EEG Applied: 2

EEG Applied: Example 2

Michal Teplan’s (Mgr. PhD) research in Bio-Mechanics with EEG.

Here are a few articles published by Michal Teplan and colleagues exploring biomechanics – the application of EEG to mechanics.

Teplan was awarded his PhD in 2006 with his research and thesis on the impact of Audio-visual stimulation on brainwaves using EEG to measure changes in mind waves. Here is a glimpse into his research, based on his thesis: ‘Audiovisual Stimulation of Human Brain. Linear and Nonlinear Measures.’

‘Abstract of the article.

One of the most fundamental problems in brain signal analysis is an absence of reliable measures of certain brain states. For purpose of study and detection of such states (especially the state of the mental relaxation which is still not exactly defined) we decided to investigate the influence of commercially well-known mind machines (light & sound machines) on subject’s brain. In this paper we discuss changes in common linear and novel nonlinear measures applied on series of EEG signal recorded before and after mind machine sessions. We will namely discuss linear correlation, mutual information content, spectral entropy, spectral edge frequency and relative power of alpha, beta, delta and theta band.’

Description of the Experiment: … ‘The mind machine’ decreased frequency stimulation from 18 Hz to 2 Hz in order to affect the participants audiovisual nervous system sensors. The frequency was returned back to 18 Hz at the end of each session.

At the start and end of each session recordings of the EEG signal were read from 6 specific channels, following ‘the International 10-20 system: F3C3, F4C4, C3P3, C4P4, P3P1, P4O2. The reference electrode was placed at CZ point and ground electrode at FPZ point. Each EEG record was 3 minute long what gives 90000 samples at the 500 Hz sampling frequency.’

Conclusions: The rise of alpha frequencies in frontal areas and delta-theta frequencies in occipital areas can be observed. It may indicate mental state of brain relaxation and thus positive effect of the mind machine. It is also supported by decreasing trend in occipital areas in both entropical measures (entropy and spectral entropy). Surprisingly we have detected decrease of synchronization between hemispheres in frontal and occipital areas (linear correlation and mutual information content). This is usually considered as an indicator of the state of alertness

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  About Audiovisual Stimulation of Human Brain. Linear and Nonlinear Measures

Teplan and his colleagues describe the experiment: The experiment consisted of 25 series (days) of 20 minutes training with the mind machine in a darkened space – a Faraday chamber. The participants in this experiment  were 6 adult volunteers. The mind machine was supposed to train subjects brain to relax more efficiently using light and sound stimulation.

A summary of the findings in pictures:

Figure 1: ‘Partial correlation coefficient (black boxes) and average trend in all important points (arrows) of all measures‘. … ‘Positive change of alpha 1 (8-10 Hz) and alpha 2 (10-12 Hz) frequencies is evident in both left and right frontal areas. Minor positive change of delta-theta frequencies can be observed in the occipital areas.

Fig 1.

teplans-partial-correlation-coefficient-black-boxes-and-average-trend

Figure 1: Partial correlation coefficient (black boxes) and average trend in all important points (arrows) of all measures. Included EEG data were recorded before mind machine sessions. Size of black boxes is equal to (1-|PCC|).

Fig 2.

teplans-evolution-of-spectral-power-in-bands-2

Figure 2: ‘Evolution of the spectral power in selected bands‘. … ‘Positive change of alpha 1 (8-10 Hz) and alpha 2 (10-12 Hz) frequencies is evident in both left and right frontal areas. Minor positive change of delta-theta frequencies can be observed in the occipital areas.

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Results:

Measures show that synchronization significantly decrease in frontal and occipital areas.

Teplan describes the most common indicators in neurophysiology of relaxation and sleep as being:

  • The increase of alpha frequencies
  • The synchronization of the activity in the brain in both hemispheres
  • A decrease is evident in the complexity of the EEG signal.

This experiment showed a clear positive change of alpha band in frontal areas’ and also ‘a positive change of delta-theta band in right occipital area‘.

There was also a visible ‘decrease of frequency in both left and right occipital areas’ suggesting that that the delta-theta band gained in power’ (the lower spectral bands).

Measures of entropy  show a decrease of complexity in occipital areas’ but also a ‘strong increase in frontal areas‘.

From subjective point of view only 2 of 6 participants were optimistic about the impact of a mind machine. Nevertheless they described significant increase (45%) of relaxation depth after all training sessions.

 The article: Audiovisual Stimulation of Human Brain. Linear and Nonlinear Measures

Written by:  S. Štolc, A. Krakovská, M. Teplan

Contact details: umerstol@savba.sk

From:   Institute of Measurement Science, Slovak Academy of Sciences, Dúbravská cesta 9, 842 19 Bratislava, Slovak Republic

Download the PDF at:  http://www.canal6.com.br/cbeb/2014/artigos/cbeb2014_submission_799.pdf

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More resources and articles:

EEG for Positive THORT

About EEG: An introduction

Survey of EEG Fundamentals

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