December 6, 2001
Scanning for brain functions
By Walter Neary
HS News & Community Relations
Dr. Dean Shibata, assistant professor of radiology, presented two studies at the annual meeting of the Radiological Society of North America, held in Chicago the week of Nov. 26. The research work was performed while Shibata was at the University of Rochester School of Medicine, before joining the UW faculty this fall.
Both of the studies captured media attention and showed different ways the relatively new technique of functional magnetic resonance imaging (fMRI) can be used to help researchers and physicians understand how the brain works.
This technique is still largely a research tool, but shows promise in helping to localize critical areas of brain function before surgery and is sometimes performed on patients. Although MRI scanners are usually used to look at anatomic structures such as tumors, fMRI indirectly monitors changes in cerebral blood flow, “lighting up” areas of brain activity.
In the first study, his scans revealed that deaf people sense vibration in the same part of the brain that other people use for hearing – which helps explain how deaf musicians can sense music, and how deaf people can enjoy concerts and other musical events.
“These findings suggest that the experience deaf people have when ‘feeling’ music is similar to the experience other people have when hearing music. The perception of the musical vibrations by the deaf is likely every bit as real as the equivalent sounds, since they are ultimately processed in the same part of the brain,” says Shibata.
“The brain is incredibly adaptable. In someone who is deaf, the young brain takes advantage of valuable real estate in the brain by processing vibrations in the part of the brain that would otherwise be used to process sound,” he adds.
The deaf students in the study came from the National Technical Institute of the Deaf at the Rochester Institute of Technology. Shibata used fMRI to compare brain activity between 10 volunteers from the college and 11 volunteers with normal hearing. They agreed to let Shibata scan their brains while feeling intermittent vibrations on their hands.
Both groups showed brain activity in the part of the brain that normally processes vibrations. But in addition, the deaf students showed brain activity in a golf ball-sized area, the auditory cortex, otherwise usually only active during auditory stimulation. The people with normal hearing did not show such brain activity.
“These findings illustrate how altered experience can affect brain organization. It was once thought that brains were just hard-wired at birth, and particular areas of the brain always did one function, no matter what else happened. It turns out that, fortunately, our genes do not directly dictate the wiring of our brains. Our genes do provide a developmental strategy – all the parts of the brain will be used to maximal efficiency,” Shibata says.
At the National Technical Institute of the Deaf, where musical productions are an important part of the deaf culture, audience members attending musicals are provided with balloons which they can hold on their fingertips in order to “feel” the musical vibrations.
Neurosurgeons should be aware of the findings before performing surgery on a deaf patient; in particular, a surgeon should be careful while operating around a deaf person’s auditory cortex, since it clearly has a function, Shibata says.
He notes that here at the UW, he is looking forward to continuing his research into brain function among the deaf.
In the second study, Shibata found that people use the emotional parts of their brain to make so-called rational personal decisions.
“Neuropsychologists have begun to believe that emotional and rational parts of the brain may be more closely intertwined than previously thought. Our imaging research supports the idea that every time you make choices in your personal life, you need to “feel” the projected emotional outcome of a choice – subconsciously, or intuitively. That feeling guides you and gives you motivation to make the best choice, often in a split second,” says Shibata.
During the brain scans, Shibata showed 11 people a series of personal questions, such as asking them to choose a preference for receiving a camera or bicycle or having a warm bath or dinner. The subjects were then supposed to roll the question over in their mind while their brain activity was measured. Shibata also asked the subjects more impersonal, cost-related questions, such as, “What would cost you more – a bicycle burglary or theft of your car?”
The goal was to measure what happens to the brain while making personal decisions, as opposed to what seemed like impersonal decisions. “The point was to test the hypothesis that when people make decisions that affect their own lives, they will utilize emotional parts of the brain, even though the task itself may not seem emotional,” Shibata says.
Shibata is not alone in this view, and says he was inspired by the work of neurologist Antonio Damasio, who has worked with patients who’ve suffered frontal lobe brain injuries. Evidence suggests that when someone suffers an injury to the part of the frontal lobe that governs emotion, the person may have normal memory and be able to solve abstract problems. But the person will often have trouble making routine, rational decisions. They seem to get caught in “infinite loops” where they are unable to prune through the various options and make a decision.
