Chapter 8 Study Questions

  1. How are fMRI data typically organized, from subjects down to voxels?
  2. Define “signal” and “noise.”
  3. What are the differences between “raw signal-to-noise ratio,” “contrast-to-noise ratio,” and “functional signal-to-noise-ratio”?
  4. What theoretical effect should field strength have upon raw SNR, and why? What is the effect of field strength upon functional SNR, in practice?
  5. At high field, what component of the vascular system would most contribute to the fMRI BOLD signal?
  6. What causes thermal noise in an MRI scanner? How does thermal noise vary across the brain?
  7. What is the difference between thermal noise and system noise? What are common causes of system noise?
  8. What is actually drifting in “scanner drift”?
  9. What are common forms of physiological noise?
  10. How does the balance between thermal and physiological noise change with increasing field strength? What implications does this have for fMRI?
  11. What are some sources of behavioral or task-related variability in many fMRI experiments?
  12. How does intersubject variability in BOLD activation compare to intersession variability in BOLD activation?
  13. What is preprocessing? How is it distinct from experimental analysis?
  14. What is the first rule of quality assurance?
  15. What are phantoms?
  16. If you saw an fMRI activation map that was highly positively active along the edge of the right hemisphere, but highly negatively active along the edge of the left hemisphere, what might you conclude?
  17. What can be done to help prevent head motion, in terms of designing the experiment and setting up the subject?
  18. How do researchers correct for head motion?
  19. What benefits are provided by spatial normalization? What problems can be introduced?
  20. How large is the average adult human brain, in cubic centimeters?
  21. Name two commonly used stereotaxic spaces for human MRI.
  22. What is temporal filtering? Under what circumstances would it be useful?
  23. What is spatial filtering (i.e., smoothing)? Under what circumstances would it be useful?
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