Functional connectivity changes in long-Covid patients with and without cognitive impairment.

Long-Covid is associated with cognitive deficits in memory, attention, or executive function. However, the associated cerebral structural and functional changes are insufficiently studied to date. We investigated 39 long-Covid patients with (n = 16) and without (n = 23) cognitive impairment. Impairment was defined by a pronounced deficit (-1.5 SD) in at least one cognitive domain including memory, attention, executive function, and verbal fluency. All participants underwent structural and functional resting-state magnetic resonance imaging (MRI). We assessed differences in resting-state networks (within and between networks) between both groups as well as structural differences in total gray matter and subcortical volumes. Both groups did not differ in demographic or disease-related characteristics. Patients with cognitive deficits showed higher functional connectivity (FC) between the default mode network (DMN) and parts of the posterior supramarginal gyrus, angular gyrus and posterior-occipital part of the middle temporal gyrus, compared to those cognitively unimpaired. In addition, inter-network analyses indicated a stronger connectivity between the visual and ventral stream network in those with cognitive impairment. We found no volumetric differences between the two groups. Our results indicate that altered FC with the DMN as well as a stronger connectivity between the visual and ventral stream network in cognitively impaired long-Covid patients are associated with worse cognitive performance and therefore suggests a maladaptive functional change.