[Eeglablist] How phase is calculated in linear decomposition

Wed Jul 26 13:44:56 PDT 2017

Dear Georges,

I agree that the source of EEG is the post-synaptic potential arising from
dendritic structure of the pyramidal neurons. I believe my understanding is
the same as yours.

Sorry to hear that your message to the list has not appeared yet. I
included Ramon who manages the list for investigation.

Makoto

On Wed, Jul 26, 2017 at 12:08 AM, otte georges <georges.otte at pandora.be>
wrote:

> Dear Makoto
>
>
>
> These are wise words born from scientific humbleness and relentless search
> for a deeper truth. I look forward to hear your further views on ICA as I
> am to very worried about phase contortion in reconstruction of signals from
> a limited set of components. I am aware that most researchers on the EEGLab
> list are working with 256 or more high density channel EEG recordings but
> we must also  be aware that in the clinical scene 19 channels are
> conventionally used and reconstruction after rejection of 4-5 components is
> of course quite a different story than rejecting one component in a 256 ch
> recording. New techniques will at the end of the day pop up in the clinical
> theater and I think it is wise that controversies are straightened out or
> at least be documented and discussed so that the necessary caveats can be
> drawn.
>
>
>
> That being said I wonder a bit about your remark on EEG models. Are you
> not a bit too pessimistic? As a clinician and neurologist, I had the
> impression that after all this time and basic scientific work we do have
> quite clear ideas about the generating mechanisms in pyramidal cells
> embedded in cortical columns, synaptic channel dynamics and its equations,
> dendritic and axonal conduction and its correlation with the electrical
> activity recorded at the scalp.
>
>
>
> What is missing? (or what am I missing?)
>
>
>
> Sincerely
>
>
>
> Georges
>
>
>
>
>
> PS My latest mail to this list (dated start of July) concerning the
> transit from EEG (or MEG) channel recordings to network parameters in a
> graph theory model  was not published. Was something wrong with it?
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> *From:* Makoto Miyakoshi [mailto:mmiyakoshi at ucsd.edu]
> *Sent:* Wednesday, July 26, 2017 3:01 AM
> *To:* Robert Thatcher <rwthatcher2 at yahoo.com>
> *Cc:* EEGLAB List <eeglablist at sccn.ucsd.edu>; Georges Otte <
> georges.otte at telenet.be>
> *Subject:* Re: How phase is calculated in linear decomposition
>
>
>
> Dear Robert,
>
>
>
> Sorry for belated response.
>
> I updated my wiki page to explain how phase is synthesized and split when
> components are rejected.
>
>
>
> https://sccn.ucsd.edu/wiki/How_phase_is_calculated_in_linear_decomposition
>
>
>
> As I explained above, you are calling the difference between 18 Bitcoins
> and 19 Bitcoins 'distortion'.
>
>
>
> > In addition to mathematics, there is empirical proof of “distortion” or
> “adulteration” that has been repeated over and over again on this forum and
> accepted to be true by Arnaud and Stephan and Georges and Robert Larson and
> Ramesh but apparently not yet by you.
>
>
>
> I don't think Arno and Stefan accepted 'the proof' because they will write
> a rebuttal paper with me. It's a good opportunity for us anyways to refute
> the Montefucso-Siegmunt paper.
>
>
>
> By the way Robert, I like your claim that people tend to be trapped by
> their own dogma and make errors in circular logic. That's a good point. I
> believe that this criticism actually applies to the entire EEG research
> field, since we do not have a *ground truth* in generative model of EEG
> signals; and do we not tend to compensate the lack of the ground truth by
> using fancy signal processings? All computational EEG analysts need a good
> introspection on this issue. We also need to know the difference between
> engineering and science, models and truth, etc; Good engineering is not
> necessarily a good science!
>
>
>
> I also enjoy and sympathize your criticism against dogmatic people.
> However, your criticism against ICA is invalid and unsatisfactory to me.
> Let me invite you to the next thread to share my real criticisms against
> ICA.
>
>
>
> Makoto
>
>
>
>
>
>
>
> On Fri, Jul 7, 2017 at 11:07 AM, Robert Thatcher <rwthatcher2 at yahoo.com>
> wrote:
>
> Dear Makoto,
>
>       It is correct that a linear decomposition where one decomposes a 19
> channel time series into 19 ICA components then, like the inverse Fourier
> transform, one can recover the phase information if one uses all 19 ICA
> components.   However, one cannot recover the phase information in 19
> channels if one uses 18 or 17 or 16 or any number less than 19 components
> to reconstruct a new 19 channel time series.
>
> The mathematics proving “distortion” by ICA reconstruction with a small
> number of components is explained by Taken’s Theorem (& other theorems in
> differential geometry, e.g. Shannon's) where a lower dimensional time
> series does not preserve phase when used to reconstruct a higher
> dimensional time series.  Therefore mathematically (including the inverse
> Fourier transform) there is always a loss of information when using a
> smaller number of components to reconstruct a larger number of channels.
> Also, commonsense tells one that it is not possible to create something out
> of nothing, e.g., if I give you 18 Bitcoins will you give me 19 Bitcoins?
> (credit to Georges for asking this question).
>
>
>
> In addition to mathematics, there is empirical proof of “distortion” or
> “adulteration” that has been repeated over and over again on this forum and
> accepted to be true by Arnaud and Stephan and Georges and Robert Larson and
> Ramesh but apparently not yet by you.   The empirical proof can be
> demonstrated by yourself if you compute the phase differences between all
> channel combinations in the original EEG time series vs the ICA
> reconstructed time series using a smaller number of ICA components.  Anyone
> can demonstrate the phase difference “distortion” for themselves using the
> Hilbert transform for instantaneous phase differences (i.e., each time
> point) or the FFT for an average.
>
> Here is a URL of a You Tube Video that provides additional empirical proof
> that ICA reconstruction distorts or adulterates the physiologically based
> phase differences in the original EEG recording.
>
> https://youtu.be/Q36ojib5OZE
>
>
>
> Here is a url to four power points of two different time points that
> compares the phase difference before and after Arnaud’s ICA
> reconstruction.
>
> http://www.appliedneuroscience.com/Phase_Differences-
> between-Original_&_Delorme-Post-ICA.pptx
>
> Please download and expand the power points so that you can verify for
> yourself that the phase differences in the original recording have been
> distorted or altered.  I would be happy to issue a temporary license to
> Neuroguide so that you can launch two Neuroguides and import and compare
> the original time series and Arnaud’s ICA reconstructed time series to
> verify for yourself that phase differences for all channel combinations for
> each and every time  point have been distorted by ICA reconstruction.
>
>
>
> I offer this same opportunity to all of the members of this forum.
> Download, install and launch NG-2.9.4 and paste the key A to
> qeeg at appliedneuroscience.com.   Here is the download url:
>
> http://www.appliedneuroscience.com/Download_NeuroGuide.htm
>
> I will mail step by step mouse instructions so that anyone interested can
> verify for themselves that ICA reconstruction distorts the phase
> differences for all channel combinations and all time points.
>
> This is important because if the primary level of measurement is distorted
> then all subsequent analyses are invalid as a matter of verifiable fact.
>
> Best wishes,
>
>
>
> Robert
>
>
>
>
>
>
>
> On Thursday, July 6, 2017, 2:31:56 PM PDT, Makoto Miyakoshi <
> mmiyakoshi at ucsd.edu> wrote:
>
>
>
>
>
> Dear Robert and list,
>
>
>
> If I remember correctly, one of the critical issue was how phase changes
> in 'channel data' after removing independent components. Let me focus on
> this point only.
>
>
>
> 1. To show my rebuttal and mathematical proof, I prepared a wiki page. In
> this page. I described how a phase is split/synthesized before and after
> linear decomposition. Note that this applies to any linear decomposition
> and not specific to ICA. In doing so, made it nice and educational to show
> my respect to Arno's effort. Hopefully this mathematical clarification
> helps.
>
>
>
>           https://sccn.ucsd.edu/wiki/How_phase_is_calculated_in_linear
> _decomposition
>
>
>
> Robert, if you do not agree,* please show the right process in a form of
> math*.
>
>
>
> 2. Apart from this scientific/mathematical dispute, I insist that one
> should not use the word 'distortion' in this context because it includes
> subjective judgement.
>
>
>
> Makoto
>
>
>
>
>
>
>
> --
>
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>
>
>
>
>
> --
>
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>

-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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