Arousal, performance and absence seizures in rats.

Rats of the WAG/Rij strain show bilateral symmetrical spontaneous spike-wave discharges in the EEG, with clinical concomitants. The present experiment investigated whether, during a learning task, the number of discharges would be diminished compared to a period of rest. Additionally, it was investigated whether behavioural differences would be noticed within the task in trials with and without spike-wave discharges. The length of the post reinforcement pause in a fixed interval task was used as a performance index. Eleven rats were extensively trained to press a lever for food in a fixed (60 sec) interval task until a stable response pattern emerged: a post-reinforcement pause of about half the interval. Next, EEG electrodes were implanted and baseline EEGs were made, before and after the first and fifth test sessions. In addition, the behavior of the animals in the task was monitored when an EEG was recorded. During the task, a significantly smaller number of spike-wave discharges was found, compared to the preceding and succeeding baseline hours. This reduction is probably related to a higher level of vigilance during the task compared to the rest hour. Furthermore, the post-reinforcement pause was significantly enhanced in trials with spike-wave discharges compared to trials without discharges, indicating a clear change in performance. Both results are in agreement with what could be expected in patients with absence epilepsy and provide further evidence for the validation of the spike-wave discharges as genuine epileptic phenomena.