Dear Anne Lise.
> Hi Karl,
>
> I am revising a paper. One of the reviewers asks me to provide formula of
> the models used in the analysis.
> I used three different analyses on the same set of fMRI data:
> 1- epoch-related analysis
> 2- event-related
> 3- a mixed model: boxcar allowing for an exponential decay
>
> What should I answer ? Is there a paper where the recipes of SPM are
> explained ?
I would include something like
'The statistical analysis employed a generalized linear model (Worsley
and Friston 1995) with a design matrix that comprosed event- and epoch-
related regressors. These regressors obtain by convolving series of
delta functions (placed at the onset of each event or epoch type) with
a set of temporal basis functions, giving one regressor for each trial
type and each basis function. The basis functions model (in linear
combination) event- or epoch-related responses. For example the basis
set for events included a canonical hemodynamic response function (HRF)
and its temporal deriviative (e.g. Friston et al 1998). The basis set
for epochs comprised a box-car and exponential function of peri-onset
time (c.f.Friston et al 1995) to model within-epoch adaptation (both
convolved with a HRF).'
Worsley KJ and Friston KJ Analysis of fMRI time-series revisited - again
NeuroImage 1995; 2:173-181
Friston KJ Fletcher P Josephs O Holmes A Rugg MD Turner R Event-related
fMRI: characterizing differential responses NeuroImage 1998;7:30-40
Friston KJ Frith CD Turner R and Frackowiak RSJ Characterizing evoked
hemodynamics with fMRI NeuroImage 1995; 2;157-165
All the very best - Karl
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