Brief visual oddball events evoke CSF flow in the spinal canal

The measurement of cerebrospinal fluid (CSF) flow with fMRI, made possible by exploiting edge artifacts of spin saturation when the bottom acquisition slice lies in a CSF reservoir, allows researchers to investigate an aspect of brain health that has been increasingly linked to cognitive aging and neurodegenerative disease via its role in glymphatic clearance. The initial demonstration of this technique used the fourth ventricle, but recent reports show it can also be done when the bottom acquisition slice lies in the spinal canal in the foramen magnum. We present a method to automatically identify the spinal canal without manual tracing, and measure CSF flow with high confidence using multi-echo acquisition to separate out BOLD-like and non-BOLD-like signal components, along with physiological regression to improve signal to noise ratio. Using these methods we found that CSF flow correlated with decreases in BOLD activity in 70 adults aged 19-76. We further found that brief, infrequent salient stimuli (visual oddballs, requiring a button press) were capable of provoking measurable CSF flow.