Split-second changes made in decision-making processes are playing a major role in neuroscientists understanding drug addiction, according to scientists at the Salk Institute for Biological Studies in California, USA.
In the March 9, 2017, issue of Neuron, scientists at the Salk Institute report that the concentration of a brain chemical called dopamine governs decisions about actions so precisely that measuring the level right before a decision allows researchers to accurately predict the outcome.
The work may open new avenues for treating disorders both in cases where a person cannot select a movement to initiate, like Parkinson’s disease, as well as those in which someone cannot stop repetitive actions, such as obsessive-compulsive disorder (OCD) or drug addiction.
“Because we cannot do more than one thing at a time, the brain is constantly making decisions about what to do next,” says Xin Jin, a Salk assistant professor and the paper’s senior author.
“In most cases our brain controls these decisions at a higher level than talking directly to particular muscles, and that is what my lab mostly wants to understand better.”
Neurodegenerative diseases like Parkinson’s damage the dopamine-releasing neurons, impairing a person’s ability to execute a series of commands. Before researchers can develop targeted therapies for such diseases, they need to understand exactly what the function of dopamine is at a fundamental neurological level in normal brains.
Jin’s team designed a study in which mice chose between pressing one of two levers to get a sugary treat.
As the mice performed the trials, the researchers used a technique to measure dopamine concentration in the animals’ brains via embedded electrodes much finer than a human hair.
The results showed that fluctuations in brain dopamine level were tightly associated with the animal’s decision. The scientists were actually able to accurately predict the animal’s upcoming choice of lever based on dopamine concentration alone.
“We think that if we could restore the appropriate dopamine dynamics—in Parkinson’s disease, OCD and drug addiction—people might have better control of their behaviour. This is an important step in understanding how to accomplish that,” says Jin.