Science Proves Men And Women Have Different Brains

Just found this little biddy off the newswires.  Turns out that a recent study has proven that men and women have different types of brains, which could explain the differences in how the two sexes feel, move, and act.  I’ve reposted most of the article here for your reading convenience.

Controversial Matters

The brains in Witelson’s freezer are contested terrain in a controversy
over gender equality and mental performance.

Her findings — published in Science, the

New
England Journal of Medicine, the Lancet and other peer-reviewed
journals — buttress the proposition that basic mental differences between men
and women stem in part from physical differences in the brain.

Witelson is convinced that gender shapes the anatomy of male and female
brains in separate but equal ways beginning at birth.

On average, she said, the brains of women and men are neither better nor
worse, but they are measurably different.

Men’s brains, for instance, are typically bigger — but on the whole, no
smarter.

"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.

But even at this relatively early stage in exploration of the brain’s
microanatomy, battle lines between scientists, equal rights activists and
educators have formed.

Some activists fear that research like Witelson’s could be used to justify
discrimination based on gender differences, just as ill-conceived notions of
human genetics once influenced laws codifying racial stereotypes about blacks,
Asians and Jews.

Other experts argue that the physical differences Witelson observed may
result not from the brain’s basic design but from conditioning that begins in
infancy, when the brain produces neurons at a rate of half a million a minute
and reaches out to make connections 2 million times a second.

Spurred by learning, neurons and synapses are ruthlessly pruned, a process
that continues in fits and starts throughout adolescence, then picks up again in
middle age.

"The brain is being sculpted gradually through sets of interactions," said
Anne Fausto-Sterling, a gender studies expert at Brown University. "Even when
something in the brain appears biological, it may have come to be that way
because of how the body has experienced the world."

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."

Yet, for the most part, scientists have been unable to document such patterns
conclusively.

No one, however, had scrutinized as many brains as Witelson.

Detailing Differences

She began by studying the corpus callosum, the cable of nerves that
channels all communication and cooperation between the brain’s two hemispheres.

Examining tissue samples through a microscope, she discovered that the more
left-handed a person was, the bigger the corpus callosum.

To her surprise, however, she found that this held true only for men. Among
women there was no difference between right-handers and left-handers.

"Once you find this one difference," she remembered thinking, "it implies
that there will be a cascade of differences."

As she systematically analyzed the brains in her refrigerator, she discovered
that other neural structures seemed larger or smaller among men, depending on
whether the man had been right-handed or left-handed.

They were relatively the same size in women. "The relationships that we were
finding were always — and I do mean always — different for men and women," she
said.

She narrowed her study to right-handed men and women, still looking for
differences in microscopic anatomy between the left side of the brain and the
right side. She meticulously counted the neurons in sets of tissue in which each
sample measured 280 microns wide — about twice the thickness of a human hair —
and 3 millimeters deep.

Staring through the microscope, she was baffled.

"I had the first two patients, and they were so very different," Witelson
said. "I kept looking and looking at them, trying to see what the difference
could be."

Then she consulted the donor documentation for each tissue sample. "Finally,
I saw that one was a man, and one was a woman."

Among women, the neurons in the cortex were closer together. There were as
many as 12% more neurons in the female brain.

That might explain how women could demonstrate the same levels of
intelligence as men despite the difference in brain size.

"So among female brains, the cortex is constructed differently, with neurons
packed more closely together," she said.

Witelson probed deeper. She knew that the human cortex was a sandwich of six
layers, each packed with neurons.

She peeled away the sheets of the temporal lobe — a region associated with
perception and memory — in several of her brain specimens. She discovered that
the increased neural density occurred only on layers 2 and 4, which form the
hard wiring for signals coming into the brain.

Then she analyzed the microscopic structure of the prefrontal cortex. There
the crowding of neurons was evident only in layers 3, 5 and 6, which carry the
wiring for outbound signals.

Just to be sure, she checked left-handed brains as well as right-handed
brains. She found the same sex differences when she surveyed her left-handed
brains.

Perhaps, she speculated, these neuron-rich layers in an area associated with
perception and speech were the reason women scored more highly than men on tasks
involving language and communication.

Slowly, she formed a theory: The brains of men and women are indeed different
from birth. Yet the differences are subtle. They might be found only among the
synapses in brain structures responsible for specific cognitive abilities.

For so long, scientists had championed the idea of larger brains as an
indicator of intellect. Witelson, however, gradually became convinced that
overall brain size didn’t matter.

"One of the things that firmed it up for me," she recalled, "was the case of
Einstein."

An Odd Pursuit

By taking Einstein’s brain, Thomas Harvey had succumbed to an impulse
older than medicine.

Since the days of Hippocrates, philosophers and scholars have been arguing
over how the brain houses an intangible human spirit. St. Augustine was
convinced that the soul lodged in the fluid-filled cavity of the organ’s middle
ventricle. Galen, the ancient pioneer of medicine, argued that vital spirits
resided in the fourth ventricle.

When modern scientists discovered that intellect could be traced to neural
tissues, brains became precious curios. Pathologists collected the brains of
gifted musicians, scientists and other notables the way 18th century literary
enthusiasts held onto the hearts of poets such as Percy Bysshe Shelley and Lord
Byron.

Researchers at the Moscow Brain Institute measured dozens of the most
brilliant brains. Vladimir Lenin, the leader of Russia’s Soviet revolution, had
a brain weighing about 3 pounds, they determined. The brain of writer Ivan
Turgenev weighed 4.4 pounds. That of satirist Anatole France was 2.1 pounds.

At Princeton Hospital, Harvey weighed Einstein’s brain on a grocer’s scale.
It was 2.7 pounds — less than the average adult male brain.

He had the fragile organ infused with fixative and dissected it into 240
pieces, each containing about two teaspoons of cerebral tissue. He shaved off
1,000 hair-thin slivers to be mounted on microscope slides for study.

For years, Harvey agonized over how next to proceed. His odd pursuit inspired
two books: "Possessing Genius" by Carolyn Abraham and "Driving Mr. Albert" by
Michael Paterniti. Through the decades, however, he drifted in obscurity.

Finally in 1985, pioneering neuroanatomist Marion Diamond at UC Berkeley
persuaded him to part with four small plugs of brain tissue. Diamond discovered
that the physicist’s brain had more cells servicing, supporting and nurturing
each neuron than did 11 other brains she studied. These unusual cells were in a
region associated with mathematical and language skills.

When they published their findings, the researchers speculated that these
neurons might help explain Einstein’s "unusual conceptual powers."

Critics contended the study was riddled with flaws, its findings meaningless.

Eventually, Harvey mailed bits of Einstein’s motor cortex to a researcher at
the University of Alabama, who reported that the cortex appeared to be thinner
than normal but with more tightly packed neurons.

Had it simply been compacted by time and storage conditions?

DNA testing revealed nothing. The preservative fluids apparently had
scrambled Einstein’s genetic code.

Then in 1995, Harvey happened across Witelson’s work. He read her research
paper on gender differences and neuron density in the Journal of Neuroscience.

"It was impressive," he recalled. He was even more intrigued to learn about
her collection of brains. He was 84, still hoping that his tissue samples had
something to teach about the neural geography of genius. To make ends meet, he
was working in a plastics factory. Worrying about Einstein’s brain, like the
years, had become a burden.

Harvey carefully packed it in the back of his battered Dodge and drove north
to Witelson’s laboratory. "I had the brain in a big jar," Harvey, now 94,
recalled.

At midnight, he crossed over the Rainbow Bridge by Niagara Falls into Canada.

Customs officials asked if he had anything to declare. Just a brain in the
trunk, he told them.

They waved him through.

Pieces Fall Into Place

Witelson could barely contain her curiosity.

Einstein’s brain — so far from ordinary in its intellectual achievement —
might reveal a telltale anatomical signature. Size alone certainly could not
account for his brain power.

"Here was somebody who was clearly very clever; yet his overall brain size
was average," Witelson said. "It certainly tells you that, in a man, sheer
overall brain size can’t be a crucial factor in brilliance."

For a moment, she was like a schoolchild picking candies from a

Valentine’s
Day sampler. She judiciously selected 14 pieces of Einstein’s brain.
She took parts of his right and left temporal lobes, and the right and left
parietal lobes.

Never had Harvey given away so much 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."

She took it as confirmation of her suspicions about the anatomy of
intelligence. If there were differences affecting normal mental ability, they
would show up in the arrangements of synapses at particular points in the brain.

Einstein, she was convinced, had been born with a one-in-a-billion brain.

"We suggest that the differences we see are present at birth," Witelson said.
"It is not a consequence of environmental differences."

She turned again to the brains in her refrigerator. Wherever she looked, she
began to see evidence of how microanatomy might underlie variations in mental
abilities.

As she matched the brain specimens to the intellectual qualities of their
owners, she discovered that differences in the size of the corpus callosum were
linked to IQ scores for verbal ability, but only in women. She found that memory
was linked to how tightly neurons were packed, but only in men.

Witelson determined that brain volume decreased with age among men, but
hardly at all among women. Moreover, those anatomical changes appeared to be
closely tied to a gradual decline in mental performance in men. "There is
something going on in the male brain," she said, "that is not going on in the
female brain."

Brain Conquers All

Last year, a worried farming couple brought their youngest child to
McMaster University Medical Center.

They were no longer certain whether their child was a girl or a boy. The
youngster had traits of both, as occurs in about one in 5,000 births. In this
child, nature had devised a living test of gender and the brain.

The medical experts determined that the child’s body was a composite of
normal and abnormal cells. Some had a girl’s usual complement of two female sex
chromosomes. Many, perhaps due to a mutation, had only one female chromosome and
consequently were almost male.

"Which cells got to the brain?" wondered Witelson, who was called in as a
consultant. "You have to consider the sex of the brain."

The doctors all suspected the child’s brain was masculine. There was no way
to know for sure. They could not safely take a sample of neural tissue to
biopsy.

Until recently, reconstructive surgery based on a doctor’s best guess was the
rule in such cases. But in Hamilton, they counseled patience, Witelson recalled.

"We said, ‘Let the child’s behavior tell us what sex the child is.’ "

Given time, she believed, the brain would reveal itself.