TBI, often sustained in traffic accidents, is one of the most common causes of disability in young adults. People with TBI frequently complain of memory problems that interfere with their daily function and ability to work, yet many eventually recover memory function and return to work or school.
The study, led by scientist Brian Levine of The Rotman Research Institute at Baycrest Centre for Geriatric Care, compared brain function in two groups of adults -- six patients who had suffered a moderate to severe TBI four years earlier (with several days of coma in some cases)and made a strong recovery, and 11 healthy adults who matched the TBI group in age and education.
The two groups performed a memory test that involved seeing related word pairs flash on a computer screen (for example, penguin - tuxedo) every few seconds. The subjects were then shown the first word of each pair and asked to recall the second word. While they performed this test, their brain activity was monitored with positron emission tomography.
The important finding in the study came when the research team compared the patterns of brain activity in both groups as they tried to remember the second word. Although the patterns were roughly similar during this memory retrieval task, patients with TBI showed 'larger' areas of activation in frontal and posterior brain regions known to be involved in memory. This was the case even for patients whose performance was the same as the healthy adults. The larger areas reflect 'reorganization' of brain function that likely occurred in the weeks and months during these patients' recovery from their significant brain injury.
The approach used in this study is very different from more widely used clinical measures of brain activity while the patient is in a resting state. These studies tend to emphasize 'reduced' activation in patients with TBI.
The findings of this study by Dr. Levine and his team paint a more hopeful picture by identifying potentially positive brain changes in patients who make a good recovery from TBI. Similar studies have been done in patients with dementia and healthy older adults, but this is the largest and best-controlled study of its kind in patients with significant TBI.
"The brain is a flexible organ that can compensate for damage by engaging new systems to perform the same memory tasks," says Dr. Levine. "A major goal of clinical research is to find new ways of enhancing the recovery process, both through behavioral techniques and with drugs. Brain imaging studies like this one can help to track these changes and to understand why some patients make a good recovery and others do not."
The investigators assisting Dr. Levine included some of the top minds in the field of neuroscience -- Drs. Sandra Black, Donald Stuss, Randy McIntosh, Cheryl Grady and Roberto Cabeza.
The study was funded by the Canadian Institutes of Health Research, the Ontario Mental Health Foundation, and The Rotman Research Institute.