Study Finds Mental Fatigue of Multiple Sclerosis Impacts Brain Activation Patterns

Research may address the lack of effective treatments for mental fatigue among patients with multiple sclerosis.

A pilot study conducted at the Kessler Foundation indicates significant differences in brain activation patterns between people with and without multiple sclerosis (MS), indicating differences in the 2 groups’ recruitment of neural resources in response to increased task demands.

The study is an extension of the Kessler Foundation’s research into the neural correlates of mental fatigue in patients with MS. According to a press release, mental fatigue comprises 2 types, state and trait, which are measured subjectively. The current study focused on state fatigue, which the researchers said fluctuates over minutes to hours. On the other hand, trait fatigue is stable over longer periods, usually weeks.

Investigators included 36 participants, 19 with MS and 17 without. The participants underwent functional magnetic resonance imaging (fMRI) while performing the Symbol Digit Modalities Test, which is a standard cognitive test modified for use with fMRI. Changes in brain activity were recorded while the test was administered under both high and low cognitive loads.

“We found higher levels of fatigue and longer response times in the MS group,” said study author Michelle Chen, PhD, in a statement. “With increasing mental fatigue, the control group showed increased activation of the anterior brain regions and faster speed of response, to meet the demands of the high load condition. The MS group did not show activation of these regions or an increase in processing speed, suggesting a less efficient response to the higher cognitive demands of the task.”

According to the press release, these results are consistent with prior research into the functional reorganization of brain activity as a result of mental fatigue. The authors said that understanding these mechanisms is essential, especially given the lack of effective treatment for this fatigue.


Mental Fatigue of Multiple Sclerosis Linked to Inefficient Recruitment of Neural Resources [news release]. Kessler Foundation; July 28, 2020. Accessed August 3, 2020.

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