[Eeglablist] Coherence or Correlation among set of electrodes

[Gregory Perry]

Hardware has everything to do with it.  More than a few cm of wire between the electrode and acquisition platform results in significant signal loss, EEG signals are too faint.  The use of an active electrode actively performing waveform analysis and daisy chained in the digital domain to all the other electrode sites would absolutely shred any software-based system that attempts to correlate EEG data across different regions.

From: Jeff Eriksen [mailto:eriksenj at ohsu.edu]
Sent: Tuesday, October 16, 2012 02:18 PM
To: Gregory Perry; eeglablist at sccn.ucsd.edu <eeglablist at sccn.ucsd.edu>
Subject: Re: [Eeglablist] Coherence or Correlation among set of electrodes

I have several comments on this post:

  1.  Hardware has nothing to do with it – it is software that allows us to localize and correlate
  2.  "hi-res timebase" I suppose means a high sampling rate – this will not help much either as volume conduction is close to the speed of light
  3.  Active electrodes are good for reducing noise and the use of gel, but provide nothing to help with localization or correlation analysis
  4.  "triangulation" implies what the field calls source localization/imaging/analysis etc, and there is a vast body of knowledge and literature on this broad topic available – including using individual cortical folding patterns for modeling the putative generators
  5.  A lot of 3D analysis and research is going on – perhaps you are only familiar with clinical systems?

-Jeff Eriksen

From: Gregory Perry <Gregory.Perry at govirtual.tv<mailto:Gregory.Perry at govirtual.tv>>
Date: Monday, October 15, 2012 7:52 PM
To: "Iman M.Rezazadeh" <irezazadeh at ucdavis.edu<mailto:irezazadeh at ucdavis.edu>>, "eeglablist at sccn.ucsd.edu<mailto:eeglablist at sccn.ucsd.edu>" <eeglablist at sccn.ucsd.edu<mailto:eeglablist at sccn.ucsd.edu>>
Subject: Re: [Eeglablist] Coherence or Correlation among set of electrodes

Even the most recent generation EEG acquisition hardware leaves a lot to be desired in terms of correlating areas within the brain that are interrelated.  This doesn't seem like a hard problem to solve with active electrodes placed at each 10/20 region, if they all shared a high resolution time base.  Think reverse GPS, by measuring timing variances between each electrode site (and especially at EEG spectrum frequencies), there is no reason why specific physical regions in the brain could not be triangulated for analysis.  For extra credit, cortical folding patterns could be integrated with the acquired data to derive subject-specific brainwave signatures.

Current EEG analysis methods are stuck in a 2D world unfortunately.

________________________________
From: eeglablist-bounces at sccn.ucsd.edu<mailto:eeglablist-bounces at sccn.ucsd.edu> [eeglablist-bounces at sccn.ucsd.edu<mailto:eeglablist-bounces at sccn.ucsd.edu>] on behalf of Iman M.Rezazadeh [irezazadeh at ucdavis.edu<mailto:irezazadeh at ucdavis.edu>]
Sent: Monday, October 15, 2012 8:17 PM
To: eeglablist at sccn.ucsd.edu<mailto:eeglablist at sccn.ucsd.edu>
Subject: [Eeglablist] Coherence or Correlation among set of electrodes

Hi,
Just wonder if there is a way to calculate the coherence measure between two regions( set of channels—instead of two single channels) in EEGLAB or any other software?  In other word, how can we find regions in the brain which their activities are mostley related to each other using EEG ?

Best,
Iman

Iman M.Rezazadeh, PhD
Center for Mind and Brain
University of California, Davis
irezazadeh at ucdavis.edu<mailto:irezazadeh at ucdavis.edu>
cell:310-490-1808

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