Activation patterns in multiple sclerosis on the Computerized Tests of Information Processing

Abstract

Rationale Multiple sclerosis (MS) patients exhibit cognitive deficits that negatively impact quality of life. The Relative Consequence Model suggests that problems with information processing speed (IPS) may be the basis for many of these cognitive difficulties. Objective To investigate, with functional magnetic resonance imaging (fMRI), if an IPS task (the Computerized Test of Information Processing (CTIP)) would reveal neurophysiological differences between MS patients and matched controls. Methods Performance and neural activation were investigated in twelve cognitively impaired MS patients and 12 matched controls as each performed the CTIP. The CTIP measures reaction time (RT) and errors on three tasks (simple RT, choice RT and semantic search RT) with increasing cognitive demands. Results Participants demonstrated increased RT with increased task complexity. Patients showed longer RTs for the choice RT condition than controls but the pattern of performance across tasks did not vary between groups. Errors were not significantly different between groups. Imaging results for both the choice and the semantic search conditions revealed significant differences between groups involving a compensatory increase in activation in MS participants compared to controls in prefrontal cortex and right temporal gyri. However, there were also areas of decreased activity in MS participants when compared with controls in left temporal gyri. Conclusions Significantly different neural activation patterns between MS patients and controls were associated with IPS, as measured by the CTIP.