Functional MRI of the brain
von Denis Hoa
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
- 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.
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