Abstract:Objective. To assess whether abnormalities on functional magnetic resonance imaging (fMRI) are related to cognitive function in patients at presentation with clinically isolated syndrome (CIS) suggestive of MS. Methods. Eighteen CIS patients and 15 healthy controls (HC) performed an adapted fMRI version of the Paced Auditory Serial http://mc.manuscriptcentral.com/multiple-sclerosis Multiple Sclerosis Journal F o r P e e r R e v i e w Addition Test (PASAT). According to their PASAT performance, CIS patients were divided into two groups: 10 with a low PASAT performance (< 1SD from the mean value of HC) were considered "cognitive impairment" (CI); 8 patients were defined as "cognitively preserved" (CP). Between-group differences in the patterns of brain activations and effective connectivity were assessed. Results. During PASAT, compared to HC, CIS patients showed increased activations of the bilateral inferior parietal lobe (IPL), bilateral precuneus, bilateral middle frontal gyrus (MFG), left anterior cingulate cortex (ACC), left claustrum, right thalamus and right caudate nucleus. When CIS patients were analyzed, the CI group had a more significant activation of the bilateral IPL than HC and CP patients. Compared to CP patients, they also had more significant recruitment of the right superior parietal lobe, right cerebellum, left MFG and left ACC. The analysis of effective connectivity showed stronger connections between several regions of the right hemisphere involved in working memory function in CI patients vs. CP and HC. Conclusions. The observed differences in the patterns of cortical recruitment and connectivity in CI patients during PASAT performance are likely to be adaptive and have a role in limiting cognitive dysfunctions early in the course of MS. Methods. Eighteen CIS patients and 15 healthy controls (HC) performed an adapted fMRI version of the Paced Auditory Serial Addition Test (PASAT). According to their PASAT performance, CIS patients were divided into two groups: 10 with a low PASAT performance (< 1SD from the mean value of HC) were considered "cognitive impairment"(CI); 8 patients were defined as "cognitively preserved" (CP). Between-group differences in the patterns of brain activations and effective connectivity were assessed. Conclusions. The observed differences in the patterns of cortical recruitment and connectivity in CI patients during PASAT performance are likely to be adaptive and have a role in limiting cognitive dysfunctions early in the course of MS.