Studiensammlung 4: (Prenatale) Hormone und Geschlechterunterschiede im Gehirn und Verhalten

Und weil wir heute eh schon eine Studie hier zu Gehirnunterschieden haben hier ein paar weitere Studien:


Fetal Testosterone Influences Sexually Dimorphic Gray Matter in the Human Brain

In nonhuman species, testosterone is known to have permanent organizing effects early in life that predict later expression of sex differences in brain and behavior. However, in humans, it is still unknown whether such mechanisms have organizing effects on neural sexual dimorphism. In human males, we show that variation in fetal testosterone (FT) predicts later local gray matter volume of specific brain regions in a direction that is congruent with sexual dimorphism observed in a large independent sample of age-matched males and females from the NIH Pediatric MRI Data Repository. Right temporoparietal junction/posterior superior temporal sulcus (RTPJ/pSTS), planum temporale/parietal operculum (PT/PO), and posterior lateral orbitofrontal cortex (plOFC) had local gray matter volume that was both sexually dimorphic and predicted in a congruent direction by FT. That is, gray matter volume in RTPJ/pSTS was greater for males compared to females and was positively predicted by FT. Conversely, gray matter volume in PT/PO and plOFC was greater in females compared to males and was negatively predicted by FT. Subregions of both amygdala and hypothalamus were also sexually dimorphic in the direction of Male > Female, but were not predicted by FT. However, FT positively predicted gray matter volume of a non-sexually dimorphic subregion of the amygdala. These results bridge a long-standing gap between human and nonhuman species by showing that FT acts as an organizing mechanism for the development of regional sexual dimorphism in the human brain.


(FT was measured from amniotic fluid samples collected between 13 and 20 weeks of gestation (mean FT, 0.79 nmol/L; SD, 0.34 nmol/L; range, 0.25–1.70 nmol/L).


The Impact of Sex, Puberty, and Hormones on White Matter Microstructure in Adolescents

Background: During adolescence, numerous factors influence the organization of the brain. It is unclear what influence sex and puberty have on white matter microstructure, as well as the role that rapidly increasing sex steroids play. Methods: White matter microstructure was examined in 77 adolescents (ages 10–16) using diffusion tensor imaging. Multiple regression analyses were performed to examine the relationships between fractional anisotropy (FA) and mean diffusivity (MD) and sex, puberty, and their interaction, controlling for age. Follow-up analyses determined if sex steroids predicted microstructural characteristics in sexually dimorphic and pubertal-related white matter regions, as well as in whole brain. Results: Boys had higher FA in white matter carrying corticospinal, long-range association, and cortico-subcortical fibers, and lower MD in frontal and temporal white matter compared with girls. Pubertal development was related to higher FA in the insula, while a significant sex-by-puberty interaction was seen in superior frontal white matter. In boys, testosterone predicted white matter integrity in sexually dimorphic regions as well as whole brain FA, whereas estradiol showed a negative relationship with FA in girls. Conclusions: Sex differences and puberty uniquely relate to white matter microstructure in adolescents, which can partially be explained by sex steroids.


Hormonal Assessment
Four milliliters of blood was collected via venipuncture between the hours of 7:00 to 10:00 AM at the Oregon Clinical and Translational Research Institute in the same week as the imaging session.


Regional sex differences in grey matter volume are associated with sex hormones in the young adult human brain

Previous studies suggest organizing effects of sex hormones on brain structure during early life and puberty, yet little is known about the adult period. The aim of the present study was to elucidate the role of 17β-estradiol, progesterone, and testosterone on cortical sex differences in grey matter volume (GM) of the adult human brain. To assess sexual dimorphism, voxel-based morphometry (VBM) was applied on structural magnetic resonance images of 34 healthy, young adult humans (17 women, 17 men, 26.6 ± 5 years) using analyses of covariance. Subsequently, circulating levels of sex hormones were associated with regional GM using linear regression analyses. After adjustment for sex and total GM, significant associations of regional GM and 17β-estradiol were observed in the left inferior frontal gyrus (β = 0.39, p = 0.02). Regional GM was inversely associated with testosterone in the left inferior frontal gyrus (β = −0.16, p = 0.04), and with progesterone in the right temporal pole (β = −0.39, p = 0.008). Our findings indicate that even in young adulthood, sex hormones exert organizing effects on regional GM. This might help to shed further light on the underlying mechanisms of both functional diversities and congruence between female and male brains.


Pubertal hormones organize the adolescent brain and behavior

Maturation of the reproductive system during puberty results in elevated levels of gonadal steroid hormones. These hormones sculpt neural circuits during adolescence, a time of dramatic rewiring of the nervous system. Here, we review the evidence that steroid-dependent organization of the adolescent brain programs a variety of adult behaviors in animals and humans. Converging lines of evidence indicate that adolescence may be a sensitive period for steroid-dependent brain organization and that variation in the timing of interactions between the hormones of puberty and the adolescent brain leads to individual differences in adult behavior and risk of sex-biased psychopathologies.


Prenatal hormones and childhood sex-segregation: Playmate and play style preferences in girls with congenital adrenal hyperplasia

We investigated playmate and play style preference in children with congenital adrenal hyperplasia (CAH) (26 females, 31 males) and their unaffected siblings (26 females, 17 males) using the Playmate and Play Style Preferences Structured Interview (PPPSI). Both unaffected boys and girls preferred same-sex playmates and sex-typical play styles. In the conflict condition where children chose between a same-sex playmate engaged in an other-sex activity or an other-sex playmate engaged in a same-sex activity, boys (both CAH and unaffected brothers) almost exclusively chose playmates based on the preferred play style of the playmate as opposed to the preferred gender label of the playmate. By contrast, unaffected girls used play style and gender label about equally when choosing playmates. Girls with CAH showed a pattern similar to that of boys: their playmate selections were more masculine than unaffected girls, they preferred a boy-typical play style and, in the conflict condition, chose playmates engaged in a masculine activity. These findings suggest that prenatal androgen exposure contributes to sex differences in playmate selection observed in typically-developing children, and that, among boys and girls exposed to high levels of androgens prenatally, play style preferences drive sex segregation in play.


Prenatal Hormones and Postnatal Socialization by Parents as Determinants of Male-Typical Toy Play in Girls With Congenital Adrenal Hyperplasia

Toy choices of 3- to 10-year-old children with congenital adrenal hyperplasia (CAH) and of their unaffected siblings were assessed. Also assessed was parental encouragement of sex-typed toy play. Girls with CAH displayed more male-typical toy choices than did their unaffected sisters, whereas boys with and without CAH did not differ. Mothers and fathers encouraged sex-typical toy play in children with and without CAH. However, girls with CAH received more positive feedback for play with girls’ toys than did unaffected girls. Data show that increased male-typical toy play by girls with CAH cannot be explained by parental encouragement of male-typical toy play. Although parents encourage sex-appropriate behavior, their encouragement appears to be insufficient to override the interest of girls with CAH in cross-sexed toy


Increased aggression and activity level in 3- to 11-year-old girls with congenital adrenal hyperplasia

Experimental research in a wide range of mammals has documented powerful influences of androgen during early development on brain systems and behaviors that show sex differences. Clinical research in humans suggests similar influences of early androgen concentrations on some behaviors, including childhood play behavior and adult sexual orientation. However, findings have been inconsistent for some other behaviors that show sex differences, including aggression and activity level in children. This inconsistency may reflect small sample sizes and assessment limitations. In the present study, we assessed aggression and activity level in 3- to 11-year-old children with CAH (38 girls, 29 boys) and in their unaffected siblings (25 girls, 21 boys) using a questionnaire that mothers completed to indicate current aggressive behavior and activity level in their children.

Data supported the hypotheses that:

  • 1. unaffected boys are more aggressive and active than unaffected girls;
  • 2. girls with CAH are more aggressive and active than their unaffected sisters; and
  • 3. boys with and without CAH are similar to one another in aggression and activity level.

These data suggest that early androgens have a masculinizing effect on both aggressive behavior and activity level in girls.


Prenatal androgen exposure alters girls’ responses to information indicating gender-appropriate behaviour

Individual variability in human gender-related behaviour is influenced by many factors, including androgen exposure prenatally, as well as selfsocialization and socialization by others postnatally. Many studies have looked at these types of influences in isolation, but little is known about how they work together. Here, we report that girls exposed to high concentrations of androgens prenatally, because they have the genetic condition congenital adrenal hyperplasia, show changes in processes related to selfsocialization of gender-related behaviour. Specifically, they are less responsive than other girls to information that particular objects are for girls and they show reduced imitation of female models choosing particular objects. These findings suggest that prenatal androgen exposure may influence subsequent gender-related behaviours, including object (toy) choices, in part by changing processes involved in the self-socialization of gendered behaviour, rather than only by inducing permanent changes in the brain during early development. In addition, the findings suggest that some of the behavioural effects of prenatal androgen exposure might be subject to alteration by postnatal socialization processes. The findings also suggest a previously unknown influence of early androgen exposure on later processes involved in self socialization of gender-related behaviour, and thus expand understanding of the developmental systems regulating human gender development.


How early hormones shape gender development

Prenatal androgens influence sex-related characteristics to varying degrees.
• Androgens facilitate male-typed activities through interest in things versus people.
• Androgens are associated with some aspects of brain structure and activation.
• Current work is focused on interplay of hormones and social environment.
• Relevant to questions regarding sex-related psychopathology, prenatal programming.
Many important psychological characteristics show sex differences, and are influenced by sex hormones at different developmental periods. We focus on the role of sex hormones in early development, particularly the differential effects of prenatal androgens on aspects of gender development. Increasing evidence confirms that prenatal androgens have facilitative effects on male-typed activity interests and engagement (including child toy preferences and adult careers), and spatial abilities, but relatively minimal effects on gender identity. Recent emphasis has been directed to the psychological mechanisms underlying these effects (including sex differences in propulsive movement, and androgen effects on interest in people vs things), and neural substrates of androgen effects (including regional brain volumes, and neural responses to mental rotation, sexually arousing stimuli, emotion, and reward). Ongoing and planned work is focused on understanding the ways in which hormones act jointly with the social environment across time to produce varying trajectories of gender development, and clarifying mechanisms by which androgens affect behaviors. Such work will be facilitated by applying lessons from other species, and by expanding methodology. Understanding hormonal influences on gender development enhances knowledge of psychological development generally, and has important implications for basic and applied questions, including sex differences in psychopathology, women’s underrepresentation in science and math, and clinical care of individuals with variations in gender expression.


The organizing actions of adolescent gonadal steroid hormones on brain and behavioral development


• Adolescence is a sensitive period for the effects of hormones on brain and behavior.
• Testicular hormones masculinize and defeminize social and reproductive behaviors.
• Ovarian hormones have both feminizing and defeminizing effects on female behavior.
• Gonadal steroid hormones drive many brain structural changes during adolescence.
• Adolescence may be part of a protracted postnatal steroid-sensitive period.

Adolescence is a developmental period characterized by dramatic changes in cognition, risk-taking and social behavior. Although gonadal steroid hormones are well-known mediators of these behaviors in adulthood, the role gonadal steroid hormones play in shaping the adolescent brain and behavioral development has only come to light in recent years. Here we discuss the sex-specific impact of gonadal steroid hormones on the developing adolescent brain. Indeed, the effects of gonadal steroid hormones during adolescence on brain structure and behavioral outcomes differs markedly between the sexes. Research findings suggest that adolescence, like the perinatal period, is a sensitive period for the sex-specific effects of gonadal steroid hormones on brain and behavioral development. Furthermore, evidence from studies on male sexual behavior suggests that adolescence is part of a protracted postnatal sensitive period that begins perinatally and ends following adolescence. As such, the perinatal and peripubertal periods of brain and behavioral organization likely do not represent two discrete sensitive periods, but instead are the consequence of normative developmental timing of gonadal hormone secretions in males and females.


Effects of chromosomal sex and hormonal influences on shaping sex differences in brain and behavior: Lessons from cases of disorders of sex development

Sex differences in brain development and postnatal behavior are determined largely by genetic sex and in utero gonadal hormone secretions. In humans however, determining the weight that each of these factors contributes remains a challenge because social influences should also be considered. Cases of disorders of sex development (DSD) provide unique insight into how mutations in genes responsible for gonadal formation can perturb the subsequent developmental hormonal milieu and elicit changes in normal human brain maturation. Specific forms of DSDs such as complete androgen insensitivity syndrome (CAIS), congenital adrenal hyperplasia (CAH), and 5α-reductase deficiency syndrome have variable effects between males and females, and the developmental outcomes of such conditions are largely dependent on sex chromosome composition. Medical and psychological works focused on CAH, CAIS, and 5α-reductase deficiency have helped form the foundation for understanding the roles of genetic and hormonal factors necessary for guiding human brain development. Here we highlight how the three aforementioned DSDs contribute to brain and behavioral phenotypes that can uniquely affect 46,XY and 46,XX individuals in dramatically different fashions

Aus der Studie:

CAH ein Schaubild

CAH, CAIS und 5-alpha reductace Deficiency: ein Schaubild

Weiteres aus der Studie:

Research focused on cases of DSD have helped the scientific community better understand the interplay between gonadal hormones and sex chromosome complement with regard to generating some of the sex differences observed in humans. These works have shed light on the likelihood that testosterone exposure, as opposed to sex chromosomes, is a larger contributing factor for guiding one’s sexual orientation and to a lesser extent gender identity. We see that 46,XX CAH individuals that have been exposed to in utero testosterone experience a greater degree of dissatisfaction in gender assignment in addition to above-average levels of homosexual and bisexual fantasies, a proxy for sexual preference. As previously mentioned, other variables are present in CAH cases such as life-long medical interventions and psychosocial confounds. These variables may constitute an environmental factor that, when coupled with biological predispositions, generates variations in sexual orientation and gender identity. That sexual orientation is determined solely by in utero hormonal milieu is unlikely. We see that the vast majority of CAH women, despite having been exposed to above-average levels of testosterone, identify as heterosexual as measured by both partners and sexual fantasies. The science of sexual orientation is still weakly understood at the mechanistic level; however, considerable amounts of research have proposed many possibilities for the causes of same-sex attraction (LeVay, 2012; Bailey et al., 2016).

The strongest evidence that adds support for the influence of testosterone in structuring gender identity comes from the work focused on 46,XY CAIS, in which nearly all individuals researched indicate feelings typical of female gender. In addition to self-reports and clinical evaluations, recent fMRI studies have also demonstrated that CAIS women not only feel female but also neurologically respond more similarly to 46,XX women than to 46,XY men when observing sexual images. However, new studies are continually emerging suggesting that gender identity and sexual orientation in individuals with CAIS are not as clear as once thought, and the rates of nonheterosexual and gender dysphoria may be much higher than currently stated. In addition to CAH and CAIS, 5α-reductase deficiencies have also demonstrated the strong role of testosterone’s ability to organize the human brain hormonally and influence adult gender identity and behavior. If early in utero exposure had no influence in guiding brain gender, we would expect considerable difficulty with the female-to-male transition observed in pubertal years in those with 5α-reductase deficiency. What we observe, however, is that an overwhelming majority of individuals with this condition comfortably transitioned into the new gender role at puberty, a worldwide observation occurring throughout many different types of social environments. Despite the convincing findings for the role of testosterone in generating these observations, the influence of social and other environmental variables are also factors that require consideration.

Cognitive Conclusions
Studying cases of DSDs has also provided insight into some of the biological parameters that generate sex differences in cognitive abilities such as visuospatial awareness and targeting ability. From studies with 46,XX CAH individuals it has been well established that in utero androgen exposure seems to enhance the ability to mentally rotate objects as well as improving hand–eye coordination during targeting tasks. This trait appears to be dependent on sex chromosome complement in addition to hormone exposure, insofar as 46,XY males with CAH actually perform worse than their matched controls, which is unexpected given the fact that CAH males would have equal or elevated levels of circulating testosterone. This raises the notion, as mentioned above, that proper timing and dosage are also likely to be important for enhancing such abilities and that simply having above-average levels of testosterone during development would not generate a “super-male.” CAIS provides another insight into this matter, demonstrating that the ability to respond to testosterone on an XY background is critical to establishing baseline spatial performance abilities. fMRI studies demonstrate that 46,XY CAIS had less inferior parietal lobe neuroactivation when performing spatial rotation tasks, a feature that resembles 46,XX females more than control genetic males. These fMRI studies on CAIS individuals once again minimize social influences and allow for a more unbiased assessment of the requirement for testosterone over genetic composition for shaping these cognitive performance sex differences.
Structural Conclusions
From the MRI studies that have been conducted in patients with CAH, it is clear that DSDs affect more than gonadal development. As highlighted, the central nervous system is highly sensitive to various hormones, and imbalances of these can greatly affect downstream behavior as well as overall brain structure. Variations in amygdala volume seem to be present in some individuals with CAH; however the effect is different depending on sex chromosome composition. Specifically, 46,XY males with CAH show unilateral reductions in the left amygdala, whereas 46,XX females with CAH show bilateral reductions in overall volume. Alterations in amygdala volume seem to be consistent with long-term glucocorticoid replacement therapies because findings for non-CAH patients on such hormone regiments also show amygdala abnormalities. The documentations of white matter irregularities seem to be unaffected by chromosomal sex and to cause similar variations in both males and females with CAH. The explanations for these results are not agreed upon, and more research will be needed before causations can be associated with the unusual white matter findings. Although limited, these discoveries have opened a new area for potential investigation focusing on the role of glucocorticoid influences in the developing brain in addition to the more frequently studied gonadal hormonal contributions. Unfortunately, no extensive structural studies have been conducted in patients with CAIS or 5α-reductase deficiencies. These findings would be invaluable in determining the direct effect of testosterone on the structures that in MRI studies have shown alterations in CAH. Future work focusing on outcomes in individuals with DSD will continue to aid in deciphering the contributions of chromosomal sex and hormones to shaping the sexually dimorphic human brain.


Feminists wrestle with testosterone: Hormones, socialization and cultural interactionism as predictors of women’s gendered selves 

Sociology of gender has developed beyond a personality-centered idea of ‘‘sex-roles’’ to an approach that stresses interaction and social structure. At the same time, there has been a concurrent development in the psychological sex-differences and medical literatures toward including the biological bases of sex-typed behavior and gender identities. In this paper, while we conceptualize gender as a social structure, we focus only on the individual level of analysis: testing the relative strength of (maternal circulating) prenatal hormones, childhood socialization, and the power of expectations attached to adult social roles (cultural interactionist) as explanations for women’s self-reported feminine and masculine selves. Our findings are complex, and support some importance of each theory. Prenatal hormones, childhood socialization, and cultural interactionism were all influential factors for gendered selves. While cultural expectations predicted only feminine selves, prenatal hormones were more robust predictors of masculine sense of self. While personality may be a relatively stable characteristic influenced by the body and childhood socialization, our results reinforce the importance of studying how the social world responds to and reinforces gendered personality.


Genetic association suggests that SMOC1 mediates between prenatal sex hormones and digit ratio


Men and women differ statistically in the relative lengths of their index and ring fingers; and the ratio of these lengths has been used as a biomarker for prenatal
testosterone. The ratio has been correlated with a wide range of traits and conditions including prostate cancer, obesity, autism, ADHD, and sexual orientation. In a genome-wide association study of 979 healthy adults, we find that digit ratio is strongly associated with variation upstream of SMOC1 (rs4902759: P = 1.41 9 10-8) and a meta-analysis of this and an independent study shows a probability of P = 1.5 9 10-11. The protein encoded by SMOC1 has recently been shown to play a critical role in limb development; its expression in prostate tissue is dependent on sex hormones, and it has been implicated in the sexually dimorphic development of the gonads. We put forward the hypothesis that SMOC1 provides a link between prenatal hormone exposure and digit ratio.

Anmerkung: Finde ich interessant: Wenn das Protein, welches Einfluss auf die Entwicklung der Gliedmaßen hat, wiederum abhängig von Testosteron ist, dann würde das durchaus erklären, warum die Digit Ratio ein Indikator  für pränatales Testosteron ist, es könnte je nach Zusammenspiel auch zeigen, warum es ein teilweise unzuverlässiger Anzeiger ist, eben weil die Mechanismen unterschiedlich sind.


Exposure to prenatal life events stress is associated with masculinized play behavior in girls

Previous research has shown that prenatal exposure to endocrine-disrupting chemicals can alter children’s neurodevelopment, including sex-typed behavior, and that it can do so in different ways in males and females. Non-chemical exposures, including psychosocial stress, may disrupt the prenatal hormonal milieu as well. To date, only one published study has prospectively examined the relationship between exposure to prenatal stress and gender-specific play behavior during childhood, finding masculinized play behavior in girls who experienced high prenatal life events stress, but no associations in boys. Here we examine this question in a second prospective cohort from the Study for Future Families. Pregnant women completed questionnaires on stressful life events during pregnancy, and those who reported one or more events were considered “stressed”. Families were recontacted several years later (mean age of index child: 4.9 years), and mothers completed a questionnaire including the validated Preschool Activities Inventory (PSAI), which measures sexually dimorphic play behavior. In sex-stratified analyses, after adjusting for child’s age, parental attitudes towards gender-atypical play, age and sex of siblings, and other relevant covariates, girls (n=72) exposed to prenatal life events stress had higher scores on the PSAI masculine sub-scale (β=3.48, p=0.006) and showed a trend towards higher (more masculine) composite scores (β=2.63, p=0.08). By contrast, in males (n=74), there was a trend towards an association between prenatal stress and higher PSAI feminine sub-scale scores (β=2.23, p=0.10), but no association with masculine or composite scores. These data confirm previous findings in humans and animal models suggesting that prenatal stress is a non-chemical endocrine disruptor that may have androgenic effects on female fetuses and anti-androgenic effects on male fetuses.

Anmerkung: Die Werte sind allerdings anscheinend sehr gering


Relations between prenatal testosterone levels and cognitive abilities at 4 years.

Relations between prenatal testosterone (T) levels and cognitive abilities at age 4 were examined for 28 girls and 30 boys. Prenatal T levels were measured in 2nd trimester amniotic fluid samples obtained by amniocentesis and were examined in relation to scores on tests of cognitive abilities. For girls, prenatal T levels showed a curvilinear (inverted U-shaped) relation to language comprehension and classification abilities. Linear relations also were observed in that prenatal T levels were inversely related to girls‘ scores on tasks assessing counting and number facts. Similarly, girls with high average block building scores had lower prenatal T and cognitive abilities were not observed. The observation of relations in girls and not boys is discussed, and the findings are examined in relation to theories of hormone-behavior relations.


Relations between prenatal testosterone and cerebral lateralization in children.

Several theorists have proposed that the sex steroid testosterone acts on the fetal brain during a critical period of development to influence cerebral lateralization (N. Geschwind & A. M. Galaburda, 1987; M. Hines & C. Shipley, see PA, Vol 71:8996; S. F. Witelson, see PA, Vol 79:26441. In the present study. relations were examined between prenatal testosterone levels in 2nd trimester amniotic fluid and lateralization of speech, affect, and handedness at age 10. Girls with higher prenatal testosterone levels were more strongly right-handed and had stronger left-hemisphere speech representation. Boys with higher prenatal testosterone levels had stronger right-hemisphere specialization for the recognition of emotion. This pattern of results is most consistent with Witelson’s (1991) claim that prenatal testosterone leads to greater lateralization of function.

Testo-kain oder Koka-steron? Zur Wirkung von Testosteron

Dies ist ein Gastartikel von Nina Radtke

Vor nicht all zu langer Zeit habe ich Testosteron mit Kokain verglichen. Zu diesem Schluss bin ich gekommen, da ich, im Gegensatz zu den meisten Menschen, in meinem Leben bereits verschiedenste Mengen an Testosteron im Blut hatte.

Dazu muss ich nun erst einmal kurz meine Vorgeschichte erklären: Bis ich 21 wurde, war ich der männlichen Adoleszenz unterworfen. Je mehr die Männlichkeit mein Ich bestimmte, umso schlechter fühlte ich mich. Das lag allerdings an meinem inneren Konflikt, dem Umstand, das ich trotz bereits lange vorher bestehendem andersartigem Bedürfnis, ein Mann werden sollte statt eine Frau.

Nun, ich habe dann, zuerst in Eigenregie und später mit ärztlicher Unterstützung eine Hormontherapie begonnen (und viele Operationen mitgemacht), dabei war mein Androgenspiegel oft signifikanten Änderungen unterworfen und ich habe inzwischen Alles erlebt von Testosteron quasi auf 0 bis hin zu den furchtbar hohen Testosteronspiegeln die ich angesichts meiner damals sehr ausgeprägten Muskulatur und Maskulinität gehabt haben muss.

Natürlich ist Testosteron nur ein Faktor, auch die Östrogenspiegel sowie mein weiterer Lebensweg hatten und haben sicher einen Einfluss auf mein Verhalten.

Dennoch ist es meine persönliche Empfindung, das Testosteron / Dihydrotestosteron (Wird mit Hilfe einer Aromatase zB in Prostata und Haarfolikeln aus Testosteron hergestellt und wirkt deutlich stärker) folgendermaßen wirkt:

  • Testosteron gibt Selbstvertrauen
    Wenn mein Testosteronspiegel sehr sehr niedrig ist, dann geht mir zunehmend das Selbstvertrauen flöten. Als mein Testosteronspiegel deutlich höher war, hatte ich im Umgang mit Menschen keine Selbstzweifel. Und auch keine Selbstzweifel (nur Verbitterung) beim Blick in den Spiegel. Bei sehr niedrigem Testosteron fühle ich mich einfach nicht sicher, aber es ist mehr. Mit viel Testosteron hat mein Selbstvertrauen oft dazu geführt, das Leute ohne Wiederworte Dinge mitgemacht haben, um die ich sie jetzt wirklich bitten müsste. Ich stand auch sehr viel mehr im Mittelpunkt.
  • Testosteron macht aktiv
    Kaum Testo – Lange Schlafen | „Normales Testo“ (Wert den ich die meiste Zeit hatte, etwas über weibl. Norm) – Halbwegs Aktiv | Hohes Testo – Aufgedreht (zB hin und her laufen beim Warten) ——- Hab aber glaub ich auch ADHS was sich überwiegend in sprunghaften Gedanken aber auch in physischer Unruhe äußert
  • Testosteron macht Unangreifbar
    Keine Angriff hätte mein Ego treffen können. Sowieso ist Ego glaube ich ein Produkt des zirkulierenden Testosterons, jedenfalls hat der Wettbewerbsgeist und der Geltungswahn mit der Hormontherapie schrittweise abgenommen und hat nun (T < weibliche Norm) Nichts mehr zu sagen. Ich bin jetzt auf mein Potential fokussiert und nicht auf den Vergleich mit Anderen. Ich ordne mich ohne Hierachiebewusstsein in eine Gruppe ein, früher undenkbar, aber vielleicht war mein Fokus auf Hierachie auch teilweise durch die Tipps in den Flirtratgebern statt nur durchs Testosteron bestimmt.
  • Testosteron macht Triebhaft
    Drogen, Party, Alkohol, Fressen – früher konnte ich mir den Driss jeden Tag geben und habs auch getan weil ich immer Bock drauf hatte. Eine neurobiologische Erklärung könnte sein, das Testosteron die Dopaminausschüttung stimuliert: Der gleiche Belohnungsreiz wirkt mit viel Testosteron deutlich stärker als mit wenig Testosteron. Vermutlich ein Grund, warum exzessives Verhalten bei Männern verbreiteter ist: Mehr Dopamin = Mehr Risikobereitschaft.
  • Testosteron macht gefühllos
    Schlimmer als unter Antidepressiva hat das Testosteron damals wie eine unsichtbare Mauer meine Gefühle eingesperrt. Ich konnte Gefühle ansatzweise fühlen, aber es gab immer einen Punkt, wo die Gefühle geblockt waren. Nur besonders starke „Einschläge“ konnten mich emotional aus der Ruhe bringen. Emotionen sind unter Östrogen ohne Testosteron weit fließender und natürlicher.

Mehr kann ich dazu nicht sagen, es ist noch heftig wie stark anabol Testosteron wirkt, ich merke es innerhalb weniger Wochen wenn mein Testosteron mal wieder sinkt oder steigt, das die Einkaufstasche mal schwerer und mal leichter ist. Aber das weiß glaub ich Jeder über das Hormon Testosteron^^

Zur Ergänzung des Gastartikels noch einige Links:

Liebe als Sucht bzw. Sucht als Liebe und das Liebesleben von Wühlmäusen

Ich habe das sehr interessante Buch „The Chemistry between us“ gelesen, welches ich empfehlen kann. Es werden einige sehr interessante Punkte dargestellt, sowohl zur Forschung von Geschlechterunterschieden als auch insbesondere dazu, wie wir Lieben und wie sich Bindung entwickelt.

Es sind interessante Punkte in dem Buch enthalten, zu denen man dutzende Artikel schreiben könnte. Ich fange mal mit einem an, der auch in dieser Kurzzusammenfassung hier dargestellt wird:

Young has devoted his career to studying the behaviors and neural circuitry of love in the prairie vole, a rodent whose monogamous tendencies resemble our own. Once a prairie vole has found “the one,” the pair will most likely remain companions for life. Young’s research has implicated a range of chemical activities—mainly during sex—that build this lifelong bond. In particular, he uncovered how two hormones in the brain, vasopressin in male voles and oxytocin in female voles, regulate social behavior and memory—promoting the recognition of a loved one and the urge to cuddle or defend. In addition, the circulation of dopamine and opioids allows the vole to associate his or her partner with pleasure, thus strengthening their bond. Many of these molecules are identical to those activated in human bonding.

Interessant ist daran, dass es zwei Arten von Voles (Wühlmäuse) gibt, die eine ist monogam, die andere nicht. Der Wesentliche Unterschied ist wohl eben der, dass bei dem einen über Vasopressin und Oxytocin eine Bindung erfolgt und bei dem anderen nicht. Der Unterschied zwischen den beiden Arten ist relativ gering, die Unterschiede im Verhalten aber enorm.

Young führt dann verschiedene Tests auf, die nahelegen, dass die gleichen Mechanismen eben auch beim Menschen wirken.

That loving feeling comes at a price. A hormone called corticotropin-releasing factor, or CRF, builds up in the brains of paramours and parents alike. The CRF system activates a stress response, and this system elicits the painful sensations you feel when your baby cries or your boyfriend dumps you. The system may seem like a nasty trick, but it has its uses. Even when passion fades or a diaper needs changing, the sharp pangs of the CRF system keep families and loved ones together. The CRF system also contributes to the agony an addict feels after the elation wears off. Thus, the authors argue, the highs of intimacy and withdrawals of separation parallel the highs and lows that drug addicts experience.

Wenn ich mich recht erinnere, dann stellt der Autor es so dar, dass die erste Liebe (oder der erste Kick bei einer Droge) oft noch tatsächliches Glück ist, weil man in Oxytocin gebadet ist und andere glücklichmachende Hormone ausgeschüttet werden. Das bewirkt eine Bindung. Wie bei vielen positiven Reizen wird diese Ausschüttung von reinen Glückshormonen aber mit der „Gewöhnung“ an den Partner immer geringer. Es greift dann ein anderes System: Wenn man das, was einen bisher glücklich gemacht hat, nicht mehr hat, dann baut sich das oben genannte Stresshormon auf und dieser lässt dann nach, wenn man den „Reiz“ wieder ausgesetzt ist. Das bewirkt dann den Trennungsschmerz und kann in bestimmten Fällen zu einem „ich kann nicht mit ihr und ich kann nicht ohne sie“ führen: Wenn sie da ist hat man dann eben „Belohnungseffekt“ mehr, weil dieser zu abgestumpft ist, ist sie aber weg, dann stellt sich der Trennungsschmerz ein.

Ähnlich ist es wohl auch bei Drogennutzern, die eine Droge eben wie eine Liebe empfinden: Am Anfang ist es pures Glück, dann brauchen sie eine immer höhere Dosis und schließlich ist es schlicht der „Trennungsschmerz“ der bekämpft wird und man hält es nicht mehr aus und will diesen beseitigen. Hat man ihn beseitigt, dann meint man vielleicht jederzeit aufhören zu können, aber dann treten wieder die Entzugserscheinungen auf.

Hier eine andere Besprechung des Buches in der man auch sieht, wie sich dieser „Liebesentzug“ auswirkt:

To investigate the rodent version of getting hugs, and what happens in the absence of hugs from a bonded partner, Bosch took virgin males and set them up in vole apartments with roommates—either a brother they hadn’t seen in a long time or an unfamiliar virgin female. As males and females are wont to do, the boy-girl roommates mated and formed a bond. After five days, he split up half the brother pairs, and half the male-female pairs, creating what amounted to involuntary vole divorce. Then he put the voles through a series of behavioral tests.

The first is called the forced-swim test. Bosch likens it to an old Bavarian proverb about two mice who fall into a bucket of milk. One mouse does nothing and drowns. The other tries to swim so furiously the milk turns into butter and the mouse escapes. Paddling is typically what rodents will do if they find themselves in water; they’ll swim like crazy because they think they’ll drown if they don’t. (Actually, they’ll float but apparently no rodent floaters have ever returned to fill in the rest of the tribe.)

The voles that were separated from their brothers paddled manically. So did the voles who stayed with their brothers and the voles who stayed with their female mates. Only the males who’d gone through vole divorce floated listlessly as if they didn’t care whether they drowned.

„It was amazing,“ Bosch recalls. „For minutes, they would just float. You can watch the video and without knowing which group they were in, you can easily tell if it’s an animal separated from their partner, or still with their partner.“ Watching the videos of them bob limply, it’s easy to imagine them moaning out „Ain’t No Sunshine When She’s Gone“ with their tiny vole voices.

Die armen Wühlmäuse.

Man stelle es sich mit ihm an der Gitarre vor:

Prairie vole (Prärie Wühlmaus)

Prairie vole (Prärie Wühlmaus) (ein Bild mit Gitarre war nicht zu finden, aber er schaut immerhin traurig)

Das Leben von Laborwühlmäsuen ist allerdings auch so hart:

Next Bosch subjected the voles to a tail-suspension test. This test uses the highly sophisticated technique of duct taping the end of an animal’s tail to a stick and suspending it. As in the swim test, a rodent thus suspended will usually flail and spin his legs like a cartoon character who’s run off the edge of a cliff. Once again, though, while the other males did just that, the divorced males hung like wet laundry.

In a final behavior test, Bosch placed the voles on an elevated maze, like the ones we’ve already described that tested anxiety. On such a maze, the animal’s desire to investigate fights with its fear of exposed areas. Compared to the other voles, the divorced males were significantly less likely to explore the open arms of the maze.

All these tests, commonly used to test lab animals for depression, showed that if you separate a pair-bonded male vole from his mate, you’ll get a very mopey vole who uses what’s called passive-stress coping to deal with the overwhelming anxiety of partner loss. „When the separation takes place, this is what causes the animals to feel so bad,“ Bosch explains. „We found this increased depressive behavior and that tells us the animal is not feeling well.“ He doesn’t mean „under the weather,“ he means the divorced voles are emotionally miserable. „It is like when my wife went to the States for a post-doc for one year, so I knew I wouldn’t see her for at least six months. Well, I was sitting at home, laying on the couch, not motivated to do anything, not to go out and meet friends like I usually would.“

Es ist interessant, dass wir hier den Tieren ganz ähnlich sind und das in beiden Fällen bestimmte Chemikalien am Werk sind, ohne die wir uns nicht auf diese Weise verhalten würden (wie die andere Art von Voles zeigt, die nicht monogam ist).

Dann wurde versucht, die Wirkung mit Drogen nachzustellen:

Koob and others have used drugs to create the very same behavior in other lab animals. When the drugs are taken away from rats and mice, they display the same passive responses to elevated mazes. They withdraw socially. They mope. Human addicts do the same, Koob points out, mentioning characters in movies like Leaving Las Vegas and Trainspotting as examples.

To explain the physiology behind this passive depression state in the separated voles, Bosch checked their chemistry. The males separated from their mates had much higher levels of corticosterone, a stress chemical, in their blood than did any of the other groups, including voles separated from their brothers. Their HPA axis was working so hard, their adrenal glands weighed more. Bosch nailed CRF’s role in driving both the HPA axis overdrive and the mopey behavior by blocking CRF receptors in the voles‘ brains. When he did, the divorced voles no longer hung limply from the sticks. They didn’t float for as long in the water. They still remembered their mates, and were still bonded to them; they just didn’t worry about it when they left them.

Das finde ich recht eindrucksvoll: Wenn bestimmte Rezeptoren blockiert sind, dann gab es keinen Liebeskummer mehr. Was die „Macht“ biologischer Systeme aus meiner Sicht gut darlegt. Theoretisch könnte man dies sicherlich auch bei Menschen machen, aber entsprechende Tests wären unethisch. Ich würde aber vermuten, dass es Menschen mit einer geringeren Ausschüttung an Stresshormonen oder schwächeren Rezeptoren gibt, die dann eben eher auf „Short Time Mating“ setzen und nicht sehr anfällig für Liebeskummer sind. Ich vermute, dass sie dann eben auch ein anderes Verhalten zeigen.

But here’s the strange thing: both the voles who stayed with their female mates and the voles who were forced to split from the females had much more CRF in the BNST than did males who lived with, or were separated from, their brothers. In other words, loads of this stress-related hormone were being pumped in both the voles who got depressed after separation and voles who were still happily bonded and didn’t show signs of passive-stress coping.

„Bonding itself produces high CRF,“ Bosch says. „But this does not mean the system is also firing.“ There is something fundamental about living with a mate that results in more CRF stress hormone in the brain, but that also prevents the engagement of the HPA stress axis as long as the mates stay together. Using an interesting metaphor for bonding, Bosch says „I compare it to a rifle. As soon as they form a pair-bond, the rifle is loaded with a bullet. But the trigger isn’t pulled unless there is separation.“ He thinks that vasopressin serves as the chemical trigger to fire off the HPA axis during separation, though the exact roles of both oxytocin and vasopressin are still unclear.

Addicted drug users load the rifle, too. The gun won’t fire unless they stop taking the drug. For the bonded voles, „it won’t fire unless the partner leaves the nest,“ Bosch says.

Das ist ein interessanter Mechanismus. Er bewirkt zum einen Bindung, aber er lässt uns wahrscheinlich auch gleichzeitig eher die Möglichkeit, den Partner zu wechseln. Bei einem neuen Partner wird eben dann wieder Vasopressin, Oxytocin etc ausgeschüttet und damit das System wieder in Schach gehalten. Weswegen derjenige mit neuem Partner die Trennung auch besser verkraftet während der Verlassene das weit weniger kompensieren kann. Es verhindert also ein Verlassen sofern man nicht etwas besseres findet (statt wie beim ersten Verliebt sein den Partner unter der Ausschüttung der Hormone zu verklären). Wobei der Trennungsschmerz den Wechsel auch nicht zu einfach machen wird.

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


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


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.

Die Vorteile der Einsicht, dass wir biologische Grundlagen haben

Noch eine interessante Stelle von dem Buch „Genome: The Autobiography of a Species in 23 Chapters“ (PDF) (S. 160). Diesmal deutlich kürzer:

Meanwhile, the discovery that personality has a strong genetic component can be used in some very non-genetic therapy. When naturally shy baby monkeys are fostered to confident monkey mothers, they quickly outgrow their shyness. It is almost certainly the same with people – the right kind of parenting can alter an innate personality. Curiously, understanding that it is innate seems to help to cure it. One trio of therapists, reading about the new  results emerging from genetics, switched from trying to treat their clients‘ shyness to trying to make them content with whatever their innate predispositions were. They found that it worked. The clients felt relieved to be told that their personality was a real, innate part of them and not just a bad habit they had got into. ‚Paradoxically,depathologising people’s fundamental inclinations and giving group members permission to be the way they are seemed to constitute the best insurance that their self-esteem and interpersonal effectiveness would improve.‘ In other words, telling them they were naturally shy helped them overcome that shyness. Marriage counsellors, too, report good results from encouraging their clients to accept that they cannot change their partners‘ irritating habits – because they are probably innate – but must find ways to live with them. The parents of a homosexual are generally more accepting when they believe that homosexuality is an immutable part of nature rather than a result of some aspect of their parenting. Far from being a sentence, the realisation of innate personality is often a release.

Danach ist es also für viele Leute eine Erleichterung und gut für ihr Selbstbewußtsein, wenn sie sich oder andere so akzeptieren können, wie sie sind und dies als Grundlage eröffnet ihnen dann gleichzeitig die Möglichkeit, auch an sich zu arbeiten und so etwas wie Schüchternheit eher zu verbessern. Weil es einem eine Grundlage bietet und auch eine Erklärung: Man muss sich keine Vorwürfe mehr machen und kann daher leichter mit der Sache umgehen.

Ein ähnliches Phänomen hatte ich schon einmal bezüglich der Geschlechterrollen dargestellt:

Eine interessante Beobachtung machte Trautner bei Längsschnittstudien mit anfangs auffällig streng einteilenden Kindern: Wer als Kleinkind seine Welt besonders klar in männlich/weiblich aufteilte, konnte später lockerer mit den Kategorien umgehen. Das entspricht der Alltagswahrnehmung. Männer und Frauen, die früh in eine sichere Geschlechtsrolle gefunden haben, müssen sich nicht mehr ständig ihrer sexuellen Identität durch präpotentes oder püppchenhaftes Gebaren versichern. Sie können sich auch vom Rollenklischee abweichendes Verhalten erlauben.

Die klare Vorstellung von der Geschlechterdifferenz und der eigenen Zugehörigkeit ist offenbar eine gute Basis für einen späteren freien Umgang mit Stereotypen. Man kann sich dann Interesse und sogar Freude und Spaß an der Differenz leisten. Und man kann dann auch Unterschiede ertragen. Denn Differenz, darauf weist der Sozialwissenschaftler Amendt hin, macht eben nicht nur stolz. Sie erzeugt auch Neid. Penisneid ist da bloß ein Beispiel. Nur starke Menschen halten die Unterschiede zwischen den Geschlechtern aus.

Auch hier sind also Menschen, die meinen, sich selbst gefunden zu haben, sicherer. Und auch dabei kann einem dann vielleicht das Wissen, dass man eben auf eine bestimmte Weise ist, helfen.

Ich vermute, dass es auch durchaus Nachteile geben kann, wenn man ohne Grund annimmt, wegen bestimmter angeblich bestehender Geschlechterunterschiede etwas nicht zu können, zB eine Frau, die meint, sie kann keine Bohrmaschine bedienen oder ein Mann, der meint, dass er nicht kochen kann. Allerdings wären das eben auch Vorstellungen, die sehr essentialistisch sind und den Rahmen der Biologie stark überziehen.

Des weiteren vermute ich, dass genau dieser Umstand, dass man sich gern in einer Rolle sicher ist, bestimmte Leute, die in die normalen Rollen und Muster nicht passen, eher motiviert, sich mit Queertheorie und Genderfeminismus zu beschäftigen. Denn dort ist man eben auch plötzlich „richtig“, alle anderen sind falsch. Ich vermute allerdings, dass dort des häufigeren die kognitiven Dissonanzen größer werden, weil man dort ja darauf achten muss, dass man nicht doch ein falsches verhalten, etwas zu stereotyp, zeigt. Da bieten aus meiner Sicht die biologischen Theorien, wenn sie richtig verstanden werden, mehr halt.