in affect and gaze from interaction to still face) and three parenting dimensions were examined using cross‐lagged structural equation models. Infant still‐face response predicted later parenting behavior, while the reverse association was not significant. Specifically, infants with a greater reduction in positive affect from interaction to still face had parents with more positive parenting and less negative parenting behaviors 2 months later, controlling for prior parenting and concurrent infant behavior. Furthermore, infants who increased gaze to mother from interaction to still face had mothers who used more mental state talk 2 months later. Findings underscore the importance of examining transactional relations between infant and parent behaviors, and in particular highlight the influence of infants on parents. Acknowledging these infant‐effects is critical to the development and implementation of interventions targeting parent‐infant interactions.

The maternal reward system in postpartum depression

The experience of motherhood is most often emotionally positive and rewarding, but for many new mothers suffering from postpartum depression (PPD), this is not the case. Preclinical and clinical research has sought to uncover brain changes underlying PPD in order to gain a better understanding of how this disorder develops. This review focuses on the mesolimbic dopamine system, particularly the ventral tegmental area-nucleus accumbens pathway which has been implicated in the regulation of critical functions disrupted in PPD including mood, motivation, and mothering. Specifically, we discuss normative changes in the mesolimbic system during motherhood in both rodents and humans and how these are impacted in PPD. We also consider modulation of mesolimbic dopamine by the hypothalamic neuropeptide oxytocin and how oxytocin-dopamine interactions regulate mood and mothering during the postpartum period. In addition to providing an overview of reward mechanisms in PPD, our goal is to highlight open questions which warrant further research.

Becoming a sexual being: The 'elephant in the room' of adolescent brain development

The onset of adolescence is a time of profound changes in motivation, cognition, behavior, and social relationships. Existing neurodevelopmental models have integrated our current understanding of adolescent brain development; however, there has been surprisingly little focus on the importance of adolescence as a sensitive period for romantic and sexual development. As young people enter adolescence, one of their primary tasks is to gain knowledge and experience that will allow them to take on the social roles of adults, including engaging in romantic and sexual relationships. By reviewing the relevant human and animal neurodevelopmental literature, this paper highlights how we should move beyond thinking of puberty as simply a set of somatic changes that are critical for physical reproductive maturation. Rather, puberty also involves a set of neurobiological changes that are critical for the social, emotional, and cognitive maturation necessary for reproductive success. The primary goal of this paper is to broaden the research base and dialogue about adolescent romantic and sexual development, in hopes of advancing understanding of sex and romance as important developmental dimensions of health and well-being in adolescence.

The Neurobiology of Postpartum Anxiety and Depression

Ten to twenty percent of postpartum women experience anxiety or depressive disorders, which can have detrimental effects on the mother, child, and family. Little is known about the neural correlates of these affective disorders when they occur in mothers, but they do have unique neural profiles during the postpartum period compared with when they occur at other times in a woman's life. Given that the neural systems affected by postpartum anxiety and depression overlap and interact with the systems involved in maternal caregiving behaviors, mother-infant interactions are highly susceptible to disruption. Thus, there is an intricate interplay among maternal mental health, the mother-infant relationship, and the neurobiological mechanisms mediating them that needs to be the focus of future study.