Brain function characteristics of chronic fatigue syndrome: A task fMRI study, Shan et al, 2018

@Trish - D'oh, that's twice I've forgotten to put in the link - I'm clearly more foggy than I realise Thanks for putting the link up!

 

I wonder what the reasons are, making Fukuda (1994) still preferred instead of the Canadian Consensus Criteria (2003) and the International Consensus Criteria (2011).

 

Interesting study.

I'm not familiar with the SampEn measure they used, but from what they say, it appears to be a measure of neural processing efficiency.

The main conclusion of the study was that CFS patients are less efficient at recruiting neural resources to accomplish a challenging task (the Stroop task) than are controls. The two findings that led them to this conclusion are:

1. CFS patients showed more widespread brain activation than healthy controls during the task, suggesting a lack of efficiency.
2. SampEn measures in some regions were lower in CFS patients than in controls, which (I think) they interpreted as less coherent, synchronous activity. Most of these regions are ones that are not normally associated with the the Stroop task.

They conclude that the brain recruits wider regions in CFS patients to compensate for the lower processing capacity.

Its important to remember that fMRI indexes blood flow, so its hugely affected by a person's cardiovascular health. However, these authors do not think these abnormalities are due to cardiovascular factors because: 1) the CFS patients' heart rate and pulse pressure during the task were not different from controls'; and 2) if it were all down to cardiovascular factors, then the SampEn measures would be higher in all brain areas, not just in the few they found (I don't think this necessarily follows, but its what they said).

They suggest instead that the problem in the CFS patients is to do with neurovascular coupling. So in healthy people, activating a part of the brain initiates a chain of events, which result in increased dilation of the blood vessels supplying that area. These authors suggest that something is going wrong in this chain of events, so the blood isn't getting where it needs to efficiently.

On the whole, its pretty true to the results (in fact, frustratingly so, there's not much speculation about how this might all fit in with the clinical picture in CFS). I only spotted one instance of clear cherry picking:

The results said (my bold):

The conclusion said:

Also, I have absolutely no idea why they chose the Stroop task, and I'm not sure they do either. I think they just thought it was "hard".

 

hypoperfusion is the same cause of cognitive difficulties mentioned by dr ramsey and dr Byron hyde a very long time ago before expensive mri testing was possible it seems the science is going in circles.

 

I guess sticky blood may effect blood flow to the brain?

Putting aside the dubious reasoning, I think it’s good to have a study that shows the cognitive challenges we face, even if it drifts off into the complicated when a more simple physiological explanation may exist...although it may be complicated of course?

The challenge with repeating this on a larger sample is the variance within the sample I guess. It would be interesting to look at other measures alongside as a way of predicting poor cognitive function. Perhaps using the test after being laid down, or perhaps expose the subject to stimulus and measure before and after for controls and patients? Stimulus could be watching a debate on tv or something similarly challenging ?

 

Since this is a task-related fMRI study, what you're seeing in the maps is not absolute blood oxygen uptake, but a difference score (task minus control).

So you're seeing how much additional oxygen the brain is taking up during the key (interference) condition of the task, over and above what you see in the control condition.

This pattern - of more diffuse, less "targeted" activity - is observed in a lot of clinical populations, and you see it even in normal ageing. Its like a marker of how efficient you are at performing a task.

It seems to me that the SampEn measure is sort of capturing the same thing - how much useless activity you're engaging in over and above the useful and targetted activity you're doing to actually accomplish the task. Notice how its all the irrelevant regions that have the abnormal SampEn measures - not the regions people actually need to accomplish the task.

 

Thanks for the explanation, @Woolie

I write a blog about cognitive tests and fatigue a few years ago:
http://phoenixrising.me/archives/16688

I can’t remember all the details of the research, but I think the Stroop test is one of those that has shown differences between patients and controls.

Here’s my intro to the Stroop test:

Do the Stroop & other cognitive tests

The Stroop is a quirky test of attention, 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 color each word is displayed in, as quickly as you can. Not so easy… Try it online!

 

Okay, sure, but this is a task-related fMRI study, they ought to have proper theoretically motivated reason for choosing the task they did. The Stroop is "hard", but then so too are lots of tasks. Why did they pick that? First thing that came to mind? The Stroop is a language control task - its about overriding the language element that's most strongly in your mind in order to produce another one. Is language control what you want to measure? A different sort of "hard" task - for example, a sustained attention task - would likely produce some very different patterns of activation.

I would just have liked to see some sort of justification.

 

Sorry, I've not read any of the detail but this made me think - wouldn't we expect to see a difference in patients heart rates? I'm assuming, fairly safely I think, that this test will need to be done outside of the patients home, so you have the travel from home to test centre, interacting with those at the test centre, and then taking the test. The only way I could see this avoided would be if a rest period was built in before taking the test.

Wouldn't be NCNED without some cherry picking

 

I thought that was odd too. I know I have a pretty high resting heart rate, and I've heard quite a few others here say the same.

 

Yes. I was a subject in this study. The tests were conducted lying down in a fMRI machine.

 

I was a subject in this study.

In answer to two of the questions above:
* the test was conducted lying down in an fMRI machine, and took about 45 mins in total for each subject
* the first 15 minutes or so was calibrating the machine for each subject. In one sense, this could be considered a 'rest', but it also allowed time to adjust to being in the machine itself.

 

I wish researchers would learn more about our illness. Having patients lie down or relaxed is unlikely to show the same results as when they're standing or if they're in PEM.

 

The difficulty for me with this sort of study is that we would expect patients to have different thoughts from controls while taking part in a test like this. The regions with increased blood flow may simply reflect the different emotional connotations for patients and controls. For a control it might be 'this is better than sorting out that paper work Jenny asked me to do yesterday - hoho!' For a patient it may be 'am I actually doing this right, it is quite stressful thinking that the results of this test will be used to create theories about my illness'.

I think you absolutely need patients with other illnesses as controls and you really need them to think the test is just as relevant to their illness as to ME.