Dear Dr Preibisch,
>I still have some concerns about the comparability between the results of
>spm96 and spm99.
>I have performed the analysis of different datasets (single subjects,
>simple motor and speech tasks, block design) with spm96 and spm99 with
>identical preprocessing and as similar as possible modelling in the
>statistics section. I always got "better" results using spm96.
>This means the locations of activations were basically the same. However,
>the significance was higher with spm96. At equal thresholds, there were
>(more and especially) larger clusters with spm96 (identical smoothing!).
>Altogether, activation appeared to be more robust with spm96.
Could you clarify one point for the list? Do you mean that at equal
thresholds of CORRECTED significance you got bigger clusters with SPM96?
If so, I guess that this is not so surprising. I believe that SPM99 uses a
different method of correction (owing to theoretical advances) which is
more stringent but more robust than that used in SPM96 (ie. it is far less
likely to overestimate the significance of a given peak).
If you mean that when using an equal UNCORRECTED threshold you obtained
bigger clusters with spm96 then this is surprising, as the underlying
method for obtaining this significance level should be the same, as I
understand it.
Clarifying this issue will make it easier for the SPM guys to answer the
question,
Best wishes,
Richard Perry.
>Dear all,
>
>
>Can anyone comment on this impression? Did anybody else compare the
>results of the analysis using spm96 and spm99 respectively?
>
>Thank you, Christine Preibisch
>
>-------------------------------------------------------------------------------
>Christine Preibisch
>Klinikum der Universitaet Frankfurt
>ZRAD - Institut fuer Neuroradiologie
>Schleusenweg 2-16
>60528 Frankfurt
>Germany
>
>Phone: ++49 69 6301 4651
>Fax: ++49 69 6301 5989
>
>email: [log in to unmask]
>-------------------------------------------------------------------------------
from: Dr Richard Perry,
Clinical Research Fellow, Wellcome Department of Cognitive Neurology,
Darwin Building, University College London, Gower Street, London WC1E 6BT.
Tel: 0171 504 2187; e mail: [log in to unmask]
Pager: 04325 253 566.
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