Speed of information processing in patients with multiple sclerosis

To determine the extent to which multiple sclerosis (MS) slows cognitive processes, speeded tasks were administered to 11 patients with MS and to 11 comparison subjects without MS. On all tasks, patients with MS responded more slowly than comparison subjects. More important, response times (RTs) for patients with MS increased systematically as a function of RTs for comparison subjects, and the increase was best described by a power function. These data are consistent with the view that MS produces a general slowing of cognitive processes, and with the view that the cognitive slowing associated with aging reflects neural noise.