A prominent Stanford neuroscientist and psychiatrist, and his colleagues gives some clues about what makes some people risk-averse and others risk-taking. Answers could have implications for how to treat, curb or prevent destructively risky behavior, like pathological gambling or drug addiction.. The study, published Wednesday in the journal Nature, reports that a specific type of neuron or nerve cell, in a certain brain region helps galvanize whether or not a risky choice is made.The study was led by Dr. Karl Deisseroth.

The study was conducted in rats, but experts said it built on research suggesting the findings could be similar in humans. If so, they said, it could inform approaches to addiction, which involves some of the same neurons and brain areas, as well as treatments for Parkinson’s disease because one class of Parkinson’s medications turns some patients into problem gamblers.

In a series of experiments led by Kelly Zalocusky, a doctoral student, researchers found that a risk-averse rat made decisions based on whether its previous choice involved a loss (in this case, of food). Rats whose previous decision netted them less food were prompted to behave conservatively next time by signals from certain receptors in a brain region called the nucleus accumbens, the scientists discovered. These receptors, which are proteins attached to neurons, are part of the dopamine system, a neurochemical important to emotion, movement and thinking, according to a report in today’s New York Times written by Pam Belluck.

The study was conducted in rats, but experts said it built on research suggesting the findings could be similar in humans. If so, they said, it could inform approaches to addiction, which involves some of the same neurons and brain areas, as well as treatments for Parkinson’s disease because one class of Parkinson’s medications turns some patients into problem gamblers.

Step by step, the researchers built evidence that neurons with a dopamine receptor called D2 in the nucleus accumbens, a region integral to brain reward circuitry, play a critical role in risky-or-not decision-making. Strikingly, they found they could alter the message those neurons send.

Rats were given a choice of two food levers. One released a consistent amount of sucrose each time; the other often delivered a tiny amount, but in 25 percent of presses, it unleashed a delicious sucrose flood. Over time, both levers gave the same quantity, so rats did not go hungry and their choices came down to whether or not they were gamblers.

Risky rats gambled on the iffier lever more than half the time. Risk-averse rats were strongly influenced by their last choice; if they picked the risky lever and received a trickle, they picked the consistent lever next time.