The human mind has an amazing capacity for absorbing and analyzing information as it perceives the world and moves from thought to thought. As a result, learning — the act of acquiring new information or modifying and reinforcing information that already exists — occurs constantly.
This complex process is not fully understood, but a new study from MIT provides a remarkable view of the orchestrated way different brain regions work together during learning.
Two key brain regions involved in learning, the prefrontal cortex and the striatum, actually synchronize their brain waves in order to form new communication circuits, an effect never seen before. The study, done on monkeys, provides direct evidence of this interaction during learning.
These new learning circuits appear to be “rhythm based,” a relatively new concept in neuroscience.
Our brains are composed of millions of cells that produce their own electrical signals. These combined signals generate oscillations known as brain waves, which can be measured. Scientists now believe that learning depends on the formation of new connections between these brain cells. Interestingly, the brain-wave synchronization actually takes place before any formation of new connections, according to the researchers.
The first thing that happens is that certain brain circuits start ‘humming’ together. Only then can learning begin to happen.
“If you can change your thoughts from moment to moment, you can't be doing it by constantly making new connections and breaking them apart in your brain,” Earl Miller, Picower Professor of Neuroscience at MIT and senior author of the study, said in a statement.
“There's got to be some way of dynamically establishing circuits to correspond to the thoughts we're having in this moment, and then if we change our minds a moment later, those circuits break apart somehow. We think synchronized brain waves may be the way the brain does it.”
The research team found that as monkeys shifted from rote memorization to categorical learning, there was a corresponding change in brain wave patterns. Certain waves known as “beta bands,” produced independently by the prefrontal cortex and the striatum, began to synchronize with each other, suggesting that a communication circuit was forming between the two regions.
The work showed that once the prefrontal cortex learns the basics, it relays that information to the striatum, where it undergoes further modification as new information comes in, allowing more expansive learning to take place. This sequence can occur over and over.
As the animals learned two different mental exercises, researchers observed two separate circuits forming between these brain regions, each corresponding to a different exercise. The cortex is learning these new exercises and then forming circuits that can send the information down to the striatum as if it's just brand-new material for the brain to elaborate on.
“That's how you get the open-ended nature of human thought. You keep expanding your knowledge,”said Miller.
The study is published in Neuron.