The Frontal Cortex

The Limits of fMRI

My latest article for the Boston Globe Ideas section looks at some recent criticisms of fMRI, at least when it’s misused:

The brain scan image – a silhouette of the skull, highlighted with bright splotches of primary color – has also become a staple of popular culture, a symbol of how scientific advances are changing the way we think about ourselves. For the first time in human history, the black box of the mind has been flung wide open, allowing researchers to search for the cortical source for every flickering thought. The expensive scanners can even decode the hidden urges of the unconscious, revealing those secret feelings that we hide from ourselves. The machine, in other words, knows more about you than you do: It’s like a high-tech window into the soul.

“These [fMRI] images get people excited in a way that other research just doesn’t,” says Kelly Joyce, a sociologist at the College of William & Mary. “The pictures have a tremendous authority, not only among scientists but among people who might just glance at a brain scan picture in a newspaper.”

In recent weeks, however, several high-profile papers have ignited a fierce debate over whether brain scanners are being widely misused and their results over-interpreted. Some eminent figures in the field have taken issue with the metaphors typically used to describe brain imaging, criticizing descriptions of scanners that rely on what Joyce refers to as the “myth of transparency.”

The scanners, they say, excel at measuring certain types of brain activity, but are also effectively blind when it comes to the detection of more subtle aspects of cognition. As a result, the pictures that seem so precise are often deeply skewed snapshots of mental activity. Furthermore, one of the most common uses of brain scanners – taking a complex psychological phenomenon and pinning it to a particular bit of cortex – is now being criticized as a potentially serious oversimplification of how the brain works. These critics stress the interconnectivity of the brain, noting that virtually every thought and feeling emerges from the crosstalk of different areas spread across the cortex. If fMRI is a window into the soul, these scientists say, then the glass is very, very dirty.

Here’s a link to the Logothetis article in Nature that began a lot of this discussion. What do you think? What psychological states are amenable to localization experiments in brain scanners? How will we feel about most of these brain imaging experiments in ten or twenty years? Frankly, I was surprised by just how critical many scientists were.

As I point out several times in the article, however, fMRI remains an extremely valuable experimental tool, at least when used properly. It’s still our best way to make sense of functional networks in the brain, such as the default system. It’s also very handy when used in conjunction with other experimental techniques, such as EEG or electrophysiology. But I think only time will tell how well these localization studies hold up.

Comments

  1. #1 PhysioProf
    August 18, 2008

    How will we feel about most of these brain imaging experiments in ten or twenty years?

    I suspect that we will consider them to have been mostly a waste of time and effort and a misallocation of resources.

  2. #2 locklin
    August 18, 2008

    How will we feel about most of these brain imaging experiments in ten or twenty years?

    Probably the same as we think about research done ten or twenty years ago. Mostly irrelevant and at times misguided, but with a few jewels that seeded everything we currently do.

  3. #3 Kevin H
    August 18, 2008

    I think I made this comment about your post on the logothetis paper, but I’ll make it again. The idea that one spot of cortex is responsible for a complex function was not generated in fMRI, nor is it the only current branch of neuroscience to make that assumption. Basically, all of it does. This is because of the past 50 years that approach has proved incredibly fruitful in finding the underlying mechanisms of a host of cognitive processes.

    We are now beginning to get a more nuanced view of cognitive processes which involve large networks of regions, however, far from hold these findings back, fMRI has actually been at the forefront of this movement. The work from single and multi cell recording, cellular neuroscience, slice work, and to some extent EEG have a much harder time disambiguating the relative roles of local and global processing in complex psychological processes.

    Not really directed at anyone it particular, I just want to make sure that the POV is out there.

  4. #4 Luci
    August 18, 2008

    So which cortical spot is responsible for the human urge to take something amazingly complex and explain it with an easily digested, brightly colored, sound bite answer? The only MRI scans I’ve spent time with are the plain, monochrome, non ‘f’ style. The scans provide only a piece of a puzzle, with no one involved in their review making claims otherwise.

    Will we just need to wait for fMRI to stop being the sexy new toy and settle down before the quick fix folks move on to the next tech advance and leave the calmer researchers in control? Medical advances always require patients – and patience.

    And if someone will come up with really effective earplugs, MRI sessions will be much more fun.

  5. #5 bsci
    August 19, 2008

    locklin says it best. Much is misguided, but there are gems that will last. Kevin H also correctly notes that fMRI is probably the leading edge of research getting away from pure function localization to network models.

    Luci, It’s amazing what happens when earplugs are put in correctly. If someone knows that they are doing and really gets them into the outer ear canal they really work well. There are several companies also working on active noise cancelation systems. These are theoretically possible within an MRI, but there are many challenges to getting it done right.

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