How exactly do you imagine the brain working? Magnetic resonance imaging (MRI) is a tool that enables scientists to study the brain, using powerful magnets to change the alignment of the atoms in brain tissue. The atoms give out radio signals that an MRI scanner detects and that a computer translates into an image.
Dr. Seiji Ogawa, director of the Ogawa Laboratories for Brain Function in Tokyo and one of this year’s winners of a Gairdner Award for medical research, gave a lecture about functional MRI (fMRI): fMRI works in a similar way to traditional MRI but can provide more information about brain function, not just brain anatomy.
Before studying the brain, Dr. Ogawa studied hemoglobin, the protein found in red blood cells that carries oxygen throughout the human body. He found that hemoglobin behaves like a magnet when it isn’t carrying oxygen (called deoxy hemoglobin). These magnetic properties would allow deoxy hemoglobin to be detected by an fMRI scanner, which could then show what parts of the brain are receiving blood at a given time. Activities such as talking and hearing sounds lead to increased blood flow in specific regions of the brain. During his experiments, Dr. Ogawa made several discoveries about the regions of the brain involved in various tasks.
During experiments on mice, Dr. Ogawa observed cross-hemisphere interaction. The brains of many animals, including mice and humans, have two sides called hemispheres: the left hemisphere controls the right side of the body and vice versa. The right side of the brain was activated when a mouse’s left paw was stimulated, but if the right paw was stimulated 40 milliseconds afterwards the left side of the brain did not respond. Dr. Ogawa also discovered that there is a functional network in the brain: performing one task would activate different parts of the brain instead of just one specific area. This phenomenon is called site-site interaction. Dr. Ogawa observed site-site interaction when testing the effects of visual stimuli on humans. He found that a visual stimulus, such as a pulse of light, activates two regions in the human brain, one for vision and one for emotions. This finding is surprising because earlier it was thought that only one part of the brain was involved in vision. Dr. Ogawa’s work using fMRI shows that even simple tasks require the use of several different and seemingly unrelated parts of the brain.
