This image shows the distribution of a gadolinium-based CSF tracer in the rat brain 80 minutes after it was infused into the Cisterna Magna. The movement of the tracer through the network of perivascular spaces to the brain is driven by arterial pulsation and is reduced in prolonged hypertension, demonstrating impairment of the glymphatic system. For more information, see the article by Mortensen et al. (pages 6365–6377).