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Cognitive testing causes mental exhaustion lasting days

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Simon McGrath takes a brief look at a recent paper that reveals some of the most powerful evidence of cognitive problems in people with ME/CFS to date...

It might not come as a huge surprise to patients, but a new study has found that mental fatigue can persist long after mental exertion is over.

Specifically, after a 3-hour session of cognitive testing of memory and attention, healthy controls took an average of 7 hours to recover, compared with 57 hours - more than two days - for CFS patients.

While one previous study found mental fatigue continues days after physical exertion, this appears to be the first research paper to demonstrate that mental exertion itself leads to prolonged mental fatigue.

To me, the large difference found between patients and controls makes this some of the most powerful evidence of the cognitive problems in ME/CFS.

Interestingly, this finding only came about thanks to the alertness of Susan Cockshell, the lead researcher who told me:

“I hadn’t originally planned to collect this data, but I had to follow up one of my first participants a few days after testing and she told me she was still fatigued.”

So, post-test mental fatigue was added to the measures.

Mental fatigue for both healthy controls and patients peaked several hours after testing (albeit at lower levels for controls), but 24 hours later, controls were back to pre-test levels while patients were not.

It’s hard to believe we've waited till now to even see testing of post-exertional mental fatigue. Cockshell commented that surprisingly little data existed in this area, but her study shows it is an issue that needs further investigation.

Subjective measures don't match objective measures

The main aim of the study was actually to see if patients’ reports of problems with mental tasks were backed up by objective test of cognitive function - specifically of memory and concentration, two distinctive problems with ME/CFS.

The result? There was no significant correlation between patient reports of fatigue and measured cognitive performance. But this doesn’t mean that patients don’t really have problems with mental tasks because, as Cockshell pointed out, there was also no correlation in healthy controls either (healthy controls reported some problems with memory and concentration too).

The paper concludes:

“There is little evidence for a relationship between subjective and objective measures of cognitive functioning for both people with CFS and healthy controls, which suggests that they may be capturing different constructs.”

In fact, a lot of evidence now shows that people’s self-reported cognitive problems aren't matched by the kind of objective tests used in these studies, which does beg the question: Do we need better tests of cognitive problems in the real world?

stroop1.jpg
To understand this issue better, let’s take the example of concentration, which in the real world means problems such as focusing on reading or blocking out background noise. One measure of concentration (or ‘attention’ in the jargon) is the "Stroop" - a quirky test with a quirky name.

The simplest way to see how it works is just to look at the two lists above. Don’t read them, instead say the colour each word is displayed in, as quickly as you can. Not so easy, but try it online!

Of course, we never have to do tasks like this in real life (and most other cognitive tests are similarly contrived), so is this a meaningful way to measure patients’ problems?

One researcher and clinician, Gudron Lange, has highlighted how everyday tasks, such as going shopping, involve multi-tasking, something that most cognitive tests miss.

Lange has suggested using cognitive tests that include multi-tasking – and virtual reality now provides a way to test real-life scenarios using multi-tasking in the lab.

Cockshell agrees that more work is needed in this area:

“I think a better understanding of the cognitive problems occurring in the real world is required ... but that's a whole other area of research.”

Patients don’t overestimate their problems

Some researchers have argued that the problem in CFS isn't that patients can't do much or perform well, but that they simply underestimate how much they actually do, almost seeing CFS as a delusion syndrome. But this new study, like several others, found that the theory doesn’t hold up:

“Self-reported problems were not due to people with CFS overestimating their problems, as they were able to accurately evaluate their performance on most cognitive tests.”

In fact, patients were at least as good as controls at judging their own performance.

The future...

These clear findings of extended fatigue after the testing fit with an earlier fMRI study (also by Lange), indicating that CFS patients had to use more brain areas to achieve the same results as healthy controls. As Cockshell says:

“People with CFS may perform comparably to their peers by expending additional cognitive effort, and this may subsequently impact on their levels of fatigue.”

This paper provides powerful new evidence of the problems faced by patients with our condition. Yet the mismatch between reported issues and objective performance suggests there we still haven’t found the best way to measure the very real problems experienced by ME/CFS.

Hopefully, this will soon change.

Susan Cockshell will be speaking about her work at the IACFS Conference on Sunday 23.3.14. Read more: Brain Fog: The research.

Simon McGrath tweets on ME/CFS research:




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Years ago there was a good article somewhere how thinking and concentrating is completely exhausting for us and I totally agree.

I know that is one of the huge reasons I can't drive and when I try to fill out forms I can barely last 10 minutes.
I have to admit that part of my interest in this is that mental fatigue is my most disabling symptom, the thing that stops me doing what I'd like to do more than anything.

I hope it's possible to disprove any claims by psychologists/psychiatrists that our cognitive difficulties aren't psychological in origin!
think there might be some cognitive problems showing there :).
 
I wonder at the extent to which this might be said to be a permanent thing, or whether permanence should also be measured in some way. If for example, I took the test referred to in the article, tomorrow, and then was subsequently tested to see how long it took for me to recover mentally. Then I took the original test again. And again. And Again.

Might the results over a period of time, show any improvement in recovery time or might they show no change? This would be interesting to learn - perhaps also if the method of testing were varied - but as intense each time - so as to avoid familiarity.

Anyway, it's definitely an area that we see relatively little research in. And definitely the area - cognitive function and decline - that has affected me most in terms of 'this is upsetting me more than anything else'. I can live with the physical disability - it's this loss of mental agility and inability to recover quickly from the mental exertion and the other cognitive issues: that really *cked me up over the years.

If you can't walk you can use a wheelchair, if you can't think straight - there are no props :(
 
Thanks Simon.

I'm with you. There's been too much emphasis on 'malaise' following physical exertion which feeds into the whole deconditioning and GET as rehabilitation meme.

Although I've never been deconditioned as such, physical capacity was pretty irrelevant to my deskbound job and wouldn't have hampered me any more than any other sedentary office worker.

It was a severe lack of cognitive stamina that was a major contributor to my inability to work and which still interferes with everyday tasks.

I also agree that real world challenges that involve multi-tasking are more likely to highlight cognitive deficits and their lasting effects that are more than mild or trivial.

I wrote about this large study that found profound cognitive deficits using a multi-tasking paradigm :

http://www.cortjohnson.org/blog/2013/07/28/japanese-sensory-gating-stud-reveals-profound-cognitive-deficits-present-in-chronic-fatigue-syndrome/

This is a very under-researched area and one that I feel may be much more relevant to what's going on than physical fatigue.
 
Thanks @Simon.

One example of a situation like this is an exam. Although with exams, the exam itself isn't the only mental exertion involved as someone will invariably be studying or revising in the days and/or hours before an exam.

I have an exam coming up with the OU. They say they make allowances for disabilities etc, but all they are offering is an exam in the home - which is good, but I don't know how I am going to get through it, especially with all the revising beforehand and the stress of the worry of it all. Other universities will allow other types of assessment if you cant sit exams, but no the Open University - and they tell me they have no plans to ever do so.

Such a shame as I am doing very well on my assessed work, sure the exam will bring my overall grade down.

(Sorry a bit off topic)
 
I have an exam coming up with the OU. They say they make allowances for disabilities etc, but all they are offering is an exam in the home - which is good, but I don't know how I am going to get through it, especially with all the revising beforehand and the stress of the worry of it all. Other universities will allow other types of assessment if you cant sit exams, but no the Open University - and they tell me they have no plans to ever do so.

Such a shame as I am doing very well on my assessed work, sure the exam will bring my overall grade down.

(Sorry a bit off topic)

They should allow you break periods. I used to do my OU exams at home too, and it had to be on computer as I can't write for long before my hands pack up. Do you have a hammer to bang all the facts into your head? (I used to feel as though I needed this!)

Good luck!!!!:)
 
That is most unlike the OU. I am very disappointed in them - this is the first time I have ever said that.:(

I wish you all the best, Justy! :thumbsup:
I hope you're having a really good day on the day of the exam and will cope with it as easily as is possible.
Plenty of sleep - you need sleep to consolidate anything you've learned.

If it does go badly, you do have your continuous assessment marks to support an appeal.:hug:



There is a test I know is available on computers which is a dual task thing. Not multitasking, but it tests straight memory and working memory at the same time. (I used it in my Hons. thesis)

There is a word recognition task and an arithmetic task. I found that under duress, the word recognition task was no different to not under duress, but that the arithmetic task went right downhill.
The task seperates working memory function from simple recall.
 
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It also explains why, when you are being grilled and you are stressed out, you can produce words, but cannot think straight at all, and end up looking stupid.
It's "the wheel is turning but the hamster is dead" thing.