Washington D.C. [USA], Nov 18 : A recent study uncovered a possible explanation for why a person with mental sluggishness often faces illness.
Scientists at the University of Birmingham in collaboration with the University of Amsterdam have uncovered a possible explanation for the mental sluggishness that often accompanies illness.
A team in the University's Centre for Human Brain Health investigated the link between this mental fog and inflammation -- the body's response to illness.
In a study published in - Neuroimage -- they show that inflammation appears to have a particularly negative impact on the brain's readiness to reach and maintain an alert state.
Dr Ali Mazaheri and Professor Jane Raymond of the University's Centre for Human Brain Health are the senior authors of the study.
"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," said Dr Mazaheri.
"Our research has identified a specific critical process within the brain that is clearly affected when inflammation is present," added Dr Mazaheri.
The study focussed 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 analysing 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 prioritising 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," said Dr Mazaheri. "This could explain 'brain fog'."