How Brains Predict Future Events

Dopamine system helps brain make short term predictions

(RxWiki News) The human brain is capable of making short term predictions on a daily basis ranging from who is calling on the phone to whether a dropped glass will break. Scientists are beginning to understand how that works.

A new theory being constructed about how predictive perception works suggests that a major portion of predicting the future is maintaining a mental model of what is happening now. That model needs constant updating to take in to account unpredictable environmental changes.

"The finding could lead to treatments for Parkinson's."

Jeffrey M. Zacks, lead author and a Washington University in St. Louis associate professor of psychology in arts and sciences, pointed out that it is valuable to be able to run away when a lion lunges at you, but even more so if you are able to hop out of the way before the lion jumps. He said being able to look over the horizon even a little bit is a big adaptive advantage.

The research focused on the mid-brain dopamine system, which provides signals to the brain when unexpected events happen. Using a functional MRI, researchers discovered that this system encodes prediction error when participants were asked to predict what would happen next in videos showing everyday events.

Healthy young volunteers were shown movies of everyday events such as washing a car, building a Lego model or washing clothes. Participants watched a portion of the movie. Then it was stopped.

They were asked to predict what would happen five seconds later when the movie was restarted by selecting an image showing what would happen. About half of the time, the movie was stopped before an event boundary -- when a new event was about to start, while the remainder of the time it was stopped in the middle of an event.

Participants were correct 90 percent of the time in predicting what would happen when it was halted in the middle of an event. However, the accuracy was 80 percent when stopped at an event boundary. Volunteers also were less confident in predicting during event boundaries.

During the functional MRI testing, researchers found significant activity in several midbrain regions, including the substantia nigra, the part of the brain hit hardest by Parkinson's. It is important for movement control and adaptive decisions.

Brain activity was most substantial when subjects tried to make their choice, and immediately after feedback on whether they were right, but particularly when they made the wrong choice.

The finding could someday benefit patients with neurological diseases such as schizophrenia, Parkinson's and Alzheimer's diseases, and possibly also lead to earlier diagnosis.

The study will be published in an upcoming issue of the Journal of Cognitive Neuroscience.

Review Date: 
August 20, 2011