Ahmadreza Attarpour1, James Ward2, and J. Jean Chen1,2
1Medical Biophysics, University of Toronto, Toronto, ON, Canada, 2Rotman Research Institute, Baycrest, Toronto, ON, Canada
1Medical Biophysics, University of Toronto, Toronto, ON, Canada, 2Rotman Research Institute, Baycrest, Toronto, ON, Canada
The CSF signal in resting-state fMRI is routinely used for estimating cardiac fluctuations, but its association with vascular oscillations remains unclear. In this study, we quantify this relationship in the 0.1 Hz range using photoplethysmography.
Figure 1. Regions of interest, specifically CSF and vascular ROIs, for a representative subject, overlaid on the T1 anatomical. The lines indicate the fMRI slice orientation, and the arrow indicates the aqueduct. A = anterior, P = posterior, R = right.
Figure 2. The frequency spectrum of the fMR time series in CSF-related ROIs, contrasting spectra from other ROIs as well as the PPG-associated spectra. Spectra are averaged across subjects, and error bars represent standard error. CSF-related ROIs include the lateral ventricles (LV), the third ventricle (3rd V) and the cerebral aqueduct. All signals have been resampled (to the maximum frequency of the rs-fMRI data). Notice that for the PPG spectrum, the cardiac peak is substantially higher than the low-frequency peak.