Cognitive Deficits in Multiple Sclerosis Attributed to Brain Regional Disconnect

Patients with multiple sclerosis (MS) experience decreased connectivity between brain regions leading to the cognitive changes that are a trademark of the disease, according to research published in Neuropsychology.

A global team of researchers observed 29 participants with relapsing remitting MS and 23 age and sex matched healthy controls in order to assess the extent to which cognitive slowing in MS was predicted by changes in brain networks. The investigators administered functional magnetic resonance imaging (fMRI) tests to each participant, who were instructed to complete a measure of cognitive processing speed. The patients had 4 seconds to view a 9 item key of number and symbol pairs (such as the plus sign above the number 3, etc) and one number/ symbol pair probe. Patients were then asked to signal with a left or right thumb button if the probe appeared in the key.

“Our study is the first to really zero in on the physiology of cognitive speed, the central cognitive deficit in MS,” Center for BrainHealth principal investigator Bart Rypma, PhD, said in a press release. “While white matter is essential to efficient network communication, white matter degradation is symptomatic of MS. This study really highlights how tightly coupled connectivity is to performance and illuminates the larger, emerging picture of white matter’s importance in human cognitive performance.”

The researchers found that the accuracy was similar for the healthy controls and the MS patients, though the response times for the MS patients was much slower. After analyzing the fMRI data, the researchers additionally found that while completing the task, MS patients demonstrated weaker brain region connections.

“These findings reveal a diffuse pattern of disconnectivity with executive areas of the brain,” continued lead author Nicholas Hubbard, a doctoral candidate at the Center for BrainHealth, in the statement. “Importantly, these decreases in connectivity predicted MS related cognitive slowing both in and out of the fMRI environment suggesting that these results were not specific to our task, but rather were able to generalize to other situations where cognitive speed is required.”

The researchers said this analysis aligns with the need for therapies that target white matter structures and white matter proliferation. Both study contributors are currently conducting more studies to explore the makeup of white matter and better understand cognitive deficits in MS but also healthy aging individuals.