Is there a change in water proton density associated with functional magnetic resonance imaging? |
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Authors: | Thies H. Jochimsen,David G. Norris,Harald E. M ller |
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Affiliation: | Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstrasse 1a, D-04103 Leipzig, Germany. thies@jochimsen.de |
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Abstract: | In a recent series of studies (see, for example, Stroman et al. Magn Reson Imag 2001; 19:827-831), an increase of water proton density has been suggested to correlate with neuronal activity. Owing to the significant implications of such a mechanism for other functional experiments, the functional signal changes in humans at very short echo times were re-examined by spin-echo EPI at 3 T. The results do not confirm the previous hypothesis of a significant increase in extravascular proton density at TE = 0. Instead, an alternative explanation of the effect is offered: The use of a low threshold to identify activated voxels may generate an artificial offset in functional contrast due to the inclusion of false-positives in the analysis. |
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Keywords: | spin‐echo fMRI proton density BOLD |
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