Standing in her vaultlike walk-in refrigerator, Sandra F. Witelson pries open a white plastic tub that looks like an ice cream container. There, soaking in diluted formaldehyde, is a gleaming vanilla-colored brain: the curvy landscape of hills and valleys (the gyri and sulci) that channeled the thoughts of the late mathematician Donald Coxeter, known as the man who saved geometry from near extinction in the 20th century.
“His brain is amazingly plump,” Dr. Witelson says. She ought to know.
Here at McMaster University in Hamilton, Ontario, where she is a neuroscientist with the Michael G. DeGroote School of Medicine, Dr. Witelson has a collection of 125 brains. They are all from Canadians: business people, professionals, homemakers, and blue- and white-collar workers.
By weighing her specimens, calculating their volumes and measuring their proportions, Dr. Witelson (pronounced WIT-il-son) investigates the relationship between brain structure and cognition, a focus of her research for three decades.
When I saw Einstein’s brain, that was a pretty strong feeling. I realized this was the brain that had provided our current conception of the universe.
It was Dr. Witelson’s 1999 study of Albert Einstein’s brain that made headlines by revealing some remarkable features overlooked by other neuroscientists: the parietal lobe, the region responsible for visual thinking and spatial reasoning, was 15 percent larger than average, and it was structured as one distinct compartment, instead of the usual two compartments separated by the Sylvian fissure.
Dr. Witelson is continuing her analysis of Einstein’s brain, but with a histological study, probing features of the cellular geography in the parietal lobe, like the packing density of his neurons.
These specimens of Einstein’s brain came to Dr. Witelson via Thomas Harvey, the pathologist at the Princeton hospital where Einstein died in 1955. Shortly thereafter Dr. Harvey stole away with the great man’s gray matter (and lost his job as a result).
Now 94, Dr. Harvey has received requests for Einstein’s brain from many neuroscientists and turned most of them down. But hearing of Dr. Witelson’s extensive brain bank, he sent her a handwritten note by fax in 1995 asking simply, “Do you want to study the brain of Albert Einstein?”
She sent a fax back: “Yes.”
Receiving her Ph.D. in neuropsychology from McGill University, in her hometown of Montreal (followed by a postdoctoral fellowship at the New York University School of Medicine), Dr. Witelson began her brain bank early in her career after winning a contract from the National Institutes of Health in 1977. The goal was to study why language capacity is lateralized — that is, represented in the left hemisphere for 90 to 95 percent of people.
Dr. Witelson’s research team sought out donors with metastatic cancer in which the brain was unaffected — people who knew they faced death but were willing to undergo extensive testing while they were alive. So Dr. Witelson’s brain bank not only is the world’s largest collection of “cognitively normal” brains, but also includes a repository of personal data on each person.
Dr. Coxeter, the geometer, died in 2003 at 96. A brain that old is apt to have suffered considerable deterioration from loss of neural matter. But Dr. Coxeter, a lifelong vegetarian who rarely drank alcohol and did headstands every morning, remained intellectually active almost to the end of his life and had the brain of a much younger man. Like Einstein, he had a large parietal lobe.
Dr. Witelson is known not only for her brain bank. She has also been in the forefront of controversial studies on the biological basis of intelligence, sex differences in the brain and sexual orientation.
While her N.I.H. study has yet to yield many answers on why language is lateralized, she said something unexpected “fell out” of the research: marked differences between male and female brains.
In 1995, after a 10-year study, Dr. Witelson published findings showing that on average the packing density of neurons was 12 percent greater in the adult female brain than in the adult male brain in the language region of the temporal lobe. A subsequent study of the frontal lobes, soon to be published, revealed similar sex differences.
On first interpretation, she said, this might lead to the conclusion that a woman’s brain is more tightly packed with neurons simply to make up for the well-documented fact that the average female brain is 10 percent smaller than the male brain.
“But that’s not correct,” she said, “because only some of the cortical layers show the difference.”
Layers 2 and 4, those important in processing the input of information, exhibited the differences in neuron capacity.
“Knowing that,” Dr. Witelson said, “one can ask the question of whether the processing of speech sounds could be related to the anatomy, and in fact that’s what we’re doing now.”
Sex differences also turned up in a number of other studies.
In 2005 Dr. Witelson and her colleagues reported that verbal ability was correlated with brain volume, but more strongly in women than in men. And they announced findings indicating that extremely premature birth affects the brain development of boys more adversely than girls.
Though she says the differences among female and male brains should not be discussed in terms of “better” and “worse,” they cannot be denied.
I have a bias towards brains.
For that reason, her work was often cited by defenders of the former Harvard president Lawrence H. Summers after his suggestion that innate differences might help explain the gender gap on science faculties.
Interviewed on “The NewsHour With Jim Lehrer” on PBS in February 2005, Dr. Witelson said, “If we’re going to try to understand the disparity between the number of women and men in different professions, and this would go for positions way beyond just academia, we have to put all the factors on the table.”
In a recent interview, she said, “It’s clear societal influences are relevant, but that doesn’t preclude the possibility that there are also contributing factors from nature.”
Dr. Witelson does not have a female genius in her brain bank. She is considering broadening the demographic, seeking exceptional individuals regardless of age or sex in a wide spectrum of fields: language, music, chess, even professional sports.
She has not met many of the people whose brains she studies. (Dr. Coxeter was an exception.) But the fact that she is handling the essence of their individualism sometimes gives her pause.
“I have to admit,” she said, “when I saw Einstein’s brain, that was a pretty strong feeling. I realized this was the brain that had provided our current conception of the universe.
“I’m not a cardiologist or a nephrologist, so I don’t hold hearts or kidneys, but I don’t think I would get as touched by those organs. On the other hand. I have a bias towards brains.”