High distinctness of circadian rhythm is related to negative emotionality and enhanced neural processing of punishment-related information in men

For years, research on the human biological clock has focused primarily on chronotype (phase of the circadian rhythm). However, a second dimension - distinctness (subjective amplitude) of the rhythm, has so far been overlooked. This study aimed to explore the intricate interplay between psychometric traits and reward-punishment processing, considering both chronotype and distinctness. Circadian rhythmicity characteristics of 37 healthy men (aged 20-30) were measured using the Morningness-Eveningness-Stability-Scale improved (MESSi) questionnaire. We also employed a battery of psychometric questionnaires and used functional magnetic resonance (fMRI) during the Monetary Incentive Delay task, which is a common method of assessing reward-punishment processing. We found a positive association between distinctness and the activity in the bilateral Superior Frontal Gyrus (SFG), Supplementary Motor Area (SMA), and Ventral Tegmental Area (VTA) during processing of punishment cues. These results are consistent with psychometric findings - a significant positive association between distinctness and sensitivity to punishment, neuroticism, behavioral inhibition system (BIS), attention deficits, and negative emotionality. As regards eveningness, we found its negative association only with sensitivity to punishment and BIS. These results highlight the crucial role of distinctness in human functioning, especially in terms of punishment processing and negative emotionality.