Volumetric imaging of brain activity with spatial-frequency decoding of neuromagnetic signals

• Published in: Journal of neuroscience methods Vol. 239; pp. 114 - 128
• Main Authors: Xiang, Jing, Korman, Abraham, Samarasinghe, Kasun M., Wang, Xiaopei, Zhang, Fawen, Qiao, Hui, Sun, Bo, Wang, Fengbin, Fan, Howard H., Thompson, Elizabeth A.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.01.2015
• Subjects: Acoustic Stimulation; Adult; Brain; Brain - physiology; Brain - physiopathology; Brain Mapping; Brain Waves - physiology; Computer Simulation; Diagnostic Imaging; Electroencephalography; Epilepsy - pathology; Female; Fourier Analysis; High-frequency oscillation; Humans; Magnetoencephalography; Male; Middle Aged; Models, Neurological; Nervous System Physiological Phenomena; Neuroimaging; Retrospective Studies; Spatial filter; Wavelet; Wavelet; Neuroimaging; Brain; Spatial filter; Magnetoencephalography; High-frequency oscillation
• ISSN: 0165-0270; 1872-678X; 1872-678X
• DOI: 10.1016/j.jneumeth.2014.10.007

•Analyses of multi-frequency brain activity at the source level.•A novel grid-frequency kernel for volumetric imaging of brain activity.•Detection of high-frequency brain activity with a non-invasive MEG approach.•Localization of bilateral auditory cortical sources with frequency signatures.•Delineation of epileptogenic zones with high-frequency neuromagnetic signals. The brain generates signals in a wide frequency range (∼2840Hz). Existing magnetoencephalography (MEG) methods typically detect brain activity in a median-frequency range (1–70Hz). The objective of the present study was to develop a new method to utilize the frequency signatures for source imaging. Morlet wavelet transform and two-step beamforming were integrated into a systematic approach to estimate magnetic sources in time–frequency domains. A grid-frequency kernel (GFK) was developed to decode the correlation between each time–frequency representation and grid voxel. Brain activity was reconstructed by accumulating spatial- and frequency-locked signals in the full spectral data for all grid voxels. To test the new method, MEG data were recorded from 20 healthy subjects and 3 patients with verified epileptic foci. The experimental results showed that the new method could accurately localize brain activation in auditory cortices. The epileptic foci localized with the new method were spatially concordant with invasive recordings. Compared with well-known existing methods, the new method is objective because it scans the entire brain without making any assumption about the number of sources. The novel feature of the new method is its ability to localize high-frequency sources. The new method could accurately localize both low- and high-frequency brain activities. The detection of high-frequency MEG signals can open a new avenue in the study of the human brain function as well as a variety of brain disorders.