What is the impact of a viral infection on our memory, attention, or concentration? The Covid-19 pandemic has revived interest in this question, now extended to other infections such as HIV, herpes, or hepatitis.
Despite several decades of research, the effects of viral infections on cognitive functions - memory, concentration, attention - remain poorly understood. Most studies rely on global screening tools, applied separately to each disease.
The emergence of the SARS-CoV-2 virus, as well as the frequency and persistence of post-infectious cognitive sequelae, have nevertheless revived interest in this field of research.
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The emergence of the SARS-CoV-2 virus, as well as the frequency and persistence of post-infectious cognitive sequelae, have nevertheless revived interest in this field of research.
In a new study, a team from UNIGE and HUG gathered and analyzed the results of 931 scientific articles focusing on the links between the immune system and cognitive functions, across different viral infections such as SARS-CoV-2, HIV, herpes, or hepatitis.
"Our goal was to adopt a transversal approach to go beyond the fragmented view that prevails in this field," explains Julie Péron, associate professor at the Clinical and Experimental Neuropsychology Laboratory of the Faculty of Psychology and Educational Sciences and at the Interfaculty Center for Affective Sciences of UNIGE, and a consulting neuropsychologist at the Neurology Service of the Department of Clinical Neurosciences of HUG.
Several biological "signatures" identified
This analysis confirms that persistent inflammation - initially the body's natural response to an aggression - could be associated with memory and concentration disorders. But above all, it highlights certain biological markers of the immune system linked to variations in cognitive performance.
"High levels of white blood cells called 'activated monocytes' and pro-inflammatory cytokines - proteins that allow the immune system to communicate - are correlated with a decline in episodic memory and information processing speed," says Anthony Nuber-Champier, a PhD student at the Clinical and Experimental Neuropsychology Laboratory of the Faculty of Psychology and Educational Sciences and at the Interfaculty Center for Affective Sciences of UNIGE, and the study's first author.
Conversely, some markers, such as activated CD4+ T lymphocytes - also white blood cells - or anti-inflammatory cytokines, seem to be associated with better preservation of cognitive abilities. "However, immune responses vary from person to person. What appears to be decisive is the balance between these different inflammatory signals to maintain lasting cognitive stability," emphasizes the researcher.