When Brenda Milner began working at McGill University's Montreal Neurological Institute in 1950, her doctoral supervisor advised her to "make herself useful" in assessing neurosurgical patients under the care of the legendary Wilder Penfield and his colleagues. Her response led to the creation of an entire new field of research – a combination of psychology and neurology that was later christened cognitive neuroscience. In the years that followed, she helped it bloom into an invaluable tool for learning about the human brain.
She remains a pre-eminent figure in her field, and her achievements have made her one of the finalists for the Gerhard Herzberg Canada Gold Medal for Science and Engineering.
Much of Dr. Milner's internationally renowned work has focused on memory, specifically in patients who have brain damage or who have undergone surgery for epilepsy or other conditions.
Some of her most dramatic discoveries came through her work with a patient known as HM, who had unexpectedly lost his ability to transform new experiences into long-term memory following an operation that removed a large part of the hippocampal region in both hemispheres of his brain in order to stop his epileptic seizures. To the surprise of many, rigorous experiments designed by Dr. Milner revealed that HM remained capable of certain kinds of learning. In one famous example, she showed that he could learn and retain certain motor skills without keeping any memory of having done so. "This was the most important and exciting thing I discovered," she says.
By studying HM and other patients, she demonstrated that people have multiple memory systems that govern different activities. Before the advent of today's imaging technology, she developed a battery of cognitive tests that led to dramatic new conclusions about how the brain works, particularly regions known as the medial temporal lobe and the frontal lobe.
"Everything was detective work initially, because you could not look into the brain at all," she says. "Every clinical clue, every behavioural clue, everything they could do on tests was giving us clues as to where the epilepsy focus might be."
Her research has had a profound impact on the pre-surgical evaluation of patients and on surgical techniques by creating a better road map of the brain. For example, difficulty with verbal memory suggests that the problem lies in the left temporal lobe, in the dominant hemisphere for speech, while difficulty solving problems points to the frontal lobe. This type of information helps guide neurosurgeons in their quest to fix problems without inadvertently causing patients to lose function in other areas.
Individual differences between people still have to be taken into account in determining the precise location of a problem. "These are never 100 per cent valid for everybody, but they are statistically quite powerful," she says. "If you can have these very solid results acquired over the years, they are very helpful indicators."
Some of Dr. Milner's early conclusions were not immediately accepted, since the prevailing understanding of the brain during the 1950s held that loss of function was more related to the amount of damage in a brain than the location, and that a loss of memory should be accompanied by a loss of intellectual function.
She stuck to her guns, though, and prevailed. "I've always had confidence in my data and in the observations I make," she explains. "I don't always understand why we're getting these effects, but I never question the observations I make."
Technological advances such as magnetic resonance imaging and positron emission tomography transformed her field. In combination with cognitive testing, they have vastly increased the precision with which the brain can be imaged and different functions understood.
Dr. Milner is still working to improve our understanding of the critical role played by the hippocampus in memory, currently focusing her attention on the right hemisphere of the brain and on object-location memory. That is a specific type of memory that we share with animals who might need to remember where they stored food or which place to avoid because of danger. For humans, it may be more helpful in answering the age-old question of where you left the car keys. One aspect that fascinates her is the fact that the brain automatically stores location information, unlike other kinds of memory that call for repetition or concentrated study to retain the information.
Throughout her career, Dr. Milner has drawn motivation from her strong curiosity and her love of the university environment. As for what the future of brain research holds, she avoids speculating too much about specific discoveries. "We've had so many surprises over the last 50 years. I could not have envisaged that it would develop with such breadth and so quickly. I'm not given to pipe dreams, but I'm sure there will be some very exciting things discovered."