Control vs. salience: a new axis of circadian brain-body organization

Circadian robustness is usually cast on a single weak-strong continuum, but multi-system data suggest a different picture. We followed 52 healthy young adults for ~30 days with wearable locomotor (accelerometry; ACC) and autonomic (heart rate; BPM) signals and paired these with structural and resting-state fMRI. From person-level circadian feature vectors (stability, amplitude, acrophase, and ACC-BPM alignment/lag), we uncovered a Control-Salience axis of brain-body organization. A control-anchored archetype showed ACC-dominant rhythms-higher activity stability and amplitude, later BPM acrophase, and a longer ACC → BPM phase lead-together with stronger connectivity in cognitive control networks. A complementary salience-anchored archetype exhibited BPM-dominant rhythms-earlier BPM acrophase, higher BPM relative amplitude, tighter ACC-BPM coupling-and stronger connectivity in salience and attention networks. Across individuals, cross-system alignment (ACC-BPM lag) tracked control-network coherence, whereas rhythm timing and amplitude related selectively to cortical geometry and network strength. These findings recast circadian health as axis-based and system-specific: individuals organize along a spectrum from stability-anchored, locomotor-led profiles to coupling-anchored, autonomic-dominated profiles with distinct neural correlates. The Control-Salience axis refines mechanistic models of circadian risk and points to alignment-aware, network-targeted strategies for monitoring and intervention.