DesignBasics - MRC CBU Imaging Wiki

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Design basics

Please see Rik Henson's excellent discussion of fMRI DesignEfficiency

MatthewBrett gave a talk at HBM2006 on avoiding errors in design and analysis. The text below is a slight expansion of the last few slides.

The importance of having an anatomical hypothesis

This is my (MatthewBrett) personal view for what it's worth.

  • An interesting imaging experiment has to go further than where brain activity is, and tell us something about what the brain activity means in terms of how the brain works
  • As a consequence, a brain imaging experiment without an anatomical hypothesis rarely tells us much about how the brain works
  • It is very rare for an experiment to have no anatomical hypothesis atall, but an experiment with a weak anatomical hypothesis asks a question like "where in the brain is activity for task T"
  • An strong anatomical hypothesis usually leads to a question like "what does activity in region R tell me about the contribution of R to the computations of task T"

How to make sure you have a strong anatomical hypothesis

  • Sketch your ideal of how the paper will turn out while you are designing the study
  • Draw a cartoon or your expected brain activation and brain activation if your hypothesis is not correct
  • Make sure that you know how to use the difference between the activations above to be able to test your hypothesis
  • The following may be signs that you have a weak anatomical hypothesis:

    • "Neural correlates" in your title!
    • Introduction that concentrates on the task much more than the brain
    • Long list of activations in your discussion with lists of previous studies activating these areas