Paternal brain

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Changing hormone levels during pregnancy and postpartum as well as parental experience cause changes in the parental brain. Both the father and mother undergo distinct biological changes as they transition to parents, but the changes that occur in the paternal brain are not as well studied. Similar to the changes that occur in the maternal brain, the same areas of the brain (amygdala, hypothalamus, prefrontal cortex, olfactory bulb etc.) are activated in the father, and hormonal changes occur in the paternal brain to ensure display of parenting behavior. In only 5% of mammalian species, including humans, the father plays a significant role in caring for his young. Paternal caregiving has independently evolved multiple times in mammals, and can appear in some species under captivity. [1]

Contents

Paternal behavior in humans takes many forms, including feeding, carrying, and playing with one's child. [2]

Paternal brain networks

The same neural systems that motivate maternal behavior also are responsible for paternal behaviors. There is evidence for this in rodents; the same neurons in a small region of the hypothalamus responsible for maternal behavior is also responsible for paternal behavior. Specifically, galanin neurons in the medial preoptic area of the hypothalamus are responsible for parental motivation. The medial preoptic area activates the mesolimbic dopamine system, typically a reward pathway but is also responsible for motivation to approach offspring. [3] Parental empathy is thought to rely on the thalamocingulate pathway. [4] These brains areas and others are activated and made sensitive to infants with changing hormonal levels and increased sensitivity to hormones by up-regulating hormonal receptors. [1]

The embodied simulation network (anterior insula; premotor areas; inferior parietal lobule) are significantly activated in the paternal brain while watching or hearing their own infants compared to unknown infants. [5]

In humans, in addition to the subcortical areas there is recruitment of higher order neural systems to respond to infant cues such as the neocortex and the prefrontal cortex. [4]

fMRI studies have looked at brain activation in response to cues such as a baby's cry and show that this exposure activates the prefrontal cortex and the amygdala in both fathers and mothers, but not in non-parents.

Fathers show activation of the emotional regulation network, just like mothers, as seen in activation of the anterior insula, inferior frontal gyrus, hippocampus, and medial prefrontal cortex. [5] This network is associated with caregiving sensitivity, and may become more robust through direct involvement in caregiving.

Fathers show activation in mentalization-related brain areas in response to their infant. These regions are important for processing others' emotional cues and mental states, allowing fathers to understand and process the emotional state of their infant. [5]

Paternal neural changes

Changes in neurogenesis in the prefrontal cortex of the paternal brain have been linked in some species to recognition of kin. In father rats, just as in the mother rats, a decrease in neurogenesis in the hippocampus occurs postpartum. Just like in mothers, fathers also have increased levels of glucocorticoids which are thought to suppress the production of new cells in the brain.

Marmoset fathers have enhanced dendritic spine density in the prefrontal cortex. This increase correlates with increase in vasopressin receptors in this area of the paternal brain. With age, this effect is reversed, and is therefore believed to be driven by father-infant interactions.

Human males show changes in gray matter and cortical thickness after becoming fathers. [6] After becoming fathers, males show decreases in gray matter volume in the orbitofrontal cortex, posterior cingulate cortex and insula, and show increases in gray matter volume in the hypothalamus, amygdala and striatum and lateral prefrontal cortex, regions that are important for parental motivation. [7]

Paternal hormonal effect

An increase in levels of oxytocin, glucocorticoids, estrogen and prolactin occur in the paternal brain. These hormonal changes occur through the father's interaction with the mother and his offspring.

Testosterone

Testosterone levels have been shown to decrease with the onset of parenthood. Fathers experience large declines in both waking and evening levels of testosterone in comparison to nonfathers. [8] Childcare has been shown to correlate with declining levels of testosterone, with more time spent with the child corresponding to a greater decline in testosterone. [8] This relationship also has been found in fathers that cosleep with their child. [9] The level of testosterone in the paternal brain also correlates with the effectiveness of the father's response to the baby's cry.

Oxytocin

Oxytocin has been shown to correlate with many aspects of paternal care, but its mechanisms and the systems involved are not fully understood. Oxytocin is associated with behaviors involving contact with the child. Increases in oxytocin following high contact interactions have been shown in correlational studies. [10] Oxytocin's interactions with other hormones is thought to be responsible for creating variability in parent behaviors such as sensitivity to infant cues and parent-child synchrony. It is being researched as a possible area for intervention in parents that are considered high risk (premature birth, postpartum depression, environmental conditions). [11]

Prolactin

Prolactin levels rise in males after becoming fathers in many species, including those that do not lactate. [12] They are highest during the infantile period of the offspring, and positively correlate with caregiving. Increased prolactin corresponds to different behavioral changes in different species. In some bird species it is shown to correlate with increased gathering of resources. In humans, it has been shown to correlate with many aspects of care such as the level of involvement in care and increased exploratory play with the child. [13] Increased levels of prolactin in the paternal brain has also been correlated with a more positive response to the infant's cry.

Experienced fathers of newborns show a significantly greater increase in prolactin after hearing their baby's cries or holding their babies than first-time fathers, suggesting that learning is important for males to develop responsiveness. [14]

Vasopressin

In prairie voles, the neuropeptide vasopressin was found to induce paternal behaviors in virgin-offspringless males suggesting it has a critical role. [15]

Cortisol

Cortisol concentrations are highest just prior to birth in both mothers and fathers. [16] Higher basal cortisol and higher cortisol in response to holding the infant is associated with greater paternal behavior in men. [17]

Related Research Articles

<span class="mw-page-title-main">Estrogen</span> Primary female sex hormone

Estrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal activity: estrone (E1), estradiol (E2), and estriol (E3). Estradiol, an estrane, is the most potent and prevalent. Another estrogen called estetrol (E4) is produced only during pregnancy.

<span class="mw-page-title-main">Hypothalamus</span> Area of the brain below the thalamus

The hypothalamus is a small part of the brain that contains a number of nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus is located below the thalamus and is part of the limbic system. It forms the ventral part of the diencephalon. All vertebrate brains contain a hypothalamus. In humans, it is the size of an almond.

<span class="mw-page-title-main">Hypothalamic–pituitary–adrenal axis</span> Set of physiological feedback interactions

The hypothalamic–pituitary–adrenal axis is a complex set of direct influences and feedback interactions among three components: the hypothalamus, the pituitary gland, and the adrenal glands. These organs and their interactions constitute the HPA axis.

<span class="mw-page-title-main">Oxytocin</span> Peptide hormone and neuropeptide

Oxytocin is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. Present in animals since early stages of evolution, in humans it plays roles in behavior that include social bonding, reproduction, childbirth, and the period after childbirth. Oxytocin is released into the bloodstream as a hormone in response to sexual activity and during labour. It is also available in pharmaceutical form. In either form, oxytocin stimulates uterine contractions to speed up the process of childbirth. In its natural form, it also plays a role in maternal bonding and milk production. Production and secretion of oxytocin is controlled by a positive feedback mechanism, where its initial release stimulates production and release of further oxytocin. For example, when oxytocin is released during a contraction of the uterus at the start of childbirth, this stimulates production and release of more oxytocin and an increase in the intensity and frequency of contractions. This process compounds in intensity and frequency and continues until the triggering activity ceases. A similar process takes place during lactation and during sexual activity.

<span class="mw-page-title-main">Anterior pituitary</span> Anterior lobe of the pituitary gland

A major organ of the endocrine system, the anterior pituitary is the glandular, anterior lobe that together with the posterior lobe makes up the pituitary gland (hypophysis) which, in humans, is located at the base of the brain, protruding off the bottom of the hypothalamus.

Neuroeconomics is an interdisciplinary field that seeks to explain human decision-making, the ability to process multiple alternatives and to follow through on a plan of action. It studies how economic behavior can shape our understanding of the brain, and how neuroscientific discoveries can guide models of economics.

Couvade syndrome, also called sympathetic pregnancy, is a proposed condition in which an expectant father experiences some of the same symptoms and behavior as his pregnant partner. These most often include major weight gain, altered hormone levels, morning nausea, and disturbed sleep patterns. In more extreme cases, symptoms can include labor pains, fatigue, postpartum depression, and nosebleeds. The labor pain symptom is commonly known as sympathy pain.

Human bonding is the process of development of a close interpersonal relationship between two or more people. It most commonly takes place between family members or friends, but can also develop among groups, such as sporting teams and whenever people spend time together. Bonding is a mutual, interactive process, and is different from simple liking. It is the process of nurturing social connection.

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<span class="mw-page-title-main">Nesting instinct</span> Instinct in pregnant animals related to estradiol

Nesting behavior refers to an instinct in animals during reproduction to prepare a place with optimal conditions for offspring. The nesting place provides protection against predators and competitors that mean to exploit or kill offspring. It also provides protection against the physical environment.

<span class="mw-page-title-main">Lactation</span> Release of milk from the mammary glands

Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process naturally occurs with all sexually mature female mammals, although it may predate mammals. The process of feeding milk in all female creatures is called nursing, and in humans it is also called breastfeeding. Newborn infants often produce some milk from their own breast tissue, known colloquially as witch's milk.

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The challenge hypothesis outlines the dynamic relationship between testosterone and aggression in mating contexts. It proposes that testosterone promotes aggression when it would be beneficial for reproduction, such as mate guarding, or strategies designed to prevent the encroachment of intrasexual rivals. The positive correlation between reproductive aggression and testosterone levels is seen to be strongest during times of social instability. The challenge hypothesis predicts that seasonal patterns in testosterone levels are a function of mating system, paternal care, and male-male aggression in seasonal breeders.

<span class="mw-page-title-main">Parental brain</span>

Parental experience, as well as changing hormone levels during pregnancy and postpartum, cause changes in the parental brain. Displaying maternal sensitivity towards infant cues, processing those cues and being motivated to engage socially with her infant and attend to the infant's needs in any context could be described as mothering behavior and is regulated by many systems in the maternal brain. Research has shown that hormones such as oxytocin, prolactin, estradiol and progesterone are essential for the onset and the maintenance of maternal behavior in rats, and other mammals as well. Mothering behavior has also been classified within the basic drives.

<span class="mw-page-title-main">Social monogamy in mammalian species</span> Monogamy in mammals

Social monogamy in mammals is defined as sexually mature adult organisms living in pairs. While there are many definitions of social monogamy, this social organization can be found in invertebrates, reptiles and amphibians, fish, birds, mammals, and humans.

In biology, paternal care is parental investment provided by a male to his own offspring. It is a complex social behaviour in vertebrates associated with animal mating systems, life history traits, and ecology. Paternal care may be provided in concert with the mother or, more rarely, by the male alone.

Even though intimacy has been broadly defined in terms of romantic love and sexual desire, the neuroanatomy of intimacy needs further explanation in order to fully understand their neurological functions in different components within intimate relationships, which are romantic love, lust, attachment, and rejection in love. Also, known functions of the neuroanatomy involved can be applied to observations seen in people who are experiencing any of the stages in intimacy. Research analysis of these systems provide insight on the biological basis of intimacy, but the neurological aspect must be considered as well in areas that require special attention to mitigate issues in intimacy, such as violence against a beloved partner or problems with social bonding.

Endocrinology of parenting has been the subject of considerable study with focus both on human females and males and on females and males of other mammalian species. Parenting as an adaptive problem in mammals involves specific endocrine signals that were naturally selected to respond to infant cues and environmental inputs. Infants across species produce a number of cues to inform caregivers of their needs. These include visual cues, like facial characteristics, or in some species smiling, auditory cues, such as vocalizations, olfactory cues, and tactile stimulation. A commonly mentioned hormone in parenting is oxytocin, however many other hormones relay key information that results in variations in behavior. These include estrogen, progesterone, prolactin, cortisol, and testosterone. While hormones are not necessary for the expression of maternal behavior, they may influence it.

Behavioural responses to stress are evoked from underlying complex physiological changes that arise consequently from stress.

Darby Saxbe is a clinical psychologist and professor of psychology at the University of Southern California, who researches stress within the context of relationships.

References

  1. 1 2 Rilling, James K; Mascaro, Jennifer S (2017). "The neurobiology of fatherhood". Current Opinion in Psychology. 15: 26–32. doi:10.1016/j.copsyc.2017.02.013. PMID   28813264.
  2. ↑ Storey, Anne E.; Ziegler, Toni E. (2016-01-01). "Primate paternal care: Interactions between biology and social experience". Hormones and Behavior. Parental Care. 77: 260–271. doi:10.1016/j.yhbeh.2015.07.024. ISSN   0018-506X. PMC   4968077 . PMID   26253726.
  3. ↑ Wu, Zheng; Autry, Anita E.; Bergan, Joseph F.; Watabe-Uchida, Mitsuko; Dulac, Catherine G. (2014-05-15). "Galanin neurons in the medial preoptic area govern parental behaviour". Nature. 509 (7500): 325–330. Bibcode:2014Natur.509..325W. doi:10.1038/nature13307. ISSN   1476-4687. PMC   4105201 . PMID   24828191.
  4. 1 2 Rilling, James K. (2013). "The neural and hormonal bases of human parentalcare". Neuropsychologia. 51 (4): 731–747. doi:10.1016/j.neuropsychologia.2012.12.017. PMID   23333868. S2CID   23008342.
  5. 1 2 3 Provenzi; et al. (June 2021). "The Paternal Brain in Action: A Review of Human Fathers' fMRI Brain Responses to Child-Related Stimuli". Brain Science. 11 (6): 816. doi: 10.3390/brainsci11060816 . PMC   8233834 . PMID   34202946.
  6. ↑ Martínez-García, Magdalena; Paternina-Die, María; Cardenas, Sofia I.; Vilarroya, Oscar; Desco, Manuel; Carmona, Susanna; Saxbe, Darby E. (1 April 2023). "First-time fathers show longitudinal gray matter cortical volume reductions: evidence from two international samples". Cerebral Cortex. 33 (7): 4156–4163. doi:10.1093/cercor/bhac333. hdl: 10016/36450 . PMID   36057840 . Retrieved 2023-09-11.
  7. ↑ Kim, Pilyoung; Rigo, Paola; Mayes, Linda C.; Feldman, Ruth; Leckman, James F.; Swain, James E. (2014-09-03). "Neural plasticity in fathers of human infants". Social Neuroscience. 9 (5): 522–535. doi:10.1080/17470919.2014.933713. ISSN   1747-0919. PMC   4144350 . PMID   24958358.
  8. 1 2 Gettler, Lee T.; McDade, Thomas W.; Feranil, Alan B.; Kuzawa, Christopher W. (2011-09-27). "Longitudinal evidence that fatherhood decreases testosterone in human males". Proceedings of the National Academy of Sciences. 108 (39): 16194–16199. doi: 10.1073/pnas.1105403108 . ISSN   0027-8424. PMC   3182719 . PMID   21911391.
  9. ↑ Gettler, Lee T.; McKenna, James J.; McDade, Thomas W.; Agustin, Sonny S.; Kuzawa, Christopher W. (2012). "Does cosleeping contribute to lower testosterone levels in fathers? Evidence from the Philippines". PLOS ONE. 7 (9): e41559. Bibcode:2012PLoSO...741559G. doi: 10.1371/journal.pone.0041559 . ISSN   1932-6203. PMC   3434197 . PMID   22957016.
  10. ↑ Feldman, Ruth; Gordon, Ilanit; Schneiderman, Inna; Weisman, Omri; Zagoory-Sharon, Orna (2010). "Natural variations in maternal and paternal care are associated with systematic changes in oxytocin following parent–infant contact". Psychoneuroendocrinology. 35 (8): 1133–1141. doi:10.1016/j.psyneuen.2010.01.013. PMID   20153585. S2CID   23925657.
  11. ↑ Feldman, Ruth; Bakermans-Kranenburg, Marian J (2017-06-01). "Oxytocin: a parenting hormone". Current Opinion in Psychology. 15 (Supplement C): 13–18. doi:10.1016/j.copsyc.2017.02.011. hdl: 1887/66458 . PMID   28813252.
  12. ↑ Gettler, Lee T.; McDade, Thomas W.; Feranil, Alan B.; Kuzawa, Christopher W. (July 2012). "Prolactin, fatherhood, and reproductive behavior in human males". American Journal of Physical Anthropology. 148 (3): 362–370. doi:10.1002/ajpa.22058. ISSN   1096-8644. PMID   22576125.
  13. ↑ "Is prolactin the "breastfeeding hormone"? What is it doing in fathers? - fatherhood". fatherhood. 2016-11-11. Retrieved 2017-09-27.
  14. ↑ Aviv, Elizabeth C.; Cardenás, Sofia I.; León, Gabriel; Waizman, Yael H.; Gonzales, Cassin; Flores, Genesis; Martínez-García, Magdalena; Saxbe, Darby E. (2023-10-01). "Prenatal prolactin predicts postnatal parenting attitudes and brain structure remodeling in first-time fathers". Psychoneuroendocrinology. 156: 106332. doi:10.1016/j.psyneuen.2023.106332. ISSN   0306-4530. PMC  10529357. PMID   37478587. S2CID   259504243.
  15. ↑ Wang, Z.; Ferris, C. F.; De Vries, G. J. (1994-01-04). "Role of septal vasopressin innervation in paternal behavior in prairie voles (Microtus ochrogaster)". Proceedings of the National Academy of Sciences of the United States of America. 91 (1): 400–404. Bibcode:1994PNAS...91..400W. doi: 10.1073/pnas.91.1.400 . ISSN   0027-8424. PMC   42955 . PMID   8278401.
  16. ↑ Storey, Anne E.; Walsh, Carolyn J.; Quinton, Roma L.; Wynne-Edwards, Katherine E. (2000-03-01). "Hormonal correlates of paternal responsiveness in new and expectant fathers". Evolution and Human Behavior. 21 (2): 79–95. doi:10.1016/S1090-5138(99)00042-2. ISSN   1090-5138. PMID   10785345.
  17. ↑ Kuo, Patty X.; Braungart-Rieker, Julia M.; Burke Lefever, Jennifer E.; Sarma, Mallika S.; O'Neill, Molly; Gettler, Lee T. (2018-11-01). "Fathers' cortisol and testosterone in the days around infants' births predict later paternal involvement". Hormones and Behavior. 106: 28–34. doi:10.1016/j.yhbeh.2018.08.011. ISSN   0018-506X. PMID   30165061. S2CID   52131763.
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