Exploratory data analysis reveals visuovisual interhemispheric transfer in functional magnetic resonance imaging.

We used an exploratory data analysis approach to detect interhemispheric processing of complex visual stimuli in functional magnetic resonance imaging (fMRI). A crossed-uncrossed visual field paradigm was used to elicit interhemispheric transfer of picture/word information. Under the uncrossed (control) condition, the stimuli were presented to the preferential hemispheres (pictures to the left visual field/right hemisphere and words to the right visual field/left hemisphere). Under the crossed condition, the visual field presentation was switched in order to elicit increased interhemispheric processing. Fuzzy cluster analysis revealed significantly more crossed activity in cortical areas near the splenium of the corpus callosum. As expected, examination of the activation revealed smaller responses in perisplenial regions (relative to visual responses in the medial extrastriate regions). The exploratory results were compared with those obtained from parametric and masked analyses. The findings confirm that fMRI can be used to detect interhemispheric transfer of picture/word information. The activation was optimally characterized using exploratory data analysis. (c) 2006 Wiley-Liss, Inc.