Electrographic study was carried out in Wistar rats and the rats of genetical catalepsy (GC) strain. In contrast to Wistar rats epileptiform activity was observed in ECoG of GC rats being enhanced at the transition to a cataleptic state. Analysis of spectra and coherence of EEG revealed the presence of interhemispheric brain asymmetry in all the rats. In some frequency bands in GC rats inversion of interhemispheric asymmetry was found, which had been characteristic for Wistar strain. The highest interhemispheric synchronization of biopotentials was observed in the frontal cortical areas in GC rats and in the occipital areas in those of Wistar strain.