Sex of the brain

Neuroscientists show the anatomical, chemical and functional differences of the brain between men and women. These changes occur throughout the brain, in areas related to language, memory, emotions, vision, hearing .

(Photo: lowculture)

Researchers are looking at how these gender-related changes are related to differences in perceptions and behavior of men and women. Their findings could point to specific treatments for men and women with diseases such as schizophrenia, depression, addiction and post-traumatic stress disorder.

In January 2005, Lawrence Summers - Harvard University Principal, made comments about the innate differences in the structure of male and female brains that could be a relatively rare female-related factor in science. . His remarks imply a latent controversy for a century, when some scientists estimate women's brains tend to be smaller, to defend the notion that women are mentally inferior to men. . However, no one has ever presented anatomical evidence or differences that may make it impossible for women to achieve mathematical, physical or technical defects. Men and women 's brains have been found to be similar in many ways. Over the past decade, researchers have documented the strange expression of structural, chemical and functional changes in male and female brains.

Differences in brain structure by gender show that the ability to treat diseases specifically for men and women . In addition, they also noted that researchers investigating the structure and function of the brain must consider the gender of the subject in data analysis, including men and women in future studies or risks. when false results are obtained.

Not long ago, neuroscientists believed that gender differences in the brain were limited primarily in areas responsible for mating behavior. In an article published in Scientific American 1966 entitled "Sexual Differences in Brain ," Seymour Levine of Stanford University described sex hormones that control different reproductive behavior in mice. In the article, Levine describes only one area of ​​the brain that is the hypothalamus, a small base in the brain bottom that regulates hormonal production and controls basic behaviors such as eating and sex. A generation of neuroscientists believes that 'brain differences' are mainly related to mating behavior, sex hormones and hill formations.

That view raises findings that undermine the influence of gender on many cognitive and behavioral areas, including memory, emotions, vision, hearing, facial expressions and brain responses. stress hormones. This progress has increased rapidly over the past 5-10 years due to sophisticated techniques, non-intrusive displays such as positron emitter display (PET) and functional magnetic resonance display (fMRI), which can be viewed closely in the brain. of living objects. These photo-making experiments show anatomical changes in many areas of the brain.

(Stunning-stuff) Jill M. Goldstein at Harvard Medical School and colleagues used MRI to measure the size of many areas of the cortex and under the cortex. They found parts of the forehead - where there are many cognitive functions, in females larger than males (associated with emotional reactions). In contrast, in the male part of the crust, associated with spatial perception, larger than female, such as almonds (amygdala) - the structure is a nut-shaped, reacting to emotional information via rhythm. heart and adrenalin flow. These size differences are relative and are thought to reflect relative importance in animals. For example, sight-based monkeys are more than olfactory, and vice versa. As a result, monkey brains hold areas with greater proportions for sight, and mice spend more space on the sense of smell. Thus, the existence of multiple anatomical differences between men and women suggests that gender affects how the brain works.

Other studies are investigating gender-based anatomical differences. Sandra Witelson and colleagues at McMaster University found that in women there is a greater density of neurons (neurons) in parts of the temporal lobe, associated with language and cognitive processing. When counting neurons in samples of people after death, they found that in 6 layers in the shell, two classes of females had more neurons according to unit weight than men. With such information, can neuroscientists now find out whether gender differences in neurons are correlated with different cognitive abilities? Does the increase in density in the female auditory cortex be associated with an increase in their performance against fluent speech tests?

That anatomical diversity is most likely due to the activity of the fetal brain wetting hormones . These steroids guide the organization and brain binding during development, affecting the structure and neuron density of many regions. Interestingly, the brain regions that Goldstein found differing between men and women were also areas in animals that contained the most sex hormones during development. The correlation between adult brain size and the effect of gut steroids at least suggests some sex differences in cognitive function not due to cultural influence or hormonal changes associated with puberty, which is innate.

Natural tendency

Some interesting behavioral studies provide more evidence of brain gender differences before the baby cries out. For many years, many researchers have demonstrated that when choosing toys, boys and girls also choose different. Boys like to choose a ball or a car, and girls like dolls better. But no one really thinks that these hobbies are caused by wrong culture or innate brain biology.

To solve this problem, Melissa Hines at London University and Gerianne M. Alexander at Texas A&M University studied monkey. They let a group of long-tailed monkeys choose toys, including rags, rickshaws and some sexually neutral items like books and pictures. They found that male monkeys spend more time playing with 'masculine' toys than female monkeys, while females spend more time playing with toys that girls still like. Both genders spend the same time on gender-neutral books, pictures and other toys.

Because long-tailed monkeys are probably not influenced by social pressures of human culture, the results imply toy preferences in children at least partly due to innate biological differences. This difference, and indeed, the entire anatomical sex difference in the brain, may be due to selective pressure during evolution.

When stressed .

In many cases, gender differences in chemistry and brain structure affect how men and women react to the environment or with stressful events and recall them. Return to the example of almonds. Goldstein and other authors say almonds in men are larger than women. In male mice, neurons in this brain region are more interconnected than female mice. These anatomical changes can create different responses to the stresses of men and women, male and female objects.

To assess how almonds of male and female almonds actually react differently to stress, Katharina Braun and colleagues at Otto von Guericke University, Magdeburg (Germany) have withdrawn. Quickly drive the baby out of their mother. They then measured levels of serotonin receptors in many brain regions (serotonin is a neurotransmitter or molecule that carries signals, primarily mediating emotional behavior). Researchers let their children hear their mother's voice while being isolated and found that the concentration of serotonin receptors increased in the male almonds, but decreased in females. Although it is difficult to deduce from this study to human behavior, the results still suggest that if the same thing happens in children, the separation anxiety may affect different emotional interests in the children. man and woman. These types of experiments are necessary, for example, if we want to understand why anxiety disorders are much more common in girls than boys.

Another brain region has anatomical differences according to gender and in its response to stress that seahorses - an important structure for storing memory and mapping physical space. Appropriate display shows that seahorses in females are larger than males. This anatomical difference may be more or less related to how men and women differ. Many studies suggest that men probably follow the way of estimating spatial and orientation, while women rely on landmark tests. Interestingly, similar sex differences are also seen in mice. Male mice in the maze tend to rely more on directional and location information, while female rats in the same maze rely on available landmarks. Even neurons in male mouse seahorses also exhibit different female mice.

Sometimes male rats get better at stress.

Professor Tracey J. Shors
(Photo: rci.rutgers.edu)

Tracey J. Shors of Rutgers University and colleagues found that when mass collisions in the tail of a rat for about a second increased academic achievement and density of binding neuronal fibers to other neurons in male rats but reduces the link performance and density in female mice. These findings have remarkable social significance. When we discover how the learning mechanism of the brain is between two genders, perhaps we need to consider how different learning environments should be different for boys and girls.

Although seahorses in female rats show poor response to acute stress, it appears to be more resilient than male mice before long-term stress. Researchers at the University of Arizona locked the mice in a 6-hour mesh cage. They then evaluated how damaged seahorses neurons when killed with a neurotoxin - a standard measure of the effects of stress on these cells . They found that long-term confinement caused seahorse cells in male mice to be more susceptible to toxins but had no effect on female mice. These findings suggest that, for brain damage, female mice are probably better equipped to tolerate longer-term stress than male mice. It is still unclear what makes seahorses cells in female mice unaffected by long-term stress, but are likely to play the role of sex hormones.

When expanding the work to see how the brain processes and remembers stressful events, Larry Cahill (author of the article) and colleagues saw the contrast in memory in men and women about the impact emotions (is the process in research in animals known to be related to almonds). In an experiment in humans, they allowed volunteers to watch a series of violent films, while measuring the brain activity of subjects with PET. A few weeks later, when they checked again, they found that the number of movies that the subjects could recall correlated with the positive performance of almonds while watching the movie. Later experiments also confirm this general finding. But in some studies, almond activation is only associated with the right hemisphere of men and in other studies only shown in the female left hemisphere.

To confirm this, the authors used propanolol, a beta inhibitor for the activity of adrenalin and noradrenalin, thereby inhibiting almond activation and reducing the recall of emotional stimulating memory. Participants were shown a brief picture of a teen who had an accident and walked while walking with his mother. The memory of the test subjects was tested a week later. As a result, propanolol makes it more difficult for men to recall more comprehensive aspects (ie the main one), while women fall back into secondary details. Along with similar studies, it is thought that in some concentrated health care units, beta inhibitors reduce memory of traumatic events in women, not in men, so Physicians may need to consider the gender of the patient when giving the medicine.

Sex and psychological disorders

Not only is propanolol, it has been shown that average serotonin production is 52% higher than in men and women, which can make it clear why women are more susceptible to depression - a disorder commonly used to make drugs. increase serotonin levels.

The same situation is common in addiction. In this case, the relevant neurotransmitter is dopamine - a sensory-related chemical associated with drug abuse. A team at the University of Michigan, found that in female mice, estrogen increased dopamine release in brain regions, which is important for regulating drug behavior. Furthermore, this hormone has a long-lasting effect, causing female mice to tend to pursue cocaine weekly after the last week of receiving the drug. Sensitivity differences, especially for stimulants such as cocaine and amphetamine, may explain why women are more vulnerable to the effects of those drugs and why they progress faster. from the first time to the time when it depends on the male.

Some brain defects manifested in schizophrenia also differ between men and women . Researchers at the University of Pennsylvania found that the ratio of eyed forehead / almonds to females was larger than that of males. These findings lead people to deduce that, in general, women can control emotional reactions more than men. Schizophrenia is a slightly different disease between men and women, and the treatment of this disease should take into account the gender of the patient.

In a comprehensive report in 2001 on gender differences in human health, the National Academy of Sciences confirmed that: 'Gender, meaning male or female, is a key underlying variable. The importance of people to consider when designing and analyzing research projects in all fields and at all levels of research is related to biomedical and health '.

Although there are still many issues to consider, studies have shown that differences have widened, beyond the structure of the hill and mating behavior. Researchers and doctors are still unclear about the best way to interpret the full gender influence of the brain, behavior and response to drugs.

The author is Nguyen Ngoc Hai - Post in the Journal of Scientific Activities, No. 03, 2006