Fig. 5

Sleep enhances fluid penetration into brain tissue. a The fluid particle trajectories for 60 s of simulation for the awake state (20% vessel dilation, once every 10 s with \({\zeta }_{{R}_{f}}^{2}=0.2\)). b The fluid particle distribution for the awake state simulation. c The PVS fluid distribution at t = 30 s for simulated awake and sleep states, along with the cases where only the dilation and porosity are changed. The increase in porosity increased fluid movement into the ECS without affecting the fluid movement into the SAS, while larger dilations increased fluid movement to both SAS and ECS. d The fluid particle trajectories for 60 s of simulated sleep. The large amplitude vasodilation during sleep, combined with the increased porosity drives PVS fluid penetration into the brain. e The distribution of fluid position for 60 s of simulated sleep. a, b are repeated from the right side of Fig. 4d, c, respectively for better comparison with the sleep state