Hi Eugene,
I was wondering then that even if im interested in the differences in deactivations then still the [1 – 1 ] [-1 1] contrast will give me the answer? Im trying to look differences in the pattern of deactivations in a group comparison and im not sure about what contrast to use.
Best wishes
--
Andres
From: Eugene Duff <[log in to unmask]" target="_blank">[log in to unmask]>
Reply-To: FSL - FMRIB's Software Library <[log in to unmask]" target="_blank">[log in to unmask]>
Date: Mon, 16 Apr 2012 17:30:06 +0100
To: <[log in to unmask]" target="_blank">[log in to unmask]>
Subject: Re: [FSL] Comparisons of deactivations
Hi Andres -
If the region is deactivating, then a [1 -1] contrast will still identify regions with greater signal in responses associated with ev 1 - i.e. reduced deactivation in the ev 1 responses.
Eugene.
On 16 April 2012 16:39, Andres Roman <[log in to unmask]" target="_blank">[log in to unmask]> wrote:
I have been doing two groups comparisons and a question came up which I wasn’t sure how to answer correctly. Usually in the group level I use a [1 –1] [-1 1] contrast which gives me the directionality of the differences between groups. My questions is that I am particularly interested in the differences in the ‘deactivations’ or in other words not the [1 0] contrast of the first level but rather the [-1 0] contrast. I was wondering if the directionality is based exclusively on the activation pattern I propose it to handle? Thank you very much.