New neuroimaging research sheds light on the brain regions involved in extracting structure from past experiences when making decisions. The study, which appears in Cell Reports, indicates that the hippocampus and orbitofrontal cortex play key roles in this process.
The hippocampus, a seahorse-shaped structure located deep within the brain, is known to play a major role in learning and memory. The orbitofrontal cortex, located in the frontal lobes of the brain, is known to be involved in several cognitive processes related to decision-making. But it has been unclear how these two brain regions interact to guide decisions that rely on past experiences.
“For instance, when you are buying oranges from your local supermarket, what information do you use to make this decision? Will you choose to purchase the oranges based on your past experiences of buying oranges in that specific supermarket? Or do you have general knowledge about quality of oranges in all the supermarkets that you visit in your neighborhood?”
“We use memories to guide a decision like grocery shopping. If memories of past experiences are used to guide a decision, then the critical question is, how is decision-relevant information is represented in memory?”
In the study, which included 22 participants, the researchers used functional magnetic resonance imaging to examine what type of information the hippocampus and orbitofrontal cortex represented in a memory guided decision-making task.
The participants first learned the desirability of various foods by trial and error based on the feedback they received. They were repeatedly shown images of eight different food items superimposed over images of four different grocery stores. They had two seconds to guess whether the food item at that specific store was generally liked or generally disliked by customers. After each guess, the participants received feedback in the form of a message saying “correct” or “incorrect” along with a picture of a customer’s reaction to that food.
Some of the food items were either liked or disliked depending on the specific store (dubbed “context-dependent foods”). Other items, however, were liked or disliked regardless of the particular store (dubbed “context-independent foods”). After learning the desirability of the foods, the participants were scanned while they decided whether a food item in a particular store was desired or not by customers.
Although the difference between context-dependent and context-independent foods was not explicitly explained to the participants, the researchers found that the participants successfully differentiated between the two categories of food items. In addition, the researchers found that brain activity patterns in the hippocampus and lateral orbitofrontal cortex carried information about whether the participants were making context-dependent or context-independent decisions.
“The way we make decisions recruits generalized information across past experiences instead of memories for individual events. So we show that when people are making these decisions, they rely on their collective knowledge of grocery shopping in their neighborhood instead of store-specific information,” Mizrak and Bouffard told PsyPost.
“These types of memories are supported by two important regions in the brain: the hippocampus and the orbitofrontal cortex. These two regions are usually studied separately, the orbitofrontal cortex in the decision-making research and the hippocampus in memory research. However, recent studies suggest that this kind of structured knowledge about our environment is represented jointly by both of these regions and is then recruited to make these memory-based decisions.”
“One remaining question is whether the orbitofrontal cortex and hippocampus represent similar aspects of the information about our past experiences (i.e., stores and food items) or separate aspects and complement each other. Our study was not designed to test this question,” the researchers added.
The study, “The hippocampus and orbitofrontal cortex jointly represent task structure during memory-guided decision making“, was authored by Eda Mızrak, Nichole R. Bouffard, Laura A. Libby, Erie D. Boorman, and Charan Ranganath.