Interhemispheric Asymmetry of Connections of EEG Rhythms on Spontaneous Waking after Transient Episodes of Sleep while Performing a Monotonous Psychomotor Test

Objectives. To study interhemispheric asymmetry (IHA) by electroencephalography (EEG) in healthy subjects during cognitive waking from stage II daytime sleep prior to recovery of the performance of a psychomotor test. Materials and methods. IHA of the amplitude-amplitude coupling of EEG rhythms was studied in healthy adult subjects using 20-sec trace segments recorded in the state preceding spontaneous waking, as defined by the moment the α rhythm appeared on the EEG, and the subsequent onset of psychomotor activity. The state of subjects during this period (the initial stage of so-called cognitive waking preceding behavioral waking), when theperson is unable to movebut is able to perceive external stimuli, is an experimental model for identifying signs of conscious activity in patients coming out of coma. Wavelet transformation was used to compute the rhythmic characteristics of bioelectrical activity. The Kendall correlation coefficient served as a measure of interactions between rhythms. Results. IHA of the interaction of EEG rhythms was found to be dynamic in nature and to be formed due to the connections of the θ rhythm with the α2 and β rhythms in the left hemisphere of the brain and δ–θ connections in the right. Conclusions. The marked left-hemisphere asymmetry is probably associated with the onset of the retrieval of instructions from memory, which subsequently allows return to the activities interrupted by sleep.