July 25 2019
How much effort would you expend if you knew a reward was headed your way?
Michael Treadway, Ph.D., an associate professor of psychology at Emory University, is looking at neural circuitry and why some people work hard for a known payoff while others do not.
Treadway’s research broadly focuses on people with mental illnesses such as depression and schizophrenia and their decisions to engage in certain behaviors—such as getting out of bed or off the couch. If someone does not get up, is it because of lack of—or loss of—motivation, or difficulty making decisions, or a combination, and to what extent is brain chemistry a factor?
“We need to understand how that same behavior [loss of motivation], either in the same person or different people, can result from different cognitive processes and how different circuits are affected,” says Treadway, a recipient of a 2019 Federation of Associations in Behavioral & Brain Sciences (FABBS) Early Career Impact Award. He was nominated by the Society for Research in Psychopathology.
Treadway created a behavioral measure, the Effort Expenditure for Rewards Task (EEfRT or “effort”), to study the amount of effort people are willing to expend for a given reward. The EEfRT was primarily inspired by John D. Salamone’s rodent studies, in which rodents could choose between pressing a lever multiple times for a tasty treat or not at all for food with no taste. Salamone’s studies showed a link between levels of the chemical neurotransmitter dopamine in the brain and a willingness to expend energy for a greater reward.
The EEfRT uses a similar principle to study motivation and decision making in humans and involves a test requiring energy expenditure in exchange for a reward. Treadway invited participants to press a button a set number of times for a reward ranging from $1 to $4.
Combining EEfRT with PET images of the brain, Treadway confirmed similarities between people and rodents in terms of willingness to expend energy and dopamine levels.
Mental illnesses were contributing factors as well.
We need to understand how that same behavior [loss of motivation], either in the same person or different people, can result from different cognitive processes and how different circuits are affected.
Participants diagnosed with depression or schizophrenia were less willing to expend energy than participants with no diagnosed mental illnesses. Importantly, however, this may result from different types of problems. While patients with depression may feel less motivation, one recent study of 150 patients with schizophrenia found that approximately half struggled to utilize the information about monetary rewards presented during the task, and they exhibited difficulty in making consistent choices.
A new direction for Treadway’s lab involves the role of chronic inflammation in relation to dopamine levels. He notes that chronic inflammation is associated with psychological stress, poor diet and lack of exercise, which also are risk factors for depression. This research is funded by a grant from the National Institutes of Health.
“We’re trying to reverse these risk factors with potent anti-inflammatory medications,” he says.
