How Does the Brain Assemble New Ideas from Old?

A computational model finds common ground between biology and computer science.

Posted Sep 25, 2013

Sometimes a research paper comes along that is so important—and so far over my head—that I know I have only one way to translate it for this column. That's when I contact the researcher and ask, "Please, could you explain this the way you would to guests at your dinner table?" I came across such a research report this week, and so I turned to neuroscientist Trent Kriete of the University of Colorado and asked for the "tell it to your friends" version. Here's what he told me about a computational framework he's developed that just might explain a lot about how the human brain works:

Every day we encounter situations where we must understand parts of the world around us in ways that we have not used before. Maybe a coworker switches roles at work, or perhaps we hear a word used in a new way. Typically, we handle these situations with such ease that we don't appreciate what an impressive feat we are performing; but for decades, biologists have been debating how our brains can possibly accomplish such a difficult task.

The problem is, biology does not always solve things in the same way an engineer would. The brain has billions of neurons connected together in complicated ways, and those neurons must work in concert to solve all the problems we encounter in our everyday lives. The central question becomes, then: How does the human brain allow us to generalize things we have never seen before? To answer that question, researchers have offered two very different ideas. The first says that the brain must work exactly like a computer—integrating variables to solve a problem. The other idea argues that we have to take biology seriously and that our brains are, at their core, learning systems. Researchers who support the latter idea argue that the computer-variable mechanism is unlikely because it’s hard to imagine how all the relevant variables could be learned, given what we know about how the brain works.

University of Colorado neuroscientist Trenton Kriete

The researchers—Trenton Kriete, Randall O’Reilly, David Noelle, and Jonathan Cohen—believe their work builds a bridge between two different sides of a debate that has persisted for decades. Their research shows that, on the one hand, the brain has some structure that allows it to encode variables and generalize to things it has never experienced before, suggesting that those who said that the brain had to implement a computational variable system were at least partly right. On the other hand, by building a biologically realistic model of the brain, the results ground the theory in what we know about how the brain is structured and how it learns. Critically, this system has limits since it must learn the mapping between these brain structures and, as a result, will not be perfect as a true computer system would be.

For More Information

Trenton Kriete, David C. Noelle, Jonathan D. Cohen, and Randall C. O’Reilly. Indirection and symbol-like processing in the prefrontal cortex and basal ganglia. PNAS. Published online before print September 23, 2013


Many thanks to Trent Kriete for serving as guest author for this report.