MEG source imaging method using fast L1 minimum-norm and its applications to signals with brain noise and human resting-state source amplitude images.
The present study developed a fast MEG source imaging technique based on Fast Vector-based Spatio-Temporal Analysis using a L1-minimum-norm (Fast-VESTAL) and then used the method to obtain the source amplitude images of resting-state magnetoencephalography (MEG) signals for different frequency bands. The Fast-VESTAL technique consists of two steps. First, L1-minimum-norm MEG source images were obtained for the dominant spatial modes of sensor-waveform covariance matrix. Next, accurate source time-courses with millisecond temporal resolution were obtained using an inverse operator constructed from the spatial source images of Step 1. Using simulations, Fast-VESTAL's performance was assessed for its 1) ability to localize multiple correlated sources; 2) ability to faithfully recover source time-courses; 3) robustness to different SNR conditions including SNR with negative dB levels; 4) capability to handle correlated brain noise; and 5) statistical maps of MEG source images. An objective pre-whitening method was also developed and integrated with Fast-VESTAL to remove correlated brain noise. Fast-VESTAL's performance was then examined in the analysis of human median-nerve MEG responses. The results demonstrated that this method easily distinguished sources in the entire somatosensory network. Next, Fast-VESTAL was applied to obtain the first whole-head MEG source-amplitude images from resting-state signals in 41 healthy control subjects, for all standard frequency bands. Comparisons between resting-state MEG sources images and known neurophysiology were provided. Additionally, in simulations and cases with MEG human responses, the results obtained from using conventional beamformer technique were compared with those from Fast-VESTAL, which highlighted the beamformer's problems of signal leaking and distorted source time-courses.
Radiology Services, VA San Diego Healthcare System, San Diego, CA, USA; Research Services, VA San Diego Healthcare System, San Diego, CA, USA; Department of Radiology, University of California, San Diego, CA, USA. Electronic address: mxhuang@ucsd.edu.
Ming-Xiong
MX
Huang
Charles W
CW
Huang
Ashley
A
Robb
AnneMarie
A
Angeles
Sharon L
SL
Nichols
Dewleen G
DG
Baker
Tao
T
Song
Deborah L
DL
Harrington
Rebecca J
RJ
Theilmann
Ramesh
R
Srinivasan
David
D
Heister
Mithun
M
Diwakar
Jose M
JM
Canive
J Christopher
JC
Edgar
Yu-Han
YH
Chen
Zhengwei
Z
Ji
Max
M
Shen
Fady
F
El-Gabalawy
Michael
M
Levy
Robert
R
McLay
Jennifer
J
Webb-Murphy
Thomas T
TT
Liu
Angela
A
Drake
Roland R
RR
Lee
D000328:Adult; D000465:Algorithms; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D012146:Rest / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio
Beamformer; Brain noise; L1-norm; Median-nerve; Minimum norm; Resting-state