In a recent issue of Nature, Nikos Logothetis, director of the Max Plank Institute for Biological Cybernetics, wrote some surprisingly harsh sentences about the experimental limitations of fMRI. The piece is especially noteworthy because Logothetis has probably done more than anyone else to document the tight correlation between what fMRI measures (changes in cortical blood flow) and the underlying neural activity of the brain. (His 2001 Nature paper, "Neurophysiological investivation of the basis of the fMRI signal," has been cited more than 1200 times.)
Although brain scanner technology is often described as a "window into the brain," Logothetis, in this most recent article, makes it clear that the metaphor of transparency is inappropriate. He cites a long list of factors that complicate the interpretation of fMRI data, from the challenge of distinguishing between excitation and inhibition to the difficulty of measuring the relative activation of different brain areas. If brain scanners are like a window, then the window has some very dirty glass.
The limitations of fMRI are not related to physics or poor engineering, and are unlikely to be resolved by increasing the sophistication and power of the scanners; they are instead due to the circuitry and functional organization of the brain, as well as to inappropriate experimental protocols that ignore this organization.
The one thing missing from this otherwise excellent article was a few choice examples of bad experimental design. I've complained before about the reticence among scientists to criticize each other in public forums, but the omission seems especially glaring in an article that is, in large part, about "what we cannot do with fMRI".
Bonus question: has fMRI research jumped the shark?
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Currently, there is a widespred recognition in the brain science community that fMRI or neuroimaging only provides a loosely coupling between fMRI signal and brain activity (age variation in fMRI signal complicates the interpretation, neural vascularity abnormalities disturbe the BOLD hemodynamics...)
But on the other hand, neurosrugeons, those specialists that test in practice and for very "real" world applications the neurotechnology available, say that neuroimaging is an excellent tool to map certain brain regions underlying important cognitive functions (fMRI can discover what is the dominant hemisphere for language during presurgical procedures etc.)
So, is really neuroimaging a good tool a "window to the brain" or not.
The complain is justified because scientists should say what experimental design protocols (made by who if reasonable) are appropiate for neuroimaging and what psychological theories can be confirmed or disconfirmed by the use of neuroimaging.
Could part of the problem with fMRI research be that a lot of the studies aren't done by neuroscientists?
I wouldn't call Logothesis' article harsh. It is a good summary of our current state of knowledge that anyone who seriously uses and grapples with the technology and data interpretation understands. Considering he's mostly citing other articles that discuss the limitations of the technology, I'm not sure it is accurate to say that scientists are reluctant to publicly criticize each other. The real unique thing is that Nature published a critique like this. Perhaps, rather than placing the blame on scientists, it's more accurate to say that top journals don't like to talk about the limitations of science.
fMRI is particularly tempting for bad science and unethical commercialization (as in the linked Slate article) because it is so easy to make clean pictures and stories to fit around those pictures. That said when FKF, the company mentioned in the Slate article got free publicity in the NY times last Fall, many prominent fMRI researchers very publicly pushed back. Alas, they seem to keep finding other science-illiterate journalists who are willing to give them more free publicity.
fMRI has clearly not jumped the shark. It's like saying since quack use some trappings of quantum theory to sell magic cures that quantum physics as jumped the shark.
As Anibal notes, it is increasingly being used by neurosurgeons and getting more direct clinical applications. You just need to know what you are or are not seeing. For example, we don't clearly know when or if fMRI data is neural excitation or inhibition. Fortunately the neurosurgeon also doesn't care. The neurosurgeon is hoping to avoid areas that have key roles in specific processes. Whether that role is inhibitory or excitatory is a secondary concern.
In response to Ryan, Many of the better early studies were done by psychologists with psychophysics backgrounds and neuroscientists, but there are also good neurologists, psychiatrists and others. The real key is that good studies are done by people who fully understand their tools and as the underpinnings of fMRI are being taught to more people, the boundaries where we find good research aremore fluid.
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Really nice and has a flowing narrative. Thanks
Really nice and has a flowing narrative. Thanks