Reconstruction of human brain spontaneous activity based on frequency-pattern analysis of magnetoencephalography data

Abstract

A new method for the analysis and localization of brain activity has been developed, based on multichannel magnetic field recordings, over minutes, superimposed on the MRI of the individual. Here, a high resolution Fourier Transform is obtained over the entire recording period, leading to a detailed multi-frequency spectrum. Further analysis implements a total decomposition of the frequency components into functionally invariant entities, each having an invariant field pattern localizable in recording space. The method, addressed as functional tomography, makes it possible to find the distribution of magnetic field sources in space. Here, the method is applied to the analysis of simulated data, to oscillating signals activating a physical current dipoles phantom, and to recordings of spontaneous brain activity in 10 healthy adults. In the analysis of simulated data, 61 dipoles are localized with 0.7 mm precision. Concerning the physical phantom the method is able to localize three simultaneously activated current dipoles with 1 mm precision. Spatial resolution 3 mm was attained when localizing spontaneous alpha rhythm activity in 10 healthy adults, where the alpha peak was specified for each subject individually. Co-registration of the functional tomograms with each subject's head MRI localized alpha range activity to the occipital and/or posterior parietal brain region. This is the first application of this new functional tomography to human brain activity. The method successfully provides an overall view of brain electrical activity, a detailed spectral description and, combined with MRI, the localization of sources in anatomical brain space.

Sensory-driven and spontaneous gamma oscillations engage distinct cortical circuitry

“…We use the term "spontaneous" simply to indicate oscillations that occur in the absence of a visual stimulus. We do not imply that gammaband activity that is not directly triggered by a sensory stimulus is devoid of function or information, as abundant evidence indicates that ongoing gamma oscillations may underlie a multiplicity of information processing operations (Llinas et al , 1999(Llinas et al , 2007(Llinas et al , 2015Llinas and Steriade 2006;Roy and Llinas 2008;Sekar et al 2013). Our results show that visual stimuli drive a 4-to 20-fold increase of a narrow spectral band of gamma oscillations (peak ϭ 29 Hz, width ϭ 13 Hz) in the LFP of granular and supragranular layers, which is 1.5-2 times larger than the fold increase in gamma in infragranular layers.…”

Метода анализа данных магнитной энцефалографии в облачном сервисе MathBrain

“…It can be concluded, that results of various methods are substantially similar, and generally correspond to present knowledge about the alpha rhythm localization. Variations between methods can be explained by the fact, that alpha rhythm is generated by many sources, covering rather broad space (5-8 cm), see [14].…”

“…Further development of the MathBrain service will include methods of integrated analysis, such as Functional Tomography [12][13][14], Partial Spectroscopy [15] and connectivity analysis. …”

“…During the MEG recording, three fiducial markers are applied for the correct localization of the head. In this article, we use MEG and MRI for one control subject, obtained in the brain spontaneous activity study in the Center for Neuromagnetism of New York University School of Medicine [13,14]. The MEG data were recorded with a 275-channel synthetic third order gradiometer (VSM MedTech LTD) in a magnetically shielded room, sampling rate was 1200 Hz.…”

“…The method is based on the complete utilization of the long-time series, while the multichannel nature of the data is also completely taken into account, making it possible to extract elementary sources of the brain activity. It was successively applied in alpha-rhythm studies [14] and in partial spectroscopy of the brain [15]. Mathematical foundations of this method were implemented in the MEGMRIAn software [16].…”