Changes of resting state brain networks in amyotrophic lateral sclerosis.

The defining feature of amyotrophic lateral sclerosis is degeneration of upper and lower motor neurons but extramotor involvement, evidenced for example by executive dysfunction, has also been demonstrated. Here we employed a novel functional imaging approach, the analysis of resting state activity, followed by the definition of functionally connected brain networks by independent component analysis (ICA) to assess differences between ALS patients (n=20) and healthy controls (n=20). ICA analysis revealed 5 typical brain networks among which the so-called default mode network and the sensori-motor network showed distinct differences between patients and controls. The default mode network showed less activation in patients in several regions including the ventral anterior cingulate cortex, posterior cingulate cortex and the left and right inferior parietal cortex, regions that have been linked previously to executive functions. The sensori-motor network showed group differences in the premotor cortex. We propose that resting state analysis affords a new and simple means to assess disease-related neurofunctional alterations in widespread brain networks. A decisive advantage is that no task is demanded from the subjects and, thus, the problem of differential task difficulty and effort between groups is circumvented.