Two publications on the human circadian rhythm and its role in brain activity
27 08 2025
How does the human circadian rhythm affect brain function? How do we respond to rewards and punishments? Answers to these questions are provided by the findings of two new publications from an international team of researchers, which includes Patrycja Ściślewska and Prof. Piotr Bębas from the Faculty of Biology at the University of Warsaw.
Morning, evening, or in between
In a study published in the journal Scientific Reports scientists examined two dimensions of the human circadian rhythm: chronotype (a preference for mornings, evenings, or times in between) and rhythm amplitude (the subjective amplitude of the rhythm, describing how strongly we feel changes in our energy levels during the day).
“Until now, most research has focused solely on the first of these dimensions. We wanted to check whether rhythm amplitude, like chronotype, can play a significant role in shaping the brain’s responses to rewards and punishments,” says Patrycja Ściślewska, lead author of the two publications.
In the first study, 37 healthy men aged 20–30 participated. They completed a set of psychometric tests and then underwent functional magnetic resonance imaging (fMRI). During scanning, they performed the Monetary Incentive Delay (MID) task, which allows the recording of brain responses to situations involving potential financial gain or loss.
Analyses showed that individuals with a pronounced circadian rhythm responded more strongly to negative stimuli – greater activation of the ventral tegmental area (VTA) while anticipating punishment, and of the left occipital pole when receiving negative feedback. Furthermore, the neural-level associations between rhythm amplitude and the processing of punishment-related stimuli were mirrored in personality traits – higher rhythm amplitude was associated with greater neuroticism and a tendency toward avoidance behaviors.
Meanwhile, an evening chronotype was linked to increased activation of the left frontal pole, middle temporal gyrus, inferior temporal gyrus, and middle frontal gyrus when receiving positive feedback.
The researchers emphasize that these relationships are correlational—we cannot yet point to a cause-and-effect link. However, this is the first study to show that circadian rhythm amplitude can be as important as chronotype and should be considered in research on brain functioning.
Open data for science
The study’s data – comprising detailed psychometric measurements and high-resolution anatomical brain scans, field maps, and fMRI recordings during the MID task – have been anonymized, prepared in accordance with the international BIDS (Brain Imaging Data Structure) standard, and made openly available on the OpenNeuro.org platform. The team’s second publication, describing and validating the dataset, was published in the journal Scientific Data.
“In our analyses, we focused on brain activity related to human motivation and circadian rhythmicity, but our dataset contains much more information. We encourage researchers from all over the world to use our dataset in their analyses – it can be useful for studies on emotionality, affective processing, or attention,” adds Patrycja Ściślewska.