Parental experience, as well as changing hormone levels during pregnancy and postpartum, cause changes in the parental brain. [1] 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. [2] 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. [3] [4] [5] [6] [7] [8] Mothering behavior has also been classified within the basic drives (sexual desire, hunger and thirst, fear, power/dominance etc.). [9]
Less is known about the paternal brain, but changes in the father's brain occur alongside the mother. [1] Research on this topic is continuing to expand as more researchers examine fathers. Many of the brain regions and networks responsible for parental behavior are responsible for parental behavior in human fathers after having a child. [10] Changes in hormones, brain activation and brain structure (mainly changes in gray matter) are seen in both human mothers and fathers, with hormonal changes beginning in both males and females before the birth of their children, with changes continuing to develop after the birth of children. [11]
Different hormone levels in the maternal brain and the overall well being of the mother account for 40%–50% of differences in the mother's attachment to her infant. [12] Mothers experience a decrease in estrogen and an increase in oxytocin and prolactin caused by lactation, pregnancy, parturition and interaction with the infant. [13]
The levels of oxytocin in the maternal brain correlate with maternal behaviors such as gazing, vocalization, positive affect, affectionate touch and other similar mother-infant relationship behaviors. [12]
High mother-infant attachment correlates with a higher ratio of estradiol/progesterone at the end of pregnancy, than at the beginning. [12]
In the first few days after giving birth the levels of cortisol are high which correlates with maternal approach behavior and positive maternal attitudes. [14] [15] Mothers with high levels of cortisol were also found to be more vocal towards their children. [14] [15] Mothers who experienced adversity in their own childhood, had higher daily patterns of cortisol levels, and were less maternally sensitive. [16]
Glucocorticoids are not essential for displaying maternal behaviors, but in mothers, the levels of glucocorticoids are elevated as to initiate lactation. [17] [18]
Different areas/structures of the brain are associated with different factors which contribute to maternal behavior. One's own infant acts as a special stimulus which triggers activation of different areas of the brain. These brain areas together allow for maternal behavior and related systems. [2]
The Medial Preoptic Area (MPOA) of the hypothalamus contains receptors for estradiol, progesterone, prolactin, oxytocin, vasopressin and opioids. [19] All these hormones are involved in some way in activating maternal behavior in the brain. [19] The following are other behavioral changes necessary for mothering that the MPOA is responsible for: [19]
The amygdala and medial prefrontal cortex also contain receptors for the hormones which are most likely to be changing behavior at the time of pregnancy, and may be the sites where these changes occur. [19] Increased activity has also been observed in the amygdala as the mother is responding to emotions seen in negative (fearful) faces, [21] positive faces [22] [23] [24] or familiar faces [25] that her baby makes. Primate mothers with damage to the prefrontal cortex have also been associated with disrupted maternal behavior. [26]
The dorsolateral prefrontal cortex (DLPFC) plays a role in the attention, cognitive flexibility and working memory of the mother. [2] It helps the mother identify infant cues. In any environment and efficiently, it allows for the decision-making and action planning process involved in attending to the infant's cues. [2]
The thalamus, parietal cortex, and brain stem serve for processing the smell, touch and vocalization associated with the infant. [27]
Changes in estrogen, oxytocin and prolactin in the early postpartum period cause changes in the structures of the maternal brain. [28]
Postpartum, new neuron production is suppressed due to decreased levels of estrogen and increased levels of glucocorticoids mother rats. [17] [29] Mother-infant interaction is also thought to suppress neurogenesis in the hippocampus postpartum in the rat maternal brain. [17] [29] [30] Maternal experience increases neurogenesis in the subventricular zone (SBZ) which is responsible for producing the neurons of the olfactory bulb. [31] Prolactin is the hormone which mediates the increase in neurogenesis in SBZ. [31] [32]
In animals, structures of the mother's brain change postpartum due to the increased interaction of the mother with the infant. [33]
The volume of gray matter increases postpartum in the following brain regions: [33]
These changes in the brain may occur in order to promote appropriate mothering behavior. [33] The mother's positive attitude towards the infant can be used as a predictor for the increase in gray matter in the above stated brain structures. [33]
Also in rats, the increased interaction with pups causes an increase in density in the MPOA. [34] Postpartum increase in gray matter volumes may help the mother activate the motivation to perform maternal behavior in response to cue from their offspring. [33]
Postpartum, the substantia nigra activates positive responses to the pup stimuli via dopamine neurons. [33]
The amygadala, prefrontal cortex and hypothalamus begin to change during pregnancy due to the high levels of stress experienced by the mother during this time. [35]
In human mothers there was a correlation between increased gray matter volume in the substantia nigra and positive emotional feelings towards the infant. [36] [37]
Other changes such as menstrual cycle, [38] hydration, weight and nutrition [39] [40] may also be factors which trigger the maternal brain to change during pregnancy and postpartum.
Maternal experience alters behaviors which stem from the hippocampus such as enhancing spatial navigation learning and behaviors linked with anxiety. [29]
Recent research has begun to look at how maternal psychopathology affects the maternal brain in relation to parenting. Daniel Schechter and colleagues have studied specifically interpersonal violence-related posttraumatic stress disorder (PTSD) and comorbid dissociation as associated with specific patterns of maternal neural activation in response to viewing silent video-stimuli of stressful parent-toddler interactions such as separation versus less-stressful ones such as play. [41] [42] Importantly, less medial prefrontal cortex activity and greater limbic system activity (i.e. entorhinal cortex and hippocampus) were found among these post-traumatically stressed mothers of toddlers compared to mothers of toddlers without PTSD in response to stressful parent-child interactions as well as, within a different sample, in response to menacing adult male-female interactions. In the latter study, this pattern of corticolimbic dysregulation was linked to less observed maternal sensitivity during mother-child play. [43] Decreased ventral-medial prefrontal cortex activity in violence-exposed mothers, in response to viewing their own and unfamiliar toddlers in video-clips of separation versus play, has also been associated with increased PTSD symptoms, parenting stress and decreased methylation of the glucocorticoid receptor gene. [44]
Women who had a positive experience involving their family in their childhood are more likely to be more maternally sensitive and provide that same experience for their own children. [45] Mothers that had negative experiences involving their families undergo neurobiological changes which lead to high stress reactivity and insecure attachment. This causes lower maternal responsiveness to their infant's needs. [46] [47]
Rat mothers provide high levels of maternal care (licking and grooming) to their offspring if they themselves received high maternal care as a pup from their own mothers. [48] [49] Rat mothers who received low levels of maternal care as pups have lower levels of expression of the glucocorticoid receptor gene and lower synaptic density in the hippocampus. [50] In human mothers, lower hippocampal volume has been associated with a lower ability to regulate emotions and stress, which can be linked with decreased maternal sensitivity as a mother. [50] [51] [52] Mothers with insecure attachments to their own mothers display higher amygdala sensitivity to negative emotional stimuli, like hearing their infant cry. [53] Having more difficulty dealing with stress makes mothers less responsive to their infant's cues. [54]
Larger gray matter and increased activations of the following brain areas occur in mothers who had experienced higher quality maternal care as infants: [55]
This allows the mother to be more sensitive to her own infant's needs. [55]
Postpartum depression has also been associated with mothers who received low quality maternal care early in their own life. [56]
In only 6% of mammalian species, including humans, the father plays a significant role in caring for his young. [57] [58] 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. [1]
An increase in levels of oxytocin, glucocorticoids, estrogen and prolactin occur in the paternal brain. [13] [59] These hormonal changes occur through the father's interaction with the mother and his offspring. [1] Oxytocin levels are positively correlated with the amount of affection the father displays towards the child. [60] In humans, and in other primate species, lower levels of testosterone have been linked to the display of paternal behavior. [59] [61]
In father rats, just as in the mother rats, a decrease in neurogenesis in the hippocampus occurs postpartum. [62] Just like in mothers, fathers also have increased levels of glucocorticoids which are thought to suppress the production of new cells in the brain. [59]
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. [1] [63]
Changes in neurogenesis in the prefrontal cortex of the paternal brain have been linked in some species to recognition of kin. [64]
Being exposed to crying babies activates the prefrontal cortex and the amygdala in both fathers and mothers, but not in non-parents. [65] [66] The level of testosterone in the paternal brain correlates with the effectiveness of the father's response to the baby's cry. [61] Increased levels of prolactin in the paternal brain has also been correlated with a more positive response to the infant's cry. [61] Similar to mothers, fathers have a reduction of gray matter in the orbitofrontal cortex areas, and increase of gray matter in the hypothalamus and amygdala after having a child. [67] [11]
The hypothalamus is a part of the brain that contains a number of small 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. In the terminology of neuroanatomy, it forms the ventral part of the diencephalon. All vertebrate brains contain a hypothalamus. In humans, it is the size of an almond.
The amygdala is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex vertebrates, including humans. Shown to perform a primary role in the processing of memory, decision making, and emotional responses, the amygdalae are considered part of the limbic system. The term "amygdala" was first introduced by Karl Friedrich Burdach in 1822.
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.
The limbic system, also known as the paleomammalian cortex, is a set of brain structures located on both sides of the thalamus, immediately beneath the medial temporal lobe of the cerebrum primarily in the forebrain.
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.
Pavlovian fear conditioning is a behavioral paradigm in which organisms learn to predict aversive events. It is a form of learning in which an aversive stimulus is associated with a particular neutral context or neutral stimulus, resulting in the expression of fear responses to the originally neutral stimulus or context. This can be done by pairing the neutral stimulus with an aversive stimulus. Eventually, the neutral stimulus alone can elicit the state of fear. In the vocabulary of classical conditioning, the neutral stimulus or context is the "conditional stimulus" (CS), the aversive stimulus is the "unconditional stimulus" (US), and the fear is the "conditional response" (CR).
A maternal bond is the relationship between a mother and her child. While typically associated with pregnancy and childbirth, a maternal bond may also develop in cases where the child is unrelated, such as an adoption.
Elizabeth Gould is an American neuroscientist and the Dorman T. Warren Professor of Psychology at Princeton University. She was an early investigator of adult neurogenesis in the hippocampus, a research area that continues to be controversial. In November 2002, Discover magazine listed her as one of the 50 most important women scientists.
The ventromedial prefrontal cortex (vmPFC) is a part of the prefrontal cortex in the mammalian brain. The ventral medial prefrontal is located in the frontal lobe at the bottom of the cerebral hemispheres and is implicated in the processing of risk and fear, as it is critical in the regulation of amygdala activity in humans. It also plays a role in the inhibition of emotional responses, and in the process of decision-making and self-control. It is also involved in the cognitive evaluation of morality.
Memory and trauma is the deleterious effects that physical or psychological trauma has on memory.
Prenatal stress is exposure of an expectant mother to psychosocial or physical stress, which can be caused by daily life events or by environmental hardships. This psychosocial or physical stress that the expectant mother is experiencing has an effect on the fetus. According to the Developmental Origins of Health and Disease (DOHaD), a wide range of environmental factors a woman may experience during the perinatal period can contribute to biological impacts and changes in the fetus that then causes health risks later in the child's life.
Olfactory memory refers to the recollection of odors. Studies have found various characteristics of common memories of odor memory including persistence and high resistance to interference. Explicit memory is typically the form focused on in the studies of olfactory memory, though implicit forms of memory certainly supply distinct contributions to the understanding of odors and memories of them. Research has demonstrated that the changes to the olfactory bulb and main olfactory system following birth are extremely important and influential for maternal behavior. Mammalian olfactory cues play an important role in the coordination of the mother infant bond, and the following normal development of the offspring. Maternal breast odors are individually distinctive, and provide a basis for recognition of the mother by her offspring.
Freezing behavior, also called the freeze response or being petrified, is a reaction to specific stimuli, most commonly observed in prey animals. When a prey animal has been caught and completely overcome by the predator, it may respond by "freezing up/petrification" or in other words by uncontrollably becoming rigid or limp. Studies typically assess a conditioned freezing behavior response to stimuli that typically or innately do not cause fear, such as a tone or shock. Freezing behavior is most easily characterized by changes in blood pressure and lengths of time in crouching position, but it also is known to cause changes such as shortness of breath, increased heart rate, sweating, or choking sensation. However, since it is difficult to measure these sympathetic responses to fear stimuli, studies are typically confined to simple crouching times. A response to stimuli typically is said to be a "fight or flight", but is more completely described as "fight, flight, or freeze". In addition, freezing is observed to occur before or after a fight or flight response.
The neuroscience of sex differences is the study of characteristics that separate the male and female brains. Psychological sex differences are thought by some to reflect the interaction of genes, hormones, and social learning on brain development throughout the lifespan.
The central nucleus of the amygdala is a nucleus within the amygdala. It "serves as the major output nucleus of the amygdala and participates in receiving and processing pain information."
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.
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 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.
Breastfeeding and mental health is the relationship between postpartum breastfeeding and the mother's and child's mental health. Research indicates breastfeeding may have positive effects on the mother's and child's mental health, though there have been conflicting studies that question the correlation and causation of breastfeeding and maternal mental health. Possible benefits include improved mood and stress levels in the mother, lower risk of postpartum depression, enhanced social emotional development in the child, stronger mother-child bonding and more. Given the benefits of breastfeeding, the World Health Organization (WHO), the European Commission for Public Health (ECPH) and the American Academy of Pediatrics (AAP) suggest exclusive breastfeeding for the first six months of life. Despite these suggestions, estimates indicate 70% of mothers breastfeed their child after birth and 13.5% of infants in the United States are exclusively breastfed. Breastfeeding promotion and support for mothers who are experiencing difficulties or early cessation in breastfeeding is considered a health priority.
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ignored (help)Newborns placed skin-to-skin with their mothers to study maternal oxytocin release.