From who we marry to how we invest to the words we type, some of our most important decisions are based on how we process instantaneous feedback.
Daphna Shohamy, Ph.D., an assistant professor of psychology and founder and director of The Learning Lab at the Columbia University Mind Brain Behavior Initiative, focused on how the brain supports learning, memory, and decision-making in a lecture hosted by the initiative and sponsored by the Dana Foundation.
Shohamy began by showing two images side-by-side, one freezing terrain and the other, a sun-filled beach. She explained that at age 10, her family moved from Minneapolis to Tel Aviv, and the images depicted both environments. The stark differences between the cultures and her surroundings led her to wonder about the way we learn, and sent her on an academic path that would begin at Tel-Aviv University and include graduate work at Rutgers and Stanford universities before moving to Columbia University five years ago.
“Your brain is changing right now, based on the information I’m giving you,” said Shohamy. “Beyond the big, lofty question of understanding who we are, decisions regarding health, career, and marriage are guided by the way we learn from not just our past experiences, but from our memory of those experiences.” Fundamental biases also help predict outcomes and guide learning, she added.
Among three studies she cited was one where subjects were asked to place their hands in ice cold water for either 60 or 90 seconds. When told that the water temperature would be a minuscule one degree higher in the 90-second option, many subjects chose that option, despite knowing that the cumulative amount of pain would last longer. Planting the idea of the slight degree change led those choosing the 90-second option to not only feel positive about their decision, but also to more positively remember their experience than did the 60 seconders.
The idea that we learn from the memories of our experiences, and that our experiences can also be used to predict behavior, is linked to a neurotransmitter called dopamine. Once exclusively associated with pleasure and stimulated by recreational drugs, neuroscientists now see dopamine as a learning signal, especially when a positive response is received. She pointed out that a positive or negative experience motivates how a person will react in the future, and used the example of a waiter taking your plate away with one tasty bite left to suggest “that the dopamine neuron responds to the surprise, not the reward itself.”
Advances using functional brain imaging (fMRI)), a medical advance that helps track changes in the brain (sometimes in less than a second), has made a major difference over the last decade. “fMRI has completely changed the playing field and the way the public thinks of the potential of neuroscience because it is the first time we have a reasonable measure of what is happening in the brain in healthy humans during mental processes,” she said.
Along with patient studies, Shohamy’s lab uses fMRI to track dopamine levels that are sent to the brain’s striatum and hippocampus. The difference is that in the striatum, dopamine sends a rapid signal that “moves along with a person’s expectations,” therefore spawning learning and becoming a predictor of behavior. More gradual, observational learning and long-term memory are linked to the hippocampus.
Studying how dopamine works in both parts of the brain will help neuroscientists combat any number of diseases, including Parkinson’s, schizophrenia, Huntington’s, Tourette’s, amnesia, and Alzheimer’s. Shohamy’s lab has shown that patients (over age 50) in the very early stages of Parkinson’s show a 70 to 80 loss of dopamine in their striatum, which affects a patient’s ability to learn and informs our understanding of symptoms.
Shohamy said that a crucial and previously underappreciated finding is “the critical link between motor impairments in Parkinson’s and the idea that the striatum is important for action and motor control. We now know the striatum is learning from dopamine to choose the right action and to successfully execute the right actions in order to optimize rewards in the world ... understanding of how learning happens helps us to also understand how learning does not happen.”
-- Bill Glovin