DISTURBANCES IN TIME-ESTIMATION DURING ABSENCE SEIZURES IN CHILDREN

In the present study children suffering from primary generalized absence epilepsy were asked to estimate time under EEG monitoring. They were asked to press a button when they thought that a fixed period of time had elapsed. Only the first response after the passage of the interval was reinforced. The dependent variable was the duration of the interval between the start of the trial and the first response, the post-reinforcement time. This parameter was used as an index for the accuracy of time estimation. The performance of the subjects in trials with and without spike wave discharges was compared. Short spike wave discharges (< 3 s) prolonged the duration of the post-reinforcement pause while longer ones reduced its duration. The prolongation was longer than could be anticipated from the duration of the spike wave discharge. It was also found that the time between the end of an EGG paroxysm and the first response was significantly shorter in trials with long spike wave discharges than in trials with short spike wave discharges. There were no differences between subjects with and without spike wave discharges. It was concluded that this type of time estimation task is sensitive in detecting cognitive disturbances induced by both short and long spike wave discharges. Moreover, it seems that after long spike wave discharges patients behave differently and are perhaps more severely disturbed. The duration of the misperception of the interval after the short spike wave discharges is larger than could be predicted from the duration of the paroxysms, which seems in contrast with the view that cognitive disturbances are only limited to the period of epileptic EEG phenomena.