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Brief Research Report ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Hum. Neurosci. | doi: 10.3389/fnhum.2019.00288

Beyond the low frequency fluctuations: morning and evening differences in human brain

  • 1Department of Cognitive Neuroscience and Neuroergonomics, Institute of Applied Psychology, Jagiellonian University, Poland
  • 2Neuroimaging Group, Małopolska Centre of Biotechnology, Jagiellonian University, Poland
  • 3University of Social Sciences and Humanities, Poland
  • 4Chair of Radiology, Jagiellonian University Medical College, Poland
  • 5Department of Psychology, University of Wisconsin–Oshkosh, United States

Human performance, alertness, and most biological functions express rhythmic fluctuations across a 24-hour-period. This phenomenon is believed to originate from differences in both circadian and homeostatic sleep-wake regulatory processes. Interactions between these processes result in time-of-day modulations of behavioral performance as well as brain activity patterns. Although the basic mechanism of the 24-hour clock is conserved across evolution, there are interindividual differences in the timing of sleep-wake cycles, subjective alertness and functioning throughout the day. The study of circadian typology differences has increased during the last few years, especially research on extreme chronotypes, which provide a unique way to investigate the effects of sleep-wake regulation on cerebral mechanisms. Using functional magnetic resonance imaging (fMRI), we assessed the influence of chronotype and time-of-day on resting-state functional connectivity. 29 extreme morning- and 34 evening-type participants underwent two fMRI sessions: about one hour after wake-up time (morning) and about ten hours after wake-up time (evening), scheduled according to their declared habitual sleep-wake pattern on a regular working day. Analysis of obtained neuroimaging data disclosed only an effect of time of day on resting-state functional connectivity; there were different patterns of functional connectivity between morning and evening sessions. The results of our study showed no differences between extreme morning-type and evening-type individuals. We demonstrate that circadian and homeostatic influences on the resting-state functional connectivity have a universal character, unaffected by circadian typology.

Keywords: Resting state – fMRI, diurnal (circadian) rhythms, ALFF/fALFF, Morning and evening chronotypes, Functional Connectivity

Received: 06 Jun 2019; Accepted: 05 Aug 2019.

Edited by:

Jodie R. Gawryluk, University of Victoria, Canada

Reviewed by:

Timo Partonen, National Institute for Health and Welfare, Finland
Michal Ramot, National Institute of Mental Health (NIMH), United States  

Copyright: © 2019 Fafrowicz, Bohaterewicz, Ceglarek, Cichocka, Lewandowska, Sikora-Wachowicz, Oginska, Beres, Olszewska and Marek. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
PhD. Magdalena Fafrowicz, Department of Cognitive Neuroscience and Neuroergonomics, Institute of Applied Psychology, Jagiellonian University, Kraków, 30-348, Lesser Poland, Poland,
Mr. Bartosz Bohaterewicz, University of Social Sciences and Humanities, Warsaw, Poland,