Great descriptive article about what an MRI is & what kinds of information can be gained from using high-end MRIs (fMRIs, DTIs, etc ...) in the Dec 2005 / Jan 2006 issue of Technology Review.
MRI: A Window on the Brain by Paul Raeburn, 12/14/2005. They say: "Advances in brain imaging could lead to improved diagnosis of psychiatric ailments, better drugs, and earlier help for learning disorders."
Raeburn quotes Robert Desimone, director of the McGovern Institute for Brain Research at MIT, who indicates that MRI is "the most powerful tool for studying the human brain. I liken it to the invention of the telescope for astronomers." Desimone notes that the arrival of the telescope did not immediately revolutionize the scientific understanding of the universe. That took time, as researchers learned how to use their new tool.
The article explains a bit about MRIs (in layman's terms!) and talks about how they could be useful in diagnosing bipolar disorder and possible problems with premature babies. Fascinating stuff.
The Technology Review web is worth checking out too ...