The role of the corpus callosum in dichotic listening: a combined morphological and diffusion tensor imaging study.

The objective of the present study was to examine the role of the corpus callosum (CC) in dichotic listening. For this purpose, 40 right-handed healthy male participants were assessed with morphological and diffusion tensor imaging, which yielded macrostructural (midsagittal area) and microstructural (mean diffusion, fractional anisotropy) measures of the total CC and predefined subregions. Applying the standard consonant-vowel Bergen Dichotic Listening Test (including 3 different attentional instructions), the authors found dichotic listening performance to be substantially related to the integrity of the CC at both macro- and microstructural levels. Results indicate a dual role of the CC; it is relevant not only for the stimulus-driven (bottom-up) transfer of left-ear input to the left hemisphere but also for its attentional (top-down) modulation.