A new study by researchers at WPI-ASHBi has identified a specific brain circuit that acts as a brake on motivation, particularly in situations involving unpleasant or stressful tasks. The research provides insight into why some people struggle to initiate actions even when they know what needs to be done, a condition known as avolition.
Avolition is often seen in disorders such as depression, schizophrenia, and Parkinson's disease. People experiencing it are not lacking awareness or effort; rather, their brains seem unable to activate the "go" signal needed to begin tasks.
The research team used chemogenetics—a technique allowing precise control of neural communication—in macaque monkeys. The monkeys were trained for two types of tasks: one offering only a reward and another combining the reward with an unpleasant air puff to the face. Monkeys could choose whether or not to start each task after seeing a cue.
Findings showed that when only rewards were involved, monkeys typically began the task without hesitation. However, when an unpleasant stimulus was added, they often refrained from starting despite the reward being available.
Researchers then temporarily suppressed the connection between two brain regions associated with motivation: the ventral striatum (VS) and ventral pallidum (VP). This intervention had little effect during reward-only tasks but made monkeys more likely to start tasks that included an unpleasant stimulus. Importantly, their ability to judge rewards and punishments remained unchanged; what shifted was their willingness to take action.
Neural recordings revealed increased activity in the VS during stressful tasks—indicating its role in registering stress—while VP activity decreased as reluctance grew. These results suggest that the VS–VP pathway functions as a "motivation brake," especially under stress or discomfort.
"This discovery of the VS–VP 'motivation brake' may shed light on conditions such as depression and schizophrenia, where severe loss of motivation is common," stated the research team. "In the future, interventions such as deep brain stimulation, non-invasive brain stimulation, or new drug strategies might aim to fine-tune this brake when it becomes too tight."
However, researchers caution against removing this brake entirely: "While an overly tight brake can lead to avolition, a brake that is too loose could make it harder to stop, even in excessively stressful situations, potentially leading to burnout."
The study suggests society should reconsider how it views motivation—not simply as willpower but also as something regulated by neural mechanisms responsive to stress. According to researchers: "Rather than trying to forcibly boost motivation, the focus should shift toward how society can better support people in coping with stress. This is a question that warrants broader societal dialogue."
