Direct magnetic resonance detection of neuronal electrical activity

doi:10.1073/pnas.0603219103

Direct magnetic resonance detection of neuronal electrical activity

*Section on Functional Imaging Methods, Laboratory of Brain and Cognition,
^†Neural Network Physiology Unit, Laboratory of Systems Neuroscience, and
^¶Functional MRI Facility, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892;
^‡Cerebral Microcirculation Unit, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892; and
^§Institute for Medical Imaging and Image Analysis, Department of Electrical and Computer Engineering, George Washington University, Washington, DC 20052

Edited by Marcus E. Raichle, Washington University School of Medicine, St. Louis, MO, and approved September 5, 2006 (received for review April 20, 2006)

Abstract

Present noninvasive neuroimaging methods measure neuronal activity indirectly, via either cerebrovascular changes or extracranial measurements of electrical/magnetic signals. Recent studies have shown evidence that MRI may be used to directly and noninvasively map electrical activity associated with human brain activation, but results are inconclusive. Here, we show that MRI can detect cortical electrical activity directly. We use organotypic rat-brain cultures in vitro that are spontaneously active in the absence of a cerebrovascular system. Single-voxel magnetic resonance (MR) measurements obtained at 7 T were highly correlated with multisite extracellular local field potential recordings of the same cultures before and after blockade of neuronal activity with tetrodotoxin. Similarly, for MR images obtained at 3 T, the MR signal changed solely in voxels containing the culture, thus allowing the spatial localization of the active neuronal tissue.

Footnotes

^‖To whom correspondence should be addressed. E-mail: bandettini{at}nih.gov
Author contributions: N.P., D.P., A.C.S., M.L., J.B., and P.A.B. designed research; N.P., D.P., A.C.S., and J.B. performed research; N.P., J.B., and P.A.B. analyzed data; and N.P., J.B., and P.A.B. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS direct submission.
Abbreviations:

EEG,

electroencephalography;

FID,

free induction decay;

LFP,

local field potential;

MEA,

multielectrode array;

MEG,

magnetoencephalography;

MR,

magnetic resonance;

PRE,

preceding administration of TTX;

SE EPI,

spin-echo echo planar imaging;

TTX,

tetrodotoxin.