How we make difficult decisions

You must have felt dilemmas like whether to take a particular job - which was higher-paying, but away from your base town - or not. Such decisions, with both strong positives and negatives, arouse more anxiety than others.
Now, Massachusetts Institute Of Technology (MIT) researchers have identified a neural circuit that appears to underlie decision-making in this type of situation, which is known as approach-avoidance conflict.

The findings could help researchers to discover new ways to treat psychiatric disorders that feature impaired decision-making, such as depression, schizophrenia, and borderline personality disorder.

"In order to create a treatment for these types of disorders, we need to understand how the decision-making process is working," said lead author Alexander Friedman.

Friedman and colleagues also demonstrated the first step toward developing possible therapies for these disorders: By manipulating this circuit in rodents, they were able to transform a preference for lower-risk, lower-payoff choices to a preference for bigger payoffs despite their bigger costs.

The new study grew out of an effort to figure out the role of striosomes -- clusters of cells distributed through the striatum, a large brain region involved in coordinating movement and emotion and implicated in some human disorders.

Senior study author Ann Graybiel discovered striosomes many years ago, but their function had remained mysterious.

The researchers studied mice as they performed five different types of behavioural tasks, including an approach-avoidance scenario.

In that situation, rats running a maze had to choose between one option that included strong chocolate, which they like, and bright light, which they don't, and an option with dimmer light but weaker chocolate.

When humans are forced to make these kinds of cost-benefit decisions, they usually experience anxiety, which influences the choices they make.

"This type of task is potentially very relevant to anxiety disorders. If we could learn more about this circuitry, maybe we could help people with those disorders," said co-researcher Leif Gibb.

The researchers also tested rats in four other scenarios in which the choices were easier and less fraught with anxiety.

The researchers found that the circuit connecting the cortex to the striosomes plays a crucial role in influencing decisions in the approach-avoidance task, but none at all in other types of decision-making.

When the researchers shut off input to the striosomes from the cortex, they found that the rats began choosing the high-risk, high-reward option as much as 20 percent more often than they had previously chosen it.

If the researchers stimulated input to the striosomes, the rats began choosing the high-cost, high-reward option less often.

The findings appeared the journal Cell.