Saturday, January 1, 2011

Basic Male and Female brains differences

You've heard the saying more than once. "Men are from Mars, women are from Venus." It is actually a title of the book written by John Gray in 1992 offering many suggestions for improving men-women relationships in couples by understanding the communication style and emotional needs of the opposite gender. In contrast to some psychologists and feminists who emphasize similarities between the sexes, Gray writes almost exclusively about differences. While it is always been obvious that differences indeed exist between men and women, the theory that female and male brains differ, however, was not so clear. Now research is confirming that the brains of men and women are subtly different.

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 More than 99 percent of male and female genetic coding is exactly the same. Out of the thirty thousand genes in the human genome,  the  less  than  one  percent  variation  between  the  sexes  is small. But that seemingly non-essential percentage difference influences every single cell in our bodies—from the nerves that register pleasure and pain to the neurons that transmit perception, thoughts, feelings, and emotions. To the observing eye, the brains of females and males are not the same. Male brains are larger by about 9 percent, even after correcting for body size. In the nineteenth century, scientists took this to mean that women had less mental capacity than men. Women and men, however, have the same number of brain cells. The cells are just packed more densely in women—placed into a smaller skull.

For much of the twentieth century, most scientists assumed that women were essentially small men, neurologically and in every other sense except for their reproductive functions. That assumption has been at the heart of enduring misunderstandings about female psychology and physiology. When you look a little deeper into the brain differences, they reveal what makes woman a woman and man a man.

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Main basic differences in the brains of males and females

 (1)   Total brain size: In adults, the average brain weight in men is about 10-12% MORE than the average brain weight in women. Men's heads are also about 2% bigger than women's. . This is due to the larger physical stature of men. Male’s larger muscle mass and larger body size requires more neurons to control them. This does not suggest that due to the larger brain, males are smarter than females.

(2)   Cell number: men have 4% more brain cells than women, and about 100 grams more of brain tissue. this may explain why women are more prone to dementia (such as Alzheimer's disease) than  men, because although both may lose the same number of neurons due to the disease, "in males, the functional reserve may be greater as a larger number of nerve cells are present, which could prevent some of the functional losses."

(3)   Cellular connections: while men have more neurons in the cerebral cortex, women have a more developed neuropil, or the space between cell bodies, which contain synapses, dendrites and axons, and allows for communication among neurons.

(4)   Corpus callosum: it is reported that a woman's brain has a larger corpus collusum, which means women can transfer data between the right and left hemisphere faster than men. Men tend to be more left brained, while women have greater access to both sides.(however other studies have told a different story).

(5)   Hypothalamus: LeVay discovered that the volume of a specific nucleus in the hypothalamus (third cell group of the interstitial nuclei of the anterior hypothalamus) is twice as large in heterosexual men than in women and homosexual men, thus prompting a heated debate whether there is a biological basis for homosexuality .

(6)   Language: two areas in the frontal and temporal lobes related to language (the areas of Broca and Wernicke) were significantly larger in women, thus providing a biological reason for women's notorious superiority in language-associated thoughts. For men, language is most often just in the dominant hemisphere (usually the left side), but a larger number of women seem to be able to use both sides for language. This gives them a distinct advantage. If a woman has a stroke in the left front side of the brain, she may still retain some language from the right front side. Men who have the same left sided damage are less likely to recover as fully. Curiously, oriental people which use pictographic (or ideographic) written languages tend also to use both sides of the brain, regardless of gender.

(7)   Inferior parietal lobule (IPL): it is a brain region in the cortex, which is significantly larger in men than in women. This area is bilateral and is located just above the level of the ears (parietal cortex). Furthermore, the left side IPL is larger in men than the right side. In women, this asymmetry is reversed, although the difference between left and right sides is not so large as in men. This is the same area which was shown to be larger in the brain of Albert Einstein, as well as in other physicists and mathematicians. So, it seems that IPL's size correlates highly with mental mathematical abilities. Studies have linked the right IPL with the memory involved in understanding and manipulating spatial relationships and the ability to sense relationships between body parts. It is also related to the perception of our own affects or feelings. The left IPL is involved with perception of time and speed, and the ability of mentally rotate 3-D figures .

(8)    Orbitofrontal to amygdale ratio (OAR): In one project, they measured the size of the orbitofrontal cortex, a region involved in regulating emotions, and compared it with the size of the amygdala, implicated more in producing emotional reactions. The investigators found that women possess a significantly larger orbitofrontal-to-amygdala ratio (OAR) than men do. One can speculate from these findings that women might on average prove more capable of controlling their emotional reactions.

(9)   Limbic size: females, on average, have a larger deep limbic system than males. This gives females several advantages and disadvantages. Due to the larger deep limbic brain women are more in touch with their feelings, they are generally better able to express their feelings than men. They have an increased ability to bond and get connected to others. Females have a more acute sense of smell, which is likely to have developed from an evolutionary need for the mother to recognize her young. Having a larger deep limbic system leaves a female somewhat more susceptible to depression, especially at times of significant hormonal changes such as the onset of puberty, before menses, after the birth of a child and at menopause. Women attempt suicide three times more than men. Yet, men kill themselves three times more than women, in part, because they use more violent means of killing themselves (women tend to use overdoses with pills while men tend to either shoot or hang themselves) and men are generally less connected to others than are women. Disconnection from others increases the risk of completed suicides.


Sources and Additional Information:
The Female Brain by Louann Brizendine, 2006


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