Hernaus researches the role of dopamine and the reward system in our brains. Hernaus: “Dopamine is a kind of 'messenger substance' that facilitates communication between brain cells. Many people associate dopamine with satisfaction, enjoyment, and pleasure. Although there is a clear link between dopamine and reward, in recent years we have learned that dopamine is fundamentally not a reward substance. What’s remarkable about dopamine is that it is released when something unexpected happens. If you don’t expect a reward but suddenly receive one (and vice versa), the activation of those dopamine cells changes abruptly. It therefore is better to see dopamine as a highlighter that marks what deserves our attention. We also now know that the amount of dopamine released by brain cells signals whether and which goals are worth pursuing.”

Do you also look at other substances besides dopamine? 
“To understand how motivation arises, we also look at how the reward system interacts with other systems in our body. For instance, we have researched the role of stress hormones. When we are stressed, our kidneys release cortisol and adrenaline. Since we know that frequent stress is a risk factor for mental disorders, we recently studied how cortisol and adrenaline affect the reward system. In this research, we see that these stress hormones can cause a change in motivation. People become less interested in obtaining rewards but are more strongly motivated to avoid punishment. You could say that the reward system adjusts our ‘motivation state’ to the situation. When someone is under stress, avoiding danger is paramount. From an evolutionary perspective, this is a smart adaptation. But if someone is constantly under stress and their reward system is only set to avoid negative experiences and no longer to obtain positive stimuli, you can understand how this can lead to depression or anxiety disorders.”

Why is it important to understand how it works? What is its impact on society? 

“From my research perspective, we want to understand how motivation can become disrupted. Previously, we thought this only applied to people with depression, but nearly all mental disorders are accompanied by changes in motivation. My personal goal is to understand the points of intervention for treating these problems. If we know how to restore the dynamics of motivation, the impact will be that it also makes the treatment of other issues easier.

"The field I am in is primarily fundamental and mechanistic, but we also look at its translatability to the clinic. With the test battery, which we are developing in collaboration with Mondriaan and MUMC+, we are creating reward tasks that we can standardize for clinical practice to differentiate between people with motivational problems, such as those with depression and psychosis. Based on the individual motivation profile, you can make predictions about how people will respond to a certain treatment. We have made significant progress, but the research still needs a few more years before we have well-validated tasks that can be used by a clinician to map someone's motivation profile easily.

If we find ways to improve motivation, it will greatly help in the treatment of other associated issues. And if we can identify the mechanisms by which motivation becomes disrupted, this can eventually aid in early detection: as a warning signal for increased risk of depression-like symptoms, for example. By combining all our expertise, we will eventually solve the motivation puzzle.”