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Secrets of His and Her Brains
Posted: Thu Jun 16, 2005
Post subject: Canada: His and Her Brains - Sandra Witelson
... [The Los Angeles Times - Jun 16/05]
MAPPING THE MIND
Deep, Dark Secrets of His and Her Brains *
Sandra Witelson had studied
scores of brains looking for gender differences. Then she found one that made a
Lee Hotz - Times Staff Writer
The invitation curled from her fax machine,
a courtly question scrawled above the signature of a man whose name she did not
"Would you be willing to collaborate with me on studying the brain of Albert
It was signed Thomas Harvey. Sandra Witelson did not hesitate. She wrote "yes"
on the piece of paper and faxed it back.
"It never occurred to me that it might be a joke," she recalled. "I knew that
Albert Einstein's brain had been preserved and that it was somewhere where
someone was looking after it."
For 40 years, Harvey, a retired pathologist from Princeton, N.J., had been the
quixotic custodian of the 20th century's most famous brain.
In 1955, he had conducted a routine autopsy of Einstein after the 76-year-old
physicist died at Princeton Hospital. The remains were to be cremated. Harvey,
however, decided to preserve the organ responsible for the theory of relativity
and the principle of the atomic bomb.
It was not such an unusual thing to do. Einstein's ophthalmologist had removed
the scientist's eyeballs and put them in a safe-deposit box. Earlier acquisitive
anatomists had preserved Galileo's finger, Haydn's head and Napoleon's penis.
For Harvey, however, more than morbid curiosity was at work. He believed that
the slippery worms of Einstein's brain tissue, pickled in warm formalin,
embodied some clue to the mystery of intelligence. He held on to that hope
through 40 years of indecision.
Eventually, it led the soft-spoken Quaker to Witelson, a raven-haired Canadian
psychologist with a taste for black leather and red showgirl nails.
She had brains, dozens of them ‹ the largest collection of normal brains in the
When Witelson began acquiring human brains, sex was the last thing on her mind.
Inside her walk-in refrigerator at McMaster University here in Ontario, her
collection filled three walls of metal shelves. The 125 putty-colored specimens
sat in frosted jars and snap-top plastic tubs like quarts of boiled shrimp and
wedges of cheese.
Every one posed a riddle that had shaped her research for 30 years: How does the
structure of the brain influence intelligence?
A professor of psychiatry and neuroscience, Witelson grappled with such a
fundamental mystery by studying a somewhat smaller one: why certain abilities
develop on one side of the brain rather than the other.
The two hemispheres of the brain are almost symmetrical physically but can seem
to be separate minds when it comes to awareness and mental processing. They even
have different problem-solving styles, researchers report. Yet they work
together seamlessly to produce a single mind.
By 1977, Witelson was trying to learn why language skills developed on the left
side of the brain for all right-handers but on the right side for many
To compare the two sides, she needed normal brains ‹ more than anyone had
For 10 years, she worked through a network of doctors and nurses, hoping to
persuade terminal cancer patients to make a last contribution to medicine. Her
research was funded by the U.S. National Institutes of Health.
By 1987, 120 men and women had agreed to donate their brains after death. They
all submitted to thorough psychological and intelligence tests so that each
brain would be accompanied by a detailed profile of the mind that had animated
In the prime of life, the cerebral cortex contains 25 billion neurons linked
through 164 trillion synapses.
Thoughts thread through 7.4 million miles of dendrite fibers and 62,000 miles of
axons so compacted that the entire neural network is no larger than a coconut.
No two brains are identical, nor are two minds ever the same.
With so many well-documented donors, however, Witelson could conduct comparative
brain studies on an unprecedented scale.
She could confidently seek relationships between anatomical features and mental
capacities. She could also compare right-handers and left-handers, and sort the
organs by gender.
In an era when people probe the thought process with scanners, radioactive
tracers and super-conducting sensors, Witelson's approach was deliberately
She measured her brains.
She weighed them.
She cut them up and counted the cells.
She traced synapses, the junctures where impulses pass from one neuron to
another in the hidden root cellars of the brain.
Wherever she looked, she discerned subtle patterns that only gender seemed to
"We actually didn't set out to find sex differences," she said. "Sometimes as a
scientist, you are doing one thing and you bump into something else."
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
"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
"Yet there is a large segment of the population that wants to pretend this is
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
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
No one, however, had scrutinized as many brains as Witelson.
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
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
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
An Odd Pursuit
By taking Einstein's brain, Thomas Harvey had succumbed to an impulse older than
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
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
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,
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
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 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 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
"We said, 'Let the child's behavior tell us what sex the child is.' " Given
time, she believed, the brain would reveal itself.
- Related Stories:
Searching for the Why of Buy February 27, 2005
Anatomy of Give and Take March 18, 2005
How gender shapes brain function June 16, 2005
"It is so obvious that there are sex differences in the brain ... Yet
there is a large segment of the population that wants to pretend this is not
- Dr. Sandra Witelson, psychologist and brain collector
Copyright 2005 Los Angeles Times