Morphometric comparison of the human corpus callosum in deaf and hearing subjects: an MRI study

SummaryAuditory cortices are interconnected to each other by fibers passing through the corpus callosum (CC). In totally deaf persons no auditory impulses are conveyed to the auditory cortices, hence the auditory pathways become nonfunctional. It was reported that there has been cross-modal plasticity between auditory, visual, and somatosensory cortices. In this study, our aim was to make a comparison in the CC morphometry in hearing subjects and in a selected group in which the auditory system was deprived before the age of 2. 18 deaf and 18 hearing male, handedness matched volunteers, ages varying between 28 and 56 years old were examined. Audiometrical tests were applied to both groups and then T1-weighted midsagittal MR images were obtained. Certain dimensions and areas were measured on these images. There were no statistically significant difference between deaf and hearing subjects, either when dimensions and areas were analyzed by multivariate analysis of variance or when areas were analyzed by univariate analysis of variance. Absence of any significant morphometric difference in the CC of deaf subjects could be thought as an evidence of reflection of functional cortical plasticity.

RésuméLes fibres qui connectent les cortex auditifs passent par le corps calleux. Chez les sujets sourds, aucun signal auditif n’arrive au cortex auditif et, pour cette raison, les voies auditives deviennent non fonctionnelles. Une plasticité cross-modale entre les cortex auditifs, visuels et somatosensoriels a été rapportée. Le but de notre travail est de comparer la morphologie du corps calleux chez les personnes dont la surdité était antérieure à l’âgede deux ans et les sujets entendants. La population étudiée comportait 18 sourds et 18 volontaires sains, d’âges variant entre 28 et 56 ans, de sexe masculin et appariés selon la dominance motrice. Les tests audiomètriques ont été effectués dans les deux groupes et la coupe sagittale médiane en IRM a permis les mesures de longueur et de surface. Aucune différence significative entre ces mesures n’a été observée ; cette donnée peut être la traduction de la plasticité fonctionnelle du cortex auditif.