Neuroscience, biological basis for cognition in male and femal brains
"We held Einstein's brain in our hands and realized that this is the organ that was responsible for changing our perceptions of the universe, and we were in awe."
In June 1999 Witelson attracted global attention when she published "The exceptional brain of Albert Einstein" in the British medical journal Lancet. The article discussed what Witelson and her co-researchers -- research associate Debra Kigar and Thomas Harvey, a retired pathologist from New Jersey and keeper of Einstein's brain -- found when they compared anatomical measurements of the late physicist's brain with the brains of 35 men and 56 women who had normal intelligence. (The brain was removed and preserved upon Einstein's death in 1955 at age 76.) Harvey had contacted Witelson because she possesses one of the best brain banks in the world today.
Witelson's brain collection at McMaster now contains over a hundred brains. While the other dozen or so brain banks in the world are composed mostly of brains from people who died of various neuropsychiatric diseases like Huntington's or Parkinson's disease, Witelson's is unique in that her cases are from cognitively normal people who agreed to donate their brains and take neuropsychological tests before they died from metastatic cancer. The brain collection is a resource to neuroscientists worldwide and tissue has been given to dozens of researchers to date.
Einstein's brain was found to be similar to the other brains except for the inferior parietal region. Due to extensive development of this region on both sides of the brain, Einstein's brain was 15 per cent wider than the other brains studied. According to Witelson, visuospatial cognition, mathematical thought, and imagery of movement are strongly dependent on this region.
Witelson's research also looks at individual differences in the structure of brain regions that are involved in language and spatial cognition. Her techniques include postmortem anatomy, microscopic neuroanatomy, immunocytochemistry and in vivo MR imaging. She’s also interested in development neurobiology of dyslexia and sexual differentiation of the human brain in relation to behaviour and left-right hemisphere lateralization. She and her colleagues documented that left-right differences in anatomy of language regions exist at birth. Her work also revealed numerous differences in brain anatomy between men and women such as women having greater density of neurons (brain cells) than men in language cortex. Other work has revealed the neurobiological differences between heterosexual and homosexual people and the predominance of left-hand preference in homosexuality. Witelson’s work showed that 94% of the variation in size of the corpus callosum (the main interhemispheric pathway) is attributable to heredity. She’s also interested in the relationship between brain structure and cognitive ability, recently showing that brain size correlates strongly with intelligence test scores.
Image by: Freelance Illustration and Graphics
Source: Witelson personal webpage, McMaster Times, McMaster Courier. Photo, McMaster webpage.
Witelson was always interested in the biological sciences. Her father was a chartered accountant but he read hundreds of books in their home. He was an intellectual. As a girl Witelson used to pull books off the shelf that were about the human body. Right from the beginning she was interested in how the body was put together. In university at McGill she was going to be a mathematician because she was very good in high-school. But it became clear to her early on that while she was good at solving problems, she realized she could not compete with the other students who were more adept at mathematics. Then she found a more biological topic: psychology.
Sandra Witelson is trying to understand the neurobiological basis of variations in behaviour. How are hormones involved? What is it about the left hemisphere that makes it the language dominant centre in most people? What does the right hemisphere lack that prevents it from processing language? Witelson and other scientists have found brain differences in structure and organization of male and female brains and also between homosexual and heterosexual people. The type of brain differences that exist suggest they are likely due in part to genetic factors.
Can there be a genetic basis for variation in intellectual ability in humans? Will we be able to look at a child's genome and tell what their future aptitudes will be?
Most of Witelson's important scientific papers can be found and viewed at her personal webpage at the Community of Science.