A new study investigated what goes on in the brain when doctors make a diagnosis.
Radiologists use X-rays and other imaging techniques to diagnose diseases - but in this study, they went into the scanner themselves. Brazilian researchers Marcio Melo et al used fMRI to record neural activity while the radiologists were shown an array of chest X-rays.
Some of the scans showed evidence of disease, which the doctors were required to diagnose. There were also two control conditions, in which the stimuli were still X-rays but with little pictures of either animals or letters embedded in them, instead of diseases.
The image above shows how it worked. As well as pneumonia, one patient has a severe case of Alligator Lung, while the other looks like they've got the Influenza 'B' virus.
Now, the point of all this was to compare the mental process of making a diagnosis to that of seeing an object. The idea is that a trained radiologist sees particular diseases in the scans, in the same way that anyone can see an alligator.
Activity during diagnosis, object-recognition and letter naming was very similar (compared to doing nothing); this presumably represents the visual and language areas involved in looking at the image, recognizing what it is, and saying it out loud:
There were some slight differences, with the left inferior frontal cortex and the posterior cingulate cortex being more activated by diagnosis than animals. But this difference disappeared after controlling for the number of different possible descriptions the radiologists reported thinking about for each image.
The authors conclude that
These results support the hypothesis that medical diagnoses based on prompt visual recognition of clinical signs and naming in everyday life are supported by similar brain systems.
Which seems fair enough, although it's important to remember that the diagnoses in this study were quite easy ones. The mean response time was just 1.3 seconds and only 6% of those split-second diagnoses were wrong. Unfortunately diagnosis is not always that easy.
Anyway, this study is all very well, but why stop at chest X-rays? Last year I speculated on the fun neuroscientists could have with a real-time fMRI machine:
You could lie there in the scanner and watch your brain light up. Then you could watch your brain light up some more in response to seeing your brain light up...
We really need to scan people while they're looking at brain scans. Only then will we be able to understand the neurological basis of being a neurologist, and find the brain's looking-at-a-blob blob.
Melo M, Scarpin DJ, Amaro E Jr, Passos RB, Sato JR, Friston KJ, and Price CJ (2011). How doctors generate diagnostic hypotheses: a study of radiological diagnosis with functional magnetic resonance imaging. PloS ONE, 6 (12) PMID: 22194902