July 27, 2015 by Robert Franklin, Esq, Member, National Board of Directors, National Parents Organization
This post continues from yesterday’s.
The study published by the Proceedings of the National Academy of Sciences continues by laying out its background.
Throughout human history and across cultures, women have typically assumed primary caregiving responsibility for infants (1, 2). Although humans are among the few mammalian species where some male parental caregiving is relatively common, father involvement varies considerably within and across cultures, adapting to ecological conditions (1, 3). Involved fathering has been linked with children’s long-term physiological and social development and with increases in mothers’ caregiving-related hormones such as oxytocin and prolactin (3, 4, 5, 6). In addition, animal studies demonstrated structural brain alterations in caregiving fathers (7, 8). It has been suggested that, although maternal caregiving is triggered by neurobiological processes related to pregnancy and labor, the human father’s brain, similar to other biparental mammals, adapts to the parental role through active involvement in childcare (1, 2, 3). Despite growing childcare involvement of fathers (3, 5, 6), mechanisms for human fathers’ brain adaptation to caregiving experiences remain largely unknown, and no study to our knowledge has examined the brain basis of human fatherhood when fathers assume primary responsibility for infant care.
For social species with lengthy periods of dependence, parental caregiving is key to survival and relies on brain structures that maximize survival (2, 9).
In humans, there are two such brain structures that work together to produce effective parenting behavior in adults.
These structures implicate a phylogenetically ancient network of emotional processing that rapidly detects motivationally salient and survival-related cues (14) and enables parents to automatically identify and immediately respond to infant distress, thereby maximizing survival. In humans, this emotional processing network is complemented by a cortical mentalizing network of frontopolar-medial-prefrontal-temporo-parietal structures involved in social understanding, theory of mind, and cognitive empathy… The mentalizing network plays an important role in individuals’ ability to infer mental states from behavior, is already activated during the parents’ first weeks of parenting, and enables parents to cognitively represent infant states, predict infant needs, and plan future caregiving (11, 12, 13).
So one brain structure allows parents to identify infants’ cues and the other allows them to understand those cues and respond intelligently to them. The latter structure becomes activated very early in an infant’s life.
Oxytocin has long been known to be associated with parental caregiving behavior toward children, and oxytocin levels in mothers and fathers are similar. But the amount of oxytocin in the bloodstream is less important that which brain cells have receptors that oxytocin molecules can bond with. Unsurprisingly, the brains of males and females tend to have different areas with oxytocin receptors.
Overall, these findings suggest that distinct brain–hormone–behavior pathways may underpin maternal and paternal care; therefore, oxytocin and parenting behavior may be associated with the emotional processing network in mothers but with the socio-cognitive circuit in fathers.
The authors, recognizing the relative lack of studies of paternal brains, “sought to examine the brain basis of human fatherhood,” in part by studying gay parents.
Oxytocin levels were found to be the same in all three groups of parents studied, i.e. primary caregiving mothers, secondary caregiving fathers and primary caregiving fathers in same-sex relationships.
Although activity in most brain areas was comparable across parents, two areas showed group differences. PC-Mothers showed greater amygdala activation than SC-Fathers, who exhibited greater STS activation than PC-Mothers. Intriguingly, PC-Fathers showed high amygdala activation similar to PC-Mothers [F(2,84) = 4.775, P < 0.02], alongside high STS activation similar to SC-Fathers [F(2,84) = 4.433, P < 0.02; Fig. 2B and Table S4]. No differences emerged between biological and adoptive PC-Fathers in any brain area (Table S2).
So PC mothers tend to have higher activation of the emotional processing network than do SC fathers, but PC fathers and PC mothers were much the same in that regard. Meanwhile, fathers having sole responsibility for the care of the infant was important for the activation of paternal emotional processing networks.
For all fathers, time spent alone with the child, in direct responsibility for infant care, correlated with amygdala-STS connectivity during Self–Infant Interaction, indicating the overlap of the two networks (r = 0.330, P = 0.005; Fig. 4B).
In short, mothers and fathers have about the same brain structures that impact parental behavior as well as the same activating hormone. And varying parental roles affect how those structures are activated. Different parenting roles produce different activation of those structures, in men at least.
The current study provides compelling evidence for brain malleability with caregiving experiences in human fathers and describes one mechanism underpinning this malleability… Finally, our study is, to our knowledge, the first to chart an overall model of brain, hormones, and parenting behavior leading from the parent’s role in caregiving to parent–child synchrony as mediated by neural activation, oxytocin levels, and parents’ sex. Overall, our results describe a global parental caregiving brain network that was mainly consistent across parents and involved brain structures implicated in vigilance, salience, reward, motivation, social understanding, and cognitive empathy. These brain structures were linked with oxytocin, the hormone implicated in human and mammalian bond formation (19, 20), and with the human-specific repertoire of parental behavior, indicating that assuming the role of a committed parent and engaging in active care of the young may trigger this global parental caregiving network in both women and men, in biological parents, and in those genetically unrelated to the child…
In addition to consistency, substantial malleability was found in the human paternal brain, which resembles the plasticity observed in other biparental mammals (1, 7, 8). Whereas primary-caregiving mothers showed higher subcortical activation and secondary-caregiving fathers exhibited greater activation in cortical socio-cognitive circuits, brain malleability with caregiving experience in primary-caregiving fathers involved the coactivation of these two networks. Consistent with ethological models, our findings highlight the central role of actual caregiving behavior as an important pathway to the parental brain… The functional connectivity between the two networks in primary-caregiving fathers suggests that, although only mothers experience pregnancy, birth, and lactation, and these provide powerful primers for the expression of maternal care via amygdala sensitization, evolution created other pathways for adaptation to the parental role in human fathers, and these alternative pathways come with practice, attunement, and day-by-day caregiving.
The comparable amygdala response in mothers and primary-caregiving fathers indicates the potential to activate the evolutionary ancient pathway when fathers raise infants without mothers, demonstrating amygdala sensitivity to the primary-caregiving role.
The later-evolved paternal networks suggest that, at some point in human evolution, females began selecting as mates those males that seemed like good caregivers for children. That the more evolutionarily ancient brain centers that produce maternal behavior can also do the same in primary-care fathers I find amazing.
Needless to say, these findings should impact public policy on everything related to parenting and children’s well-being. It must be recognized that fathers are not secondary parents, that mothers aren’t “real” parents and fathers simply poor substitutes. It must also be recognized that, just because a father hasn’t played the role of primary parent doesn’t mean he can’t take up that role when the need arises. So, if parents divorce, a hitherto secondary father can easily become the primary parent or at least equal to the mother. Therefore, shared parenting is strongly favored by the results of this study.
Likewise, if a mother is found unfit to care for children, the father should invariably be sought out as a possible placement. He has the potential to become the primary parent in the most elemental of ways.
And fathers should be encouraged to take time off of work when their children are born in order for them to do the type of hands-on child care that stimulates the parental brain structures the study examined.
Finally, fathers must take on that active role irrespective of the circumstances. Mom may be a gatekeeper, but Dad needs to do what’s necessary to overcome that. He must do as much of the day-to-day childcare as he can so that his brain can respond.
That in turn means that, once again, those who argue against fathers having their children overnight during the early years of their lives are just flat wrong. Children benefit from paternal involvement and so do fathers. Indeed, denying fathers that time may well be denying them the opportunity to do the very things required to stimulate the areas of the brain that millions of years of evolution have designed expressly for the effective care of children.
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