By Sean O’Malley
When Dr. Tarek Rajji was growing up, it was believed that the physical human brain could not be improved in any way. You start out in life with a certain amount of grey matter and once the aging process begins, the brain keeps losing that grey matter bit by bit and just gets older and weaker, like a draining battery that can never be recharged.
How times have changed.
Today, as Chief of the Adult Neurodevelopment and Geriatric Psychiatry Division at CAMH and Executive Director of Toronto Dementia Research Alliance, Dr. Rajji is using advanced technology to explore the inner-working of the aging brain and look for clues that could delay, prevent or even reverse the progression of conditions like Alzheimer’s disease and related dementias.
Those clues are known in neurology as “biomarkers”, which show the presence of a mental illness through biological changes in the brain and are believed to be the key to improvements in the diagnosis and treatment age-related mental illnesses.
With the help of philanthropic support, Dr. Rajji’s team is working on a study in search of those clues that is connected to PACt-MD, the largest ever Canadian investigation into dementia prevention.
Over the duration of the PACt-MD study, CAMH has collected an extensive set of Electroencephalogram (EEG) data from people with cognitive impairment and later life depression, both risk factors for dementia.
Dr. Rajji and his team at CAMH are using this trove of data to develop a new platform for biomarkers discovery in neurodegenerative disorders called BrainHealthSpan.
The hope is that by identifying EEG biomarkers through this study, dementia-related illnesses can be diagnosed earlier and treatment can be more effective.
What Rajji is looking for on those EEG’s is evidence of ‘cognitive reserve’, an adaptive behaviour of the brain only discovered about 30 years ago. Rajji explains cognitive reserve as essentially the brain’s way of trying to keep up with cognitive demands as it gets older. Education and a lifetime of learning through work or other pursuits can build up cognitive reserve in the brain, enabling it to compensate for damage resulting from dementia or other age-related mental illnesses. The more cognitive reserve people have in their brain, the more the brain can continue to appear to function normally despite the presence of these illnesses.
By tracking the EEG oscillations of individuals’ brain waves as they do problem-solving, Dr. Rajji is looking for evidence that some brains are tapping into that cognitive reserve to make up for injuries to the brain due to a neurological or mental illness.
The way it works is that two test subjects, both of them with risk factors for dementia in the form of depression or mild cognitive impairment or both, perform problem-solving tasks while their brains are monitored by EEG. On the surface, both of them perform equally well. But under the surface, the EEG indicates that one brain—the one with undiagnosed dementia—is using cognitive reserve in other parts of the brain to compensate for the damage caused by the illness. The less cognitive reserve they have compiled over their lifetime, the sooner it will be depleted and the dementia that had been progressing invisibly inside the brain reveals itself externally.
“We can measure the plasticity of the brain in these EEGs to reflect how the brain organizes information,” says Dr. Rajji. “Cognitive reserve indicates how the brain is coping with mental illnesses. Sometimes you can’t tell the difference between someone who has mild cognitive impairment (MCI) and who has a healthy brain from the tests alone. We hope that we could tell through these EEG biomarkers. If we prove that we can, it suggests that the cognitive reserve may be depleting on subjects with MCI, but not yet below a certain threshold were it manifests itself in performance impairment.”
Future plans related to this study include expanding the BrainHealthSpan platform through engagement with other brain scientists in Canada and internationally, including partnerships with the Ontario Brain Institute and the Ontario Neurodegenerative Disease Research Initiative
The hope is that this area of brain biomarker research will not only allow for much faster diagnosis of dementias, it might actually help prevent or even reverse brain damage associated with these diseases.
“We have learned over the past few decades that at least 40 per cent of dementia cases are potentially preventable. The ultimate goal of this work is to discover treatment interventions that increase cognitive reserve so that people can maintain their cognitive ability and their functional independence in the community. We hope that by targeting these brain networks, we can actually help the brain heal. By engaging the oscillations in the brain with targeted brain stimulation, we also may be able to clear the brain of Alzheimer’s disease proteins.”