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Why, instead of doing what you know is necessary to achieve your goals, do you entertain yourself by watching silly videos on TikTok? Why do you sweep a floor that doesn’t need to be swept instead of studying, especially if you hate sweeping? Why do we put off until tomorrow what we should do today and will have to do anyway?
For a long time, motivation has been explained as an incentive problem: if a person doesn’t act, it’s because they don’t value the reward enough. However, a detailed study of what happens in the brain when we procrastinate seems to contradict that idea. In an article published in the journal Current Biology, a group of scientists led by Ken-Ichi Amemori of Kyoto University proposes that it’s possible for the brain to accurately assess the need for an action and still prevent it from being initiated.
To understand how the brain functions when faced with a task that can offer benefits but also involves discomfort, researchers worked with monkeys, a useful model because their motivational system resembles that of humans. The animals, which were kept thirsty outside the experiment, were subjected to two tests. In one, they could press two levers and receive two different amounts of water, allowing the researchers to measure the involvement of each circuit in motivation. They were then given a choice between drinking under two conditions: a small sip with no discomfort, or a larger one accompanied by an unpleasant puff of air to the face.
Like us when we are about to start a task and think about the reward, the monkey evaluated whether it was worth enduring the puff of air in exchange for the larger amount of water, or whether it was better to settle for the safe sip. This experiment made it possible to identify a brain circuit that acts as a brake on motivation: it does not decide whether the reward is worth it, but whether it is worth starting. This circuit is the connection between the ventral striatum (VS) and the ventral pallidum (VP), located in the basal ganglia, a deep part of the brain where pleasure and motivation are processed.
Amemori’s team found that two variables are involved in motivation, but that they are encoded by different neural systems. On the one hand, there is the cost–benefit calculation that weighs reward against punishment; on the other, there is the likelihood of not wanting to initiate an action. Both mechanisms have been conserved over millions of years of evolution because they helped keep our ancestors alive.
The ventral striatum is activated when there is an expectation that something will be uncomfortable, difficult, or emotionally demanding, without evaluating what the final reward will be. The ventral pallidum, by contrast, acts like a switch that triggers action and sustains it. Studying the monkeys’ brains allowed researchers to observe, using electrodes, that when the animals could choose between receiving more water along with a puff of air, the ventral striatum — whose role is to protect us from discomfort — was more active. When the choice was only between different amounts of water, it was the ventral pallidum that showed greater activity.
When the two regions were connected, the ventral striatum’s warning signal about discomfort could block the ventral pallidum’s initiation of action. But when communication between the two groups of neurons was shut down using a chemogenetic technique, that alone was enough to release the motivational brake. At that point, the monkeys began to tackle the reward-bearing task with much less hesitation, despite the anticipated discomfort.
Breaking the task down
This represents a significant shift from traditional approaches. Promising oneself large rewards, reminding oneself of the importance of a task, or increasing external pressure all act on the circuit that encodes perceived value, but they leave intact the brake applied by the ventral striatum.
“When motivation is impaired at the initiation level, reducing the cues that drive disengagement — such as the anticipated cost of starting — can be more effective than simply increasing incentives,” says Amemori, offering advice for overcoming this roadblock. Breaking the task down into smaller steps or reducing exposure to judgment or the threat of evaluation can be helpful strategies in such cases.
The researcher also believes that a stressful work environment and constant notifications from emails or cell phone messages “can keep the ventral striatal circuit, which processes signals that trigger feelings of rejection, continuously activated.” “In the long term, this can produce plastic changes and possibly structural changes in the ventral striatum–ventral pallidum pathway, throwing the system off balance and leading to excessive disengagement, a disorder clinically known as abulia,” he says.
From a social perspective, reducing the constant signaling of stress could help prevent the chronic overload of this circuit that ultimately leaves the motivational brake engaged. For Amemori, clearer task prioritization or the creation of work or school environments that allow for recovery after demanding tasks may be just as important in addressing this problem as interventions at the individual level.
During the experiment, not all of the monkeys behaved in the same way. Some became more blocked than others by the prospect of the unpleasant puff of air. These observations suggest that stress-induced paralysis may have an identifiable neurobiological basis, rather than being simply a matter of personality or character. This insight may be useful for people for whom the inability to act is a serious problem.
“Our findings indicate that abulia in depression could reflect an imbalance in the VS–VP circuit,” explains Amemori. “In principle, it would be possible to develop therapies that modulate this balance. One potential approach is deep brain stimulation [DBS], although this requires neurosurgical intervention and would only be appropriate for carefully selected cases.”
“There is also active development of less invasive neuromodulation techniques that aim to influence deep brain structures, including transcranial magnetic stimulation [TMS] and ultrasound-based approaches,” he adds. “These methods could become more promising in the future, but will require substantial further validation in terms of safety, specificity, and clinical benefit.”
Drugs could also be used, since the ventral pallidum contains opioid receptors, but such medications would not act exclusively on that brain region and could have many undesirable side effects.
Finally, Amemori emphasizes that motivational restraint “likely serves an adaptive and evolutionarily preserved function, helping individuals avoid becoming involved in excessively costly or harmful situations.” “Indiscriminately weakening it could increase vulnerability to burnout, excessive risk-taking, or difficulty disengaging from overly stressful contexts. Any therapeutic intervention would therefore need to be carefully calibrated and evaluated within a rigorous ethical framework,” he concludes.
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