Submaximal exercise provokes increased activation of the anterior default mode network during the resting state as a biomarker of postexertional malaise in Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome, by Rakib U Rayhan and  James N Baraniuk in Front. Neurosci., 15 Dec 2021 [doi.org/10.3389/fnins.2021.748426]

Research abstract:

Background: 

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is characterized by disabling fatigue and postexertional malaise. We developed a provocation paradigm with two submaximal bicycle exercise stress tests on consecutive days bracketed by magnetic resonance imaging, orthostatic intolerance, and symptom assessments before and after exercise in order to induce objective changes of exercise induced symptom exacerbation and cognitive dysfunction.

Method: 

Blood oxygenation level dependent (BOLD) scans were performed while at rest on the preexercise and postexercise days in 34 ME/CFS and 24 control subjects. Seed regions from the FSL data library with significant BOLD signals were nodes that clustered into networks using independent component analysis. Differences in signal amplitudes between groups on pre- and post-exercise days were determined by general linear model and ANOVA.

Results:

The most striking exercise-induced effect in ME/CFS was the increased spontaneous activity in the medial prefrontal cortex that is the anterior node of the Default Mode Network (DMN). In contrast, this region had decreased activation for controls. Overall, controls had higher BOLD signals suggesting reduced global cerebral blood flow in ME/CFS.

Conclusion: 

The dynamic increase in activation of the anterior DMN node after exercise may be a biomarker of postexertional malaise and symptom exacerbation in CFS. The specificity of this postexertional finding in ME/CFS can now be assessed by comparison to post-COVID fatigue, Gulf War Illness, fibromyalgia, chronic idiopathic fatigue, and fatigue in systemic medical and psychiatric diseases.

Health Rising: Exercise Challenge Reveals a “Remarkable Discordance” in the Brains of People with ME/CFS

• Using a two-day exercise challenge, Georgetown researchers found a part of the brain that gets turned off in the post-exercise period actually gets turned on in people with ME/CFS.
• The authors proposed that something called the default mode network which is associated with rumination and internal assessments had become activated in the post-exercise period in ME/CFS. (It was not activated in the pre-exercise period.
• Because the DMN has to be turned off in order for action to take place, its activation in ME/CFS made tasks more difficult to complete. The authors called the process task-related deactivation.
• As similar findings have shown up in Gulf War Illness, it’s possible that DMN activation post-exercise is a feature of all fatiguing and exertionally intolerant diseases.