Saturday, February 03, 2007

*** The Female Brain by Louann Brizendine MD

What makes a woman tick? For centuries men have pondered this imponderable. Brizendine comes closet to letting mankind inside for a closer look. For a man who's surrounded by women, it is a helpful guide to understand how different women are from men, and what helps make those differences. In addition, we can come to appreciate the vast changes that the female brain makes over its lifespan. It is far more plastic and adaptable to its biological circumstance than you think.

Male brains are larger by 9%, even after correcting for body size... Women and men, however, have the same number of brain cells. The cells are just packed more densely in women. p1

Women have 11% more neurons in the language and hearing centers of the brain than men. The principal hub of both emotion and memory function - the hippocampus - is also larger in the female brain. This means that women are, on average, better at expressing emotions and remembering the details of emotional events. p5

Men have 2.5 times the brain space devoted to sexual drive as well as larger centers for action and aggression. Sexual thoughts float through a man's brain every 52s on average, and through a woman's only once a day, and perhaps 3 to 4 on her hottest days. p5

Girls don't experience the testestorone surge in utero that shrinks the centers for communication, observation, and processiong of emotion, so their potential to develop skills in these areas are better at birth than boys'. Over the first 3 mos, a baby girl's skills in eye contact will increase by over 400%, whereas a boy during this time will not increase at all. p15

Stressed mothers naturally become less nurturing, and their baby girls incorporate stressed nervous systems that change the girls' perception of reality. This isn't about what's learned cognitively - it's about what is absorbed by the cellular circuitry at the neurological level... Neurological incorporation begins during pregnancy. Maternal stress during pregnancy has effects on emotional and stress horomone reactions, particularly in female offspring. Stressed female kids ended up startling more easily and being less calm and more anxious than the male kids. Female kids who were stressed in utero showed a great deal more emotional distress than female kids who weren't. So if you're a mom to be, take it easy so that your daughter may be able to relax. p20

Disorders that inhibit people from picking up on social nuance - called autism spectrum disorders and Asperger's Syndrome - are 8 times more common in boys. Scientists now believe that the typical male brain, with only 1 X chromosome, gets flooded with testosterone during development and becomes more easily socially handicapped. Extra testosterone in people with these disorders may be killing off some of the brain's circuits for emotional and social sensitivity. p23

By all standards, men are 20 times more aggressive than women, something a quick look around the prison system will confirm. p29

The first 2 weeks of the cycle, when estrogen is high, a girl is more likely to be socially interested and relaxed with others. In the last 2 weeks when progesterone is high and estrogen is lower, she is more likely to react with increased irritability and will want to be left alone. p35

During the juvenile pause of childhood, when estrogen levels are stable and low, a girl's stress system is calmer and more constant. Once estrogen and progesterone levels climb at puberty, her responsivity to both stress and pain start to rise, all marked by new reactions in the brain to cortisol [stress horomone]. She's easily stressed, highstrung, and looking for ways to chill out. p35

Girls speak faster than boys - 250 words/minute vs. 125 for typical males. p36

Why do girls go to the bathroom to talk? Why do they spend so much time on the phone with the door closed? They're trying to create intimacy and connection with their female peers via gossip and secrets - their tools to navigate and ease the ups and downs of stresses in life. p36

Their is a biological reason for this behavior. Connecting through talking activates pleasure centers in the brain. We're not talking about a small amount of pleasure. This is huge. It's a major dopamine and oxytocin rush, which is the biggest, fattest neurological reward you can get outside of orgasm... During midcycle, when estrogen production is peaking, the girl's dopamine and oxytocin level is at its maximum and her urge for intimacy and verbal communication is also peaking. Intimacy release more oxytocin, which reinforces the desire to connect, and connecting brings a sense of pleasure and well being. p37

Boys don't share this intense desire for verbal communication and connection, so attempts at verbal intimacy can be met with disappointing results. Girls who expect their boyfriends to chat with them the way their girlfriends do are in for a big surprise... This difference may also be at the core of the major disappointment women feel all their lives with their marriage partner - he doesn't feel like being social, he doesn't crave long talks. But it's not his fault. When he is a teen, his testosterone levels begin soaring off the charts and he dissappears into adolescence where more than anything he wants to be left alone... Testosterone has been shown to decrease talking as well as interest in socializing - except when it involves sports or sexual pursuit. In fact, sexual pursuit and body parts become pretty much obsessions. p39

A teenage boy feels alone and ashamed by his [sexual] thoughts. Until his buddies start to joke and comment about girl's bodies, he thinks he is the only one consumed by such intense sexual fantasies and the constant fear that someone will notice the erections over which he seems to have no control. Compelling masturbatory frenzies overwhelm him many times a day. He lives in fear of being found out. He's even more wary of verbal intimacy with girls, though he dreams of other kinds of intimacy. p39

Women’s self esteem is maintained in part by the ability to sustain intimate relationships with others. As a result, perhaps the greatest source of stress in the woman’s brain can be the fear of losing intimate relationships and the lack of vital social support that might ensue. P41

The formation of cliques may be the result of a girl’s stress response… Fight or flight behavior may not be characteristic of all humans. This is more likely to be a male response to threat and stress… Fighting may not have been as evolutionarily adaptive for females as it was males, because females have less chance of defeating the larger males, and because they had to also defend their helpless children. In female brains the circuit for aggression is more closely linked to cognitive, emotional, and verbal functions than is the male pathway which is more connected to physical action. As for flight, females are less generally able to run they’re pregnant, nursing, or caring for children… Female rely on social ties. Members of a group can alert each other of conflict ahead of time, they come to one another’s aid in a threatening or stressful situation. This pattern of behavior is ‘tend and befriend’. P42

At around 8 to 10 for girls (later for boys), the brain’s sleep clock begins to change, leading to later bedtimes, later wake up times, and more sleeping time overall. P44

One of the most estrogen sensitive parts of the brain – the hippocampus – is a major relay station for processing memories for words. This may be one biological reason behind women’s increased verbal performance during the highest estrogen week – week 2 – of their cycle. Female students should take their SATs or wives should argue with their husbands on day 12 of their cycles. P46

The medical name for extreme emotional reaction during the weeks before the period, triggered by ovarian estrogen and progesterone, is PMDD. Women who have committed crimes while suffering from PMDD have successfully used it as a defense in France and England by establishing temporary insanity. P48

To help some adolescents, doctors prescribe the continuous birth control pill to keep the girls’ estrogen and progesterone at moderately high but constant levels, preventing the ovaries from sending out big fluctuations that upset the brain. P49

By age 15, girls are twice as likely to suffer from depression. P53

From experiments, we know that oxytocin is released in the brain after a 20s hug from a partner – sealing the bond between the huggers and triggering the brain’s trust circuits. So don’t let a guy hug you unless you plan to trust him. P68

A Swiss experiment gave a nasal spray containing oxytocin to one group of investors, and compared them with another group who got a placebo. The oxytocin investors offered up twice as much money as did the placebo group when pitched to by a stranger posing as a financial adviser. P68

In humans, male love circuits get an extra kick when stress levels are high. After an intense physical challenge males will bond quickly and sexually with the first willing female. This may be why military men often bring home brides. Women by contrast will rebuff advances when under stress. The reason may be that the stress hormone cortisol blocks oxytocin’s action in the female brain, abruptly shutting off a women’s desire for sex and touch. For her, 9 months of pregnancy followed by caring for an infant under stressful conditions makes less sense than the quick deposit of sperm does for him. P72

Male voles who had the longer version of the vasopressin receptor gene showed greater monogamy and spent more time grooming and licking their pups. They also showed greater preference for their partners, even when given the chance to run off with young, fertile, and flirtatious females. Males with the longest gene are the most reliable and trustworthy partners and fathers. The human gene comes in 17 lengths. So the current joke is that women should care more about the length of vasopressin gene in their mates than about the length of anything else… Male monogamy may therefore be somewhat predetermined and passed down genetically. It may be that devoted fathers and faithful partners are born, not made by a father’s example. P74

When love is lost, abandoned men are 3 to 4 times more likely to commit suicide. Women, by contrast, sink into depression… Rejection, it turns out, actually hurts like physical pain because it triggers the same circuits in the brain… It may be that ‘brain pain’ of lost love evolved as a physical alarm to alert us to the dangers of social separation. P75-6

Female sexual turn-on begins with a brain turn-off… Before the amygdale – fear and anxiety center – has been turned off, any last minute worry – about work, kids, schedules, dinner, etc. – can interrupt the march toward orgasm. This fact may account for why it takes her on average 3 to 10 times longer to reach orgasm. P77

If she’s not relaxed, comfortable and warm, it’s not too likely to happen… For many women, being relaxed – thanks to a hot bath, a foot rub, a vacation, or alcohol, improves their ability to have an orgasm, even with partners they don’t feel completely comfortable with. P78

4 out of 10 girls have had some kind of sexually upsetting experience in childhood that continues to occupy their brains with worries during adult sexual encounters – not being able to reach orgasm is one of the most common symptoms. P81

Reports provided by women indicated those whose partners were most symmetrical enjoyed a significantly higher frequency of orgasms than those with less symmetrical mates. Handsome men know this firsthand. Studies show that symmetrical men have the shorted courtships before having sex. They also invest the least time and money on their dates. And handsome guys cheat on their mates more often. P85

To the researchers’ surprise, women’s romantic passion toward their mates did not increase the frequency of orgasm. Not only that, but even the conventional wisdom that using birth control and protection from disease increases female orgasm, supposedly because the allow the woman to feel more relaxed, proved no relationship between frequency of female orgasm and contraceptive use. Instead, only how good looking the guy was correlated with a high frequency of female orgasm. After all our brains are built for survival in the precontraceptive Stone Age. P86

The human mother will be able to pick out her own baby’s smell above all others with about 90% accuracy. This goes for her baby’s cry and body movements too… Maternal aggression sets in as well. Her strength and resolve to care for and protect her baby completely grab her brain circuits… Her brain has physically changed, and along with it her reality. P102

Mothers may have better spatial memory than females who haven’t given birth, and they may be more flexible, courageous, and adaptive. This transformation even holds true for adoptive mothers. As long as you’re in continuous physical contact with the child, your brain will release oxytocin and form the circuits needed to make and maintain the mommy brain. P103

A study of college aged adults who had low maternal care in childhood showed hyperactive brain responses to stress on PET scans. Researchers found these adults released more stress hormone cortisol into their blood than their high maternal care counterparts. P104

Humans evolved as cooperative breeders in settings where mothers have always relied on allomaternal care from others. So whatever a mother does and others do to help her, to ensure the predictability and availability of resources – financial, emotional, and social – may ultimately secure her children’s future well being. This was proven with monkeys, where it’s not the amount of resource that is available, but it’s predictability that is important. Rhesus monkeys were divided into 3 groups. One had plenty of food every day, one had scarce food every day, and one had plenty on some days, and scarce on others. Youngsters in the best environment with plenty of food got the most responsive nurturing from their moms, but those in the scarce group got almost as much. But those in the unprecdictable environment not only got the least amount of nurturing but received abusive and aggressive attacks from their mothers. These mothers had higher levels of stress hormones and lower levels of oxytocin their peers. P114

Men are not as adept at reading facial expressions and emotional nuance – especially signs of despair and distress. Perhaps that is why women evolved to cry 4 times more easily than men – displaying unmistakable sign of sadness and suffering that men can’t ignore. P119

Researchers place women in an MRI while they delivered brief electric shocks, some weak and some strong. Next, their romantic partners were hooked, but the women were signaled as to whether the shock to their beloved would be strong or weak. The women could not see their lovers’ face or bodies, but even so, the same pain areas of their brains that had activated when they were shocked lit up when they learned their partners were being strongly shocked… Researchers were unable to elicit similar brain responses from men. P123

Most men don’t take the time to figure out emotion, and they become impatient because it takes longer for them. This is what happens in men with the extreme male brain that is characteristic of Asperger’s disorder. These men become unable to look at a face, let alone read it. The amount of emotional input from another person’s face registers on their brains as unbearable pain. P124

Anxiety is 4 times more common in women. A women’s highly responsive stress trigger allows her to become anxious much more quickly than does a man. Although this may not seem like an adaptive trait, it actually allows her brain to focus on the danger at hand and respond quickly to protect her children. Unfortunately, this means that they are nearly twice as likely as men to suffer from depression, especially through their reproductive years. P132

What’s a hot flash?
During menopause, the hypothalamus, in response to decreased estrogen, has changed its heat-regulating cells, making a woman feel suddenly, blazingly hot even at normal temperatures. P140

Even though the life span in hunter-gatherer societies is typically less than 40, about 1/3 of all women survive past that age, and many go on to live into their 60s and 70s… The hardworking grandmother in her 60s spent more time foraging than did younger mothers, providing food for their grandchildren, increasing their chance of survival. Anthropologists have found in some societies that the presence of grandmother improves a child’s prospects much more than the presence of a father. P155

Researchers have found that postmenopausal women on estrogen were less depressed and angry and performed better on tests of verbal fluency, hearing, and memory than did women who were not on estrogen, and they outperformed men, too. By contrast, women who had never taken hormone therapy had significantly more shrinkage in all brain areas than did women who took HT. They also found that the longer women took HT, the more gray matter they had. These positive effects held and even increased the longer a woman took HT. p167

Another study examined identical twins [to rule out as much genetic variation as possible], in which one twin took HT and the other didn’t. The HT users had better scores on tests of verbal fluency and working memory than their twin sisters, showing 40% less cognitive impairment, regardless of the timing and type of HT. p167

However, when estrogen was given to older women years after menopause, no positive effect was found. These findings suggest that there is a critical time for initiating HT following menopause. This may explain why no protective effect on cognitive aging was found on the landmark WHIMS study. P168

It’s now clear how estrogen keeps blood vessels in the brain healthy. Researchers have found that estrogen increases the efficiency of the mitochondria in the brain’s blood vessels, explaining why premenopausal woman have lower rates of stroke than men their age. P174
Studies indicate that starting HT early in menopause, when neurons are healthy, reduces risk of Alzheimer’s disease. However, HT initiated once the disease has developed or decades after menopause offers no benefit. P175

2 comments:

Paula said...

I definitely think about sex more then 3-4 times a day.

The part about how talking activates pleasure centers in the brain was something I never heard before. No wonder I enjoy chatting on the phone for so long!

Longevity Science said...

Thank you for your interesting post!
I thought perhaps you may also find this related post interesting to you:
Body Size and Human Longevity
http://longevity-science.blogspot.com/2007/05/body-size-and-human-longevity_08.html