In people who have had an infection relatively easily, the volume of gray matter is reduced and intelligence is reduced.
This discovery was made by researchers from the University of Oxford (UK), whose article In the magazine Nature.
The scientists analyzed the results of magnetic resonance imaging (MRI) and brain function testing of 785 people. Scans and tests were carried out twice: the first time before, and the second time during the pandemic. In this time frame of about three years, approximately 400 participants had a mild case of covid. On average, almost five months elapsed between recovery and the second examination.
Comparison of the scan results showed that in those who had been ill, there was a decrease in the volume of the brain as a whole.
and a decrease in gray matter density in two regions of the brain — the orbitofrontal cortex and the hippocampal gyrus, in particular. The orbitofrontal cortex is associated with the senses of taste and smell, as well as emotion regulation, motivation, and decision making, while the hippocampus is responsible for memory.
Compared to the “pre-Covid” parameters, the brains of those who had been ill “shrank” by 0,2-2% — about the same amount of brain volume is reduced in a year — six years during the natural aging process. In addition, in people who had Covid, neural connections were disrupted in certain areas of the olfactory cortex.
As for the results of cognitive tests, here, the recovered patients also showed a significant deterioration compared to pre-Covid times.. They performed worst on tests of concentration and mental flexibility.
The reasons behind the negative effect that covid has on the brain have yet to be established. The researchers do not rule out that the effect of the virus on smell-related neural pathways, infection-induced inflammation in brain tissue, or sensory deprivation during the loss of smell may be to blame.