https://doi.org/10.1140/epjs/s11734-025-02104-x
Regular Article
The chronotype impact on cognitive functions and electrophysiological brain patterns during monotonous activity and sleep
1
Research Institute of Biodigital Health Systems, Saratov State Medical University named after V.I. Razumovsky, Bolshaya Kazachya St., 112, 410012, Saratov, Russian Federation
2
Institute of Physics, Saratov State University named after N.G. Chernyshevsky, Astrakhanskaya St., 83, 410012, Saratov, Russian Federation
3
Department of Biophysics and Digital Technologies, Saratov State Medical University named after V.I. Razumovsky, Bolshaya Kazachya St., 112, 410012, Saratov, Russian Federation
4
Center for Coordination of Fundamental Scientific Activities, National Medical Research Center for Therapy and Preventive Medicine, Petroverigsky Lane, 10, 101000, Moscow, Russian Federation
a
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Received:
16
November
2025
Accepted:
8
December
2025
Published online:
16
December
2025
This study aimed to investigate how an individual’s chronotype affects their cognitive performance during a monotonous activity and identify associated electrophysiological brain patterns during both waking and sleep. The study involved 103 healthy volunteers, 40 of whom were men and 63 were women, who were classified as “rhythmics” (
) or “arrhythmics” (
) based on their responses to the Horn-Ostberg questionnaire. The participants underwent psychophysiological testing, which included attention tasks (Schulte tables) and a prolonged monotonous activity. After this, they had two nights of polysomnography (PSG) with 21-channel electroencephalography (EEG) to monitor their brain activity during sleep. EEG data were analyzed using a continuous wavelet transform (CWT) and oscillatory pattern analysis to identify specific brain waves and their coherence. The wavelet bicoherence was also used to measure the strength of the coherence between different brain waves. While no significant differences were found in the standard sleep macrostructure between the two groups, cognitive testing showed that “rhythmics” performed better on tasks that required operational attention, but they also had longer reaction times and a higher error rate during monotonous activities. EEG analysis during these monotonous tasks revealed a significant decrease in the 
and 
rhythms in the motor cortex, as well as an increase in the prefrontal cortex among “rhythmics”. During REM sleep, “rhythmics” showed an increased high-frequency oscillatory energy pattern (20–36 Hz) in the occipital region and left hemisphere. Sleep-stage analysis indicated that the sleep architecture of “rhythmics” was more fragile compared to “arrhythmics”. Chronotype has a significant impact on the neurophysiological mechanisms of information processing under cognitive load, as well as on subtle aspects of sleep organization that are not captured by traditional polysomnography metrics. These findings emphasize the significance of advanced EEG analysis in uncovering brain dynamics related to chronotype and highlight the need for personalized approaches in cognitive neuroscience and sleep medicine.
Supplementary Information The online version contains supplementary material available at https://doi.org/10.1140/epjs/s11734-025-02104-x.
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Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
