Neuroimaging Research Provides Clues into the Inner Workings of Cognitive Fatigue in MS Patients

A new study is providing insights into the processes underlying cognitive fatigue in individuals with multiple sclerosis (MS). Cognitive fatigue is fatigue resulting not from physical labor but from mental work.

The new findings were published on November 1, 2013, in the journal PLoS One. This is the first study to use neuroimaging to investigate aspects of cognitive fatigue. The study was funded by grants from the US National MS Society (Washington DC, USA) and Kessler Foundation (West Orange, NY, USA;) .

The study examined the neural correlates of cognitive fatigue in MS utilizing three neuroimaging technologies: functional magnetic resonance imaging (fMRI), which allows radiologists to see where in the brain activation is tied to a task or an experience; diffusion tensor imaging (DTI), another MRI technique that allows researchers to look at the health of the brain’s white matter; and voxel-based morphometry (VBM), which allows researchers to study structural changes in the brain. These three approaches were used to examine how likely it is for an individual to report fatigue (“trait” fatigue), as well as the fatigue an individual feels in the moment (“state” fatigue). This study is the first to use neuroimaging technology to study these two distinct aspects of fatigue.

“We looked specifically at the relationship between individuals’ self-reported fatigue and objective measures of cognitive fatigue using state-of-the-art neuroimaging,” explained Helen M. Genova, PhD, research scientist in neuropsychology and neuroscience research at Kessler Foundation. “The importance of this work lies in the fact that it demonstrates that the subjective feeling of fatigue can be related to brain activation in specific brain regions. This provides us with an objective measure of fatigue, which will have incalculable value as we begin to test interventions designed to alleviate fatigue.”

In experiment 1, patients were scanned during performance of a task devised to trigger cognitive fatigue. Investigators looked at the brain activation associated with “state” fatigue. In experiment 2, DTI was used to examine where in the brain white matter damage correlated with increased “trait” fatigue in individuals with MS, as assessed by the fatigue severity scale (FSS). The findings of experiments 1 and 2 support the role of a striatothalamic-frontal cortical system in fatigue, suggesting a “fatigue-network” in MS.

“Identifying a network of fatigue-related brain regions could reframe the current construct of cognitive fatigue and help define the pathophysiology of this multifaceted yet elusive symptom of MS,” said John DeLuca, PhD, VP of research and training at Kessler Foundation. “Replication of these findings with larger sample sizes will be an important next step.”

Related Links:
US National MS Society
Kessler Foundation