EEG and Brain Connectivity: A Tutorial - Bio-Medical Instruments, Inc.

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Fig – 17. Top is coherence (y-axis) vs signal-to-noise ratio (x-axis). Coherence drops off Rapidly and is invalid. Bottom is phase angle on the y-axis and signal-to-noise ratio on the x-axis. Phase locking is minimal or absent and unstable throughout the entire simulation and fails to exhibit the 30 degree phase difference. The results of these analyses are consistent with those by Rappelsberger, 1989 who emphasized the value and validity of using a single reference and linked ears in estimating the magnitude of shared or coupled activity between two scalp electrodes. The use of re-montage methods such as the average reference and Laplacian source derivation are useful in helping to determine the location of the sources of EEG of different amplitudes at different locations. However, the results of this study which again confirm the findings of Rappelsberger and Petsche, 1988 and Rappelsberger, 1989 which showed that coherence is invalid when using either an average reference or the Laplacian source derivation. This same conclusion was also demonstrated by Korzeniewska, et al (2003). 19- What is “Inflation” of Coherence (and correlation)?
Coherence inflation is defined as any value of coherence (x) greater than zero when coherence (or correlation) is computed using pure Gaussian noise in one of the two channels and a pure sine wave in the other channel. Eq. 20- Coherence Inflation x > 0 This is the error term when one of the channels is pure Gaussian noise and the second channel is signal. Any value of coherence > 0 is due to error attributable to low degrees of freedom, inadequate signal resolution or too short of measurement interval, or improper sample rates within that interval, etc. Figure 18 below shows an example of a 5 Hz 10uVsine wave in one channel and 100 uV (p-p) gaussian noise in the second channel. The power spectrum of the two channels is shown in the upper right panel. Figure 18 is just one example of the analyses performed by the NeuroGuide Signal Generator that directly test EEG simulated EEG cross-spectra. Figure 18. Screen capture of the NeuroGuide signal generation program.
Page 1 and 2: (unpublished manuscript - Version 1
Page 3 and 4: 29- Definition of the Cross Channel
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Page 7 and 8: is because there are relatively lon
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Page 11 and 12: Fig. 3- Example of cospectrum (in-p
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Page 43: Fig - 16. Top is coherence (y-axis)
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Page 51 and 52: Example of conventional digital EEG
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Page 69 and 70: Fig. 24 - Top is filtered EEG at 25
Page 71 and 72: Fig. 26 - Top is the spontaneous EE
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Gray, C.M., Konig, P., Engle, A.K.
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localization and functional connect
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Cannon, R., Lubar, J., Sokhadze, E.
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Yoo, S. S. et al. Increasing cortic
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