Brain Fitness for Women. Sondra Kornblatt

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       Chapter 3

      Swimming in Different Hormones

      Variations Beyond Brain Structure

      On the one hand, [men will] never experience childbirth. On the other hand, we can open all our own jars.

      Bruce Willis, actor

      When women are depressed, they eat or go shopping. Men invade another country. It's a whole different way of thinking.

      Elayne Boosler, comedian

      Have you ever worked on those find-the-difference photo puzzles? On one side, you see a picture of a celebrity like Beyoncé getting out of her limo. Next to it is the same picture, but with a few changes: the rearview mirror may be backwards, a fan in the background is missing, or there's an extra gold button on her jacket.

      Male and female brains are kind of like those side-by-side pictures—mostly the same at birth but with a few differences.

      Now imagine that the left picture of Beyoncé was swished in blue tint and the right one in red. The pictures look different right away, even before you look for the changed details.

      Think of those colors as hormones. Hormones “tint” the parts of the brain, changing some behavior, emotional responses, and even vulnerability to illnesses. Certain parts of the brain readily absorb the color and other parts don't.

      Is everything colored by hormones? Yes and no. No matter how much men and women differ from each other, the individual variations within the same sex are much wider. So while men as a group tend to be more aggressive than women, you’ll find extremely aggressive women and extremely timid men.

      “Gender roles are flexible, reversible, and not all-or-none,” says Donald Pfaff, PhD, author of Man and Woman: An Inside Story. “[B]iological influences on sex differences in brain and behavior operate at so many different levels, and they interact with environmental influences in so many different ways, that rigid, stereotyped ideas about what is and is not typical male or typical female behavior have become impossible to sustain.”²⁰

      When you understand that you're swimming in different hormonal waters than men, you can have more compassion for yourself. You’ll be open to the value of your brain's perspective on the world and be more relaxed with how wide the range of women's behaviors can be.

      This chapter looks at hormones, both sexual and nonsexual, as well as other differences between men and women, including different responses and susceptibility to pain and illnesses.

      Hormones

      Hormones are chemicals released into the blood to activate or regulate bodily functions such as digestion, hunger, stress control, metabolism, growth, lactation, sex drive, circadian rhythm, and reproduction. Most hormones are secreted by specialized glands, like the thyroid gland in the throat, the pituitary gland in the brain, or the pancreas in the upper abdomen.

      What's the difference between hormones and neurotransmitters? Hormones travel throughout the body via the bloodstream. Neurotransmitters, which activate and regulate such things as memory, learning, mood, behavior, sleep, pain perception, and sexual urges, travel across synapses in the neurons that make up the brain and nervous system. (Familiar neurotransmitters include serotonin, dopamine, and norepinephrine.)

      Scientists have recently realized that in addition to hormones and neurotransmitters, we have neurohormones, which are hormones secreted by or acting on the nervous system.

      Hormones are specialized for a wide array of functions, any of which can affect our brains.

       Sexual Hormones

      There are three basic sexual hormones: androgens (which are mainly male and include testosterone) and estrogen and progesterone (which are mainly female). Both men and women have all three types, but in different amounts, at different levels, and with different receptors (neurons specialized to be sensitive to certain chemicals, including hormones).

      Oddly enough, testosterone can turn into estradiol, a type of estrogen. But no matter how complex they are or how they work, sexual hormones make sure that our bodies focus on mating and reproduction that species need to survive. And that can include behaviors that make boys be boys and girls be girls.

      Many scientists are studying hormones and behavior in hopes of finding links between the two. For example, studies of the male population show that violent behavior peaks when men have increased testosterone, in the late teens and early twenties. But that doesn't necessarily mean that other behaviors often seen as gender specific are driven by sexual hormones. In other words, it isn't estrogen that makes some people put on makeup, have in-depth discussions about feelings, and shop until they drop, or testosterone that makes others leave their socks on the floor or become fascinated with construction.

      The farther away from “nitty-gritty reproductive biology” we get, says Pfaff, the harder it is to clearly link the behavior with sexual hormones.²¹That's because the human brain is also influenced by so many things, including environment, childhood development, prenatal development, nutrition, toxins, hormones, the conscious mind, and the brain's own structure.

      To further complicate things, sexual hormones are released not only as part of internal bodily functions, but also as a response to external experiences. Say you have a date with your spouse that includes dinner, a romantic movie, sweet talk, a candlelit bedroom, and soft fingertips caressing your belly. These external actions can get your estrogen going. Similarly, sexual drive, aggression, and social dominance can make testosterone rise in men. Many studies show a correlation—a coordinated relationship—between testosterone and certain behavior, but it's mostly not known if testosterone causes the behavior or vice versa.

      The body can produce hormones in response to external experiences, such as a romantic evening.

      “When you examine testosterone levels when males [in a study] are first placed together in a social group,” said Robert Sapolsky, expert on testosterone from Stanford University, “testosterone levels predict nothing about who is going to be aggressive. Behavior drives the hormonal changes, rather than the other way around.”²²

      So what are these primary sexual hormones that make things so complex?

      Testosterone: Testosterone, the primary male hormone, СКАЧАТЬ