دکتر سید عطاالله عقیلیان روانپزشک BRAIN SEX تفاوت ذهن زن و مرد دکتر سید عطاالله عقیلیان روانپزشک زمستان 1393

Sex determination Fertilization XX or XY 6th week Fetus masculine hormone Male external Genital Fetus with out masculine hormone Female external Genital

Sex differences start early Early research on sex differences in the brain began with animal studies of the hypothalamus, the brain area involved in feeding, stress, and mating behaviors. Just as early exposure to the sex hormone testosterone guides the “masculinization” of the body — including the development of the male reproductive tract and external genitals — scientists discovered it also influences the development of the brain and behavior

Sexuality of Brain Psychological sex differences are thought by some to reflect the interaction of genes, hormones and social learning on brain development throughout the lifespan.

Hemisphere differences Males have larger total brain volumes than females. A popular theory regarding language functions is that women use both hemispheres more equally, whereas men are more strongly lateralized to the left hemisphere. The study, which used fMRI, concluded that inter-hemispheric connectivity was much stronger in women's, whereas intra-hemispheric connectivity was much stronger in the brains of men.

Amygdala The amygdala plays a large role in emotional memory formation and storage (men have a larger amygdala than women Women retain emotional memories more vividly than do men. This can have a negative effect on women and they may have impaired memory at times due to strong emotional overlap. Another negative outcome of women forming strong emotional memories is an increased 'vulnerability to depression & PTSD". Males encode emotional memories using the right side of their amygdala while women use the left. A behavioral difference that has been linked to the amygdala's size is sexual drive. Men have a greater sex drive than women; this may be due to the fact that males have a larger amygdala

Hippocampus The hippocampi of men and women differ anatomically,neurochemically.Sex influence the role of the hippocampus in learning. Males’ performance under stress was enhanced while female performance was impaired. Activation of the hippocampus is more dominant on the left side of hippocampus in females, while it is more dominant on the right side in males. Women use more verbal strategies than men when performing a task that requires cognitive thinking. Oestradiol influence hippocampal development. Neurogenesis is higher in the male hippocampus than in that of the female.

Limbic brain The ventromedial prefrontal cortex (VPMC), plays a key role in social emotional processing, the right VPMC is more dominant in an active limbic system for males while the left is more dominant in females.

White/grey matter Women have larger left orbitofrontal GM volumes and overall cortical thickness than men. Women have a higher percentage of GM. In men the percentage of GM was higher in the left hemisphere, the percentage of WM was symmetric, and the percentage of CSF was higher in the right. Women showed no asymmetries. The regression of cognitive performance and WM volume was significantly steeper in women

Orbital prefrontal cortex PET studies have shown that men and women ranging from the ages of 19 to 32 years old metabolize glucose at significantly different rates in the orbital prefrontal cortex. MRI images display reduced hemispheric brain volumes, specifically in the frontal and temporal regions, in men more so than women.

Wiring Men's brains were shown to have stronger connections between the front and back regions of the brain, and were mostly confined to individual hemispheres, whereas women's brain had stronger connections between the left and right hemispheres. The obtained maps of neural circuitry were supportive of old stereotypes according to which men's brains are more suited for perception and coordination, and women's brains are more suited for social skills and multitasking. The detected differences in neural connectivity were negligible up to the age of 13, but became much more prominent in the 14-17 year-olds.

Brain differences between homo- & heterosexuals Gay men and straight women have similar brain characteristics. Specifically, these similarities are in the overall size of the brain and the activity of the amygdala. The same is for heterosexual men and lesbian women Right hemisphere is slightly larger than the left in heterosexual males and lesbians, whereas those of gay men and straight women were more symmetrical Corpus callosum is larger in gay men than in heterosexual men 3rd interstitial nucleus of the hypothalamus has neurons that are packed more together in homosexual men than in heterosexual men.

Estrogen and the female brain Estradiol influences cognitive function, specifically by enhancing learning and memory in a dose-sensitive manner. Too much estrogen can have negative effects by weakening performance of learned tasks as well as hindering performance of memory tasks; this can result in females exhibiting poorer performance of such tasks when compared to males.

Testosterone and the male brain Testosterone has been found to play a big role during development but may have independent effects on sexually dimorphic brain regions in adulthood. Testosterone's influence on the brain is caused by organizational developmental effects. It has been shown that they increase neuronal cell death in certain brain regions. Another way testosterone affects brain development is by aiding in the construction of the "limbic hypothalamic neural networks" Similar to how estrogen enhances memory and learning in women, testosterone has been found to enhance memory recall in men. fMRI analysis revealed that higher testosterone levels were related to increased brain activation in the amygdala during encoding of neutral pictures

Cognitive tasks 3 and 4-year-old boys were better at targeting and at mentally rotating figures than girls of the same age were. Prepubescent girls, however, excelled at recalling lists of words Men excel over women at certain spatial task,, imagine rotating or manipulating an object mathematical reasoning as well as navigation, computer simulation of a maze task. Women excel over men on test that measure recollection ,figuring out words that begin with a specific letter or meet some other criteria. better at matching items and precision task. In maze or path completion task, men learn the goal route in fewer trials than women, but women remember more of the landmarks presented. This shows that women use landmarks in everyday situations to orient themselves more than men. Women are better at remembering whether objects had switched places or not. Men and women differ in their decision making processes on the neurological level. decision-making in females may be guided by avoidance of negativity while decision making in males is mainly guided by assessing the long term outcome of a situation.

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