Dear Michael,
I'm answering on behalf of Karl Friston and cc it to the SPM mailbase, I
hope you don't mind.
> I am working on a paper and I need reference literature which explain
> two functions I used.
> I was using the 'mean & decay function' for my experiment to
> describe time within-epoch adaptation.
Here you use 2 basis functions, which should capture an underlying
within-epoch adaption. I would look at it as a specific case of the
general linear model as implemented in SPM99. This could be covered by
the following two references: The first is about the general linear
model approach, providing the framework for the core of SPM.
***
Friston KJ Holmes AP Worsley KJ Poline JB Frith CD and Frackowiak RSJ
Statistical Parametric Maps in functional imaging: A general linear
approach.
Human Brain Mapping 1995;2;189-210
***
The second is about basis functions for epochs, where your mean &
exponential decay function would just be another set of basis functions.
***
Friston KJ Frith CD Turner R and Frackowiak RSJ Characterizing evoked
hemodynamics with fMRI. NeuroImage 1995; 2;157-165
***
> Also I used 'parametric linear modulation over time' to describe
> a general adaptation for ongoing stimulus tasks within a session.
The parametric linear modulation over time is implemented by a
convolution of the chosen basis function set with a series of 'stick
functions', where the height of each stick is modulated over time.
Essentially, this approach is largely equivalent to the one described in
the following paper, where the authors specify basis functions, which
are modulated versions (up to 2nd order) of a stimulus function.
***
Buchel C Wise RJS Mummery CJ Poline J-B Friston KJ Nonlinear regression
in parametric activation studies. NeuroImage 1996;4:60-66
***
Stefan
--
Stefan Kiebel
Functional Imaging Laboratory
Wellcome Dept. of Cognitive Neurology
12 Queen Square
WC1N 3BG London, UK
Tel.: +44-(0)20-7833-7478
FAX : -7813-1420
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