Arousal elicits a brain-wide hemodynamic wave independent of locus coeruleus noradrenergic tone

Arousal fluctuations during wakefulness have a major impact on physiology and behavior, including perception and task performance. Arousal is also known to be a strong modulator of neural activity, but the brain-wide spatiotemporal structure of this modulation is not fully characterized. We used functional ultrasound imaging to record brain-wide hemodynamics - a proxy for neural activity - in head-fixed mice during spontaneous and sensory-evoked arousal fluctuations, tracked via pupil diameter. Both conditions recruited a common brain-wide hemodynamic wave that followed a subcortex-to-cortex gradient. We then tested whether noradrenaline, widely associated with arousal, was necessary or sufficient to drive this wave. Sustained bidirectional optogenetic manipulations of locus coeruleus activity affected brain-wide vascular signal amplitude but, surprisingly, left arousal-linked dynamics largely intact. Together, these results identify a common spatiotemporal motif of arousal that appears independent of noradrenergic tone.