November 15, 2019
University of Birmingham
Summary:
Scientists have uncovered a
possible explanation for the mental sluggishness that often accompanies
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.
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.
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 particular 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. Dr Mazaheri says: "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."
"Our research has
identified a specific critical process within the brain that is clearly
affected when inflammation is present."
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," says Dr Mazaheri. "This could explain 'brain
fog'."
Professor Raymond says,
"This research finding is 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."
Dr Leonie Balter the first
author of the study which was completed as part of her PhD, concluded :
"Getting a better understanding of the relationships between inflammation
and brain function will help us investigate other ways to treat some of these
conditions. For example, further research might show that patients with
conditions associated with chronic inflammation, such as obesity, kidney
disease or Alzheimer's, could benefit from taking anti-inflammatory drugs to
help preserve or improve cognitive function."
"Furthermore, subtle
changes in brain function may be used as an early marker cognitive
deterioration in patients with inflammatory diseases."
The next step for the team
will be to test the effects of inflammation on other areas of brain function
such as memory.
Story Source:
Materials provided by University of Birmingham. Note:
Content may be edited for style and length.
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
DOI: 10.1016/j.neuroimage.2019.116098
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