Efficiency of callosal transfer and hemispheric interaction.

The corpus callosum (CC) is essential to hemispheric interaction, but it is unclear how individual callosal properties affect interaction between the cerebral hemispheres. A number of studies have demonstrated some relationship between morphology or structure of the CC and measures of hemispheric interaction. However, to the authors' knowledge, none of these studies has been able to show a clear, direct relationship between a behavioral measure of transfer speed through the CC, interhemispheric transfer time (IHTT), and a behavioral measure of hemispheric interaction. Eighty participants were tested over 6 sessions on 2 tasks assessing IHTT and hemispheric interaction. The Poffenberger paradigm was used to measure IHTT, and a divided split-visual-field letter-matching task was used to assess hemispheric interaction. A significant correlation that could not be accounted for by other factors such as functional lateralization, handedness, age, sex, or attention was found between these 2 measures. These results are discussed in relation to CC morphology and structure and functional and structural hemispheric lateralization.