A new brain imaging study has found an individual’s willingness to work hard is strongly influenced by the levels of dopamine in three specific areas of the brain.
In addition to shedding new light on how the brain works, the research, published May 2 in the Journal of Neuroscience, could have important implications for the treatment of attention-deficit disorder, depression, schizophrenia, and other forms of mental illness characterized by decreased motivation, according to the researchers from Vanderbilt University.
Using the brain mapping technique called positron emission tomography (PET scan), the researchers found that people who are willing to work hard for rewards had a higher release of dopamine in areas of the brain known to play a role in reward and motivation, the striatum and ventromedial prefrontal cortex.
On the other hand, those who were less willing to work hard for a reward had high dopamine levels in another area of the brain that plays a role in emotion and risk perception, the anterior insula.
The role of dopamine in the anterior insula came as a surprise, the researchers noted. It suggests that more dopamine in this area of the brain is associated with a reduced desire to work, even when it means earning less money.
The fact that dopamine can have opposing effects in different parts of the brain complicates the use of psychotropic medications that affect dopamine levels for the treatment of attention-deficit disorder, depression and schizophrenia because it questions the assumption that these drugs have the same effect throughout the brain, the researchers noted.
The study was conducted with 25 healthy volunteers ranging in age from 18 to 29. To determine their willingness to work for a monetary reward, the participants were asked to perform a button-pushing task. They were asked to select an easy or a hard task. Easy tasks earned $1, while the rewards for hard tasks ranged up to $4. The tasks lasted for about 30 seconds and participants were asked to perform them repeatedly for about 20 minutes.
While looking at just 20 minutes of behavior doesn’t conclusively show an individual’s potential for long-term achievement, it “does measure a trait variable such as an individual’s willingness to expend effort to obtain long-term goals,” said psychologist Dr. David Zald.
The research is part of a larger project designed to search for objective measures for depression and other psychological disorders where motivation is reduced, he said.
“Right now our diagnosis for these disorders is often fuzzy and based on subjective self-report of symptoms,” said Zald. “Imagine how valuable it would be if we had an objective test that could tell whether a patient was suffering from a deficit or abnormality in an underlying neural system. With objective measures we could treat the underlying conditions instead of the symptoms.”
Additional research is under way to examine whether individual differences in dopamine levels help explain the altered motivation seen in depression and addiction, he added.
Source: Vanderbilt University