Dr. Seiji Ogawa and the Past, Present, and Future of Functional MRI Research

摘要

In basic brain science and clinical investigations ofpsychiatriceurological diseases, it is very importantto be able to measure the functional state of the brainnoninvasively. Dr. Seiji Ogawa worked on this issue formany years and succeeded in developing a novel imagingmethod of brain function based on the vascular responseto functional activation of the brain. Remarkably, in theearly 1990s, he developed a technique for detecting magnetic resonance imaging (MRI) signals that depend onblood oxygenation levels in the brain. He named thesesignals BOLD (for blood oxygen level dependent) andshowed that BOLD signals can be used for functionalmapping of the human brain following sensory stimulation, thereby establishing the basic principles underlyingfunctional MRI (fMRI).1,2 This method enabled the noninvasive mapping of human brain activity without the useof radioactive isotopes.3 Currently, various noninvasivemethods for evaluating functional brain activities havebeen developed and applied, including electroencephalography (EEG) and magnetoencephalography (MEG).Although fMRI does not directly detect the electrophysiological or electrochemical activity of the brain, fMRIhas the advantage of being able to localize the functioning site of the whole brain with high resolution, comparedto other noninvasive methods including EEG and MEG.