Corpus callosum function in verbal dichotic listening: Inferences from a longitudinal follow-up of Relapsing-Remitting Multiple Sclerosis patients

This study conducted a follow-up of 13 early-onset slightly disabled Relapsing-Remitting Multiple Sclerosis (RRMS) patients within an year, evaluating both CC area measurements in a midsagittal Magnetic Resonance (MR) image, and Dichotic Listening (DL) testing with stop consonant vowel (C-V) syllables. Patients showed a significant progressive loss of posterior CC areas (isthmus and splenium) related to increasing EDSS scores and an enhancing right ear advantage (REA) over time. A significant correlation between posterior CC areas and DL scores emerged in both evaluations, being negative for the right and positive for the left ear. The pattern of correlations suggests that the CC can serve an inhibitory and also excitatory influence on the contralateral hemisphere when studying the phonological processing of language. Statement of significance to the neuroscience of language: The scope of the manuscript is language lateralization. The task used in the experiment is a verbal dichotic listening task, tapping the most basic phonological aspects of language. Finally, the available research is scarce when focusing on the interhemispheric excitation or inhibition of the corpus callosum in linguistic functioning. (C) 2009 Elsevier Inc. All rights reserved.