The Neural Mechanisms Underlying the Decision to Rest in the Presence of Fatigue

[Simon]

Interesting study about fatigue in healthy people, using a powerful method directly measuring brain activity (as opposed to, say, fMRI which measures blood flow and uses this as an indirect measure of function)

PLOS ONE: The Neural Mechanisms Underlying the Decision to Rest in the Presence of Fatigue: A Magnetoencephalography Study

Abstract
Adequate rest is essential to avoid fatigue and disruption of homeostasis. However, the neural mechanisms underlying the decision to rest are not well understood. In the present study, we aimed to clarify the neural mechanisms of this decision-making process using magnetoencephalography.

Fifteen healthy volunteers participated in decision and control experiments performed in a cross-over fashion. In the decision experiment, participants performed 1,200 reverse Stroop test trials and were intermittently asked to decide whether they wanted to take a rest or continue.

In the control experiments, participants performed 1,200 reverse Stroop test trials and were instructed to press a response button intermittently without making any decision.

Changes in oscillatory brain activity were assessed using a narrow-band adaptive spatial filtering method. The levels of decrease in theta (4–8 Hz) band power in left Brodmann's area (BA) 31, alpha (8–13 Hz) band power in left BA 10 and BA 9, and beta (13–25 Hz) band power in right BA 46 and left BA 10 were greater in trials when the participant opted to rest (rest trials) than those in control trials.

The decrease in theta band power in BA 31 in the rest trials was positively correlated with the subjective level of fatigue after the decision experiment.

These results demonstrated that the dorsolateral prefrontal cortex, frontal pole, and posterior cingulate cortex play a role in the decision to rest in the presence of fatigue.

These findings may help clarify the neural mechanisms underlying fatigue and fatigue-related problems.

 

[duncan]

This: "These findings may help clarify the neural mechanisms underlying fatigue and fatigue-related problems"

is not

This: "These results demonstrated that the dorsolateral prefrontal cortex, frontal pole, and posterior cingulate cortex play a role in the decision to rest in the presence of fatigue."

So what were they trying to assess? The processes and apparatus involved in DECIDING to rest? As opposed to deciding to forge ahead despite fatigue? Are they trying to distinguish between personality types??

I cannot help but wonder if there is a moral underpinning to the effort. Can the data from an effort such as this be used to label some people as predisposed to be quitters?

How does this data really help deal with the different fatigue strata, and is it safe from being used to disenfranchise groups?

 

[xchocoholic]

What an interesting idea. Does anyone know if the magnetoencephalography has been used to study pwcs during pem or exercise testing ?

And out of curiosity, I googled stroop test and is it always as simple as it sounds ? If so, how do they determine if someone is just bored rather than fatigued ?

Tx ... x

 

[Esther12]

This: "These findings may help clarify the neural mechanisms underlying fatigue and fatigue-related problems"

is not

This: "These results demonstrated that the dorsolateral prefrontal cortex, frontal pole, and posterior cingulate cortex play a role in the decision to rest in the presence of fatigue."

So what were they trying to assess? The processes and apparatus involved in DECIDING to rest? As opposed to deciding to forge ahead despite fatigue? Are they trying to distinguish between personality types??

I cannot help but wonder if there is a moral underpinning to the effort. Can the data from an effort such as this be used to label some people as predisposed to be quitters?

How does this data really help deal with the different fatigue strata, and is it safe from being used to disenfranchise groups?

I see what you're saying, but I also think that it is just really difficult to design a test for 'fatigue'. I'm dubious about the value of the term, and think that confusion here causes trouble for a lot of research.

 

[duncan]

Understood. As with most of us, I am interested in any mechanism or metric which tries to characterize fatigue - despite the widely acknowledged problem that the word is too amorphous and subjective, with its own built-in bias, and has a relevance that varies from patient to patient.

But that is not the stated purpose of this study. It proposes to examine the decision to act on the fatigue, to react deliberately to its presence in some way.

It appears to me its objective is not to characterize fatigue, but instead to qualify somehow the attributes of individuals who elect to act on that fatigue - or rather, not act on it, but acquiesce to it. To rest, as opposed to soldier on (would be just one potential interpretation).

To me, it seems like the intent of this effort is to elicit markers for what some people may term as "character". To distinguish individuals who would "decide" to rest, from those that would "decide" to carry on and ignore fatigue. Certainly, it would appear that fatigue is not the primary target, even though it is addressed in what may be a novel approach. Regardless, imo, as with any study yielding collateral findings, context needs to be remembered.

So, providing my concerns have some merit, I'm thinking my college ethics prof may have trouble with this one.

 

[Esther12]

I've not read the full paper, but was just curious to see what instructions the participants were given.

To me, it doesn't look like a test of 'character':

Participants were instructed that they were free to take a rest whenever they thought that it was necessary in order to maintain performance of the test trials. If they required a rest, they pressed the left button with their index finger (rest trials); otherwise they pressed the right button with their annular finger (continuation trials). For rest trials (left-button press), the fixation dot was presented for 1,300 ms before the next reverse Stroop test trial began. For continuation trials (right-button press), the fixation dot was presented for 100 ms before the next reverse Stroop test trial began.

There is not a sense there that there is anything worthy about not resting when feeling fatigued, but rather it seems to be about their own judgement about maintaining performance.

 

[duncan]

"To me, it doesn't look like a test of 'character."

You are probably correct. I just can imagine it being used for such a reason. I fear I may be growing more jaded as I age. My bad for letting that bias my interpretation.

 

[Bob]

I haven't read this paper. It may or may not be a helpful study, but it's of limited value for CFS. I make a logical and informed decision to rest, not based on my current level of fatigue, but based on my potential for delayed symptom exacerbation at any particular time. So my immediate level of fatigue is rarely my primary concern when deciding to rest (edit: although it does inform my decision making.)

 

[Sea]

What an interesting idea. Does anyone know if the magnetoencephalography has been used to study pwcs during pem or exercise testing ?

And out of curiosity, I googled stroop test and is it always as simple as it sounds ? If so, how do they determine if someone is just bored rather than fatigued ?

Tx ... x

Did you google reverse Stroop test? Although that too would get boring.

 

[Simon]

What an interesting idea. Does anyone know if the magnetoencephalography has been used to study pwcs during pem or exercise testing ?

And out of curiosity, I googled stroop test and is it always as simple as it sounds ? If so, how do they determine if someone is just bored rather than fatigued ?

I'm not aware this has been used on ME/CFS patients in any situation, but it looks like they need to get more data on how healthy people respond before trying it on anyone else.

The thing about the Stroop test is that it sounds dead easy, but doing it is altogether different: you really have to try it to see why. And it's the cognitive test where ME/CFS patients struggle most consistently compared with controls.

Re some of the other comments, I think the first sentence of the abstract is critical:

Adequate rest is essential to avoid fatigue and disruption of homeostasis

The point is that fatigue evolved as a signal to rest because it improves our survival chances. It's the body's way of protecting itself from damage.

I've always thought it weird the way CBT theories paint resting in response as abnormal when it's the most natural thing in the world, and what we are meant to do. As @Bob says, the experience of this illness might modify how we respond to fatigue (though I still find it a helpful guide), but the basic instinct is hard-wired into us.

I also agree that fatigue is hard to define and measure, but don't think it's a meaningless concept, again because fatigue is such an important natural response. For that reason I think this study is an interesting approach, but the whole area of fatigue is under-studied.

The thing is that fatigue is poorly understood in healthy people. That makes it questionable when any doctors pronounce 'there is nothing wrong' in ME/CFS: if we don't even understand healthy fatigue, how can we say there is nothing wrong with the fatigue system? (Though of course the fatigue could be secondary to some deeper problem.)

 

[xchocoholic]

Did you google reverse Stroop test? Although that too would get boring.

Definitely. I'd be wondering what they were thinking after about 6 of these.

I was just curious if this was being used in more practical applications. Is this part of the ttt ?

Polysomnography looks very similar to me and is used for sleep studies. I had that back in the early 90's.

Tc .. x