Hello Mr. McLaren,
hello Mr. Rubens,
thank you very much for your advice! You gave me some new ideas of modelling the data and also some interesting and helpful literature. Please, excuse my late response. Thanks a lot!
Best regards,
Maike Tahden
-------- Original-Nachricht --------
> Datum: Sun, 30 Jan 2011 16:06:03 -0800
> Von: Michael T Rubens <[log in to unmask]>
> An: [log in to unmask]
> Betreff: Re: [SPM] separate BOLD-functions per each single trial
> Just to note, it is not uncommon to run a GLM with separate regressors for
> each trial. This is how the beta series correlation method of functional
> connectivity is performed. See Rissman et al. Neuroimage 2004.
>
> I don't think it has ever been done with using FIR as the bf though.
>
> cheers,
> Michael
>
> On Sun, Jan 30, 2011 at 3:55 PM, MCLAREN, Donald
> <[log in to unmask]>wrote:
>
> > If I understand you correctly, this is impossible.
> >
> > It seems like you want a separate response for each trial, this would
> > require a separate set of FIR for each trial. Because of this you will
> > end up with more regressors than measurements/observations. Since you
> > have more predictors than measurements, the model is overspecified and
> > there would be multiple solutions.
> >
> > On the other hand, if you assume the same shape for each individual
> > event, then you could obtain a measure of the amplitude of the
> > response for each trial. To do this, as Cesar stated, you want to have
> > N event types in your model where N is the number of trials.
> >
> > Chapter 9, I believe, in Functional Magnetic Resonance Imaging by
> > Jezzard et al., has a section on estimating the BOLD response and its
> > limitations. Also, there were 2 papers from either 2000 or 2001 by
> > Ollinger et al. on event-related designs.
> >
> > Hope this helps.
> >
> > Best Regards, Donald McLaren
> > =================
> > D.G. McLaren, Ph.D.
> > Postdoctoral Research Fellow, GRECC, Bedford VA
> > Research Fellow, Department of Neurology, Massachusetts General
> > Hospital and Harvard Medical School
> > Office: (773) 406-2464
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> >
> >
> > On Sun, Jan 30, 2011 at 3:43 PM, Maike Tahden <[log in to unmask]> wrote:
> > > Hello Cesar,
> > >
> > > thank you very much for your response! However, I don’t think I’ll
> get
> > the information I need, if I create a different regressor for each
> event. As
> > I wrote last time, I need separate BOLD-functions per each single trial
> and
> > till now I’ve found no way to identify these with the help of SPM, so
> that
> > I’m trying to model the data by myself using the Generalized Linear
> Model.
> > In this way I hope, to get – in whatever form – the knowledge which
> > respective proportion of the signal results from the stimulus presented
> 2 s
> > before, to that one presented 4 s before, to that one presented 6 s
> before
> > and so on. But till now I don’t know how…
> > >
> > > Or maybe I haven’t understood your tip correctly?
> > >
> > > Kind regards,
> > > Maike
> > >
> > >
> > >
> > >
> > >
> > > -------- Original-Nachricht --------
> > >> Datum: Fri, 28 Jan 2011 10:02:45 +0100
> > >> Von: Cesar Caballero <[log in to unmask]>
> > >> An: [log in to unmask], [log in to unmask]
> > >> Betreff: Re: [SPM] separate BOLD-functions per each single trial
> > >
> > >> You need to specify one condition for each trial in your model
> (specify
> > >> 1st-level in SPM).
> > >> Set the duration of each trial equal to zero (event-related) and
> define
> > >> the onset for each trial.
> > >> This will create a different regressor in the design matrix for each
> > >> event.
> > >>
> > >> Then specify an F-test for the columns of the design matrix
> > corresponding
> > >> to the conditions you want to compare.
> > >>
> > >> Hope this helps,
> > >> Cesar
> > >>
> > >> You can read chapter
> > >> On Jan 27, 2011, at 10:55 PM, Maike Tahden wrote:
> > >>
> > >> > Hello,
> > >> >
> > >> > at the moment I’m writing my bachelor thesis in mathematics using
> > >> fMRI-data, which come from a biological psychology group. They
> employed
> > a rapid
> > >> event-related design so that the duration of the inter-stimulus- and
> > >> inter-trial-intervals varies between 2 and 4 s. That is why the
> > respective
> > >> BOLD-responses probably superpose each other in a linear fashion. For
> my
> > >> bachelor thesis I need separate BOLD-functions per each single trial.
> To
> > achieve
> > >> this aim, I try to model the data using the Generalized Linear Model
> > (cf.
> > >> first pages of Chapter 10 “Analysis of fMRI Timeseries” in
> “Human Brain
> > >> Function”, 2nd Edition). However, I still do not know how I get the
> > >> separate functions or rather: If you fix one point at the time
> series,
> > how do
> > >> you know which respective proportion of the signal results from the
> > stimulus
> > >> presented 2 s before, to that one presented 4 s before, to that one
> > >> presented 6 s before and so on?
> > >> >
> > >> > Does anybody know the answer?
> > >> >
> > >> > I would be most appreciative of each advice!
> > >> >
> > >> > Kind regards,
> > >> > Maike
> > >> >
> > >> > --
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> > >>
> > >
> > > --
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> >
>
>
>
> --
> Research Associate
> Gazzaley Lab
> Department of Neurology
> University of California, San Francisco
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