Synchronized delta oscillations correlate with the resting-state functional MRI signal

doi:10.1073/pnas.0705791104

Synchronized delta oscillations correlate with the resting-state functional MRI signal

*Neuroimaging Research Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD 21224; and
^†Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, MD 21201

Edited by Edward G. Jones, University of California, Davis, CA, and approved September 28, 2007 (received for review June 20, 2007)

Abstract

Synchronized low-frequency spontaneous fluctuations of the functional MRI (fMRI) signal have recently been applied to investigate large-scale neuronal networks of the brain in the absence of specific task instructions. However, the underlying neural mechanisms of these fluctuations remain largely unknown. To this end, electrophysiological recordings and resting-state fMRI measurements were conducted in α-chloralose-anesthetized rats. Using a seed-voxel analysis strategy, region-specific, anesthetic dose-dependent fMRI resting-state functional connectivity was detected in bilateral primary somatosensory cortex (S1FL) of the resting brain. Cortical electroencephalographic signals were also recorded from bilateral S1FL; a visual cortex locus served as a control site. Results demonstrate that, unlike the evoked fMRI response that correlates with power changes in the γ bands, the resting-state fMRI signal correlates with the power coherence in low-frequency bands, particularly the δ band. These data indicate that hemodynamic fMRI signal differentially registers specific electrical oscillatory frequency band activity, suggesting that fMRI may be able to distinguish the ongoing from the evoked activity of the brain.

Footnotes

^‡To whom correspondence may be addressed. E-mail: yihongyang{at}intra.nida.nih.gov or estein{at}intra.nida.nih.gov
Author contributions: H.L. and Y.Z. contributed equally to this work; H.L., Y.Z., W.Z., Y.Y., and E.A.S. designed research; H.L., Y.Z., C.A.S., and W.R. performed research; H.L., Y.Z., H.G., J.A.W., W.Z., C.A.S., and Y.Y. analyzed data; and H.L., Y.Z., H.G., Y.Y., and E.A.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0705791104/DC1.
Abbreviations:

fMRI,

functional MRI;

LFP,

local field potential;

EEG,

electroencephalographic;

CC,

cross-correlation coefficients;

S1FL,

bilateral primary somatosensory cortex;

RV,

right visual cortex;

LF,

left S1FL, RF, right S1FL.