December 6, 2013
How Does Your Brain Make Toss-Up Decisions?
Ranjini Raghunath for redOrbit.com - Your Universe Online
Some decisions are easy, but when you have two equally appealing choices, how does your brain choose between the two?
Although scientists have known such decision-making involves the orbitofrontal cortex, a region of the brain behind the eyes, the exact mechanism has been unclear – until now.
A new study published online in the journal Neuron throws some light on the inner workings of this process. The study builds on experiments involving juice choices made by monkeys, designed in 2006 by neuroeconomists at Washington University at Saint-Louis and Harvard University. The monkeys were given different amounts of either apple or grape juice in successive trials. Depending on how often they chose one juice over the other, scientists determined how the monkey’s brain 'valued' each of these juices.
“For example, if we offer a larger amount of apple juice versus a smaller amount of grape juice, and the primate chooses each option equally often, we infer that this primate likes the grape juice better than the apple juice,” explained Camillo Padoa-Schioppa, first author of the paper said. “The primate could be getting more juice by choosing the cup with apple juice, but it doesn’t always do so. That implies that the primate values grape juice more than apple juice.”
Through these experiments, they were also able to identify which brain cells carried the information needed for making such decisions.
Now, Padoa-Schioppa believes there are different sets of brain cells involved in different steps of the decision-making process. Information on specific variables such as the drink’s value before the choice is made, its value after, and the identity of the chosen drink are carried in different types of brain cells.
Padoa-Schioppa found decisions depend on how easily these brain cells communicate with each other – a property of the brain called synaptic efficiency. But sometimes, random fluctuations in the signals passed on by these brain cells – even before the monkey is offered the juice – can also influence its choice.
The brain makes these 'economic' decisions in a way that’s slightly different from perceptual decision-making – making decisions based on what information your senses can gather, the author wrote. Further research may focus on developing mathematical models that mimic this decision-making process, and testing such biases in decisions by tweaking the activity of different brain cells, he added.