What brain scans and brain scanning are really like

I had the TV show House on in the background yesterday and happened to look up during an episode that involved a functional MRI scan. This particular episode was so far from reality it prompted me to write a blog about the systematic (yet more realistic) depiction of brain scans and brain scanning. Most pictures of brain scans, whether one finds them in an advertisement for some psychopharmaceutical or in a pre-publication lab presentation of some study, are enhanced. For example, these images use colors to indicate brain activation (and misrepresent what this is). Worse still is depictions of the scanning process, as most people are limited to how these exist in TV shows and films.

Functional magnetic resonance imaging is perhaps the most commonly used neuroimaging method, at least when it comes to brain scans one finds outside of medical, neuroscience, and other scientific literature. It produces the amazingly clear images of the brain that PET scans and other neuroimaging methods can’t, it doesn’t require radioactive dyes, it isn’t so localized that any image (no matter how dressed-up) would be uninteresting to most like ERP data, and can easily produce a wealth of data readily transformed into images by researchers who have no idea how MRI (or the NMR technology it uses) works.

Functional MRI differs from MRI scans in that the former can measure brain activity while the latter can show brain structure (useful for identifying abnormalities like lesions), much like an X-Ray. However, even though you can see the images during the scanning, you can’t tell anything from them. In fact, most of the time you don’t even bother to look at the scans during scanning except to ensure the patient, subject, or participant isn’t moving (other than the eyes; when the eyes are closed you can actually scroll down the images from some series of images and see how they dart side-to-side). The only activity you can really see is movement, as it requires statistical processing to transform the signal data into pictures which differentially “color” the hemodynamic activity which serves as a proxy for neuronal activity. So we talk, we read books, we write papers, we play computer games, etc., during most of however many hours someone is being scanned. Researchers spend very little time doing anything during scanning except between runs of some task when everything happens at once: we have to check to make sure the scans are clear, that the participant is doing the task (and, sometimes, is awake), give encouragement and sometimes other feedback, etc. That takes maybe 15 minutes. Scanning often takes several hours.

So where do those amazing images which show active brain regions using bright colors come from? The equivalent of Photoshop. Mathematical photoshop, yes, but it’s still the equivalent of artificially adding a “splash of color” to make the picture look better. More importantly, there are any number of ways in which one can ensure highlighted regions demonstrate brain activity that is noise, irrelevant to the study, or otherwise meaningless.

Finally, it is true that MRI scanning (functional or not) involves huge magnets. However, unlike in TV shows, metal pins and so forth from surgery are usually safe. They don’t result in metal ripping through someone’s body. And when there is a problem (such as a mechanic who went into an MRI room with his tool belt on and got stuck to the MRI machine), the scanner isn’t shut off. It can’t be. Shutting it off does nothing- there are several emergency buttons that stop the machine and flood it with gas/chemicals that immediately reverse the magnetic field. This can ruin multimillion dollar equipment (and get one banned from access to the MRI machine).

Basically, the images and depictions of MRI scans are the scientific version of air-brushing photos even when they are real scans, the dramatizations of the scanning process ignores how little anybody can determine during the scanning process, and even the potential dangers are misrepresented.

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