Neuroimaging Tracks Mental Fatigue in CFS

[Guest guest]

I just saw this article, while going through my e-mails I hadn't

gotten to yet. I'm way behind, as fatigue and cognitive problems are

my biggest issues. I thought some of you may find it interesting.

I'm always relieved when they can prove any of our symptoms!

Sue

http://www.cfids.org/cfidslink/2007/050703.asp

Neuroimaging Tracks Mental Fatigue in CFS

The neural mechanisms underlying feelings of mental fatigue are poorly

understood. Though neuroimaging has been used to show differences in

brain responses to movement and motor skills, less attention has been

paid to understanding brain responses to demanding cognitive tasks

that produce mental fatigue. The relative lack of research in this

area is surprising because a primary complaint of individuals

reporting ongoing fatigue is the perceived inability to adequately

perform cognitive tasks.

This spurred a well-known CFS brain researcher, Gudrun Lange, PhD, and

her team of researchers led by Dane Cook, PhD, to use functional

magnetic resonance imaging (fMRI) to determine the association between

feelings of mental fatigue and brain response in people with CFS.

Functional magnetic resonance imaging is one of the most recently

developed forms of neuroimaging. When nerve cells are active they

consume oxygen carried by red blood cells from local capillaries. The

local response to this use of oxygen is increased blood flow to

regions of the brain with increased neural activity. An fMRI scan

allows researchers to track neural activity by detecting these changes

in blood flow and oxygenation. So this scan looks at the way the brain

works, rather than its physical anatomy, as a traditional MRI does.

In the study by Cook, Lange and colleagues, published in NeuroImage,

small groups of healthy non-fatigued control subjects and subjects

with CFS performed three types of tests: a fatiguing cognitive test, a

non-fatiguing cognitive test and a non-fatiguing motor test. fMRI

scans were conducted with each of the three tests. Each participant's

fatigue was measured prior to scanning and following each task during

the fMRI data collection.

The researchers hypothesized that mental fatigue would be

significantly related to brain activity during the fatiguing cognitive

task, but not during the other tasks. Did the test and fMRI scans bear

that out?

Indeed, the results showed that mental fatigue was related to brain

activity. The participants with CFS didn't differ from control

subjects for either of the non-fatiguing tasks, but exhibited

significantly greater activity in several regions of the brain during

the fatiguing cognitive task.

This suggests a direct association between subjectively reported

feelings of mental fatigue and brain responses during fatiguing

cognition—in essence validating that CFS patients' complaints of

mental fatigue have a verifiable physiologic component. With

replication by other research groups and against other types of

control groups, this type of study could have important applications

in documenting both the diagnosis of CFS and disability associated

with it.

Cook, D.B., et al., Functional neuroimaging correlates of mental

fatigue induced by cognition among chronic fatigue syndrome patients

and controls, NeuroImage (2007), doi: 10.1016/j.neuroimage.2007.02.033