- In a primate study, animals were less likely to start a task when reward came with an unpleasant consequence
- Blocking a specific brain pathway increased the likelihood of taking the first step, without changing reward or risk judgement
- The findings may help explain severe loss of motivation seen in conditions like depression, with caution about overcorrecting the system
Most people recognise the gap between knowing what needs doing and actually starting. It might be a difficult phone call, a report you worry will be judged or any task that feels unpleasant.
In clinical settings, extreme difficulty initiating action is called avolition. It is seen in several neurological and mental health conditions and it can make everyday life much harder.
A research team at Kyoto University set out to pinpoint the brain mechanism that turns “this is going to be unpleasant” into “I cannot get going”.
Their work, carried out in macaque monkeys, suggests a specific circuit acts like a brake on action initiation when a task is linked to stress or discomfort.
The monkeys learned two versions of a task. In one, completing the task led to a water reward. In the other, the same reward came with an unpleasant air puff to the face. Before each trial, the animals saw a cue and could decide whether to start.
The researchers focused on a simple question: did the animal take the first step at all?
As you might expect, when the task offered reward only, the monkeys usually began quickly.
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When the task combined reward with an unpleasant outcome, they were more likely to hold back, even though the reward was still available.
The researchers then used a technique called chemogenetics to temporarily weaken communication along a pathway between two brain regions involved in motivation: the ventral striatum and the ventral pallidum.
When the pathway was suppressed, behaviour barely changed in the reward only task.
In the reward plus air puff task, initiation improved. The monkeys were more willing to start.
Importantly, the study reports that the animals’ ability to evaluate the situation did not disappear.
They still recognised that the task carried an unpleasant component. What changed was the step between evaluation and initiation, the move from knowing to doing.
Measurements of brain activity suggested the two regions play different roles.
Activity in the ventral striatum increased during the more stressful task, which the authors interpret as a signal that the situation is aversive.
Activity in the ventral pallidum fell as the monkeys became less likely to begin, consistent with the idea that this circuit helps suppress action when the perceived cost is high.
The team describes this connection as a “motivation brake”.
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If it becomes too tight, initiation can stall, which may be relevant to conditions where avolition is prominent.
The researchers suggest that future therapies might aim to adjust the brake using approaches such as brain stimulation or drug strategies, though they stress this would need careful testing.
There is also a warning embedded in the findings: a brake exists for a reason.
If it is weakened too much, a person might push into highly stressful situations too readily, which could increase risk or contribute to burnout.
Study details: Motivation under aversive conditions is regulated by a striatopallidal pathway in primates. Current Biology (2026). DOI: 10.1016/j.cub.2025.12.035
