that's right - you can flip any combination of 2 vectors that way,
i.e. if you flip across tie and space you would not flip across
population
hth
christian
eb 2008, at 00:21, Michelle Voss wrote:
> But if I want to flip both the sign of the timecourse and the
> spatial map, I do not have to flip the subject loadings, right?
>
> Michelle
>
> On Feb 13, 2008 5:55 PM, Andreas Bartsch <[log in to unmask]
> > wrote:
> Hi,
> in the full-tensor decomposition (TICA), you can decide which one
> you want to flip: if you change the sign of the timecourses (Tmodes)
> OR the spatial maps (Bmodes), you can also change the sign of the
> subject loadings (Smodes) AND keep the Bmodes OR the Tmodes,
> respectively.
> Cheers-
> Andreas
>
>
> -----Ursprüngliche Nachricht-----
> Von: FSL - FMRIB's Software Library im Auftrag von Michelle Voss
> Gesendet: Do 14.02.2008 00:39
> An: [log in to unmask]
> Betreff: Re: [FSL] Melodic output
>
> hello,
>
> just to double-check my intuition, since subject loadings are factor
> loadings, they do not need to be flipped here right? e.g., they
> represent
> the same thing for both the original and "flipped" maps and
> timecourses,
> which is how much each subject contributes to the component.
>
> thanks
> michelle
>
>
> On Feb 13, 2008 4:54 PM, Christian F. Beckmann <[log in to unmask]
> >
> wrote:
>
> > Hi
> >
> > red-yellow shows increasing positive regression coefficient with the
> > associated time course while dark blue-light blue shows increasing
> > negative regression coefficient wrt the time course.
> > If your time course is the inverse of your canonical design then
> blue
> > values who still show negative regression against the time course)
> > will in fact have positively regression coefficient wrt the original
> > design. That is, you can freely 'flip' the time course but then also
> > need to 'flip' the spatial map to make sure that once you multiply
> > these two together you get the same result (basically 1*1 = -1 * -1)
> > In TICA the associated time course basically is the avergae temporal
> > response across all the voxels (weighted y the vaue in the spatial
> > map) and also averaged across the population according to the
> subject/
> > session mode vector. Yes, you can trial average this time course and
> > get a representation of the overall avergae (across space and
> > population) average HRF shape.
> > best
> > christian
> >
> >
> >
> > On 13 Feb 2008, at 19:57, Vishwadeep Ahluwalia wrote:
> >
> > > Hi,
> > > I need help interpreting the IC maps. I'm confused about the color
> > > coding
> > > scheme.
> > > assuming my stimulus paradigm is such: 0001100011000
> > > Instance 1: i get a component with time series 0001100011000.
> How do i
> > > interpret the red and blue voxels?
> > > Instance 2: i get a component with time series 1110011100111.
> How do i
> > > interpret the red and blue voxels?
> > >
> > > As a separate question;
> > > Using TICA on 10 datasets, i got the task related component. Is it
> > > true that
> > > the time series for this component represents the time course of
> every
> > > activated voxel in the respective spatial map? if so, can i trial
> > > average
> > > this time course and validly estimate the shape of the BOLD
> response
> > > in
> > > those voxels?
> > > These ten datasets belong to one paradigm. Can i do a similar
> > > analysis on
> > > data from another paradigm(with different stimulus timings) and
> > > compare the
> > > effect sizes between the two paradigms? or would i have to run one
> > > single
> > > analysis for both?
> > >
> > > Thanks!
> > >
> > > -Vish
> >
>
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