Spontaneous cortical vasodynamics form a multiscale propagation architecture across the awake brain

Spontaneous vasomotor rhythms and fluctuations are recognized contributors to functional MRI (fMRI) signals. Yet the spatial evolution of vasomotor contributions, which bear on the interpretation of fMRI signals in terms of functionally connected brain regions, remains unresolved. To clarify this issue, we analyze the 0.01 - 0.20 Hz space-frequency modes of 14T cerebral blood volume (CBV)-weighted fMRI across the awake mouse cortex. High-resolution CBV-fMRI identified single-vessel-aligned, frequency-specific modes of vasodynamic propagation, and ultra-fast CBV-fMRI enabled mapping of phase-gradients along tangential and radial axes. Tangential gradients extended maps of vasomotor traveling waves across the entire cortical mantle, with a median speed of 0.9 - 1.3 mm/s. Radial gradients revealed approximately three-fold slower changes in timing that support lamina-dependent regulation of perfusion. Region-specific differences in propagation speed and direction occur across cortical areas and between mice. These findings reframe vascular fluctuations as a feature of brain-wide physiology, as opposed to residual noise.