We have different ways of thinking about different things. Take cats: We can think about the tabby next door, or the lion patrolling the African veldt. Or, we can think about cats as a category of animals.
The ability’s so ingrained we’re rarely aware of it. But Earl Miller says it’s vital to making our way in a complex world.
“Virtually all voluntary behavior, which is a lot of what we do day and day out, is learned,” he says. And that requires, among other things, a brain system that can “extract information from experience.”
What kinds of information? An example is the fact that we lump objects — TV sets, bicycles, brains, cats — into categories. But it goes far beyond that.
“When you try a new restaurant,” explains Miller, “you’re drawing on the qualities of other restaurants you’ve visited, and you use that to guide your behavior.”
The brain locale that’s in charge of behaviors from crossing the street to pursuing a PhD is the prefrontal cortex. Small or non-existent in most animals, it’s comparatively big in many primates, and comparatively huge in humans.
“Because it orchestrates your behavior,” says Miller, an associate professor of brain and cognitive sciences, “it’s often called the brain’s executive.” This same region “decides” what we’ll direct our attention to at any given moment. And Miller’s painstaking studies are aimed at shedding light on how it works.
In recent work, his group created “generic” images by electronically combining pictures of three cat species — house cat, tiger and cheetah. They did the same with dogs. They also created cat-dog hybrid images: “One of them is 80 percent cat and 20 percent dog,” says Miller. “We also have one that’s 60 percent cat and 40 percent dog.” They then taught monkeys to recognize these images as well as standard cat and dog pictures.
Using a painless system to monitor the firing of small clusters of brain cells, the group probed how the images affected the prefrontal cortex. The researchers found there were cells that had become highly specialized.
“There were neurons that responded to any example of a dog, and others that responded to any kind of cat,” says Miller. “In other words, through the learning process we had instilled in their brains the concepts, ‘This is cat’ and ‘This is dog.'”
Miller has made other advances, too. He’s shown that if two types of items — say, a tree and a house — become linked in the brain, the prefrontal cortex will pull from memory a mental image of the second after an image of the first pops up on a computer display.
Next on Miller’s agenda is to map more complex brain functions. “We want to know how various rules and abstractions that guide behavior are handled in the brain,” says Miller, who quickly adds, “and that goal alone represents many years worth of work.”
Many years, meanwhile, is what McGovern Institute director Phillip Sharp talks about in weighing the tasks facing the new center. Emphasizing that he’s not a neuroscientist, Sharp says he believes significant progress on problems like schizophrenia and depression may come about within a few years. Then, there are the tougher issues: understanding the extent to which the brain’s capabilities reflect our genes as opposed to environmental influences, for example, and how the brain processes and uses information.
“These questions are answerable,” says Sharp, “but we’re talking in terms not of a few years, but decades.”