Tracing diurnal differences in brain anatomy with voxel-based morphometry - associations with sleep characteristics

ABSTRACT

Multiple aspects of brain functioning, including arousal, motivation, and cognitive performance, are governed by circadian rhythmicity. Although the recent rise in the use of magnetic resonance imaging (MRI) has enabled investigations into the macroscopic correlates of the diurnal brain processes, neuroanatomical studies are scarce. The current work investigated how time-of-day (TOD) impacts white (WM) and grey matter (GM) volumes using voxel-based morphometry (VBM) in a large dataset (N = 72) divided into two equal, comparable subsamples to assess the replicability of effects. Furthermore, we aimed to assess how the magnitude of these diurnal differences was related to actigraphy-derived indices of sleep health. The results extend the current knowledge by reporting that TOD is predominantly associated with regional WM volume decreases. Additionally, alongside corroborating previously observed volumetric GM decreases, we provide the first evidence for positive TOD effects. Higher replicability was observed for WM, with the only two replicated GM clusters being volumetric increases in the amygdala and hippocampus, and decreases in the retrosplenial cortex, with the latter more pronounced in individuals with shorter sleep times. These findings implicate the existence of region-specific mechanisms behind GM effects, which might be related to cognitive processes taking place during wakefulness and homeostatic sleep pressure.

KEYWORDS:

• Voxel-based morphometry
• time-of-day
• sleep length
• grey matter
• white matter

Acknowledgments

This research was supported in part by PL-Grid Infrastructure. We thank Prof. Patricia Reuter-Lorenz for her constructive suggestions during the planning and development of the Harmonia project and her valuable support. We also thank Anna Beres, Piotr Faba, Koryna Lewandowska, Monika Ostrogorska, Barbara Sikora-Wachowicz for their assistance with the fMRI data collection, Aleksandra Zyrkowska for help with the process of participant selection, and Magdalena Debowska for help in collecting actigraphy data.

Disclosure statement

No potential conflict of interest was reported by the author(s).

CRediT author statement

MRZ: Conceptualization, Methodology, Investigation, Formal Analysis, Validation, Data Curation, Writing – Original Draft, Visualization. MF: Conceptualisation, Methodology, Investigation, Data Curation, Writing – Review & Editing, Funding Acquisition. TM: Conceptualisation, Methodology, Writing – Review & Editing, Funding Acquisition. HO: Investigation, Formal Analysis, Writing – Review & Editing. EB: Investigation, Formal Analysis, Validation, Writing – Review & Editing. AD: Conceptualisation, Methodology, Investigation, Formal Analysis, Validation, Data Curation, Writing – Review & Editing, Supervision. All authors contributed to the article and approved the submitted version.

Ethical statement

The authors declare that all experiments on human subjects were conducted in accordance with the Declaration of Helsinki and that all procedures were carried out with the adequate understanding and written consent of the subjects. The study was approved by the Ethics Committee of the Institute of Applied Psychology at Jagiellonian University (approval code: 3/2017).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/07420528.2024.2301944.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by the National Science Centre, Poland (NCN) under grant Harmonia [2013/08/M/HS6/00042].