The effect of low frequency visual stimulation on CSF flow in the fourth ventricle measured with BOLD-fMRI

Motivation: Glymphatic clearance is impaired in neurodegenerative disease. Vasomotion has been suggested to drive CSF flow and influence clearance. Furthermore, low frequency sensory stimulation can enhance vasomotion. Whether low frequency visual stimulation can drive CSF flow in humans is still unclear. Goal(s): To study the effect of different visual stimulation frequencies on BOLD signal and CSF flow. Approach: 7T BOLD-fMRI scans were acquired in healthy volunteers watching a checkerboard flashing at 0.025, 0.05, or 0.1 Hz. Results: Visual cortex BOLD responses clearly oscillated at the stimulation frequencies, with increased power at lower frequencies. CSF flow responses observed in the fourth ventricle, however, were modest. Impact: This preliminary study confirms that BOLD responses can be evoked locally in the brain with low frequency visual stimulation, but that there is only modest effect on ventricular CSF flow.