On Thu, 21 Feb 2008 23:13:42 +0800, Ada Leung <[log in to unmask]> wrote:
>Dear SPMers,
>I like to arise some questions about the concepts of percent signal change
>and welcome answers from anyone who are interested in it.
<snip>
By activation map, do you mean thresholded activation map, e.g. when you
go through the steps after pressing the results button? If so...:
>(3) Is there a situation that there is positive signal change but no
>activation shown in the activation map?
Because it fails to reach significance.
<snip>
>(5) Why does negaitve signal change not give deactivation in the
activation
>map?
The t-tests in SPM are one-tailed. To see the notional deactivation, use
the contrast with weights of opposite sign to the given contrast.
<snip>
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