Dr. Wael Asaad, Brown University - Surprise and Memory Formation
Albany, NY – In today's Academic Minute, Dr. Wael Asaad of Brown University reveals the important roles expectation and surprise play in the learning process.
Wael Asaad is an assistant professor of neurosurgery at Brown University where his research lab seeks to improve the understanding of the basic neural mechanisms of learning and to develop strategies to repair the brain following disease, traumatic injury, or stroke. He holds a Ph.D. in Systems Neuroscience from the Massachusetts Institute of Technology and an M.D. from Yale University.
Dr. Wael Asaad - Surprise and Memory Formation
Understanding how we learn on at the level of neurons and brain circuits is important because it may be the key to restoring brain function after neurological damage such as from stroke or traumatic brain injury. Even if we had the ability to replace lost and damaged neurons, that would not be enough. Their connections are the products of years of learning. Having some way to boost this process, perhaps by tapping into the brain's natural and remarkable mechanisms for learning, might provide a way to aid recovery, making it faster or more complete. That's our goal.
To understand learning, we need to focus on what drives it: Learning happens when you encounter something surprising or unexpected. That surprise can take at least two different forms: You might receive some benefit or reward you didn't see coming, or you might fail to get some reward you expected. These are examples of what are called "prediction errors." The first type getting something pleasant and unexpected results in a positive prediction error, while the second type missing out on something good generates a negative prediction error. Positive prediction errors encourage you to repeat the activity that led to the reward, whereas negative prediction errors nudge you to try an alternative strategy.
There's been a fair amount of debate about whether these different signals are processed in the same circuits, or whether distinct brain regions are responsible for each. In our experiments, Emad Eskandar of Massachusetts General Hospital and I found that both types of signal do indeed coexist within the same brain regions, in this case in the prefrontal cortex and basal ganglia. We even found that the same neurons could play a role in signaling both types of prediction error. This was itself surprising, and hopefully will help us learn how to help patients in the long run.