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Magnetic resonance imaging of neuronal and glial swelling as an indicator of function in cerebral tissue slices
Author(s) -
Stroman P.W.,
Lee A.S.,
Pitchers K.K.,
Andrew R.D.
Publication year - 2008
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.21534
Subject(s) - magnetic resonance imaging , extracellular , nuclear magnetic resonance , depolarization , central nervous system , functional magnetic resonance imaging , chemistry , premovement neuronal activity , signal (programming language) , spinal cord , neuroscience , biophysics , medicine , biology , physics , biochemistry , radiology , computer science , programming language
Here we demonstrate a new basis of signal change in magnetic resonance imaging (MRI) related to neuronal function, independent of blood oxygenation or flow. Time series MRI data acquired from living, superfused brain slices of adult rats revealed that the signal intensity reversibly increased with depolarization evoked by briefly elevating extracellular K + . This was presumably a consequence of increased tissue water in the intracellular compartment. Reversible increases in light transmittance (LT) demonstrating a similar time course in response to K + elevation supported cellular swelling as generating the MRI signal intensity changes. This was confirmed by reversibly swelling cells in the slice under hypoosmotic challenge, which increased both MRI and LT signals with an identical time course. Conversely, shrinking cells under hyperosmotic challenge reversibly decreased the MRI and LT signals. We propose that specific MRI of neuronal function (fMRI) signals detected under identical parameters during predominantly proton‐density‐weighted fMRI of the spinal cord can now be explained by neuronal and glial swelling in activated central nervous system (CNS) regions. These observations demonstrate the biophysical basis of the fMRI contrast mechanism that has been termed “signal enhancement by extravascular water protons,” or SEEP. Magn Reson Med 59:700–706, 2008. © 2008 Wiley‐Liss, Inc.