Mental sluggishness explained by inflammation in new study

Source: Daniel Lombraña González (via Flickr)

By Holly Giles


12m UK citizens have chronic medical conditions, of which a side effect is ‘mental sluggishness’. This is a feeling of mental fatigue or lethargy meaning it can be difficult to process commands, interpret information and process cues affecting everyday life and a general feeling of wellness. Despite affecting so many people it is not known what causes mental sluggishness, explains Dr Mazaheri from Birmingham  University’s Centre for Human Brain Health; “Scientists have long suspected a link between inflammation and cognition, but it is difficult to be clear about the cause and effect. For example, people living with a medical condition… 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”. However, in a recent paper published in NeuroImage, scientists from the University of Birmingham and the University of Amsterdam, have been able to prove this neurophysiological link between inflammation and mental lethargy. 


Work was conducted by both teams under the supervision of PhD student Leonie Balter. The study recruited twenty young men who received an injection and were then subjected to various mental processing tasks while their brain activity was monitored and recorded via an EEG. This injection was varied between a placebo of of water that had no effect and a substance known to cause temporary inflammation in the brain. The tests were designed to study  three different processes of the brain: alerting which involves maintaining an alert state of mind, orientiating which is the process of prioritising incoming sensory information and executive control which decides what stimuli to pay attention to. 


Despite completing the same tests on both occasions the results showed that inflammation directly affects brain activity. Balter concluded this with the statement “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”.


The success of the study was seconded by Dr Mazaheri who said “these results show quite clearly that there’s a very specific part of the brain network that’s affected by inflammation” and that “this could explain brain fog”. 


These results are significant not only for increasing our understanding of the reasoning behind the mystery of mental sluggishness but also for potential treatments of inflammatory diseases. The next step for researchers is to look at the effect of inflammation on working memory with hopes to transfer this knowledge to clinical cases, such as those of alzheimers and dementia. Balter explained that she hopes this research could eventually help patients with conditions of chronic-inflammation, such as obesity, kidney disease and alzheimer’s through anti-inflammatory drugs to improve or preserve cognitive function.


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