Dear Tom
> Excerpts from SPM-help#: 3-Feb-100 Re: Fw: comparision bet... by K Friston
> > The only difference between SPM96
> > and SPM99 (in terms of estimtation and inference) is that the spatial
> > smoothness estimator has been upgraded. This upgrade accommodates
> > non-stationary spatial correlations among the errors when correcting
> > for the search volume using tests based on peak height (but not on
> > those based on spatial extent, at this stage). This advance (due to
> > Keith Worsley) allows one to be more confident about corrected
> > inferences in situations where the smoothness may change from region to
> > region (e.g. VBM).
>
> Is there a reference for this improved smoothness estimator?
Worsley KJ et al Detecting changes in nonisotropic images (1999) Human
Brain Mapping 8:98-101
Its not so much an 'improved smoothness estimator' but a more general
estimator that gives the appropriate expectation for both stationary
and nonstationary fields. This reduces to taking the expectation of
the determinant of the variance-covariance matrix of the partial
derivatives of the normalized residuals (as opposed to taking the
determinant of the expectation as in SPM96).
All the very best - Karl
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