Alternative Neuropsychological and Magnetic Resonance Imaging Measures in Multiple Sclerosis. Exploring the relation between brain lesion measured by diffusion tensor magnetic resonance imaging and interhemispheric communication and processing speed in multiple sclerosis

Article history:Accepted 3 June 2008Available online 11 June 2008In this study, callosal function was behaviourally tested in MS patients with a redundantstimuli task. Reaction times to uniand bilateral visual stimuli are recorded. Normalsubjects respond faster to bilateral than to unilateral stimuli. This effect is called theredundancy gain effect. In patients with agenesis of the corpus callosum, the redundancygain exceeds that predicted by probability summation, suggesting a mediating influence ofthe corpus callosum in healthy controls. The aim of this study is to investigate the effect ofcallosal damage on the redundancy gain in MS patients by investigating the probabilitysummation model. Seventeen MS patients and as many matched healthy controlsperformed the redundancy gain task. In order to objectify callosal damage in our MSgroup, diffusion tensor imaging (DTI) derived measures such as fractional anisotropy (FA)and mean diffusivity (MD) in the corpus callosum were obtained. Callosal FA and MDsignificantly differed in our MS group compared to the healthy controls, indicatingpathological callosal involvement. Since the amount of callosal damage was highlyvariable within the MS group, the MS cohort was split into a low and a high callosal-injured group as quantified by FA. The high FA group performed like the healthy controls,whereas violations of the probability (race) model were found for the low FA group. Weconclude that behavioural measures obtained by the redundancy gain paradigm reflectcallosal pathology in MS as measured by DTI.© 2008 Elsevier B.V. All rights reserved.