Over the past few hundred years, as scientists have grappled with understanding the source of the amazing processing power in our skulls, they have employed a number of metaphors based on familiar technologies of their given era. The brain has been thought of as a hydraulic machine (18th century), a mechanical calculator (19th century) and an electronic computer (20th century).

Today, early in the 21st century, we have another metaphor driven by the capabilities of the current technology—this time colorful images from modern brain scans. Evolutionary psychologists, for example, have conceptualized the brain as a Swiss Army knife, with a collection of specialized modules that have evolved to solve specific problems in our evolutionary history, such as language for communication, facial recognition to separate friends from foes, cheating detection to prevent free riders, risk taking to raise the odds of individual or group success, and even God to explain the world and to find individual happiness in thoughts of an afterlife. Many neuroscientists have employed the module metaphor to describe specific regions of the brain “for X,” with X being whatever happens to be the task given to subjects while a machine scans their brains. Such tasks might include selecting brand logos they prefer (say, Coke or Pepsi) or political candidates they would vote for (conservatives or liberals).

3 Comments

1. 1. philgrimm 04:03 PM 10/1/08

   fMRI is at least two physiological steps removed from the data that is most important, which is neuronal activity. Blood flow brings oxygen, but which cells are using it--neurons or suportive glial cells? But beyond that, the real information which is desired is the activity of the neural-networks, and networks cannot be visualized, only inferred. Some vital portions of a specific network may activate only 1-10,000 cells in a given area and therefore go unrecognized, while another, suppressed or suppressing networks may have activated 100,000 cells in a different area, an area which is then recognized and its importance overemphasized.
   
   Also, the artificiality of the scanning moment cannot be overstated. The subject is prone, confined, and assaulted by loud noises. The rhythm, pitch and 'melody' of each acquisition sequence is different, and itself can create a mood change in the subject. Some sequences are soothing, others agressive. Music is sometimes played for distraction. Few important imaging sequences take less than a minute to acquire. Also, detailed exams can take 40 minutes of longer, and the subject/patient's overriding emotion can become impatience, rather than cooperation.
   
   Feedback regarding the subjects true level of participation is poor. You can not place electrodes on the scalp to do a realtime match of the MRI images with an EMG, because the electrodes will get hot and burn the patient...
   

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2. 2. oneflame 07:18 PM 1/25/09

   I would appreciate a clarification on point #2. It is implied that there is a logical fallacy here, or an error in the scientific process. However, the argument states that scans are indirect measurements of brain activity.
   
   We know that indirect evidence is significant and not significant in some circumstances. So, how does using indirect measurements lead to falibility in THIS case? What would a direct measurement look like? I guess I am not certain as to why this is an issue as this section mainly went into a lot of technical detail without any exposition on its impact and/or meaning.
   
   Thanks!

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3. 3. oneflame in reply to philgrimm 02:18 AM 1/27/09

   Thank you very much for your explanation! What I understood from your explanation is that fMRIs are not measuring the actual object of the study, which is Neuronal behavior, and that since we are only measuring the effects of this activity, we really are not getting valid data.
   
   However, it does not seem that this points to evidence that there is a "false cause" scenario. The blood flow changes are predictable based on the simulous being provided.
   
   I think I understand this, (please let me know if I didn't).
   
   But, I guess the essence of my question is more of a philosophical one, or one pertaining to logic.
   
   Does taking indirect measurements somehow invalidate the tests? Don't we indirectly measure things all the time to determine a Truth value? We measure someone's temperature via a thermometer under the tongues; we measure the light that is present around an absence of light to find a black hole.
   
   So, if we are measuring effects of a "cause", (stimulus) in this case, how could we be mislead?
   
   If you are saying that the "noise" of the machine is really the cause of the visual data in a particular test, that would make sense. But, since these tests are measuring the effects of different stimuli, and the patterns are vastly different between each test, then we should easily be able to see the "Common Denominator" of machine noise between each test, right? Shouldn't we just be able to pull out everything that is the same between all tests and identify the machine noise? (I think this would work especially given a single person undergoing multiple tests in the same setting)?
   
   I hope my question doesn't sound to unreasonable. I as given this article to review by a Psychology professor, and was a little confused by this point. All of the others points seem to point directly to a logical fallacies, (false causes, confirmation biases, etc).
   
   I just don't see it here yet.
   
   I appreciate your patience!

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