Veränderungen im weiblichen Gehirn durch und nach der Schwangerschaft

Ich lese gerade „The Chemistry between us“ und bisher ist es ein sehr interessantes Buch, auf das ich sicherlich noch häufiger zurückkommen werde.

Ein Kapitel behandelt den „Mutterinstinkt“, der nach den dortigen Angaben durch Hormone in der Schwangerschaft verstärkt aktiviert wird und bei dem bestimmte Teile des Gehirns so umgebaut werden, dass gewisse Denkweisen verändert/gefördert werden, also zb das Gehirn stärker auf klassische Reize, etwa ein Kinderlächeln anspricht.

Die ersten dort erwähnten Studien sind solche an Ratten:

This article reviews the current state of our knowledge about the hormonal basis of maternal behavior in the rat. Considered are the ovarian hormones estrogen and progesterone, the pituitary hormones β-endorphin and prolactin, and the hormone oxytocin, secreted by several hypothalamic nuclei and associated brain regions. The hormones of pregnancy, estrogen and progesterone, prime the female to respond to a terminal rise in estrogen that stimulates a high level of maternal responsiveness even before parturition begins. Studies on the role of prolactin, using hypophysectomy, prolactin release blockers and anterior pituitary and prolactin replacement, indicate that prolactin is required for the ovarian hormones to be effective in stimulating maternal behavior. During the latter half of pregnancy, placental lactogen may displace prolactin in this role. Although prolactin serves as a chronic stimulus for maternal behavior, it also may act over a short period. Oxytocin stimulates maternal behavior in a specific strain of rat, but not in other strains, and only when administered introcerebroventricularly (ICV) in estrogen-primed females. The decline in the high brain levels of β-endorphin around parturition has been proposed as a requirement for the onset of maternal behavior, morphine blocks the onset of maternal behavior and disrupts ongoing maternal behavior and maternal aggression in lactating females. However, blocking β-endorphin action at parturition interferes with pup cleaning and eating of the placenta as well.

Quelle: Hormonal basis during pregnancy for the onset of maternal behavior in the rat

Oder:

Intracerebroventricular administration of oxytocin to virgin female rats that had been ovariectomized and primed with estrogen 48 hours previously induced a rapid onset of full maternal behavior. The maternal behavior persisted and its incidence was dose-related. Tocinoic acid, the ring structure of oxytocin, also rapidly induced the onset of persistent, full maternal behavior. Arginine vasopressin induced persistent maternal behavior, but this behavior had a later onset. Prostaglandin F2 alpha induced strong partial maternal behavior, which showed early onset but did not persist. Many other peptides, ovarian steroids, and prostaglandin E2 were no more effective than saline. These findings suggest that the release of oxytocin and prostaglandin F2 alpha during labor may promote maternal behavior in rats.

Quelle: Oxytocin induces maternal behavior in virgin female rats

Oder:

ABSTRACT Oxytocin produces uterine contractions and milk ejection, functions related to parturition and nurturing. Studies were conducted to determine if this peptide, native to the brain and the posterior pituitary gland, plays a role in the induction of maternal behavior. Intact virgin female rats were given 0.4 ,g of oxytocin, 0.4 1&g of [Arg8Jvasopressin, or saline through lateral ventricular cannulae. Forty-two percent of intact
rats receiving oxytocin displayed full maternal behavior towards foster pups. None of the saline- or vasopressin-treated animals displayed full maternal behavior. Criteria in five behavioral categories had to be fulfilled by an animal within 2 hr of injection for its behavior to be considered fully maternal. When partial maternal responses were considered, oxytocin was significantly more effective than saline and marginally more effective than vasopressin. Five animals responding fully maternally after oxytocin injection were allowed to stay with pups for 10 days. All five continued to display full maternal behavior during this time. Nearly all animals that responded fully maternally to oxytocin injection were in the last day of diestrus or in proestrus or estrus. This suggested that elevated or recently elevated levels of estrogen may be necessary for the induction
of full maternal behavior by oxytocin. Twenty-seven virgin female rats were ovariectomized and given either 100 fig of estradiol benzoate per kg in oil subcutaneously or oil alone immediately after operation. Forty-eight hours later, all animals received 0.4 gtg of oxytocin intracerebroventricularly. Eleven of 13 estrogen-primed animals became fully maternal; none of 14 nonprimed animals became fully maternal.

Quelle: Induction of maternal behavior in virgin rats after intracerebroventricular administration of oxytocin (PDF)

Bei Menschen finden sich einige interessante Angaben zu den diesbezüglichen Veränderungen:

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.[33]

In human mothers there was a correlation between increased gray matter volume in the substantia nigra and positive emotional feelings towards the infant.[34][35]

Other changes such as menstrual cycle,[36] hydration, weight and nutrition[37][38] 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.[27]

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 Post-traumatic Stress Disorder (PTSD) and comorbiddissociation 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.[39][40] Importantly, less medial prefrontal cortexactivity 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.[41] 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.[42]

Dort findet sich auch ein interessanter, wenn auch kurzer Abschnitt zu Veränderungen im Gehirn des Vaters.

Und eine andere Studie wird hier besprochen:

New moms may feel their brain cells dying with every cumulative hour of sleep loss. But a new study offers hope.

In the first months after giving birth, the study found, parts of a mother’s brain may actually grow. Even better news, doting mamas who gushed the most about how special and perfect their babies were showed the most growth.

The parts of the brain that grew are involved in motivation, reward behavior and emotion regulation. That suggests that, by reshaping itself, the post-partum brain motivates a mother to take care of her baby, and then feel happy and rewarded when she does.

The findings may eventually help women who feel disconnected from their babies or even hostile toward them in the early months, said lead author Pilyoung Kim, a developmental psychologist, now at the National Institutes of Mental Health in Bethesda, Md.

„We could maybe compare brain changes in mothers who were depressed or had problems bonding with their infants to normal mothers,“ said Kim, who was at Yale University when she did the work. „And we might be able to develop some kind of intervention programs to help mothers feel more rewarded about their parenting and their baby.“

During pregnancy and the post-partum period, women often feel their brains turning to mush. New moms report that they have trouble remembering things that they used to remember easily. It’s such a common phenomenon that women often call it „Mommy Brain.“ Some research has even shown that women’s brains shrink slightly during pregnancy.

But studies in mice, rats, and other mammals have shown growth and other physical changes in the brains of new mothers. These changes appear to prepare the animals for their new roles. And the mothers‘ brains remain altered for the rest of their lives.

To see if the similar changes might happen in people, Kim and colleagues scanned the brains of 19 mothers a few weeks after giving birth and again three to four months later. Their results, published in the journal Behavioral Neuroscience, showed a small but significant amount of growth in a number of brain regions, including the hypothalamus, prefrontal cortex and amygdala.

These are the areas that motivate a mother to take care of her baby, feel rewarded when the baby smiles at her, and fill her with positive emotions from simple interactions with her infant. These brain areas are also involved in planning and foresight, which might help a mother anticipate her infant’s needs and be prepared to meet them.

In other words, basic changes in the brain might explain the unconditional love, constant worrying and snack-packing habits that many people call a „maternal instinct.“

The researchers speculate that pregnancy hormones prime the brain to be open to reshaping when a newborn arrives. And while it’s not yet clear whether changes in a mother’s brain stimulate her to care for her child, or whether caring for a child changes the brain, the study showed a clear relationship. What’s more, mothers who talked most positively about their babies underwent the biggest changes.

There are good genetic reasons why having a baby might re-sculpt a woman’s brain for the benefit of her baby, said Craig Kinsley, a neuroscientist at the University of Richmond in Virginia. A mother passes her genes to her children, after all, and she’ll do what it takes to keep them alive. (Some studies suggest that the brains of fathers might undergo similar changes, too).

In one of his own studies, Kinsley found that, compared to virgin rats, mother rats were much faster at learning where to find food in a maze. In nature, that might mean that moms are quicker to find food and return to their nests, allowing them to both feed their little ones and protect them from predators.

„From an evolutionary standpoint, a mother is faced with a really significant challenge,“ Kinsley said. „She had to do everything she did before, plus a whole new suite of behaviors to keep her offspring alive. How females evolved in nature is to have their brains adapt in pregnancy, so that their young enhance their behaviors.“

As for the complete loss of memories for names, trivia and other ordinary things that come with giving birth, the brains of new moms may simply have new priorities.

„We are clearly showing that mothers have better memories about things related to their infants,“ said Kim, who has a four-month old of her own. „There are a lot of things going on, and mothers might feel forgetful about things that are not related to their infants. It’s just dependent on what is really important for us to remember at the time.“

Die dort erwähnte Studie müsste diese hier sein:

Animal studies suggest that structural changes occur in the maternal brain during the early postpartum period in regions such as the hypothalamus, amygdala, parietal lobe, and prefrontal cortex and such changes are related to the expression of maternal behaviors. In an attempt to explore this in humans, we conducted a prospective longitudinal study to examine gray matter changes using voxel-based morphometry on high resolution magnetic resonance images of mothers’ brains at two time points: 2–4 weeks postpartum and 3–4 months postpartum. Comparing gray matter volumes across these two time points, we found increases in gray matter volume of the prefrontal cortex, parietal lobes, and midbrain areas. Increased gray matter volume in the midbrain including the hypothalamus, substantia nigra, and amygdala was associated with maternal positive perception of her baby. These results suggest that the first months of motherhood in humans are accompanied by structural changes in brain regions implicated in maternal motivation and behaviors.

Quelle: The Plasticity of Human Maternal Brain: Longitudinal Changes in Brain Anatomy During the Early Postpartum Period

Aus der Studie:

This study identified structural changes in similar brain regions among human mothers during the first few postpartum months. Increased gray matter volumes in large regions of the prefrontal cortex, parietal lobe, and midbrain were found. Furthermore, a mother’s positive thoughts on her baby at the first month postpartum predicted gray matter volume increase from the first month to 3–4 months post-partum. This postpartum period marks a critical time for the development of sensitive mothering and changes in these brain regions may be important to promote sensitive maternal behaviors.

Several key maternal motivation and behavior regions including bilateral hypothalamus, amygdala, substantia nigra, and globus pallidus showed increases in gray matter volume during the early postpartum period. The animal literature underlines the importance of these structures for parenting and lesions in the hypothalamus including MPOA impairs maternal motivation and in the MPOA regions increase the likelihood of infanticide (Flannelly, Kemble, Blanchard, & Blanchard, 1986; Novakova, Sterc, Kuchar, & Mozes, 1993). Structural reorganization in the MPOA was also found to be sensitive to postpartum experience; the increased amount of interactions with pups was associated with greater density in MPOA in rat mothers (Featherstone et al., 2000; Fleming & Korsmit, 1996; Lonstein et al., 1998). An increase in gray matter volumes was also found in the right substantia nigra, a key region of the mesolimbic dopaminergic system responsible for processing reward signals (Schultz, Dayan, & Montague, 1997). During the postpartum period, SN serves an important function in activating positive responses to pup stimuli through dopamine neurons. The ventral pallidum, a part of the globus pallidus, receives inputs from substantia nigra and regulates motor activities and behavioral reactivity (Nestler, 2001). Hypothalamus and globus pallidus have previously been implicated in maternal responses to infant stimuli in humans (Bartels & Zeki, 2004; Lorberbaum et al., 2002). Finally, amygdala activations has been found to be important for maternal behaviors in rodents and nonhuman primates (Kling & Steklis, 1976; Sheehan, Paul, Amaral, Numan, & Numan, 2001). Activations of the amygdala, particularly the medial amygdala, inhibit maternal responses to pup in virgin rats. However, animal studies suggest that once mothers are exposed to their offspring, such pathways involving the medial amygdala may be a key to consolidating maternal learning about the infant (Fleming, Gavarth, & Sarker, 1992; Mayes, 2006). Thus, interactions with the infant during the first postpartum months may be associated with the increased gray matter volumes in the hypothalamus, substantia nigra, globus pallidus, and amygdala may help the mothers activate their maternal motivation and respond to infant cues.

Furthermore, the structural changes in the midbrain region including the hypothalamus, substantia nigra, globus pallidus, and amygdala over time were predicted by a mother’s positive perception of her baby at the first month postpartum. Thus, the mother’s positive feelings on her baby may facilitate the increased levels of gray matter volume. fMRI studies with human mothers have similarly shown that greater substantia nigra responses to infant stimuli were correlated with the mother’s self-reported positive emotional reactions to infant stimuli (Bartels & Zeki, 2004; Noriuchi et al., 2007).

Several brain regions implicated in somatosensory information processing also showed an increase in gray matter over the first postpartum months. These findings may provide evidence that these changes in parent brain structure require exposure to infant-related stimuli. In rats, a rich amount of olfactory, auditory, somatosensorial, and visual information during physical interactions with pups and suckling stimuli during nursing were associated with the reorganization of the thalamus, parietal lobe, and someosensory cortex in lactating mothers (Kinsley et al., 2008; Lonstein et al., 1998; Xerri et al., 1994). Moreover, these changes in the parietal cortex only occurred when mothers interacted with their pups but not when they were only exposed to the pups’ smells or sounds (Fleming & Korsmit, 1996). It would be of interest to examine whether the increased gray matter volumes found here in the thalamus, precentral and postcentral gyrus, and superior parietal lobe from the first to fourth month postpartum are related to the frequency and quality of the mother’s interactions with her infant.

Another large area that showed an increase in gray matter volume was the prefrontal cortex (PFC), including the superior, middle and medial frontal cortices. Afonso and colleagues (2007) found that mother rats with medial prefrontal cortex lesions exhibited deficits in a certain maternal behaviors such as pup retrievals and licking behavior, but not in nest building or pup mouthing. Thus, it is possible that the increase in gray matter volumes in the PFC reported here is associated with the mothers’ adaptation to orchestrate a new and increased repertoire of complex interactive behaviors with infants during the early postpartum. Neuroimaging data highlights the importance of the PFC in parenting behaviors; greater activations in frontal regions including superior and middle frontal gyrus (BA 9, 10) and medial frontal guys (BA8) have been found in almost every fMRI study of human mothers’ responses to infant stimuli (reviewed in Swain et al., 2007).

In addition to parenting experience during the early postpartum period, several other factors may be associated with changes in gray matter volumes in mothers’ brain should be monitored in future studies. Animal studies demonstrate that hormones including estrogen, oxytocin, and prolactin act in several brain areas to activate maternal behaviors in response to infant-related stimuli (Pedersen, Caldwell, Peterson, Walker, & Mason, 1992; Wamboldt & Insel, 1987) and changes in these hormones during the early postpartum period affect anatomical changes (Rosenblatt, 2002). Experience during the pregnancy, for instance, increased amount of stress, may also be associated with structural changes in mothers’ brain regions susceptive to stress exposure including amygdala, hypothalamus, and PFC (McEwen, 2007). A future study may include gray matter volumes during the pregnancy as a baseline and compare them with the ones during the postpartum period. Other factors such as changes in menstrual cycles (Protopopescu et al., 2008) or in hydration, weight and nutritional status (Castro-Fornieles et al., 2009; Raji et al., 2010) may also produce alterations in the brain structure. Studies comparing the gray matter volumes between new mothers and age-matched women with no parenting experience would be helpful to control these factors to assess the apparent new learning that may be occurring (Draganski & May, 2008; Driemeyer, Boyke, Gaser, Büchel, & May, 2008).

Auch noch eine interessante Studie dazu:

Infant cues, such as smiling or crying facial expressions, are powerful motivators of human maternal behavior, activating dopamine-associated brain reward circuits. Oxytocin, a neurohormone of attachment, promotes maternal care in animals, although its role in human maternal behavior is unclear. We examined 30 first-time new mothers to test whether differences in attachment, based on the Adult Attachment Interview, were related to brain reward and peripheral oxytocin response to infant cues. On viewing their own infant’s smiling and crying faces during functional MRI scanning, mothers with secure attachment showed greater activation of brain reward regions, including the ventral striatum, and the oxytocin-associated hypothalamus/pituitary region. Peripheral oxytocin response to infant contact at 7 months was also significantly higher in secure mothers, and was positively correlated with brain activation in both regions. Insecure/dismissing mothers showed greater insular activation in response to their own infant’s sad faces. These results suggest that individual differences in maternal attachment may be linked with development of the dopaminergic and oxytocinergic neuroendocrine systems.

Quelle:  Adult Attachment Predicts Maternal Brain and Oxytocin Response to Infant Cues

Hier könnte man vermuten, dass die sicherere Bindung eben gerade die Folge davon ist, dass ihr Gehirn auf bestimmte Reize mit „Belohnung“ reagiert.Wie immer gibt es in der Natur Vielfalt.