Paroxysmal activity in the rabbit visual cortex induced by photostimulation.

The combination of two epileptogenic factors--rhythmic photostimulation at frequencies of 5-6 Hz, and local injury to the visual cortex by freezing--were used to induce paroxysmal spike-and-wave type activity in rabbits. This activity (5-6 discharges per second) was observed near the injured site, as well as in the mirror foci, but it never extended to the frontal cortex. Spike-and-wave discharges were also observed in the lateral geniculate body and the superior colliculus. Diazepam completely inhibited this epileptic activity, but pentylenetetrazol and caffeine potentiated its manifestation. The dominant theta-rhythm frequency coincides with the main electroencephalogram synchronization frequency, and with the frequency of rhythmical photostimulation which was able to induce the seizures. These findings are discussed with respect to the theory of synchronization of biorhythms in the brain.