By testing adolescents and young adults on the same memory task as children, Bunge and her research team have tracked the gradual development of key connections, documenting how brain function matures. (Karin Higgins/UC Davis photo)
Neuroscientist checks into kids' brains to see into how they behave
Silvia Bunge is getting her hands on answers to one of Western philosophy's greatest quandaries in a way that her father could only dream of a generation ago.
“My father is a philosopher of science. He wrote a book on the mind-body problem,” says Bunge, a neuroscientist at the Center for Mind and Brain and an assistant professor of psychology at UC Davis. The “mind-body problem” is the quest to understand how our complex human consciousness arises from the brain.
As Bunge (pronounced "BOON-ghe") grew up in Montreal, she had many conversations with her dad about the relationship between the intangible mind and the tangible body. Today, Bunge studies goal-directed behavior, looking at the neuron networks that make that relationship possible.
Her research examines how the brain uses rules to guide decisions and actions. That Bunge is doing this research at all reflects a sea change in science. Because they lacked the tools to tackle it, scientists used to leave the mind-body problem to philosophers and religious thinkers.
But in the 1990s, non-invasive scanning techniques gave neuroscientists new windows to the brain. Now, by using scans to learn how parts of the brain interact during complex thought processes, scientists like Bunge are deepening our understanding of mind-brain links.
Bunge’s research uses functional magnetic resonance imaging (fMRI), a non-invasive scanning method that shows the brain at work. These fMRI scans let researchers observe, in real time, which brain regions are receiving the greatest flow of oxygenated blood.
Greater blood flow means greater neural activity. And greater neural activity means that by scanning test subjects as they perform assigned tasks, Bunge and her team can pinpoint the brain locations used for each task.
How learned rules are used for behavior
“In adults, we are looking at how learned rules are used for behavior,” she said. “When we learn that ‘green means go’ and ‘red means stop,’ where and how is that information stored? And how do we access that rule for later use?”
By testing subjects’ responses during fMRI scans to familiar rule-associated stimuli such as road signs, Bunge’s team has discovered that the brain constructs a hierarchy of rules within the cortex, or gray matter.
“An easy rule such as ‘apples taste good; garbage tastes bad’ uses the part of the cortex that develops earliest in childhood,” Bunge said. “At the very, very front of the brain, in the most developed part of the cortex, we store complex sets of rules – for example, all the rules for how you behave in a classroom.”
In essence, the brain takes advantage of the structural hierarchy that already exists due to differing levels of sophistication between brain regions.
In addition to studying adults, Bunge’s team uses fMRI scans to examine brain development in late childhood and adolescence. Before non-invasive scans were invented, there was no way to visualize brain maturation.
‘When we learn that ‘green means go’ and ‘red means stop,’ where and how is that information stored? And how do we access that rule for later use?’
Silvia Bunge, UC Davis neuroscientist
How older kids' brains differ
“We knew that older kids, aged 8 to 12, already do a lot of the things that adults do,” Bunge said. “We wanted to know how their brains differ from those of adults.”
Bunge’s team scanned the brains of 8-to-12-year-olds during a test of working memory, the form of memory that keeps information accessible for immediate use. The children saw a set of pictures — of grapes, a ship and a rooster — and were asked to recall the images either in their original order or in reverse order.
The children were quite good at simple recall, but had difficulty manipulating the order of the images.
“Kids are failing to recruit the brain regions that are used for manipulation by adults,” Bunge explained. The necessary regions are already there, but the brain has not learned to use them efficiently.
“The connections between brain regions are still being strengthened,” Bunge said.
By testing adolescents and young adults on the same memory task as children, Bunge’s team tracked gradual development of the key connections, documenting how brain function matures.
Parental encouragement
Bunge’s own intellectual development was strongly encouraged by both her parents.
“I was between 8 and 12, the same age as my youngest research subjects, when my dad and I started talking about the mind-body problem,” she said. As her interest grew, she could not decide whether to study biology or psychology, “so neuroscience seemed like the right choice.”
Her interest in science also was nurtured by her mother, a mathematician.
“My mom was the only female mathematician in her department,” Bunge said. “She is a great role model for me.”
Now, Bunge is encouraging her own students. When she teaches cognitive neuroscience, she introduces the mind-body problem by discussing a man with a brain tumor.
“I ask my students, ‘Do you think you’re responsible for your actions?’ Then I tell them about a man who was arrested for beating his girlfriend’s infant. It turned out that an enormous tumor was pressing on his hypothalamus, the brain region that controls rage responses. When surgeons removed the tumor, the man became himself again.”
Many students reconsider the man’s culpability after they hear this story.
For students who are particularly drawn to neuroscience, Bunge is an enthusiastic mentor. Here, again, she is following her mom’s lead. “It’s still my favorite thing,” she says, “to encourage girls and young women to go into science and stick with it.”