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Learning objectives

After reading this chapter, you should be able:

  • Describe the cascade of phenomena linking neuronal activation and BOLD contrast
  • List the MRI sequences adapted to functional explorations
  • Present the basic steps of a functional MRI study: design of activation tasks, choice of paradigm, data acquisition, signal processing and statistical analysis of the results

Key points

  • Functional MRI will only detect brain activation very indirectly, as variations in the T2* signal, following changes in the oxyHb/deoxyHb ratio, after neurovascular coupling triggered by neuronal activity.
  • Data acquisition is carried out in T2*-weighted ultrafast sequences of the echo planar type, sensitive to BOLD contrast, during a succession of different repeated tasks following a paradigm.
  • The signal variations are very weak and their analysis is based on a statistical comparison between different states of activation.
  • The temporal resolution of fMRI, combined with the possibilities of morphological imaging, make MRI a modality of choice in the neurosciences.

References

  1. Habas. [Physiological basis of functional MRI]. Journal de radiologie. 2002 Nov;83(11):1737-41.
  2. Le Bihan and Lehericy. [Practical aspects of realization of a functional MRI]. Journal of neuroradiology. 1999 Mar;26(1 Suppl):S54-8.
  3. Gore. Principles and practice of functional MRI of the human brain. The Journal of clinical investigation. 2003 Jul;112(1):4-9.
  4. Voss, Zevin. Functional MR imaging at 3.0 T versus 1.5 T: a practical review. Neuroimaging clinics of North America. 2006 May;16(2):285-97, x.
  5. Golay, de Zwart. Parallel imaging techniques in functional MRI. Top Magn Reson Imaging. 2004 Aug;15(4):255-65.
  6. Di Salle, Esposito. High field functional MRI. European journal of radiology. 2003 Nov;48(2):138-45.
  7. Delmaire, Krainik. [Functional magnetic resonance imaging: physiopathology, techniques and applications.]. Journal de radiologie. 2007 Mar;88(3 Pt 2):497-509