EEG interhemispheric correlation after callosotomy: one case study.

High interhemispheric EEG correlation (INTERr) or coherence has been interpreted as a consequence of callosal interconnections. The EEG of a callosotomized (two anterior thirds) 32-yr.-old patient was recorded during relaxed wakefulness with eyes closed. 100 2-sec. artifact-free epochs were digitally filtered into traditional broad bands and INTERr was calculated by means of Pearson product-moment coefficients. INTERr between anterior regions, where they should be expected, showed very few differences between data of this patient and those of two control groups of healthy persons. Only a few differences were observed between posterior regions where the callosum was intact. These results suggest that the role of the callosum is not crucial for INTERr and that subcortical influences and functional differentiation between hemispheres may be more plausible explanations for INTERr.