Selective effects of acute low-grade inflammation on human visual attention (2019) Balter et al.

[rvallee]

Link between inflammation and mental sluggishness shown in new study

An estimated 12M UK citizens have a chronic medical condition, and many of them report severe mental fatigue that they characterize as ‘sluggishness’ or ‘brain fog’. This condition is often as debilitating as the disease itself.

In a study published in Neuroimage, they show that inflammation appears to have a particular negative impact on the brain’s readiness to reach and maintain an alert state.

If those numbers are reliable this is a borderline epidemic level crisis. Nearly 1/5 of the UK population reporting significant cognitive symptoms interfering with daily life but are typically brushed off by medicine. The worldwide numbers would place this at above 1B. That's staggering.

Journal Reference: Leonie JT. Balter, Jos A. Bosch, Sarah Aldred, Mark T. Drayson, Jet JCS. Veldhuijzen van Zanten, Suzanne Higgs, Jane E. Raymond, Ali Mazaheri.

Selective effects of acute low-grade inflammation on human visual attention.

NeuroImage, 2019; 202: 116098

Link: https://www.sciencedirect.com/science/article/abs/pii/S1053811919306895

DOI: 10.1016/j.neuroimage.2019.116098

Highlights

• Typhoid vaccination induced a transient mild inflammatory state.

• Mild inflammation selectively increased alerting-related alpha suppression.

• A greater inflammatory response was correlated with more alpha suppression.​

Abstract

Illness is often accompanied by perceived cognitive sluggishness, a symptom that may stem from immune system activation. The current study used electroencephalography (EEG) to assess how inflammation affected three different distinct attentional processes: alerting, orienting and executive control. In a double-blinded placebo-controlled within-subjects design (20 healthy males, mean age = 24.5, SD = 3.4), Salmonella typhoid vaccination (0.025 mg; Typhim Vi, Sanofi Pasteur) was used to induce transient mild inflammation, while a saline injection served as a placebo-control. Participants completed the Attention Network Test with concurrent EEG recorded 6 h post-injection. Analyses focused on behavioral task performance and on modulation of oscillatory EEG activity in the alpha band (9–12 Hz) for alerting as well as orienting attention and frontal theta band (4–8 Hz) for executive control. Vaccination induced mild systemic inflammation, as assessed by interleukin-6 (IL-6) levels. While no behavioral task performance differences between the inflammation and placebo condition were evident, inflammation caused significant alterations to task-related brain activity. Specifically, inflammation produced greater cue-induced suppression of alpha power in the alerting aspect of attention and individual variation in the inflammatory response was significantly correlated with the degree of alpha power suppression. Notably, inflammation did not affect orienting (i.e., alpha lateralization) or executive control (i.e., frontal theta activity). These results reveal a unique neurophysiological sensitivity to acute mild inflammation of the neural network that underpins attentional alerting functions. Observed in the absence of performance decrements, these novel findings suggest that acute inflammation requires individuals to exert greater cognitive effort when preparing for a task in order to maintain adequate behavioral performance.​

Salient points:

Almost all (98 percent) AD patients surveyed report they suffer from fatigue.

● Nine-in-10 (89 percent) say it is a "major issue" for them and six-in-10 (59 percent) say it is "probably the most debilitating symptom of having an AD."

● More than two-thirds (68 percent) say their "fatigue is anything but normal. It is profound and prevents [them] from doing the simplest everyday tasks."

Medicine finally looking at brain fog. Comments on this Reddit thread below are interesting, highlighting just how important brain fog is to patients despite seeing barely any interest from researchers and clinicians. So much agreement that this is a very significant symptom.

Surprised they used EEG, though. Very low-tech and inexpensive compared to MRIs and other complex imaging.

 

[MeSci]

What is meant by 'AD'? It usually means Alzheimer's Disease, but I'm guessing not here.

 

[feeb]

Attention deficit, I think (but I could be wrong, haven't read the paper).

 

[rvallee]

What is meant by 'AD'? It usually means Alzheimer's Disease, but I'm guessing not here.

Autoimmune diseases.

 

[Hutan]

What an interesting study @rvallee. Really nice that they blinded it.
I look forward to seeing the whole paper. @Woolie, maybe one for you to look at?

requires individuals to exert greater cognitive effort when preparing for a task in order to maintain adequate behavioral performance

So no difference in the performance, but the same level of performance seemed to be taking more effort.

Specifically, inflammation produced greater cue-induced suppression of alpha power in the alerting aspect of attention and individual variation in the inflammatory response was significantly correlated with the degree of alpha power suppression.

I've read the Wikipedia page on alpha waves and I'm none the wiser really. This was interesting:

Following this lapse-of-attention line of thought, a recent study indicates that alpha waves may be used to predict mistakes. In it, MEGs measured increases of up to 25% in alpha brain wave activity before mistakes occurred. This study used common sense: alpha waves indicate idleness, and mistakes are often made when a person is doing something automatically, or "on auto-pilot", and not paying attention to the task they are performing. After the mistake was noticed by the subject, there was a decrease in alpha waves as the subject began paying more attention. This study hopes to promote the use of wireless EEG technology on employees in high-risk fields, such as air traffic controlling, to monitor alpha wave activity and gauge the attention level of the employee

So, if alpha waves suggest idleness or lack of attention, suppression of them, as seemed to be happening in the people with inflammation, suggests more effort is being made to pay attention.

 

[obeat]

Neil Harrison started his research using typhoid vaccine.

 

[MeSci]

So no difference in the performance, but the same level of performance seemed to be taking more effort.

That's how it was for me until 2016. Then my brain went doolally for a while, and it hasn't really recovered.

I got really good grades in my OU studies, but they took more effort, and sometimes I couldn't do them.

 

[rvallee]

So no difference in the performance, but the same level of performance seemed to be taking more effort.

And of note that this was mild inflammation. I really hope they can pursue this and use a gradation scale of severity and how it relates to performance. At some point there should be a significant drop in performance, especially in sustaining it past a certain point. Not sure if it's even possible to grade brain inflammation with high certainty, though. It should surely correlate strongly with overall ability to function.

In my case there would be a significant difference between my former healthy self, but then there would be another significant drop in performance during the test after exhaustion sets in. Unfortunately impossible to compare with former selves but the drop in performance from PEM would be very significant and likely drop to a shocking level if demanded to sustain too long.