Baycrest study discovers role of thalamus in post-stroke recovery

A recent study from Baycrest shows that an area of ​​the brain distinct from the stroke lesion may play a major role in causing the life-changing symptoms that survivors are often left with, including serious problems with speech, mobility and cognition. These results offer hope that innovative, non-invasive treatments can help improve or even completely reverse symptoms after a stroke.

Strokes (which affect more than 100,000 Canadians every year).¹) leave an area where brain cells have died, called a lesion. However, this cannot explain the widespread consequences of stroke, limiting the ability of scientists and doctors to treat it. The study, titled “Secondary thalamic dysfunction underlies abnormal large-scale neural dynamics in chronic stroke,” recently published in the journal Proceedings of the National Academy of Sciencesshows that degeneration of the thalamus – an area of ​​the brain distinct from the stroke lesion – is a major contributor to post-stroke symptoms.

This is both good and bad news. The bad news is that the impact on the brain caused by a stroke is not limited to the lesion seen on a brain scan. The good news is that the area showing abnormal electrical activity outside the lesion may be treatable with innovative new therapies.”

Dr. Jed Meltzer, Baycrest’s Canada Research Chair in Interventional Cognitive Neuroscience and senior author of the study

New targeted treatments, such as brain stimulation and medications, could be designed to prevent or even reverse this degeneration to optimize recovery in stroke survivors.

Key findings:

• Damage to brain tissue near the stroke lesion was not the primary cause of abnormal electrical activity in the brain.
• Instead, these abnormalities were related to the thalamus, a structure located deep in the brain center that acts as a hub connecting numerous brain areas and activities.
• More than just the lesion, the amount of degeneration in the thalamus predicted the amount of abnormal electrical activity in the brain measured by magnetoencephalography (MEG), and the individual’s language and cognitive deficits.

Dr. Meltzer, who is also a senior scientist at the Rotman Research Institute, part of the Baycrest Academy for Research and Education (BARE), and his team, which includes researchers from Baycrest, the Center for Addiction and Mental Health (CAMH) and Simon Fraser University, studied the electrical activity of the brain using MEG and the brain structure using magnetic resonance imaging (MRI) of 18 people with language deficits due to a stroke.

This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canadian Partnership for Stroke Recovery, the Canada Research Chairs Program, the Krembil Foundation, the CAMH Discovery Fund, the Labatt Family Network, and the University of Toronto EMHSeed program.