Human brain mappingJul 8, 2026

Daily Changes and Consistency Over Time of Resting Brain Activity Measures

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗OA ↗

Updated Jul 9, 2026

Abstract

ReHo demonstrated higher and more stable reliability across six fMRI sessions in 39 healthy young adults scanned throughout the day.

Circadian rhythms may significantly influence the reliability of resting-state fMRI metrics.
Amplitude-based metrics, especially fractional ALFF, showed greater variation throughout the day.
Limbic and subcortical structures exhibited low reliability in network-level and region-specific analyses.
A notable decline in reliability for ALFF, wavelet-transformed ALFF, and fractional ALFF was observed with longer inter-scan intervals.
Different resting-state fMRI metrics display distinct patterns of temporal stability.

Simplified

Resting-state fMRI (rs-fMRI) is widely used to assess intrinsic brain activity, yet concerns about its test-retest reliability and reproducibility persist. Circadian rhythms strongly influence brain physiology, but their impact on rs-fMRI reliability remains poorly understood. In this study, we scanned 39 healthy young adults six times within a single day (08:00-20:00) under standardized conditions. For each session, we computed four common rs-fMRI metrics, including amplitude of low-frequency fluctuations (ALFF), wavelet-transformed ALFF (wALFF), fractional ALFF (fALFF), and regional homogeneity (ReHo), and assessed reliability using intraclass correlation coefficients (ICCs). ReHo showed relatively higher and more stable reliability across sessions, whereas amplitude-based metrics, particularly fALFF, exhibited greater diurnal variation. Both network-level and region-specific analyses revealed low reliability in the limbic and subcortical structures, with a mid-morning dip at 10:00. Moreover, ICCs for ALFF, wALFF, and fALFF declined with increasing inter-scan intervals, whereas ReHo remained robust. These findings demonstrate diurnal fluctuations in rs-fMRI reliability, with different metrics exhibiting distinct temporal stability profiles. We recommend that scan timing and circadian influences should be explicitly considered in the design, analysis, and interpretation of future rs-fMRI studies.

Full Text

Full text is available at the source.

View Full Text ↗

Featured in

Circadian BiologyIssue #45

80% of FDA-approved drug targets show clock-dependent activity — timing may be everything

↗

Daily Changes and Consistency Over Time of Resting Brain Activity Measures

Abstract

Full Text

Featured in

You found one interesting study. We’ll send the next 7.

What Lands in Your Inbox Each Week:

Recent issues from the circadian biology brief