master Gland Psychiatry and Psychology Bokulić E, Mikulec S. How a new father’s brain changes. pp. 107 – 111 hoW a NeW faTher’s braiN chaNGes Ema Bokulić University of Zagreb, School of Medicine 0000-0002-5732-7560 Sonja Mikulec University of Zagreb, School of Medicine 0000-0002-6192-1554 Abstract The specificity of human species is prolonged care for their infants which involves parents of both sexes. Fathers provide ‘stimulatory’ contact to their infants making them explore their surrounding and become more independent, unlike mothers who provide nurture and affectionate care. Neuroimaging studies suggest that paternal care is associ- ated with higher activity in cortical structures that are a part of the social brain - empathy, mentalizing and executive network (cognitive control) and mirror neuron system. Behavioural changes mediated by various hormones also serve as an adaptation to the new role of being a father. Oxytocin, testosterone and prolactin altogether help fathers to establish an emotional bond with their infant, directing their efforts towards paternal childcare, ensuring that the infant gets the best possible environment for growth and development. To support this, the mating effort of fathers decreases, along with responses to sexually provocative stimuli. However, these studies should be reproduced on a KeylargerWor sampleDs: and should consider complex interactions between hormones and neurotransmitters. hormones, mating effort, neuroimaging, neuroplasticity, parental behaviour, paternal behaviour, THE ROLE OF social FATHERS brain IN HUMAN SPECIES neuron system (inferior parental lobule (iPl), inferior (frontal gyrus (IFG) and supplementary motor area (sMa)), Human infants are, among all other species in the animal mentalizing network (superior temporal sulcus/gyrus kingdom, the ones in need of nurture for the longest STS/STG), precuneus, posterior cingulate cortex (Pcc), time. At birth, the size of their brain marks only 25% temporoparietal junction (tPj), ventromedial prefrontal of the adult brain1, which is one of the crucial reasons cortex (vmPFC), and emotion regulation and/or executive for prolonged parental care needed for human infants network/cognitive control (frontopolar cortex, dorso- to develop. One special characteristic of parenthood in lateral prefrontal cortex (dlPFC), medial orbitofrontal human species is that fathers are present from the birth cortex (mOFC), middle frontal gyrus (Mfg)). All of the of the child and long after in childhood and adolescence. aforementioned brain regions are a part of overlapping1 Moreover, studies have shown that parenting „styles“ cortical networks that constitute the ‘social’ brain. differ between sexes. Mothers are the ones who provide nurture and affectionate care, while fathers are involved Becoming a parent requires adaptation to certain novel- in stimulatory contact – they ‘stimulate’ their infants to ties in life – forming a parent-infant bond and changes explore the external world and get more independent. in relationship dynamics between both parents, just to Both parents are needed to protect the child from the name a few. This adaptation is possible because of the harsh environment and raise him into a 1,2,3human being neuroplasticity of the brain, which 1,2,3 includes remodelling capable of surviving in the outside world. of different pathways within. Some researchers even NEUROIMAGING STUDIES AND NEUROPLASTICITY hypothesize that it was the specific parental caregiving of our species in particular which gave rise to the evo- lution of the social brain, not vice versa. 1 Studies have shown that mothers display more activity in subcortical When it comes to neuroimaging studies on the brains structures, which indicates that this is an evolutionarily of fathers, there is not a sufficient amount of available conserved salience-vigilance pathway. Also, it is believed material to make clear-cut conclusions; the results only1,2,3 that subcortical structures are sensitized by pregnancy outline a picture yet to be upgraded by future research. hormones. On the other hand, fathers, unlike most of The research mostly focuses on testing responses of par- the mothers, displayed activity in the mirror network, ents’ brains to different modalities (visual, auditory or which indicates that paternal pathway is based on corti- multimodal) of infant stimuli (‘own infant’ versus control cal networks involved in perceptual-motor coupling and1 condition) using fMri. The results reveal the existence of representation of the infant’s state in the parent’s brain. a global ‘parental caregiving’ network (Figure 1.) which Besides, there is a difference in functional connectivity involves structures involved in empathy network (anterior between mothers and fathers. A research conducted on insula (AI) and anterior cingulate cortex (ACC)), mirror mothers and homosexual men as primary caregivers and 107 Gyrus January 2017 | | Vol. 4 | no. 1 master Gland Psychiatry and Psychology Bokulić E, Mikulec S. How a new father’s brain changes. pp. 107 – 111 Figure 1. Source: Feldman R.The The human adaptive parental human caregiving parental brain: network. implications for children’s social development. Trends Neurosci. 2015;38(6):387-399. doi:10.1016/j.tins.2015.04.004. Copyright © 2015 Elsevier Ltd. All rights reserved. fathers as secondary caregivers showed that, in mothers, Moreover, a study was conducted to examine whether there (there is high activation of amygdala, whereas in secondary- is activity present in the same brain regions of parents caregiving fathers high activity of superior temporal sulcus of both sexes as a reaction to their own infant. Indeed, STS) was present. However, in primary-caregiving fathers the shared activity was present in the right insula, which there was high activity of both amygdala and STS, thus was functionally connected to regions of the ‘social brain’ suggesting that the paternal brain activates maternal – ACC, motor and premotor areas, ifg, iPl and mPfc, which pathways to1 increase infant survival in the absence of are a part of the mirror and mentalizing network. This the mother. Furthermore, the paternal caregiving system suggests that there is a brain-to-brain synchrony, which involves cortical structures, whereas maternal caregiving most probably had an important1,2 role in the evolution of pathways rely more on subcortical reward and vigilance the biparental human family. structures and regions1 involved in empathy, mirror and mentalizing networks. The cortical structures involved in Furthermore, it is considered that one of the important father-infant interaction imply that this is an evolutionarily mechanisms of plasticity is brain-to-brain synchrony younger system than the1,2 one in mothers, which involves between parents of both sexes. In addition, in a research subcortical structures. using fMri in parents of both sexes as a reaction to the same (own) infant1,2 coordinated changes in bold signal were observed. Gyrus 108 | Vol. 4 | No. 1 | JaNuary 2017 master Gland Psychiatry and Psychology Bokulić E, Mikulec S. How a new father’s brain changes. pp. 107 – 111 Neuroplasticity of the brain is also quantified by looking at Increased OT in fathers could support5 the same neural the changes in volume in certain brain regions. In fathers, circuit, resulting in engaged childcare. the evidence of these changes was found as an increase in grey matter in amygdala, striatum, hypothalamus, The third hypothesis explains these changes as a way of subgenual cortex, lateral Pfc and STG. A decrease in grey1,2 channelling men’s energy and abilities toward parenting matter was found in ofc, Pcc, fusiform gyrus and insula. and away form mating. It is well researched that high The interpretation of these results is that the decrease t levels predict divorce and are negatively correlated in the aforementioned brain regions, which are a part of with 5relationship quality, whilst low t causes low li- default mode network, indicates a shift of resources to bido. Intranasal ot administration diminishes interest other regions, for example lateral ofc and striatum, in this2 in approaching unknown, attractive women in partnered way making possible focus and adaptation to parenting. men. Altogether, this evidence supports the thesis that However, future studies are needed to clarify how long hormonal changes modify the neural feedback to sexually these changes maintain and whether there are changes provocative stimuli, facilitating5 caregiving behaviour and in other structures according to2 the level of involvement reducing mating efforts. of the father in the child’s life. 1. oxytocin Neuroimaging studies comparing activity of brain regions Oxytocin is produced in both brain and body and for with levels of oxytocin showed that decreases in plasma scientific6 purposes its plasma levels are usually meas- ot in fathers were correlated to activity in cognitive ar- ured. In humans, oxytocin is found to have a significant eas responsible for regulating and organizing behavioral impact on behaviour, forming7 bonds with your significant responses to emotional salient stimuli4 (dorsolateral Pfc, other, children and friends. A research in which baseline dorsal ACC, iPc and precentral gyrus). and postpartum oxytocin levels were measured on both mothers and fathers showed that in both sexes there was Furthermore, a study measuring parents’ response to an increase in OT across the post-partum 6 months time infant cues showed a correlation between an increase in interval.