Corpus callosum and propagation of afterdischarge to contralateral cortex and thalamus.

The patterns of seizure spread were investigated in cats with experimental seizure foci in the motor cortex. Recordings were made with tungsten microelectrodes. When convulsive activity developed at the focus, there was activation of the ipsilateral thalamus before there was propagation of afterdischarge to the opposite hemisphere. Section of the corpus callosum did not prevent propagation of afterdischarge to the contralateral thalamus, and prolonged the circulation of abnormal activity between the cortex and ipsilateral and contralateral thalamus.