Magnetic Resonance Imaging, Functional
Published Online: 15 SEP 2006
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Richter, W. 2006. Magnetic Resonance Imaging, Functional. Encyclopedia of Analytical Chemistry.
- Published Online: 15 SEP 2006
Functional magnetic resonance imaging (FMRI) is an analytical method for measuring brain activity while it occurs. FMRI was first demonstrated in 1992, but it has since become the most popular neuroimaging method. Its temporal resolution is of the order of seconds and hence superior to positron emission tomography (PET). Its spatial resolution is on the order of millimeters which makes it superior to both PET and electrophysiological methods such as electroencephalography (EEG). Furthermore, FMRI is noninvasive in the sense that no external contrast agent has to be used. FMRI contrast is based on the intrinisic blood oxygenation changes that occur at the site of brain activity in response to a specific task. The exact mechanism that links activity and signal change is currently not well understood and is an area of active research.
FMRI is subject to many experimental difficulties, however. A vexing problem is that of physiological (heartbeat and breathing) and gross motion. Gross motion is often coupled to the presentation of the stimulus and hence especially prone to producing artefactual activation. The analysis of the experimental data is not a standard procedure at present. While past research has generally used paradigmatic methods of analysis (hypothesis testing), nonparadigmatic (data driven) methods like fuzzy clustering analysis (FCA) or independent component analysis (ICA) have become important tools.
A more complete understanding of the physiological mechanisms leading to the activation signal, and a better grasp of the proper statistical treatment of the data, are likely to increase the power of FMRI even further.