Jonathan Rizzo Polimeni1,
Kyoko Fujimoto1, Boris Keil1, Douglas N. Greve1,
1A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Charlestown, MA, USA; 2Computer Science & AI Lab (CSAIL), Massachusetts Institute of Technology, Cambridge, MA, USA; 3Harvard-MIT Division of Health Sciences & Technology, Massachusetts Institute of Technology, Cambridge, MA, USA
Here we provide characterization of the radial independence of the fluctuations at each depth below a given cortical location. This radial correlation length of resting state fluctuations was measured using gradient echo and spin echo EPI. The radial correlation length is strongly affected by the removal of confounding physiological signals in a counter-intuitive way--namely the global signals regressed out do not seem to produce an artifactual high-correlation between layers, but rather mask the presence of correlations between different depths. Similarly, the spin echo acquisition, which is also expected to remove relatively global fluctuations also uncovers additional underlying radial correlations.