[Eeglablist] Meaning of ITC

Makoto Miyakoshi mataothefifth at yahoo.co.jp
Sun Apr 19 20:21:23 PDT 2009 

Dear Baris,

I enjoyed your simulation script.
The ratio roughly down to 5000:100000 (5%) is still able to construct a
component-like stuff, given the phase and time-course is well constrained
at that level. It was an interesting demonstration. Thank you.

Makoto



--- P将ゥl Gunnar Larsson <Pal.Gunnar.Larsson at epilepsy.no> wrote:

> > 
> > Dear Baris,
> > 
> > Thank you for your response. I agree with you. As you mentioned,
> ITC
> > must be related to the 'optimal point which maximizes the neural
> > operation' in a certain way. In my poor understanding of neural
> > physiology, punctuality of neuronal firing should derive from the
> fact
> > that each neuron has a specifically optimized 'time limit' to
> accept
> > pulses from other neurons, and only pulses arrived within the limit
> are
> > summed to decide whether to fire. In principle, temporal regulation
> of
> > a macroscopic electrophysiological phenomenon such as EEG still
> must be
> > explained by the prerequisite... that's my guess. Any comment?
> 
> First very brief to your question. An action potential the jumps to a
> postsynaptic neuron , will change its membrane potential. The cell
> will reset the potentila relative fast. If the synaps is far from the
> cell body ithas little influence and will soon be "forgotten" as a
> synaps close to the cell body that will have much more "powewr" over
> a longer time. To that there is a significant dynamic in location and
> matabolism of reseptors which would be expected to change the system.
> To that input to the system will change the state of the system.
> Input may be sensory, chemical, activity from other parts of the
> brain and so on, so yes, there are lots of static and dynamic
> prerequisits in the system. Also, signals you put on to the system
> will probably make changes to it.
> 
> Here is a small program you can look at: If you add 100000 action
> potentials to a time segment, you get something that look like white
> noise, if there is no driving in the system. You may try this:
> 
> for i=1:100000
> punkt=floor(rand(1,1)*987)+1;
> eeg_data(punkt:punkt+11)=eeg_data(punkt:punkt+11)+action';
> end
> 
> Where action is: action=[0 -1 -2 0 2 4 2 0 -1 -3 -1 0]
> 
> If you continue with in the same variable
> 
> for i=1:10000
> punkt=floor(rand(1,1)*20)+500;
> eeg_data(punkt:punkt+11)=eeg_data(punkt:punkt+11)+action';
> end
> 
> That is 10000 now and it may only vary over a small segment of the
> time line (20 points).
> 
> Now you see that the 10000 constrained "action potentials" totally
> dominates the 100000 unconstrained.
> 
> So to conclude, anything that influences the probability of the
> firing rate will influence the signal in a larger degree than one
> would initially believe and there are lots of factors changing the
> probability. The firing rate per se is not that important.
> 
> Regards
> 
> Pセュ自l
> 
> > 
> > About task modulation on ITC, you can find it on any of Makeig's
> > papers.
> > 
> > Makoto
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > --- Sukru Baris Demiral <demiral.007 at googlemail.com> wrote:
> > 
> > > Or, the other way of asking this question is why the neural
> system
> > > needs inter trial coherence. Is it a random effect, or is the
> > > inter-trial-coherence time an optimal point which maximizes the
> > neural
> > > operation.
> > > How does the variation and timing of Trial Coherence change with
> the
> > > task demands?
> > >
> > > BAris
> > >
> > > 2009/4/16 Makoto Miyakoshi <mataothefifth at yahoo.co.jp>
> > >
> > > > Dear Pal,
> > > >
> > > > >From this reply I hope our communication is normally logged on
> the
> > > > eeglablist.
> > > >
> > > > Yes, the Bereitshcafts Potentials seems a good example, if the
> > > potential
> > > > were constructed by phase locking (I'm not sure on this point).
> By
> > > the way,
> > > > could you specify 'Alan Gevins works from around 1984' which I
> > > could not
> > > > find? I want to take a look at the illustrations.
> > > >
> > > > The immediate meaning of ITC is 'trial-by-trial EEG phase
> coherency
> > > at a
> > > > certain IC/scalp channel, time bin, and frequency range, is
> likely
> > > to be
> > > > this much'. It only reflects (at least in princiele) the timing
> of
> > > neural
> > > > firing (large portion of neurons), and does not reflect the
> amount
> > > of it
> > > > (though ERSP and BOLD do, in constrast, in my understanding).
> > > Certainly, a
> > > > physiological meaning of ITC is a event-related 'timing' of
> > > neuronal
> > > > firing.
> > > >
> > > > So, my question again may be: what is the 'psychological'
> meaning
> > > of ITC
> > > > increase/decrease, given that it does not reflect
> increase/decrease
> > > of
> > > > involved neuronal activity? Maybe I'm too much used to a simple
> > > schema that
> > > > associates ERSP/BOLD increase with 'activation' of a certain
> > > portion of
> > > > neurons.
> > > >
> > > > Makoto
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > --- P $B>-%% (Bl Gunnar Larsson
> <Pal.Gunnar.Larsson at epilepsy.no>
> > > wrote:
> > > >
> > > > > Dear Makoto
> > > > >
> > > > > > Dear Pal,
> > > > > >
> > > > > > Thank you for the reply. It is very informative and
> > > interesting...
> > > > > > almost exciting.
> > > > > >
> > > > > > It seems to me, however, that the term 'synchronization' is
> > > used in
> > > > > > different meanings between you and me. Maybe you mean it in
> a
> > > sense
> > > > > of
> > > > > > 'synchronized firing among neurons at a given moment',
> right?
> > > There
> > > > > are
> > > > > > actually papers that report inter-channel coherency, and
> that
> > > is
> > > > > > certainly a kind of synchronization. But the concept of ITC
> is
> > > > > 'inter-
> > > > > > trial'
> > > > > > synchrony: it compares EEG phases AMONG TRIALS and measure
> > > phase
> > > > > > variance, so it had nothing to do with inter-channel phase
> > > > > synchrony.
> > > > >
> > > > > You do have a point. I don't know your research at all. Is
> inter
> > > > > trial between stimuli or between sessions or between persons?
> I
> > > have
> > > > > not thought this through, but I was thinking between stimuli
> and
> > > > > something not unlike to bereitschaft-potentials, but mainly
> my
> > > pont
> > > > > was on the relation betwen bold and EEG.
> > > > >
> > > > > >
> > > > > > Maybe we'd better create a term 'Inter-neuronal coherency
> > > (INC)' in
> > > > > > contrast with inter-trial coherency (ITC).
> > > > > Coherency in EEG was very popular, but it did not lead to
> very
> > > much
> > > > > more than some papers. One of hte main reasons was that
> spatial
> > > > > filters were not applied (except by Gevins) and hence there
> were
> > > too
> > > > > much blurring of the findings. I guess you should look at
> Alan
> > > Gevins
> > > > > works from around 1984. He did 128 channel EEG and made
> arrows
> > > > > showing coherences and latencies between brain areas. His
> > > > > illustrations have been widely used in the literature. To my
> > > > > knowledge he did not look at ITC.
> > > > > >
> > > > > > I'm analyzing my EEG data and found some experimental
> effect in
> > > > > ITC,
> > > > > > but I have no idea how to interpret it... because
> theoretically
> > > it
> > > > > is
> > > > > > not related to neither ERSP (EEG power) nor BOLD.
> > > > > Back to bereitschaft - there is no expectance in this?
> > > > > >
> > > > > > I will ask EEGLABlist technicians how to post our
> > > communications to
> > > > > the
> > > > > > list. By the way, so far you are the only person who
> replied.
> > > My
> > > > > > gratitude is all yours (haha).
> > > > > >
> > > > >
> > > > > Regards
> > > > >
> > > > > P $B%;%e<+ (Bl
> > > > >
> > > > > > Makoto
> > > > > >
> > > > > >
> > > > > >
> > > > > > --- P $B<@</<'<' (Bl Gunnar Larsson
> > > <Pal.Gunnar.Larsson at epilepsy.no>
> > > > wrote:
> > > > > >
> > > > > > > Dear Makoto
> > > > > > >
> > > > > > > First - I thought it went back to the list, but did not
> check
> > > to
> > > > > see
> > > > > > > that it did.
> > > > > > >
> > > > > > > My points was mostly towards the Nunez take on this;
> > > > > synchronization
> > > > > > > does not require energy. Hence synchrony comes out with
> high
> > > EEG-
> > > > > > power
> > > > > > > and no BOLD-effect. On the other hand, interneurons in
> cortex
> > > are
> > > > > so
> > > > > > > symmetrical that they do not show up on EEG, but consumes
> > > quite a
> > > > > bit
> > > > > > > of energy and will be well seen in fMRI.
> > > > > > >
> > > > > > > According to the above, your phase locking(?) would be
> > > expected
> > > > > to
> > > > > > > influence EEG-power but not BOLD (or ?).
> > > > > > >
> > > > > > > Another point from Nunez: If you have a million
> stochastic
> > > firing
> > > > > > > neurons, they would give a resultant amplitude of
> A*sqrt(n)
> > > where
> > > > > A
> > > > > > is
> > > > > > > the amplitude and n is number of neurons. However, when
> they
> > > are
> > > > > > > synchronized, the amplitude is n*A. So a million neurons
> will
> > > > > show
> > > > > > > same amplitude as 1000 synchronized neurons! This gives
> that
> > > > > small
> > > > > > > systems may dominate the EEG you record.
> > > > > > >
> > > > > > > P $B<'<=<'t@<- (Bl
> > > > > > >
> > > > > > > -----Opprinnelig melding-----
> > > > > > > Fra: Makoto Miyakoshi [mailto:mataothefifth at yahoo.co.jp]
> > > > > > > Sendt: 14. april 2009 03:54
> > > > > > > Til: P $B<'<=<'t@<- (Bl Gunnar Larsson
> > > > > > > Emne: RE: [Eeglablist] Meaning of ITC
> > > > > > >
> > > > > > > Dear Pal,
> > > > > > >
> > > > > > > Thank you for your fast response and information.
> > > > > > > Neurovascular coupling is the essential phenomenon with
> BOLD
> > > and
> > > > > it
> > > > > > > has totally different time constant than EEG... that is
> fine
> > > with
> > > > > me.
> > > > > > > That said, what I'm wondering is the meaning of ITC. On
> the
> > > one
> > > > > hand,
> > > > > > > ERSP is a measure of EEG power, which most likely
> reflects
> > > sum of
> > > > > > > regional neuronal activities, which should be associated
> with
> > > > > BOLD
> > > > > > via
> > > > > > > neurovascular coupling (in principle). On the other hand,
> ITC
> > > has
> > > > > > > nothing to do with EEG power, since it is a measure of
> > > > > inter-trial
> > > > > > > phase variance, therefore it should not affect BOLD
> either.
> > > Then,
> > > > > > what
> > > > > > > is the meaning of ITC in contrast with ERSP/BOLD?
> > > > > > >
> > > > > > > By the way, your response does not seem to be sent to
> EEGLAB
> > > > > list.
> > > > > > > Why don't we re-send it to the list?
> > > > > > >
> > > > > > > Makoto
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > --- P $B<><B<><1<><)<><) (Bl Gunnar Larsson
> > > > <Pal.Gunnar.Larsson at epilepsy.no>
> > > > > wrote:
> > > > > > >
> > > > > > > > I think you should read the paper by PL Nunez on the
> > > relation
> > > > > > > between
> > > > > > > > EEG and fMRI from 2000 (or 1999?). EEG and BOLD is very
> > > > > different
> > > > > > > > entities. Also, the EEG- parameters are direct
> functional
> > > > > measures
> > > > > > > > which gives responsen from a few miliseconds to some
> > > seconds
> > > > > > > > (Pfurtscheller). BOLD on the other hand, is the change
> in
> > > > > > > oxygenation
> > > > > > > > due to change in bloodflow due to change in energy
> > > consumption
> > > > > due
> > > > > > > > change in activity. Hence the effect is very indirect
> and
> > > shows
> > > > > a
> > > > > > > > maximum after some 5s. E.G. AM Dale et al has shown
> some
> > > nice
> > > > > use
> > > > > > > of
> > > > > > > > the BOLD and EEG/MEG so there no reason to discard one,
> > > just
> > > > > use
> > > > > > > with
> > > > > > > > care.
> > > > > > > >
> > > > > > > > P $B<><)<><?<><)<#<(<></ (Bl
> > > > > > > >
> > > > > > > > -----Opprinnelig melding-----
> > > > > > > > Fra: eeglablist-bounces at sccn.ucsd.edu
> > > > > > > > [mailto:eeglablist-bounces at sccn.ucsd.edu] P
> > > $B<><)<><?<><)<#<(<></
> > > > (B
> > > > vegne av
> > > > > > Makoto
> > > > > > > > Miyakoshi
> > > > > > > > Sendt: 10. april 2009 11:25
> > > > > > > > Til: eeglablist at sccn.ucsd.edu
> > > > > > > > Emne: [Eeglablist] Meaning of ITC
> > > > > > > >
> > > > > > > > Dear experts,
> > > > > > > >
> > > > > > > > Let me take a question about a basic physiology.
> > > > > > > > In my intuition, ERSP (i.e. EEG power) is related to
> > > neuronal
> > > > > > > > activation, either firing frequency or number of firing
> > > cells.
> > > > > On
> > > > > > > the
> > > > > > > > other hand, ITC (i.e. inter-trial EEG phase) is NOT
> > > directly
> > > > > > > related
> > > > > > > > to them. So, by observing ITC, we may be observing some
> > > already
> > > > > > > > systematized temporal responsibility of the given
> network,
> > > > > which is
> > > > > > >
> > > > > > > > too complicated and abstract to imagine, compared to
> the
> > > case
> > > > > of
> > > > > > > > neuronal firing simply increasing/decreasing.  Does it
> > > mean,
> > > > > then,
> > > > > > > ITC
> > > > > > > > is a totally different index than, for example, BOLD?
> > > > > > > >
> > > > > > > > Makoto
> > > > > > > > _______________________________________________
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> > > > > > >
> > > > >
> > > > >
> > > >
> > > >
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> > >
> > >
> > >
> > > --
> > > SB Demiral, PhD.
> > > Department of Psychology
> > > 7 George Square
> > > The University of Edinburgh
> > > Edinburgh, EH8 9JZ
> > > UK
> > > Phone: +44 (0131) 6503063
> > >
> 
>

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