14 DAY TRIAL // When you have to choose between conflicting options, you attribute them certain values and then you choose the one you find most valuable. The options are conflicting because resources are limited - if you use something for some purpose you often cannot use it for some other purposes, it is consumed, so you have to decide which purpose is the most important. But how does the brain accomplish this task of attributing values? And on what basis does a certain option get to be considered valuable?
Scientists Dr. Camillo Padoa-Schioppa and John Assad at Harvard Medical School in Boston have now identified the neurons, located in an area of the brain known as the orbitofrontal cortex, that seem to play a role in how a person selects different items or goods. Lesions in this area of the brain are known to be involved in certain choice disorders such as eating disorders, compulsive gambling and some forms of unusual social behavior.
"The neurons we have identified encode the value individuals assign to the available items when they make choices based on subjective preferences, a behavior called economic choice," Padoa-Schioppa said in a statement.
The scientists studied the brains of macaque monkeys while they were choosing between different flavors and quantities of juices. It was already known that cells in different parts of the brain react to attributes such as color, taste or quantity. Padoa-Schioppa and Assad wanted to know whether there are also neurons that are involved in attributing values.
They discovered that different neurons in the orbitofrontal cortex were highly active when the monkeys chose between three drops of grape juice, for example, or 10 drops of apple juice. When the monkeys chose between orange juice or grape juice other neurons in the same brain area were involved. Researchers found correlations between the animal's choices and the patterns of neuronal activity in this brain area. "The monkey's choice may be based on the activity of these neurons," said Padoa-Schioppa.
What happens is that various neurons throughout the brain are activated by the different colors, flavors and quantities of the juices - but this isn't sufficient to allow a choice. The information about the color, flavor or quantity has to be furthermore evaluated, and this evaluation is conducted by the neurons in the orbitofrontal cortex - a higher activity of some neurons determines the animal to choose one juice rather than the other. And as different brains are wired differently, different individuals value the same things differently.
But when brain lesions are present in this area, the individual's ability to evaluate things is affected. "A concrete possibility is that various choice deficits may result from an impaired or dysfunctional activity of this population (of neurons), though this hypothesis remains to be tested," Padoa-Schioppa said.
In 2004 Nathalie Camille from the Institut des Sciences Cognitives in France and her colleagues from Italy and France had discovered that this same brain area is also involved with feelings of regret.
"The orbitofrontal cortex integrates cognitive and emotional components of the entire process of decision making; its incorrect functioning determines the inability to generate specific emotions such as regret, which has a fundamental role in regulating individual and social behavior," they wrote.
This lets us understand what is involved in the process of evaluating a choice, on what basis the brain attributes a higher value to a certain choice: choices are evaluated by this brain area according to their estimated consequences.
"Facing the consequence of a decision we made can trigger emotions like satisfaction, relief, or regret, which reflect our assessment of what was gained as compared to what would have been gained by making a different decision. These emotions are mediated by a cognitive process known as counterfactual thinking," wrote the authors in Science. "By manipulating a simple gambling task, we characterized a subject's choices in terms of their anticipated and actual emotional impact. Normal subjects reported emotional responses consistent with counterfactual thinking; they chose to minimize future regret and learned from their emotional experience. Patients with orbitofrontal cortical lesions, however, did not report regret or anticipate negative consequences of their choices. The orbitofrontal cortex has a fundamental role in mediating the experience of regret."
Picture: the orbitofrontal cortex