An animal model of light sensitive epilepsy

Abstract

1. 1. Intermittent light stimulation (ILS) was found to elicit EEG and motor paroxysmal responses in baboons, Papio papio, originating from the Casamance area of Senegal. Extensive studies to characterize the EEG and motor patterns to 25/sec ILS indicated three types of stimulus-bound paroxysmal responses, more or less individually determined. In certain of the animals, self-sustained epileptiform discharges, divisible into four different patterns, followed termination of ILS. Polygraphic studies showed epileptiform activity to be present in the EEG before appearance of motor seizures, EMG paroxysms or oculo-motor movements. Stability of response varied with individual animals, some of which exhibited a constant, high level of sensitivity. The majority of the paroxysmal responses were elicited at 20–30/sec with 25/sec about optimal. Light source or presence of click stimuli were unimportant; the latter alone did not elicit paroxysmal activity. 2. 2. Night-long EEG and polygraphic recordings showed the least sensitive animals to differ from cat and especially man by the absence of very high voltage, slow sleep as muscle activity lessened and by much reduced REM sleep, both in period length and in total. The two most sensitive animals showed spontaneous paroxysmal activity resembling spike and wave discharges during their nocturnal sleep and no identifiable REM sleep. 3. 3. Evoked neocortical responses to 1/sec ILS, usually studied as summed potentials in groups of 30, differed with eyes open and closed and between animals. Animals usually displaying paroxysmal responses to 25/sec ILS had more widespread distribution of evoked neocortical responses and changes in their wave form compared to pattern seen in animals relatively insensitive to 25/sec ILS. 4. 4. Papio papio showed low thresholds to pentylenetetrazol-induced seizures in the presence of ILS. Chlorpromazine increased the responsiveness to ILS and altered the neocortical evoked potential pattern to one similar to that seen in the most seizure-prone individual animals. 5. 5. Anticonvulsant activity of phenobarbital, trimethadione and diazepam was demonstrated against ILS-induced epileptiform seizures in two animals displaying stable, daily severe paroxysmal responses to ILS. Neocortical evoked responses were modified differently by the different drugs. 6. 6. It is considered that a photo-sensitive epilepsy in Papio papio has been demonstrated which in a number of ways closely parallels that seen in man.