Episodic memory causes a slow oscillation of EEG, awakening and performance recovery from sleep episodes during monotonous psychomotor test

The aim of this study is to detect changes in a functional state during the performance of monotonous psychomotor test. We propose that these changes represent the repeated episodes of short sleep and spontaneous awakenings from them. We also argue that spontaneous awakenings from sleep stage 2 are accompanied by high-amplitude slow oscillations (SO). 20 subjects participated in 27 experiments during daytime. They performed continuous psychomotor test in a supine position with eyes closed for 1 h. Expert scoring of SOs in the EEG, including K-complexes and other single slow waves, was performed in sleep episodes reaching sleep stage 2, defined as pauses in task performance longer than 3 s. 248 episodes with SOs occurred in time intervals without activity lasting from 3 s to 10 min. In 195 cases, at least one SO was recorded before the test performance was resumed. 248 sleep episodes with 1255 SOs were taken into analysis. It was shown that SOs occur much more frequently just before awakenings (SO 1 , 12 or less seconds before awakening) than within sleep episodes (12 of more seconds before awakening, SO 2 ). Some SOs were recorded within a few seconds after behavioral awakening (SO 3 ), which has not been previously reported. We propose the hypothesis that SOs which occurred just before resuming performance (SO 1 ) are associated with the unconscious episodic memory that triggers awakening followed by recovery of conscious activity performed prior to falling asleep. We also describe the novel type of SO (SO 3 ) which occurs just after awakening.