Resting-state functional connectivity alterations after mild COVID-19 infection.

The long-term effects of coronavirus disease 2019 (COVID-19) are more pronounced after severe infection, although years after the pandemic was declared, long-term neurological complications after mild infection have begun to unfold. The most common complaints include fatigue and cognitive disturbances. Brain imaging techniques have also revealed structural and functional alterations. In the present study, we included 40 subjects who recovered after mild COVID infection and 36 healthy control subjects. We administered mental health–related questionnaires assessing fatigue and sleep disturbances, performed neuropsychological tests and analysed resting-state functional connectivity using multivariate pattern analysis. Our results indicate no cognitive dysfunction in the post-infection group, but alterations in functional connectivity manifested as mixed hyper- and hypoconnectivity compared to the control group. Altered resting-state functional connectivity might be an adaptive neural response to structural alterations, as seen in viral infections in general. Our results suggest that despite the lack of any neurological complaints or neurocognitive signs, the presence of increased and decreased functional connectivity might be a part of natural recovery from mild COVID-19 infection or the sign of ongoing post-COVID neurological sequele.