A new study by substance abuse researchers has discovered that an area of the brain called the orbitofrontal cortex is responsible for decisions made on the spur of the moment. However, this brain region is not responsible for decisions made based on prior experience or habit.
University of Maryland School of Medicine researchers report that experts had previously believed a single area of the brain was responsible for both types of behavior and decision-making.
Experts say the distinction is critical to understanding the neurobiology of decision-making, particularly with regard to substance abuse. The study is published online in the journal Science.
Scientists have assumed that the orbitofrontal cortex plays a role in “value-based” decision-making, when a person compares options and weights consequences and rewards to choose best alternative.
The new study shows that this area of the brain is involved in decision-making only when the value must be inferred or computed rapidly or hastily. If the value has been “cached” or pre-computed, like a habit, then the orbitofrontal cortex is not necessary.
The same is true for learning — if a person infers an outcome but it does not happen, the resulting error can drive learning. The study shows that the orbitofrontal cortex is necessary for the inferred value that is used for this type of learning.
“Our research showed that damage to the orbitofrontal cortex may decrease a person’s ability to use prior experience to make good decisions on the fly,” said lead author Joshua Jones, Ph.D.
“The person isn’t able to consider the whole continuum of the decision — the mind’s map of how choices play out further down the road. Instead, the person is going to regress to habitual behavior, gravitating toward the choice that provides the most value in its immediate reward.”
The study enhances scientists’ understanding of how the brain works in healthy and unhealthy individuals, according to the researchers.
“This discovery has general implications in understanding how the brain processes information to help us make good decisions and to learn from our mistakes,” said senior author Geoffrey Schoenbaum, M.D., Ph.D.
“Understanding more about the orbitofrontal cortex also is important for understanding disorders such as addiction that seem to involve maladaptive decision-making and learning. Cocaine in particular seems to have long-lasting effects on the orbitofrontal cortex.
“One aspect of this work, which we are pursuing, is that perhaps some of the problems that characterize addiction are the result of drug-induced changes in this area of the brain.”
Ongoing research includes the examination of the specific coding of the neurons in the orbitofrontal cortex during this process, as well as the effects that drugs of abuse have upon this area of the brain.
“Drug addiction is marked by severe deficits in judgment and bad decision-making on the part of the addict,” said Jones. “We believe that drugs, particularly cocaine, affect the orbitofrontal cortex. They coerce the system and hijack decision-making.”
The researchers examined the orbitofrontal cortex’s role in value-guided behavior. The brain assigns two different types of values to behaviors and choices. Cached value is a value that is learned during prior experience. Inferred value happens on the spur of the moment, considering the entire model of rewards and consequences.
“Cached value is stored during prior experience,” said Jones. “For example, you learn your route home on your commute through experience — the habit of how you get home. You turn right, go left, make another right.
“Inferred values, however, are based on estimating goals and values on the fly using your knowledge of the entire structure of the environment.
“For example, instead of just habitually going home on your usual route, you have the full map in your mind of all the roads that you use. You can adjust your route, making different turns, depending on the time of day or the amount of traffic. These inferred decisions are adaptive — much more flexible based on the situation.”
Researchers admit that a flaw in the theory is that a rat model has been used for research. However, although further study of this neurobiological mechanism is needed, the results have been promising.
“Our goal here at the School of Medicine is to make groundbreaking discoveries in the laboratory that can be translated into new treatments and new hope for patients and their families,” said Albert Reece, M.D., Ph.D., M.B.A., vice president for medical affairs at the University of Maryland and dean at the University of Maryland School of Medicine.
“We are hopeful that research tells us more about the basic mechanisms in the brain and will translate to new techniques in neurobiology and in treating devastating conditions such as drug addiction.”