Past Brain Activation Revealed in Scans: What Makes Us Unique Individuals

The brain is the control center of our bodies, recording emotions, experiences and memories. Yet what if scientists could examine these recorded experiences, unpacking them to understand what makes us unique individuals? Now, researchers have discovered that this might be possible; they've found that spontaneous waves of neuronal activity in the brain bear the imprints of earlier events for at least 24 hours after the experience has taken place.

Even when the brain is resting, activity sparks along its pathways. Ultra-slow patterns of neuronal activity replace the normal bursts of nerve cell activity associated with incoming information. These "resting" waves travel in a highly organized and reproducible pattern, which made researchers wonder whether these patterns might have some meaning.

In order to examine whether or not these patterns could be "archives" for earlier experiences, the researchers conducted series of tests on volunteers. The participants undertook a training exercise that strongly activated a well-defined network of nerve cells in their frontal lobes. The volunteers' brains were then scanned with a functional magnetic resonance imaging (fMRI) scanner while they imagined a situation in which they had to make rapid decisions. They received real time auditory feedback based on the information obtained directly from their frontal lobe, which indicated the level of neuronal activity in the trained network. This feedback strategy proved highly successful in activating the frontal network--a part of the brain that's usually very difficult to activate.

After these tests, the researchers then decided to see whether or not the exercises left traces in the patterns formed by the resting brain waves. The researchers performed fMRI scans on the resting volunteers before, immediately after the exercise and 24 hours later. They found that the activation of certain areas of the cortex did actually remodel the resting brain wave patterns. They also discovered that the patterns remained into the next day and, in fact, strengthened.

The findings suggest a number of future possibilities for exploring the brain. Spontaneously emerging brain patterns could be used as a "mapping tool" for unearthing events from a person's recent past. In addition, these patterns could reveal a profile of a person, highlighting their abilities, shortcomings and biases.

"Today, we are discovering more and more of the common principles of brain activity, but we have not been able to account for the differences between individuals," said Tal Harmelech, one of the researchers, in a news release. "In the future, spontaneous brain patterns could be the key to obtain unbiased individual profiles."

The findings are published in the Journal of Neuroscience.