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no -----Ursprüngliche Nachricht----- Von: FSL - FMRIB's Software Library im Auftrag von Michelle Voss Gesendet: Do 14.02.2008 01:21 An: [log in to unmask] Betreff: Re: [FSL] AW: [FSL] Melodic output 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 > > >