Dear Dorian,
We had a similar case in Pihlaja et al. Human Brain Mapping 29 (2008)
1001-1014. We used the method of Buchel et al, Neuroimage 8 (1998)
140-148, and it worked fine.
best regards,
Simo Vanni
Dorian P wrote:
> Is there a way to detect non-linear increasing in a parametric
> modulation with 2nd order modulation?
>
> The contrast of the 2nd order regressor outputs indifferently
> increases or decreases that have slight non-linearities in U shape (1
> contrast) or inverted U shape (-1 contrast, examples attached). I need
> only those areas that has a non-linear component, but also an overall
> increase between 1 and 4 in 1-2-3-4 modulation. I am playing around
> with F-contrasts but it doesn't seem to be possible.
>
> Thank you.
>
> P.s. The effects may be reversed in the graphs due to "negative" activation.
>
> Dorian
> Ruhr University Bochum
> PhD Student
>
>
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Simo Vanni, MD PhD,
Academy Research Fellow
Vision Systems Physiology
Brain Research Unit/AMI centre
Low Temperature Laboratory
Helsinki University of Technology
PO BOX 3000, 02015-TKK, Espoo
Finland
tel: +358-9-451 6159
fax: +358-9-451 2969
e-mail: [log in to unmask]
http://ltl.tkk.fi/wiki/BRU/Vision_Systems_Physiology
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