Splitting of the magnetic encephalogram into «brain» and «non-brain» physiological signals based on the joint analysis of frequency-pattern functional tomograms and magnetic resonance images

Abstract

The article considers the problem of dividing the encephalography data into two time series, that generated by the brain and that generated by other electrical sources located in the human head. The magnetic encephalograms and magnetic resonance images of the head were recorded in the Center for Neuromagnetism at NYU Grossman School of Medicine. Data obtained at McGill University and Montreal University were also used. Recordings were made in a magnetically shielded room and the gradiometers were designed to suppress external noise, making it possible to eliminate them from the data analysis. Magnetic encephalograms were analyzed by the method of functional tomography, based on the Fourier transform and on the solution of inverse problem for all frequencies. In this method, one spatial position is assigned to each frequency component. Magnetic resonance images of the head were evaluated to annotate the space to be included in the analysis. The included space was divided into two parts: «brain» and «non-brain». The frequency components were classified by the feature of their inclusion in one or the other part. The set of frequencies, designated as «brain», represented the partial spectrum of the brain signal, while the set of frequencies designated as «non-brain», represented the partial spectrum of the physiological noise produced by the head. Both partial spectra shared the same frequency band. From the partial spectra, a time series of the «brain» area signal and «non-brain» area head noise were reconstructed. Summary spectral power of the signal was found to be ten times greater than the noise. The proposed method makes it possible to analyze in detail both the signal and the noise components of the encephalogram and to filter the magnetic encephalogram.

On the Application of Stereoscopic Technologies in Biological Research

“…A functional brain tomogram was chosen for demonstration. The method for calculating such functional tomograms is described in detail in [21].…”

Application of Stereoscopic Technologies in Biological Research

“…Для демонстрации была выбрана функциональная томограмма мозга. Подробно метод расчета таких функциональных томограмм описан в работе [21].…”

Total neuroelectric brain activity derived from resting-state MEG is invariable across the adult lifespan

“…It was successively applied to study alpha rhythm, heart and skeletal muscles (Llinás et al 2015(Llinás et al , 2020Rykunov, Boyko, and Ustinin 2023), in good agreement with anatomical data. Using this method, the magnetoencephalogram was divided into brain signal and physiological noise from the head (Llinás et al 2022). The purpose of present work is to apply MEG-based functional tomography to the large set of data in order to study age-related changes of the total brain electrical activity and age dependence of various brain rhythms.…”