| Cognitive slowing has been firmly established as one of the few primary cognitive deficits associated with multiple sclerosis (MS). Numerous studies have documented impairments in speed of information processing for MS patients relative to healthy controls, but the present study was the first to investigate individual variability in speed of information processing in persons with MS. Thirty-nine patients with relapsing-remitting or secondary progressive MS and 32 healthy control participants completed a series of RT tests, the Stroop Test and the Rey Auditory Verbal Learning Test. MS patients performed more poorly than control participants across measures of speeded processing, responding more slowly and with greater trial-to-trial variability relative to healthy controls. The most robust group differences were observed on tests posing the greatest burden on rapid processing, with effect sizes for measures of individual variability on the most demanding tasks rivaling those of traditional measures of processing speed. |
