Scientists at the University of Birmingham, in collaboration with the University of Amsterdam, have found a possible explanation for the mental sluggishness that often accompanies illness. For example, an estimated 12 million British citizens suffer from a chronic illness. Many of them also report severe mental fatigue, which they describe as “sluggishness” or “lightheadedness.” This condition is often as debilitating as the disease itself.
Mental inertia in research
A team at the university's Center for Human Brain Health investigated the connection between this mental fog and inflammation. Medicine links this to the body's response to disease. In a study published in “Neuroimage” they show that inflammation has a particularly negative impact on the brain’s readiness. As a result, the human organ cannot reach and maintain the alarm state.
Dr. Ali Mazaheri and Professor Jane Raymond from the university's Center for Human Brain Health are the study's lead authors. Dr. Mazaheri says: “Scientists have long suspected a link between inflammation and cognition, but it is very difficult to clarify the cause and effect. For example, people who suffer from an illness or are severely overweight may complain of cognitive impairment. However, it is difficult to say whether this is due to the inflammation associated with these conditions or if there are other reasons. “So research has identified a specific critical process in the brain that is clearly only affected when inflammation is present.
Conducting new study
The study specifically focused on an area of the brain responsible for visual attention. A group of 20 young male volunteers participated and received a salmonella typhoid vaccine. This causes temporary inflammation but has few other side effects. The tests tested subjects for cognitive responses using simple images on a computer screen a few hours after the injection. This allowed the scientists to measure their ability to control attention. Brain activity was clearly visible while the attention tests were running.
On another day, they were given an injection of water (a placebo) and performed the same tests. On each test day, they did not know which injection they had received. The researchers measured their condition through daily analysis by taking blood from them. The tests used in the study assessed three separate attentional processes, each involving different parts of the brain. These processes are: “alerting,” which involves achieving and maintaining an alert state; “Orienting,” which involves selecting and prioritizing useful sensory information; and “executive control,” used to clarify what to pay attention to when available information conflicts.
Scientific results
The results showed that inflammation specifically affected brain activity related to maintaining alertness, while the other attentional processes appeared to be unaffected by inflammation. “These results show quite clearly that there is a very specific part of the brain network that is affected by inflammation,” says Dr. Mazaheri. "This could explain 'brain fog'." Professor Raymond said: “This research is an important step forward in understanding the links between physical, cognitive and mental health. They tell us that even the mildest illnesses can reduce alertness.”
Dr. Leonie Balter, the first author of the study, completed as part of her doctorate, concluded: “A better understanding of the links between inflammation and brain function will help us explore other ways to treat some of these diseases. For example, further research may show that patients with chronic inflammation such as obesity, kidney disease or Alzheimer's may benefit from anti-inflammatory medications to maintain or improve cognitive function. “
“In addition, science may use subtle changes in brain function as early marker cognitive deterioration in patients with inflammatory diseases.” The next step for the team is to test the effects of inflammation in other areas of brain function, such as memory.
