The summated scores vary from 0 to 160. To estimate cognitive functions the Swedish version of the Perceived Deficit Questionnaire (PDQ; Sullivan et al. 1990) was used. In 20 items, the participant’s self-reported memory, alertness, and perceived concentration functions are graded from 0 (never) to 4 (nearly always). The summated score for PDQ is 0–80. Physical disability was assessed by a neurologist using EDSS (Kurtzke 1983). Inhibitors,research,lifescience,medical Before coming to the fMRI session, the controls were asked to fill in a health declaration form, including questions about

eventual brain surgery, present medications, drug or alcohol abuse, cognitive impairments, and PDQ. At the scanning session all participants were given a paper and pencil version of the complex working memory task (Sepantronium Bromide manufacturer Daneman and Carpenter 1980). They were also familiarized with the task they would later conduct during fMRI scanning by performing a short version of the task on a computer. In Inhibitors,research,lifescience,medical addition, all participants carried out the Digit Span task as well as vocabulary, story recall, and complex figure tasks. Before and after the fMRI session the participants marked their actual degree of fatigue, depression, anxiety, and sleepiness on visual analog scales

(VAS). The symptoms were graded from zero to ten, where zero indicated Inhibitors,research,lifescience,medical no problem and ten severe problem of each symptom, respectively. After the scanner adjustment procedure, the participants were asked to rest with their eyes closed for 4–5 minutes while resting state fMRI images were acquired (data not reported here). Thereafter, the working memory fMRI session started, as described Inhibitors,research,lifescience,medical below. Complex working memory task In the complex working memory task (working memory span) administered before the fMRI scanning, the

participants listened to a set of sentences, some of which were semantically correct and some incorrect (Daneman and Carpenter 1980). The participants were instructed to report whether Inhibitors,research,lifescience,medical the sentences were correct or not and to remember the last word in each sentence. This procedure was repeated for 1–5 sentences. After the sentences had been much presented, the participants were asked to recall all the target words in the correct order. The working memory task in the scanner was similar to the paper and pencil working memory task. The main differences were (1) the sentences were presented visually for 5 sec each, (2) after each set of sentences, five words were presented for 5 sec each and the participants were asked to indicate if these words were target words or new words (lures), (3) the procedure was repeated for 1–4 sentences. The participants were instructed to answer as quickly and as accurately as they could. Task duration was 14 min. This task is described in more detail in Engström et al. (2009).