The paper reports the results of a partial-time analysis of EEG signals from healthy volunteers obtained during the recording of polysomnography with an expanded arrangement of electrodes (19 leads). An analysis of the characteristics of frequency patterns (their number, duration, and energy power) was carried out in theta – band (4 – 6 Hz) in five brain areas (central, occipital, frontal zones, and left and right hemispheres). A comparison of the obtained characteristics was carried out according to the chronotypes of the respondents. Based on the results of the study, it was possible to demonstrate chronobiological patterns of nocturnal EEG activity in healthy volunteers. REM sleep stage in groups of participants with morning and evening chronotypes demonstrates statistically significant differences in the number and duration of EEG oscillatory patterns for different areas of brain activity. The report was presented at PhysCon 2024 “Local nocturnal EEG activity of healthy people depending on chronotype”.