Hi,
In general, detrending = temporal filtering.
Therefore, high-pass filtering is one of the many possibilities to detrend fMRI data (see Tanabe et al., 2002, doi:10.1006/nimg.2002.1053).
High pass filtering is implemented in SPM as projecting the voxel time series into a set of DCT functions (see spm_dctmtx.m) where the order of the DCT depends on the cutoff period (e.g. 128s), number of scans and TR.
Linear, quadratic and cubic detrending would be done if using Legendre polynomials instead of DCT. This option is implemented in AFNI as 3dDetrend. I am not aware whether this possibility is available in SPM, but it would not be very difficult to code it.
Hope this helps,
Cesar
On Sep 2, 2011, at 12:05 AM, Anders Eklund wrote:
> Hello,
>
> what kind of detrending is performed by default for single subject fMRI analysis in SPM? I can't see any settings for detrending. Is the highpass filtering done instead of (linear, quadratic, cubic) detrending?
>
> /Anders
Cesar Caballero Gaudes
Hôpitaux Universitaires de Genève
CIBM / Radiologie
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