Good question. Ultimately, in fMRI we are looking for changes in the local ratio of oxygenated to deoxygenated blood. As neurons begin firing in a brain region more oxygen-rich blood is dumped in by the circulatory system. If the salmon really was responding to the pictures there would need to be blood flow for these changes to be detectable using fMRI. Since the salmon had been prepared by the supermarket there was nothing to circulate blood around.
Have you ruled out zombie salmon... or salmon with commensal micro-biological activity such as a rust?
We just had the one salmon to scan, unfortunately. Regardless of the pre-existing condition of the salmon (zombie, rust, etc) there were no significant voxels of activity once we applied proper statistical corrections. This strongly points to correlated noise as the cause of the uncorrected results.
Thank you for responding.
I have been very curious on whether Rusts are active in salmon. I was not serious about zombie salmon though. One salmon is a rather small sample size regardless of the common sense reasoning around the subject at hand.