Hi, any given contrast only tests for positive Z-stat values above
threshold resulting from that contrast. If you also want to test for
strong negative values you need to add a new contrast which has negative
the values of the original contrast.
Cheers.
On Mon, 12 Sep 2005, Kaufman, Galen D. wrote:
> If an EV is defined as +1, do the resulting significant z-stat maps
> distinguish the polarity of the BOLD response? Or does that need to be
> fished out elsewhere? We expect ROIs with inhibition and others with
> excitation relative to our stimulus, but all the output so far looks
> "positive".
>
> Thanks again,
>
> Galen Kaufman
>
--
Stephen M. Smith DPhil
Associate Director, FMRIB and Analysis Research Coordinator
Oxford University Centre for Functional MRI of the Brain
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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