Fig. 3: Pulsatile CSF flow is temporally coupled to pupil diameter changes and behavioral performance during wakefulness.
a, Spontaneous pupil constriction and dilation is time locked to peaks of CSF flow. Black bars indicate significant changes in z-scored pupil diameter compared to baseline (P < 0.05; two-tailed t-test, baseline = [–30, –28] s, Bonferroni corrected). Data are presented as mean values ± s.e.; AU, arbitrary units. b, Cross-correlation between pupil diameter and CSF showing a strong correlation (maximal r = 0.25 at lag –4.75 s; n = 400 segments, 23 participants). c, During periods with pupil constriction, reaction times also showed significant increases compared to baseline (stars mark segments with P < 0.05; data were analyzed by two-tailed t-test, Bonferroni corrected). d, Omission rate during task showing a significant increase during pupil constriction and significant decrease during pupil dilation (stars mark segments with P < 0.05; two-tailed t-test relative to baseline, Bonferroni corrected). e, Significant biphasic changes in cortical BOLD activity are locked to CSF peaks (P < 0.05; two-tailed t-test relative to baseline, Bonferroni corrected). f, Mean CSF signal. g, To estimate the impulse response function (IRF) linking pupil size changes to BOLD and CSF activity, we convolved pupil diameter traces from each segment with a series of IRFs. Estimated IRF of the cortical BOLD signal to the pupil diameter shows a time to peak at 8 s. Cross-correlation between pupil diameter and BOLD showed a strong correlation (maximal r = 0.34 at lag –1.25 s; n = 400 segments, 23 participants). h, Predicting CSF flow with no additional parameter fitting, assuming that the derivative of the pupil-locked BOLD fluctuations drives CSF flow, shows significant prediction of the true CSF signals (zero lag r = 0.26; n = 400 segments). Data are presented as mean values ± s.e. (standard error across segments). Participant-level means are provided in Extended Data Fig. 3. The exact P values are in Supplementary Table 1.
