Total cerebral blood volume changes drive macroscopic cerebrospinal fluid flux in humans
Fig 3
Coupled gGM and CSF fMRI signal changes induced by a transient hypercapnia challenge.
(a) Global grey matter (left) and CSF masks (right) for extracting fMRI signals, superimposed on axial T1-weighted images. (b) Time courses of the gGM (top, black) and CSF (bottom, red) fMRI signals. Mean (solid lines) ± SEM (shaded areas) of n = 17 subjects. CO2 application periods are color-coded in purple. (c) Averaged time courses of all normocapnia to hypercapnia (N → H) transitions (n = 34 transitions from 17 subjects). gGM (black) and CSF fMRI signal (red). The shaded areas represent SEM. CO2 application periods are color-coded in purple. (d) Same as (C) for transitions from hypercapnia to normocapnia (H → N, n = 34 transitions from 17 subjects). (e) Correlation coefficients between gGM and CSF fMRI signals during N → H (n = 17, left) and H → N (n = 17, right) transitions. *p < 0.05, n.s. not significant. One-sample t test (individual groups). Two-sample t test (between groups). Source data for Fig 3e are available in the source data file (S1 Data).In summary, these results demonstrate that H → N and N → H transitions, respectively, induce total CBV changes, which underpin gGM fMRI signal changes coupling inversely with CSF signal changes in the basal cisternae of the brainstem.