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Magnetic field changes in the human brain due to swallowing or speaking
Author(s) -
Birn Rasmus M.,
Bandettini Peter A.,
Cox Robert W.,
Jesmanowicz Andrzej,
Shaker Reza
Publication year - 1998
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910400108
Subject(s) - nuclear magnetic resonance , swallowing , spin echo , magnetic resonance imaging , human brain , tongue , brain activity and meditation , functional magnetic resonance imaging , chemistry , physics , electroencephalography , psychology , medicine , neuroscience , radiology , pathology
Variations in the magnetic field in the human brain caused by the processes of swallowing or speaking are measured. In both processes, motion of the pharyngeal muscles, especially the tongue and jaw, alter the susceptibility‐induced magnetic field distribution at the brain slice being imaged. This leads to image warping, compromising the analysis of a time series of images, such as in functional magnetic resonance imaging (fMRI). These dynamic changes are assessed by acquiring a time series of images using a gradient‐echo asymmetric‐spin‐echo sequence (GREASE), a technique in which two images are acquired for each excitation–one during the gradient echo, and one during the latter part of the spin echo. The NMR phase difference between the two images is a measure of the magnetic field distribution. A series of brain images, acquired with this sequence while the subject either swallows or speaks, indicated negative magnetic field changes of up to O.087 ppm in the inferior region of the brain for both speaking and swallowing, and in some speech, additional positive changes of up to O.056 ppm in the frontal region of the brain were indicated.