[Temporal variations of excitability in photosensitive papio papio after series of intermittent light flashes (author's transl)].

After several trains of intermittent photic stimulation (IPS) each lasting 10 seconds and sometimes inducing paroxysmal electrical activity, isolated flashes or salves of 2 or 3 light flashes are capable of inducing bifrontal paroxysmal discharges in photosensitive Papio papio, an effect which is augmented by allylglycine or the use of highly photosensitive animals. Use of these salves repeated every second enabled the authors to demonstrate two types of changes in cortical excitability after intermittent photic stimulation: 1. responses which were more frequent and of greater amplitude appearing in the first 3 or 4 seconds after IPS; after paralysis of the animal amplitude and frequency of the responses are augmented. 2. if trains of intermittent photic stimulation are repeated regularly a seizure occurs after 5 to 15 trains. In the paralysed animal, more trains are required although large responses are seen after each train whereas in the non-paralysed animal the seizure occurs rapidly but the responses are on average weaker and less frequent than in 1. The relationship between photosensitive epilepsy and these responses is discussed as well as that of somatic afferents.