Glymphatic clearance is enhanced during sleep
A recent publication questioned the existing literature by reporting that glymphatic clearance is enhanced by wakefulness. We show here that this is an erroneous conclusion, in that it was based on the assumption that tracer infusion is independent of the brain activity state. Utilizing dynamic magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and fluorescent fiber photometry, we report that less tracer enters the brains of awake animals, such that after adjusting for the injected tracer dose, brain glymphatic clearance is found to be enhanced by both sleep and anesthesia, and sharply suppressed by wakefulness.