To adapt to the ever-changing context in which we live, we are constantly deciding how much effort to put into performing our behavior, or how fast to perform our actions. How do people decide how fast to act and how does the brain compute this?
Our behavior is often based on how much reward (money, food, etc.) someone expects to earn by successfully completing an action. An influential neuroscientific theory states that the average reward someone can earn by completing an action is encoded in the brain by the neurotransmitter dopamine, and that higher levels of dopamine then make people act faster. This theory therefore poses the question whether people whose brains are able to produce more dopamine would indeed be more sensitive to changes in how much reward they can earn for a given task, and in which brain area this dopamine production is particularly important.
The current researchers set out to investigate the hypothesis that people act faster when they earn a high reward for a task than when they would earn a low reward and they expected that this effect would be stronger for people who produce more dopamine in a part of the brain that is important for reward processing, called the nucleus accumbens. The research group, led by Roshan Cools, from the Department of Psychiatry and the Donders Institute, published their results in Psychopharmacology on November 4th.
They used PET imaging to measure how much dopamine human participants produce after which they played a computer task in which they could earn more money during some periods and less money during other periods. It was indeed found that people with high dopamine production in the nucleus accumbens speed up in periods of high reward compared with periods of low reward, whereas this was not the case for people with low dopamine production.
These results give more insight into why some people change their behavior more upon changes in reward than other people, and which brain area is particularly important for this effect.
Hofmans L, Westbrook A, van den Bosch R, Booij J, Verkes R-J, Cools R. Effects of average reward rate on vigor as a function of individual variation in striatal dopamine. Psychopharmacology (2021). https://doi.org/10.1007/s00213-021-06017-0