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.