Resting state functional magnetic resonance imaging (rsfMRI) has been widely used for measuring functional connectivity between cortical regions. However, there have been minimal reports of rsfMRI in white matter, presumably because of the sparse vasculature in white matter relative to gray, and the consistent failure to observe significant hemodynamic responses from tasks within white matter. In this study, we aimed to investigate and assess the nature of temporal variations in rsfMRI signals from human and monkey brains in white matter. Previous studies have reported that the correlations of time course signals in a resting state between voxels are anisotropic in white matter. We therefore constructed functional correlation tensors (FCTs) that quantify the functional relationships between neighboring voxels and their anisotropy in normal brains at rest, and compared these to underlying structural features. Furthermore, we elucidated the underlying biophysical mechanisms that account for their origins by assessing whether MRI signal fluctuations in white and gray matter vary for different baseline levels of neural activity. We found FCTs were capable of visualizing long range white matter tracts as well as short range sub-cortical fibers imaged at rest, suggesting temporal resting state signals may reflect intrinsic synchronizations of neural activity in white matter. Moreover, our monkey studies revealed that fractional power of rsfMRI signals are modulated similarly in regions of SI cortex, gray and white matter as neural baseline activity is varied. Our results imply that neural activity is encoded in white matter, and that that BOLD signal fluctuations in white matter may be detected in a resting state.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-03222016-213015 |
| Date | 23 March 2016 |
| Creators | Wu, Tung-Lin |
| Contributors | Zhaohua Ding, John C. Gore |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-03222016-213015/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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