Automatic and controlled information processing in multiple sclerosis.

The purpose of this study was to evaluate the kind of slowing of information processing associated with multiple sclerosis and how this possible slowness is related to cognitive deterioration. We selected 45 patients with definitive multiple sclerosis diagnosis and 35 control subjects. Twenty-two patients had mild cognitive deterioration and 23 patients had preserved cognitive capacities, otherwise the groups were matched. Using computerized tests, we investigated three separate stages of information processing: automatic and controlled processing, and motor programming. The results indicate that patients with mild cognitive deterioration are slower than patients with preserved capacities or controls in every stage of processing measured in this study. Additionally, the preserved patients showed signs of mild slowing in automatic visual processing. These results show that, in multiple sclerosis patients, widespread information processing slowness is associated with multiple sclerosis-related cognitive deterioration. This study emphasizes the importance of studying subgroups rather than cognitively heterogeneous patient samples and, furthermore, the need to divide information processing into different stages is indicated.