T2 * Dependence of Low Frequency Functional Connectivity

Resting state low frequency (<0.08 Hz) fluctuations in MR timecourses that are temporally correlated between functionally related areas have been observed in recent studies. These fluctuations have been assumed to arise from spontaneous blood oxygenation level-dependent (BOLD) oscillations. This work examines the T(2)(*) characteristics of the low frequency fluctuations (functional connectivity) and compares them to those of task activation induced signal changes. Multi-echo spiral data were fit using a mono-exponential decay model to generate T(2)(*) and intensity (I(0)) parameter timecourses. Resultant correlation maps show that both functional connectivity and BOLD activation modulate T(2)(*), not I(0). Regression analysis also finds that both have a linear dependence on echo time. Thus, functional connectivity and task activation MR signal changes appear to arise from the same BOLD-related origins.

[1]  S. Posse,et al.  Enhancement of BOLD‐contrast sensitivity by single‐shot multi‐echo functional MR imaging , 1999, Magnetic resonance in medicine.

[2]  B. Biswal,et al.  Cocaine administration decreases functional connectivity in human primary visual and motor cortex as detected by functional MRI , 2000, Magnetic resonance in medicine.

[3]  J Hennig,et al.  Functional Imaging by I0‐ and T2* ‐parameter mapping using multi‐image EPI , 1998, Magnetic resonance in medicine.

[4]  L. Parsons,et al.  Interregional connectivity to primary motor cortex revealed using MRI resting state images , 1999, Human brain mapping.

[5]  Bharat B. Biswal,et al.  Functionally Related Correlation in the Noise , 2000 .

[6]  M. Lowe,et al.  Functional Connectivity in Single and Multislice Echoplanar Imaging Using Resting-State Fluctuations , 1998, NeuroImage.

[7]  T. Lund,et al.  Physiological noise reduction in fMRI using vessel time-series as covariates in a general linear model , 2001, NeuroImage.

[8]  Karl J. Friston,et al.  Functional Connectivity: The Principal-Component Analysis of Large (PET) Data Sets , 1993, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[9]  V. Haughton,et al.  Mapping functionally related regions of brain with functional connectivity MR imaging. , 2000, AJNR. American journal of neuroradiology.

[10]  H. Alkadhi,et al.  Localization of the motor hand area to a knob on the precentral gyrus. A new landmark. , 1997, Brain : a journal of neurology.

[11]  D. Tank,et al.  4 Tesla gradient recalled echo characteristics of photic stimulation‐induced signal changes in the human primary visual cortex , 1993 .

[12]  K. Uğurbil,et al.  Experimental determination of the BOLD field strength dependence in vessels and tissue , 1997, Magnetic resonance in medicine.

[13]  Scott T. Grafton,et al.  Automated image registration: I. General methods and intrasubject, intramodality validation. , 1998, Journal of computer assisted tomography.

[14]  Douglas C. Noll,et al.  Analysis of fMRI signal and noise component TE dependence , 2000, NeuroImage.

[15]  J. Mazziotta,et al.  Automated image registration , 1993 .

[16]  B. Biswal,et al.  High‐resolution fMRI using multislice partial k‐space GR‐EPI with cubic voxels , 2001, Magnetic resonance in medicine.

[17]  G. Glover,et al.  Physiological noise in oxygenation‐sensitive magnetic resonance imaging , 2001, Magnetic resonance in medicine.

[18]  B. Biswal,et al.  Functional connectivity in the motor cortex of resting human brain using echo‐planar mri , 1995, Magnetic resonance in medicine.

[19]  X Hu,et al.  Retrospective estimation and correction of physiological fluctuation in functional MRI , 1995, Magnetic resonance in medicine.