In clinical practice at the National centre for epilepsy (SSE) in Norway we see many children who have subclinical epileptiform activity in EEG that increases substantially during slow wave sleep (SSEA; subclinical sleep-activated epileptiform activity). They may or may not have seizures. Hence, according to the definition some children with SSEA do not suffer from epilepsy because they do not experience seizures. Many of these children have symptoms such as: attention deficit hyperactivity disorders (AD/HD), dyslectic problems, sleep problems, tantrums or autistic symptoms . We hypothesize that this subclinical epileptiform activity during slow sleep may act negatively on cognitive functions, language and behaviour in some children; even when the spike-wave discharges are less frequent than in CSWS (continuous spike-waves during slow sleep).