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I wasn't in fmri research but some fellow students in my lab were on it. I do know there was a study with dead salmon which were showing up as having "active" b

I wasn't in fmri research but some fellow students in my lab were on it. I do know there was a study with dead salmon which were showing up as having "active" brain regions. I have to find it but am on my phone. It's easy to imagine the main difficulty with this is mapping signal to actual thoughts and regions. It's a really complex biology and physics to reduce.

leemailll 10y ago
what is your field? Neuroscience?
- goalieca 10y ago
  Electrical engineering (medical imaging - medical imaging technologies) This is the best I could find for the paper. not what I originally meant to cite. http://onlinelibrary.wiley.com/doi/10.1002/scin.5591761320/abstract http://onlinelibrary.wiley.com/doi/10.1002/scin.5591761320/a...
greenyoda 10y ago
Searching for "dead salmon fMRI" turned up the following: http://www.prefrontal.org/files/posters/Bennett-Salmon-2009.pdf http://www.prefrontal.org/files/posters/Bennett-Salmon-2009....
- acveilleux 10y ago
  Back when I was involved in MRI research, multiple comparisons correction was the rock that many a paper in the field crashed upon. Neuro psych. suffers from weak stats, which is a far cry from saying either fMRI itself is meaningless or saying MRI as a whole is.
deleted 10y ago
[deleted]
mattkrause 10y ago
The salmon thing was a statistical problem, not a technical one. fMRI data generate an incredible number of data points: imagine a movie, but in three dimensions, so you get a sequence of x/y/z-volumes. A typical scan has ~128 to 256 voxels in each spatial dimension, for ~1 million voxels per volume. This means that if your analysis contains voxel-by-voxel tests, you're going to be running a huge number of them. Even if each test has a fairly low false-positive rate (say 0.1%), there are still a huge number of tests, and thus, a huge number of false positives. There are principled ways of correcting for this; there are also hacky "folk methods" like setting a more stringent false positive threshold. The fish poster argues that the latter doesn't work, using a deliberately silly example. http://prefrontal.org/files/posters/Bennett-Salmon-2009.pdf http://prefrontal.org/files/posters/Bennett-Salmon-2009.pdf
- Alex3917 10y ago
  > The salmon thing was a statistical problem, not a technical one. How is that relevant to the question of whether or not most fMRI research is wrong?
  - mattkrause 10y ago
    1. It's trivially checkable for any existing individual paper. You skim the methods or search for "multiple comparisons" or "false discovery rate" or something like that. 2. For papers where this wasn't done, the already-collected data can be reanalyzed. In fact, you can often get correct it without access to the raw data (at least approximately). 3. It means that future papers (where future is somewhere after 2008-9 here) can be done correctly from the get-go; it's not a limitation of the technique or the signal itself.
    - Alex3917 10y ago
      If you believe that the majority of papers in the field are not incorrect, what are the assumptions behind your estimation of the numbers?
  - omginternets 10y ago

leemailll 10y ago

what is your field? Neuroscience?

goalieca 10y ago
Electrical engineering (medical imaging - medical imaging technologies) This is the best I could find for the paper. not what I originally meant to cite. http://onlinelibrary.wiley.com/doi/10.1002/scin.5591761320/abstract http://onlinelibrary.wiley.com/doi/10.1002/scin.5591761320/a...

greenyoda 10y ago

Searching for "dead salmon fMRI" turned up the following: http://www.prefrontal.org/files/posters/Bennett-Salmon-2009.pdf http://www.prefrontal.org/files/posters/Bennett-Salmon-2009....

acveilleux 10y ago
Back when I was involved in MRI research, multiple comparisons correction was the rock that many a paper in the field crashed upon. Neuro psych. suffers from weak stats, which is a far cry from saying either fMRI itself is meaningless or saying MRI as a whole is.

deleted 10y ago

[deleted]

mattkrause 10y ago

The salmon thing was a statistical problem, not a technical one. fMRI data generate an incredible number of data points: imagine a movie, but in three dimensions, so you get a sequence of x/y/z-volumes. A typical scan has ~128 to 256 voxels in each spatial dimension, for ~1 million voxels per volume. This means that if your analysis contains voxel-by-voxel tests, you're going to be running a huge number of them. Even if each test has a fairly low false-positive rate (say 0.1%), there are still a huge number of tests, and thus, a huge number of false positives. There are principled ways of correcting for this; there are also hacky "folk methods" like setting a more stringent false positive threshold. The fish poster argues that the latter doesn't work, using a deliberately silly example. http://prefrontal.org/files/posters/Bennett-Salmon-2009.pdf http://prefrontal.org/files/posters/Bennett-Salmon-2009.pdf

Alex3917 10y ago
> The salmon thing was a statistical problem, not a technical one. How is that relevant to the question of whether or not most fMRI research is wrong?
- mattkrause 10y ago
  1. It's trivially checkable for any existing individual paper. You skim the methods or search for "multiple comparisons" or "false discovery rate" or something like that. 2. For papers where this wasn't done, the already-collected data can be reanalyzed. In fact, you can often get correct it without access to the raw data (at least approximately). 3. It means that future papers (where future is somewhere after 2008-9 here) can be done correctly from the get-go; it's not a limitation of the technique or the signal itself.
  - Alex3917 10y ago
    If you believe that the majority of papers in the field are not incorrect, what are the assumptions behind your estimation of the numbers?
- omginternets 10y ago