Sleep architecture in agenesis of the corpus callosum: laboratory assessment of four cases.

Whether the corpus callosum is essential for normal human sleep cannot be decided from current knowledge. We thus studied sleep architecture in four subjects with agenesis of the corpus callosum (ACC) and four control subjects matched for age, gender, and hand preference. All-night EEG, EOG, and EMG activity were monitored in the laboratory for one adaptation night and one data acquisition night. Standard sleep variables were calculated for the second night. Agenesis subjects were found to have a greater percentage of stage 3 + 4 sleep and a lower percentage of stage 2 sleep than control subjects. Agenesis subjects also tended to have more REM sleep periods and a shorter REM cycle length than controls. The pattern of results is similar to that produced by partial callosotomy. It is also relevant to two hypotheses about the function of the corpus callosum in sleep. First, the corpus callosum may facilitate synchronization of activity between homologous regions in the two hemispheres but interfere with synchronization of neuronal populations within each hemisphere. Its absence may thus explain both an augmentation of slow-wave activity (and thus more slow-wave sleep) and a decrease in interhemispheric EEG coherence. Secondly, the corpus callosum may play a role in the regulation of the ultradian rhythm which underlies timing and duration of REM sleep.