For those curious, I found this source: http://prefrontal.org/files/posters/Bennett-Salmon-2009.pdf (Bennet et al. 2009: Neural correlates of interspecies perspective taking in the post-mortem Atlantic Salmon: An argument for multiple comparisons correction)
Essentially it's using a dead salmon as a lone control to argue that fMRI studies should be more rigorous in how they control for random noise.
There's a chemical brothers song that, while not addressing your question straightforwardly, proves that salmon can have meaningful social interactions with humans. I think.
He has ceased to be! 'E's expired and gone to meet 'is maker! 'E's a stiff! Bereft of life, 'e rests in peace! If you hadn't nailed 'im to the perch 'e'd be pushing up the daisies! 'Is metabolic processes are now 'istory! 'E's off the twig! 'E's kicked the bucket, 'e's shuffled off 'is mortal coil, run down the curtain and joined the bleedin' choir invisible!! THIS IS AN EX-PARROT SALMON!!