Important fMRI study literacy tips

I love a fMRI story as much as the next person -- there's something addictive about discovering what's going on in your brain as you do and think different things, and how they relate to one another. The reality is not as neat, however. Neuroimaging studies often involve a hypothetical average brain made by studying lots of brain scans, and come to conclusions that are even now the subject of hot debate. Here are four important caveats to consider when reading about fMRI studies (click through for full list):

1. "The Performance Burden" If neural activity is found to differ between groups or conditions, you can't necessarily make inferences about differences in neural information processing - this could reflect behavioral differences alone. For example, if younger children perform worse than older children but also recruit a few different regions, those neural regions might be operating in exactly the same way across ages (e.g., processing errors) - there's just more errors in the younger group! Even with similar levels of performance there's the possibility that children of different ages are using different strategies, different amounts of mental effort, or are differentially reacting to the closed, loud, and claustrophobia-inducing space that is an fMRI scanner...

4 Things to Keep in Mind When Reading fMRI Studies

(Image: fMRI one, a Creative Commons Attribution (2.0) image from twitchcraft's photostream)

• [Anonymous]

  i’m a bit disappointed that they made no mention of my (least) favorite fMRI interpretation issue – reverse inference. RI seems to be quite common when the popular press gets a hold of fMRI data, and works like this:

  FACT: fear activates the amygdala.
  FACT: We observe amygdalar activity.
  INCORRECT CONCLUSION: the patient must’ve been experiencing fear.

• [Anonymous]

  Glad to see I’m not the only one bothered by so much poor methodology . There is bad reporting as well. But asking 6 college students to imagine what they’d do in a hypothetical situationdoes not yeild statistically significant data. Control groups should include people not educated in contemporary westernstr ‘ herding of linear abstractions’ , or habituated to TV/ computer use.

• [Anonymous]

  A look at where the fMRI technology has been used in real life:
  http://www.neontommy.com/news/2010/09/new-lie-detector-fmri-machine-verifies-memories

• [arikol]

  Interesting!

  I would imagine that people with ADHD, ADD, Asperger’s and such might also be affected by problem number 2.

  I study cognitive science at graduate level and so this is of particular interest.

  • [dequeued]

    It’s interesting how much of a role executive function plays in cognition.

    I’m really ADHD, and if I was hooked up to an fMRI, and they asked me to do a boring task, I’m sure my brain would be dim and dark.
    But ask me to do a stimulating task, and my brain would light right up.

    It’s not a reflection of capacity, but motivation.

    Also, just sitting still in a chair and paying attention during a lecture that I don’t feel involved in requires a huge mental exertion for me, far more than for my peers.

    • [arikol]

      yeah, I know. The point is that sitting still (at least for me) is a challenge in and of itself, which might affect the results. For others, lying still in an fMRI machine may not pose a challenge. The point is just that different brain issues may make the baseline different which poses a problem in interpreting any results.
      A lot of studies have been performed on abnormal conditions (stroke, etc) but figuring out what is normal is quite hard.

    • [Mark Dow]

      Any good fMRI study controls for attention and arousal. Often this is done by having the subject perform a difficult task, so they can’t drift off while thinking about lunch. If they don’t perform well (e.g. due to lack of motivation) they are excluded from the study. Unfortunately the tasks are and often repetitive and boring by design — it makes for better comparisons across individuals and groups.

• [Anonymous]

  I wonder which parts of my brain light up when I read fMRI studies that draw sweeping conclusions based on dubious methodology?

• [apoxia]

  Plus they cut out all people with ADHD, epilepsy, psychiatric disorder, neurological disorder etc. Makes for clean data that is not easily generalised. But then again, that’s true of most research.