Re: [Marsbar-users] Calculating % signal change for block design

[Talia R. <tal...@bu...>]

Hi,
I am worried that the values are almost the same across conditions. For
example, LIFGtri is similar in that English is 4.257% signal change and
Spanish is 4.187%, which are not statistically significant(we found more
significant differences in our previous study) or in LMFG it's 3.521% and
3.555% for English and Spanish respectively. the 100th/1000th digit is not
significant, correct?
Talia

*Talia Lee Raney*
*Research Assistant at BU Aphasia Research Laboratory*
*B.A. Candidate, Honors in Neuroscience with a minor in French Language,
Boston University 2014(expected)*


On Tue, Apr 1, 2014 at 3:41 PM, Matthew Brett <mat...@gm...>wrote:

> Hi,
>
> On Tue, Apr 1, 2014 at 12:32 PM, Talia Raney <tal...@bu...> wrote:
> > Hi,
> > I figured out the problem with the design path. So here are my beta
> > extraction from the raw data
> > Based on my previous emails about the issues with exact % signal change
> > across English and Spanish conditions:
> > Hi,
> >
> > "On Thu, Jan 30, 2014 at 11:57 AM, Talia Raney <tal...@bu...> wrote:
> >> Hi,
> >> The beta values are the same across all patients, which is strange
> because
> >> in previous analyses the matrix values were different
> >> Here are the dimensions: [61 73 61]
> >> These are the values for the matrix that are the same across the 4
> >> patients:
> >> -3 0 0 93
> >> 0 3 0 -129
> >> 0 0 3 -75
> >> 0 0 0 1
> >> The technician in my lab couldn't understand why either and so maybe
> that
> >> is
> >> contributing to not statistically different results(For Example: BOLD
> >> signal
> >> for LIFG tri for English and Spanish were 2.748 and 2.731). Since all
> the
> >> patient vary in the level of bilingualism, it shouldn't happen.
> >> I will read up some more about the beta estimates.
> > I am confused - that looks like the image affine.  I was thinking of
> > the beta values from the regression.   These are the beta* images in
> > SPM, and the .beta field in marsbar.  There's an example of beta
> > extraction in marsbar here:"
> >
> > This is the beta values for LIFGtri.
> > -0.441987835592497
> > -17.6631781046321
> > -0.00584444804595380
> > -18.1993048739651
> > -1.41879647244602
> > -13.9670507802562
> > -0.764194761758106
> > -16.8519803415051
> > -2.79227983932455
> > -1.60086419296314
> > -0.804718943608214
> > 4.14987893074880
> > 289.420272008739
> > 149.868494102840
> > 10.2935059115606
> > 28.1044882261369
> > 10.1211746881779
> > 26.6752138395511
> > 9.83882094731138
> > 28.7118684627458
> > 9.78124614493613
> > 28.1860180483175
> > -5.57499518184095
> > -2.65210862167349
> > -0.611257093313648
> > -79.5111551830495
> > 137.309012987820
> > 296.308725567405
> > 186.455870630854
> > 175.695321504058
> >   What would be the next step into figuring out the problem for these
> > insignificant differences in % signal change?
>
> I think you were worried about the beta values being the same across
> patients, but I think we established that this was the affine.
>
> So - with this list of betas - what should I be looking at?  I guess I
> would not be surprised if the betas were fairly similar across
> conditions and patients, but there's probably a bug if the values are
> exactly the same.
>
> Don't forget that "most published research findings are false" [1] -
> and neuroimaging studies have low power [2] so it wouldn't be very
> surprising if you failed to find the same significant result as one or
> even more than one previous study.
>
> Cheers,
>
> Matthew
>
> [1]
> http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.0020124
> [2] http://www.nature.com/nrn/journal/v14/n5/full/nrn3475.html
>
>
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