Fig. 4

Functional hyperemia drives fluid penetration into the brain. a The initial position of particles used for particle tracking simulations. b The waveform of radial displacement of arteriolar displacement for symmetric and asymmetric dilation in the model. The asymmetric dilation waveform represents functional hyperemia. c The distribution of fluid position for 60 s of simulation with symmetric (left) and asymmetric (right) dilation waveform. Asymmetric dilation drives nearly three times (27%) PVS fluid movement into the brain compared to asymmetric dilation (9%). Both symmetric and asymmetric dilation drive similar PVS fluid movement into the SAS (5%). d The particle trajectories of fluid particles shown in (a). Asymmetric dilation moves PVS fluid deeper below the surface into the ECS and moves the fluid further into the brain