July 1, 1999 Scientists in Toronto have captured images of the brain in action as it's learning -- an exciting finding that could help in the diagnosis and treatment of brain injuries.
Remember the comic strip analogy of a lightbulb coming on in the brain to depict a person who learns and becomes aware of something? It's really a "pattern of lightbulbs" according to a study conducted by the Rotman Research Institute at Baycrest Centre for Geriatric Care.
The study, published in the May 28th issue of the international journal SCIENCE has generated quite a buzz among neuroscientists and is being billed as a significant contribution to understanding how the brain works when conscious learning is taking place.
Scientists already know that 'learning' and 'awareness' is a function of the prefrontal cortex of the brain, part of the higher thinking region. Now the Rotman study has confirmed that it's actually several regions acting in concert.
"We found that learning and awareness involves a cohesive network of brain activity," says Rotman scientist Dr. Randy McIntosh, who led the study using brain imaging technology along with co-investigators Drs. Natasha Rajah and Nancy Lobaugh.
"It's like a pattern of lightbulbs coming on. Most of the action is happening in the left prefrontal cortex, but we confirmed that areas far away from the frontal regions are activated as well. They include the sensory regions that provide the visual and auditory information needed to do the task."
In the study, 12 university students participated in an associative learning exercise on a computer. They would hear two different tones and only six in the group became 'aware' that one of the two tones always predicted a visual event on the computer screen.
During the exercise, regional cerebral blood flow (which signifies brain activity) was measured in both the aware and unaware groups using a brain imaging technique called positron emission tomography (PET).
In students who figured out or became aware that a specific tone predicted a visual event, the PET scans revealed activity changes in the prefrontal cortex and increased interaction with sensory areas -- indicating a network of brain activation. As they learned, these students started to perform the task faster. In the unaware group, there was no change in blood flow activity in the prefrontal cortex or indication of a larger system of activity, and also no improvement in their reaction times.
"This study actually catches the brain in the act of becoming aware and learning," says Dr. Sandra Black, Head of Neurology and Senior Scientist in the Aging Research Program at Sunnybrook and Women's College Health Sciences Centre.
"For those people who saw the light, that is who figured out that there was an association between the tone and visual image, you could see their brain activity changing. It's not just one brain centre where the lightbulb is coming on, but different regions turning on like a symphony of fireworks."
The Rotman study could have broad implications for the diagnosis and rehabilitation of brain injuries, says Dr. Black, who is also a senior scientist at the Rotman Research Institute.
"In certain kinds of head injuries, doctors can use this brain imaging technique to determine if awareness and learning is happening. Findings from this study could also help in the development of new therapeutic strategies for associative learning in brain injured people."
Baycrest Centre for Geriatric Care is an academic centre fully affiliated with University of Toronto. Funding for the study was provided by the Medical Research Council of Canada, and Natural Sciences and Engineering Research Council.
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