Anisotropy of local functional connectivity (LFC) in resting state fMRI time series: what does it say about the fmri signal?
Michael J. Tobia 1 , David Gallagher 1 , Rahul Dewal 1 , Prasanna Karunanayaka 1 , Sebastien Rupprecht 1 , and Qing X. Yang 1
Center for NMR Research, Penn State
University, Hershey, PA, United States
This experiment investigated anisotropic local
functional connectivity (LFC) in GE-EPI time series in
phantom and human in vivo resting state fMRI data. LFC
was computed in a neighborhood radius of 2 voxels using
Pearsons correlation. In vivo, LFC anisotropy varied
across gray and white matter sites, resembling DTI in
some aspects, while differing on others. Phantom
experiments showed that fluctuating electric current is
sufficient to generate anisotropic LFC proximal to the
current-carrying filament. In conclusion, anisotropic
correlations of fMRI time series may arise from an
alternative non-BOLD contrast mechanism, potentially
related to an electric current effect on Bo.
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