Hello SPM community,
My original search of the email archives lead me to the conclusion that contrasts with [1 0] represents regions that were significantly active where contrasts with [-1 0] represents regions that were significantly deactivated. However more recent searches reveal the interpretation is not that simple.
In my visual paradigm I showed individuals alternating blocks of control images and the active images. I was interested in regions that were significantly activated so at the second level using a one-sample anova I entered [1 0] at the contrast manager. However, after acquiring the significantly active regions I wanted to look at the percent signal change for each region using MarsBar. The results from MarsBar showed negative signal change for many of the regions. Hence my questions are:
1) Does the negative percent signal change mean deactivation, (i.e. what I thought was activation is really deactivation)?
2) How do I differentiate between activation and deactivation?
Thank you for your help in advance.
Nero
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