Nobody likes taking detours. Nor do our brains. The different parts of our brain communicate with each other via synapses that together form the shortest routes. Normally, that is. Jil Meier found that in patients with multiple sclerosis, the brains take the long way around.
With its 100 billion neurons that form hundreds of trillions of connections, the brain is a beloved research object for network scientists. Analysing the brain as a complex system has given crucial insights for understanding neurological diseases.
Studies have shown that Alzheimer’s disease primarily attacks highly connected nodes (hubs) in the brain network. This leads to longer pathways between nodes and, consequently, a less efficient communication within the brain. A similar process of “hub failures” has been found in patients with epilepsy. And now scientists can also add multiple sclerosis (MS)to the list.
In a recent paper published in Brain Connectivity, Jil Meier and Dr. Piet Van Mieghem, of the research group Network Architecture and Services (Faculty of Electrical Engineering, Mathematics and Computer Science), together with brain researcher Prejaas Tewarie of the VU Medical Centre in Amsterdam, show that in MS patients the theta and delta brain wave frequencies take slightly longer routes.
The difference between those suffering from MS and healthy people doesn’t seem spectacular, only a few tenths of a percentile, but is still highly significant, especially for the theta brainwaves.The statistical test (two sample t-test) showed a p-value of less than 0.001. This means that there is a probability of less than one percent that the observed difference is due to chance. “As a result”, said Meier, “we had no difficulty what so ever in getting this work published.”
In the VU medical centre, the researchers measured the activity of the different brain regions of 68 healthy controls and 111 MS patients using magnetoencephalography. They collected data for each person during a ‘no-task, eyes-closed condition’ for five consecutive minutes.
“Our study mostly focuses on the resting state, where individuals are just advised to close their eyes and not think about anything in particular but just let their thoughts wander”, Meier explained.
Using graph theoretical analysis, the researchers then examined six frequency bands: delta (0.5–4 Hz), theta (4–8 Hz), lower alpha (8–10Hz), upper alpha (10–13 Hz), beta (13–30 Hz), and lower gamma bands (30–48Hz).
“We observed that the link density in the brains of patients is nearly always lower on average than the link density for healthy controls”, said Meier. “MS patients thus seem to have fewer links for brain communication. Therefore, the average path length becomes longer and the communication within the functional brain network less efficient.”
MS patients will not benefit directly from these findings. Not in the short run anyway. “But this knowledge could ultimately help neurologists to identify a disease in an early stage and it might lead to new solutions for helping patients in the long run.”
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