Two cautionary notes on the use of fMRI

This week’s issues of Science and Nature each have very nice commentaries on the limitations of fMRI, a topic I’ve written about a few times before. The Nature piece is a review by Nikos Logothetis entitled “What we can do and what we cannot do with fMRI“. Logothetis is uniquely placed to comment on these matters; a very large chunk of what we know about the BOLD signal (the primary vehicle of fMRI studies) is due to his seminal work. While the review is pretty expansive (particularly for Nature, at 10 pages!) and somewhat technical, the take-home message is that the most serious limitations of fMRI are due to massive aggregation over distinct populations of neurons rather than to any technical limitations per se. Or, as he puts it much more eloquently:

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.

That’s not to say that all is lost, of course. On the whole, Logothetis is pretty optimistic about the value of fMRI, even going so far as to suggest that “MRI is currently the best tool we have for gaining insights into brain function and formulating interesting and eventually testable hypotheses”; it’s just that it’s not perfect by a long shot.  But anyway, there’s much more to the review than I can convey coherently in my current sleepy state, so if you have access to Nature, it’s definitely worth reading.

The Science piece (“Growing Pains for fMRI”) is a much lighter news article by Greg Miller, and it focuses mostly on a controversy that played out in the pages of the New York Times last year. The thumbnail sketch is  that one group of fMRI researchers did some very shoddy “research” on the way people view the different election candidates, and another (larger) group of researchers called them on it.  The exchange then led to a period of widespread soul-searching amongst cognitive neuroscientists, until ultimately, in March 2008, the Cognitive Neuroscience Society imposed a moratorium on publication of all fMRI data until a common set of guidelines for rigorous and ethical research conduct was agreed upon.  Ok, that last part is completely made up. But the point is that the article is a good read, and you should check it out if you can.  It’s not often you hear one scientist say that another scientist’s study was “really closer to astrology than it was to real science” (for the record, I agree with that assessment in this case).