Sunday, July 10, 2005

Male, female and Einstein's brains

This portrait of neuroscientist Sandra Witelson reveals some interesting details about gender differences in brain structure, and of Einstein's brain. Apparently Einstein's brain had no fissure separating the two parietal lobes.

"What is astonishing to me," Witelson said, "is that it is so obvious that there are sex differences in the brain and these are likely to be translated into some cognitive differences, because the brain helps us think and feel and move and act.

"Yet there is a large segment of the population that wants to pretend this is not true."

No one knows how these neural differences between the sexes translate into thought and behavior — whether they might influence the way men and women perceive reality, process information, form judgments and behave socially.

...As Witelson's research helped establish, however, the mental divide between the sexes is more complex and more rooted in the fundamental biology of the brain than many scientists once suspected.

In the last decade, studies of perception, cognition, memory and neural function have found apparent gender differences that often buck conventional prejudices.

Women's brains, for instance, seem to be faster and more efficient than men's.

All in all, men appear to have more gray matter, made up of active neurons, and women more of the white matter responsible for communication between different areas of the brain.

Overall, women's brains seem to be more complexly corrugated, suggesting that more complicated neural structures lie within, researchers at UCLA found in August.

Men and women appear to use different parts of the brain to encode memories, sense emotions, recognize faces, solve certain problems and make decisions. Indeed, when men and women of similar intelligence and aptitude perform equally well, their brains appear to go about it differently, as if nature had separate blueprints, researchers at UC Irvine reported this year.

"If you find that men and women have fundamentally different brain architectures while still accomplishing the same things," said neuroscientist Richard Haier, who conducted the study, "this challenges the assumption that all human brains are fundamentally the same."

[Einstein's brain:]

Witelson and her colleagues carefully compared the 40-year-old tissue samples with dozens of normal male and female brains in her collection. She also compared them with brains from eight elderly men to account for any changes due to Einstein's age at the time of his death.

She found that one portion of Einstein's brain perhaps related to mathematical reasoning — the inferior parietal region — was 15% wider than normal.

Witelson also found that it lacked a fissure that normally runs along the length of the brain. The average human brain has two distinct parietal lobe compartments; Einstein's had one.

Perhaps the synapses in this area were more densely interconnected.

"Maybe this was one of the underlying factors in his brilliance," she said. "Maybe that is how it works."

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