The human cerebellum, despite containing the majority of the brain’s neurons, remains underexplored due to its thin and tightly folded cortex. But although its volume is only about 20 percent of the entire brain, it contains more nerve cells than the rest of the brain. This small area is home to various essential motor and cognitive functions, such as balance and movement, but also attention, language, and learning.
Tightly folded
Nevertheless, the cerebellum is an underexposed area, says Matthan Caan, physicist and researcher in the field of AI and medical imaging, and leader of the Brain Imaging program of Amsterdam Neuroscience. “Much less research has been done on it than on the cerebrum. The cerebellum has many small folds. The details of this highly folded structure cannot be mapped with a regular MRI scan. We have developed a high-resolution MRI framework that integrates artifact-tolerant acquisition and optimized segmentation. We were able to image the cerebellar cortical surface with high fidelity.”
18-minute scan
“We used a very powerful scanner, the 7 Tesla MRI scanner at the Spinoza Center for Neuroimaging,” explains Caan. “Until now, this scanner was mainly suitable for measuring the cerebrum. We have made it possible to also clearly visualize the cerebellum with an 18-minute scan. We also use a technique to correct for movement, because even the slightest movement causes blurring. We can now see 15 times more detail.”
With this approach, it is now possible to map details down to 0.4 millimeters. “This turns out to be exactly the step needed to accurately measure the folds of the cerebellum. We have discovered that the distribution of blood vessels and the composition of the gray matter differ between the different parts of the cerebellum.”
Important step
The road from this type of fundamental research to clinical application is still long. Nevertheless, according to neurologist Arthur Buijink, these new insights are an important step towards possible treatments in the future.
Buijnk conducts a lot of research on people with tremors. “We don't really understand why people shake at all,” he says. "There was no good way to look at abnormalities in the different areas within the cerebellum. With this new technique, we can study it. It is now possible to see whether there are subgroups within this patient group that respond to certain medications or that are suitable for certain brain surgeries.
Benefits for patients
Buijink also sees opportunities for research into functional limitations resulting from conditions such as multiple sclerosis. "Think of balance problems, coordination problems, or cognitive problems. The cerebellum may play a major role in this. The layer of cells in the cerebellum that you want to look at is at most a millimeter thick and difficult to visualize. Now we can do that. It may explain why people have certain symptoms and whether or not they are eligible for certain medications. That's a benefit for patients."
Read the publication in Proceedings of the National Academy of Sciences: Mesoscale imaging of the human cerebellum reveals converging regional specialization of its morphology, vasculature, and cytoarchitecture
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