DOI: 10.5281/zenodo.10053962
title: Identified important EEG channels in visually impaired subjects using recurrent analysis

description: This database contains calculated channel significance indicators based on the application of recurrent analysis to EEG data, following the example of the article Runnova A, Selskii A, Emelyanova E, Zhuravlev M, Popova M, Kiselev A, Shamionov R. Modification of Joint Recurrence Quantification Analysis ( JRQA) for assessing individual characteristics from short EEG time series. Chaos. 2021;31(9):093116. doi: 10.1063/5.0055550. For each EEG channel of each subject, the channel significance indicator was separately calculated for all stimulus presentations in the cognitive test. The following is a description of the EEG setup, subjects, and experimental design.
To compare the performance of the method for identifying important channels, the frequency corresponding to the maximum amplitude and the central frequency of the spectrum were calculated using Fourier spectrum analysis. The latter was calculated so that the integral value of the probability density to the left of it and to the right of it were the same. This approach makes it possible to distinguish between high and low frequencies in the spectrum and, if necessary, evaluate them separately.
The values of the channel significance indicators for each subject are located in the «SR» folder. Frequencies corresponding to maximum amplitude are in folders «MaxFrequency». Center frequencies for all channels of each subject in the folder «CentralFrequency».
Data were recorded at 250 Hz sampling rate using the conventional monopolar method of registration with two reference points and N = 21 electrodes, located according to the "10–20" scheme. The adhesive Ag/AgCl electrodes in prewired head caps were used to detect EEG signals. Two reference electrodes, A1 and A2, were located on mastoids, while the ground electrode N was placed above the forehead. The EEG signals were filtered by a band-pass filter with cutoff points at 1.5 Hz (HP) and 35 Hz (LP) and a 50 Hz notch filter.
Children of middle school age participated as study subjects. The biomedical data were processed honoring the confidentiality and anonymity of the study respondents. Experimental work was carried out in compliance with ethical standards and approved by the local committee on research ethics at Saratov State University (Saratov, RF). Prior to the study, written consent of the parents was obtained for conducting neuropsychological experimental work, the subsequent data processing and publication of the results. The parents were present during all experiments in accordance with the requirements of the Russian Federation legislation.
The following design of experimental work was employed. All experiments were conducted in the mornings, on a typical school day. One of the classrooms was darkened with blinds. Children sat in comfortable chairs, adjusted to their heights to attain a comfortable stable position, leaning back in the chair. Their feet were flat on the floor. The total experimental work time was approximately 25 minutes for each subject.
The experiment included three short stages: background state of quiet wakefulness with eyes closed (about 3 minutes), simple cognitive test for counting sound signals (about 20 minutes), and repeated background state of quiet wakefulness with eyes closed (about 2 minutes). During the cognitive test, groups of short sounds were given: one to four per group. During listening, the subject was instructed to determine whether he perceived an even or an odd number of sounds in a single stimulus group. Depending on his assessment, the subject pressed the left or right buttons of a special remote control. Between groups of sound signals there was a silent pause lasting 5 to 11 seconds. Each child was analyzing these sound stimuli for 3 minutes, followed by a rest break lasting about 2 minutes.
The experimental work involved 4 boys 10 years of age (123,2±5,1 months). All children belonged to the health group I the Order of the Ministry of the Russian Federation Healthcare of March 13, 2019, No. 124n. They had no infectious or other acute illnesses one month prior to the experiment. Additionally, all children had no identified chronic diseases.