They found some blobs of activation - when they used an inappropriately lenient statistical method. Their point, of course, was to draw attention to the fact that you really shouldn't use that method for fMRI. You can read the whole paper here. The Atlantic Salmon who heroically volunteered for the study was no more than a prop. In fact, I believe he ended up getting eaten.
But now, a Japanese team have just published a serious paper which actually used fMRI to measure brain activity in some salmon: Olfactory Responses to Natal Stream Water in Sockeye Salmon by BOLD fMRI.
How do you scan a fish? Well, like this:
A total of 6 fish were scanned. The salmon were immobilized by adding an anaesthetic (eugenol) and a muscle relaxant (gallamine) to their tank of water. Then, they were carefully clamped into place to make sure they really wouldn't move, while a stream of oxygenated water was pumped through their tank.Apart from that, it was pretty much a routine fMRI scan.
Why would you want to scan a fish? This is where the serious science comes in. Salmon are born in rivers but they swim out to live in the ocean once they reach maturity. However, they return to the river to breed. What's amazing is that salmon will return to the same river that they were born in - even if they have to travel thousands of miles to get there.
How they manage this is unclear, but the smell (or maybe taste) of the water from their birth river has long been known to be crucial at least once they've reached the right general area (see here for a good overview). Every river contains a unique mixture of chemicals, both natural and artificial (pollutants). Salmon seem to be attracted to whatever chemicals were present in the water when they were young.
In this study, the fMRI revealed that relative to pure water, home-stream water activated a part of the salmon's telencephalon - the most "advanced" part (in humans, it constitutes the vast majority of the brain; in fish, it's tiny). By contrast, a control scent (the amino acid L-serine) did not activate this area, even though the concentration of L-serine was far higher than that of anything in the home-stream water. How this happens is unclear, but further studies of the identified telencephalon area ought to shed more light on it.
So fishMRI is clearly a fast-developing area of neuroscience. In fact, as this graph shows, it's enjoying exponential growth and, if current trends continue, could become almost as popular as scanning people...
Link: Also blogged at NeuroDojo.
Bandoh H, Kida I, & Ueda H (2011). Olfactory Responses to Natal Stream Water in Sockeye Salmon by BOLD fMRI. PloS one, 6 (1) PMID: 21264223
7 comments:
Saw the paper and knew someone had to blog about it. Awesome!
The graph understates the matter. I have heard rumors of covert projects involving sea bass and perch.
antianticamper: The paper actually cited two previous fMRI studies of carp...here's one.
Unfortunately this paper didn't cite the Dead Salmon paper...but it did nonetheless use proper multiple comparisons corrections.
I find myself unable to care about the fate of the carp. They deserve what they get. But those poor, innocent perch are a different matter entirely.
Could the same physiological homing mechanism be genetically engineered into humans, so drunk people could more easily find their way home?
problem isn't drunk people finding their home, it's all those obstacles in the way that need to be addressed.
Anxiously waiting for the first fMRI of a mosquito. Would love to know if those vicious creatures take pleasure in buzzing you before attack.
My birds divebomb my dog frequently and sit out of the way obviously enjoying the resulting temper tantrum.
Carp make excellent gefilte fish. A scan of these , with onions , might open whole new vistas
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