Asymmetry of the interhemispheric visuomotor integration in callosal agenesis.

We measured visuomotor responses following the Poffenberger paradigm in an acallosal boy, without other detectable neural defects. In this task crossed and uncrossed RT reflect the time of intra- and interhemispheric integration and the difference (CUD) estimates the interhemispheric transfer time. CUDs in the hemifields were largely asymmetrical in this subject, suggesting that visuomotor processing is extremely lengthened when the right hemisphere (RH) detects the light and the left hemisphere (LH) controls the motor output whereas it is very fast in the opposite direction. This asymmetry, which is present in comparable data available from the literature, may indicate the functional superiority of the LH in controlling the ipsilateral hand, as suggested by recent MRI findings.