In a new study, researchers have uncovered a possible explanation for the mental sluggishness that often accompanies illness.
The research was conducted by scientists at the University of Birmingham in collaboration with the University of Amsterdam.
An estimated 12 million U.K. 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.
Scientists have long suspected a link between inflammation and cognition, but it is very difficult to be clear about the cause and effect.
For example, people living with a medical condition or being very overweight might complain of cognitive impairment, but it’s hard to tell if that’s due to the inflammation associated with these conditions or if there are other reasons.
In the study, the team examined the link between this mental fog and inflammation—the body’s response to illness.
They found that inflammation appears to have a particularly negative impact on the brain’s readiness to reach and maintain an alert state.
The study focused specifically on an area of the brain which is responsible for visual attention.
A group of 20 young male volunteers took part and received a salmonella typhoid vaccine that causes temporary inflammation but has few other side effects.
They were tested for cognitive responses to simple images on a computer screen a few hours after the injection so that their ability to control attention could be measured.
Brain activity was measured while they performed the attention tests.
On a different day, either before or after, they received an injection with water (a placebo) and did the same attention tests. On each test day, they were unaware of which injection they had received.
Their inflammation state was measured by analyzing blood taken on each day.
The tests used in the study assessed three separate attention processes, each involving distinct parts of the brain.
These processes are: “alerting” which involves reaching and maintaining an alert state; “orienting” which involves selecting and prioritizing useful sensory information; and “executive control” used to resolving what to pay attention to when available information is conflicting.
The results showed that inflammation specifically affected brain activity related to staying alert, while the other attention processes appeared unaffected by inflammation.
These results show quite clearly that there’s a very specific part of the brain network that’s affected by inflammation. This could explain ‘brain fog.’
This research finding is a major step forward in understanding the links between physical, cognitive, and mental health and tells us that even the mildest of illnesses may reduce alertness.
The next step for the team will be to test the effects of inflammation on other areas of brain function such as memory.
One author of the study is Dr. Ali Mazaheri.
The study is published in Neuroimage.
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