Excerpt: 'The Male Brain'  

Excerpt: 'The Male Brain'

The Male Brain
The Male Brain
By Louann Brizendine
Hardcover, 304 pages
Broadway Books
List price: $24.99

You could say that my whole career prepared me to write my first book, The Female Brain. As a medical student I had been shocked to discover that major scientific research frequently excluded women because it was believed that their menstrual cycles would ruin the data. That meant that large areas of science and medicine used the male as the "default" model for understanding human biology and behavior, and only in the past few years has that really begun to change. My early discovery of this basic inequity led me to base my career at Harvard and the University of California–San Francisco (UCSF) around understanding how hormones affect the female and male brains differently and to found the Women's Mood and Hormone clinic. Ultimately that work led me to write The Female Brain, which addressed the brain structures and hormonal biology that create a uniquely female reality at every stage of life.

The distinct brain structures and hormonal biology in the male similarly produce a uniquely male reality at every stage of life. Yet as I considered writing The Male Brain, nearly everyone I consulted made the same joke: "That will be a short book! Maybe more of a pamphlet." I realized that the idea that the male is the "default model" human being still deeply pervades our culture. The male is considered simple; the female complex.

Yet my clinical work and the research in many fields, from neuroscience to evolutionary biology, show a different picture. Simplifying the entire male brain to just the "brain below the belt" is a good set up for jokes, but it hardly represents the totality of a man's brain. There are also the "seek and pursue" baby boy brain, the "must move or I will die" toddler brain; the sleep-deprived, deeply bored, danger-seeking teen brain; the passionately bonded mating brain; the besotted daddy brain, the obsessed-with-hierarchy aggressive brain and the fix-it-fast emotional brain. In reality, the male brain is a lean mean problem-solving machine.

The vast new body of brain science together with the work I've done with my male patients has convinced me that through every phase of life, the unique brain structures and hormones of boys and men create a "male reality" that is fundamentally different from the female one, and all too frequently oversimplified and misunderstood.

Male and female brains are different from the moment of conception. It seems obvious to say that all the cells in a man's brain and body are male. Yet this means that there are deep differences, at the level of every cell, between the male and female brain. A male cell has a Y chromosome and the female does not. That small, but significant difference begins to play out early in the brain as genes set the stage for later amplification by hormones. By eight weeks after conception the tiny male testicles begin to produce enough testosterone to marinate the brain and fundamentally alter its structure.

Over the course of a man's life, the brain will be formed and re-formed according to a blueprint drafted both by genes and male sex hormones. And this male brain biology produces his distinctly male behaviors.

The Male Brain draws on my twenty-five years of clinical experience as a neuropsychiatrist. It presents research findings from the spectacular advances over the past decade in our understanding of developmental neuroendocrinology, genetics, and molecular neuroscience. It offers samplings from neuropsychology, cognitive neuroscience, child development, brain imaging, and psychoneuroendocrinology. It explores primatology, animal studies, and observation of infants, children, and teens, seeking insights into how particular behaviors are programmed into the male brain by a combination of nature and nurture.

During this time, advances in genetics, electrophysiology and noninvasive brain-mapping technology have ignited a revolution in neuroscientific research and theory. Powerful new scientific tools, such as genetic and chemical tracers, positron-emission tomography (PET) and functional magnetic resonance imaging (fMRI), now allow us to see inside the working human brain while it's solving problems, producing words, retrieving memories, making decisions, noticing facial expression, falling in love, listening to babies cry, and feeling anger, sadness or fear. As a result, scientists have recorded a catalog of genetic, structural, chemical, hormonal and processing brain differences between women and men.

In the female brain, the hormones estrogen, progesterone and oxytocin predispose brain circuits toward female-typical behaviors. In the male brain, it's testosterone, vasopressin and a hormone called MIS (mullerian inhibiting substance) that have some of the earliest and most enduring effects. The behavioral influences of male and female hormones on the brain are major. We have learned that men use different brain circuits to process spatial information and solve emotional problems. Their brain circuits and nervous system are wired to their muscles differently -- especially in the face. The female and male brains hear, see, intuit, and gauge what others are feeling in their own special ways. Overall, the brain circuits in male and female brains are very similar, but men and women can arrive at and accomplish the same goals and tasks using different circuits.

We also know that men have two and a half times the brain space devoted to sexual drive in their hypothalamus. Sexual thoughts flicker in the background of a man's visual cortex all day and night, making him always at the ready for seizing sexual opportunity. Women don't always realize that the penis has a mind of its own -- for neurological reasons. And mating is as important to men as it is to women. Once a man's love and lust circuits are in sync, he falls just as head over heels in love as a woman -- perhaps even more so. When a baby is on the way, the male brain changes in specific and dramatic ways to form the daddy brain.

Men also have larger brain centers for muscular action and aggression. His brain circuits for mate protection and territorial defense are hormonally primed for action starting at puberty. Pecking order and hierarchy matter more deeply to men than most women realize. Men also have larger processors in the core of the most primitive area of the brain, which registers fear and triggers protective aggression -- the amygdala. This is why some men will fight to the death defending their loved ones. What's more, when faced with a loved one's emotional distress, his brain area for problem solving and fixing the situation will immediately spark.

I must have been dimly aware of this long catalog of distinctive male behaviors when I first found out, twenty-one years ago, that the baby I was carrying had a Y chromosome. I immediately thought, "Oh dear. What am I going to do with a boy?" Up until that moment, I realized, I had unconsciously been thinking "It's a girl!" and feeling confident that my own female life experiences could guide me in raising a daughter. I was right to be nervous. My lack of boy-smarts was about to matter more than I imagined. I now know from my 25 years of research and clinical work that both men and women have a deep misunderstanding of the biological and social instincts that drive the other sex. As women, we may love men, live with men and bear sons, but we have yet to understand men and boys. They are more than their gender and sexuality, and yet it is intrinsic to who they are. And it further complicates matters that neither women nor men have a good sense of what the others' brains or bodies are doing from one moment to the next. We are mostly oblivious to the underlying work performed by different genes, neurochemicals, and hormones.

Excerpted from The Male Brain by Louann Brizendine. Copyright 2010 by Broadway Books. Excerpted by permission of Broadway Books, an imprint of the Crown Publishing Group, a division of Random House Inc., New York.