Methods: This study is a prospective study including preterm infants born below 30 weeks of gestational age. Brain activity is measured by one-channel amplitude-integrated EEG (aEEG). The first aEEG measurement is performed without caffeine and/or doxapram medication. At least one hour of brain activity is registrated. The second measurement is done at least 24 hours after the start of caffeine and/ or doxapram treatment.