How does procrastination arise? The reason you decide to postpone household chores and spend your time browsing social media could be explained by the workings of a brain circuit. Recent research has identified a neural connection responsible for delaying the start of activities associated with unpleasant experiences, even when these activities offer a clear reward.
The study, led by Ken-ichi Amemori, a neuroscientist at Kyoto University, aimed to analyze the brain mechanisms that reduce motivation to act when a task involves stress, punishment, or discomfort. To do this, the researchers designed an experiment with monkeys, a widely used model for understanding decisionmaking and motivation processes in the brain.
The scientists worked with two macaques that were trained to perform various decisionmaking tasks. In the first phase of the experiment, after a period of water restriction, the animals could activate one of two levers that released different amounts of liquid; one option offered a smaller reward and the other a larger one. This exercise allowed them to evaluate how the value of the reward influences the willingness to perform an action.
In a later stage, the experimental design incorporated an unpleasant element. The monkeys were given the choice of drinking a moderate amount of water without negative consequences or drinking a larger amount on the condition of receiving a direct blast of air in the face. Although the reward was greater in the second option, it involved an uncomfortable experience.
As the researchers anticipated, the macaques’ motivation to complete the task and access the water decreased considerably when the aversive stimulus was introduced. This behavior allowed them to identify a brain circuit that acts as a brake on motivation in the face of anticipated adverse situations. In particular, the connection between the ventral striatum and the ventral pallidum, two structures located in the basal ganglia of the brain, known for their role in regulating pleasure, motivation, and reward systems, was observed to be involved.
The neural analysis revealed that when the brain anticipates an unpleasant event or potential punishment, the ventral striatum is activated and sends an inhibitory signal to the ventral pallidum, which is normally responsible for driving the intention to perform an action. In other words, this communication reduces the impulse to act when the task is associated with a negative experience.
The Brain Connection Behind Procrastination
To investigate the specific role of this connection, as described in the study published in the journal Current Biology, researchers used a chemogenetic technique that, through the administration of a specialized drug, temporarily disrupted communication between the two brain regions. By doing so, the monkeys regained the motivation to initiate tasks, even in those tests that involved blowing air.
Notably, the inhibitory substance produced no change in trials where reward was not accompanied by punishment. This result suggests that the EV-PV circuit does not regulate motivation in a general way, but rather is specifically activated to suppress it when there is an expectation of discomfort. In this sense, apathy toward unpleasant tasks appears to develop gradually as communication between these two regions intensifies.
Beyond explaining why people tend to unconsciously resist starting household chores or uncomfortable obligations, the findings have relevant implications for understanding disorders such as depression or schizophrenia, in which patients often experience a significant loss of the drive to act.
However, Amemori emphasizes that this circuit serves an essential protective function. “Overworking is very dangerous. This circuit protects us from burnout,” he said in comments reported by Nature. Therefore, he cautions that any attempt to externally modify this neural mechanism must be approached with care, as further research is needed to avoid interfering with the brain’s natural protective processes.
This story originally appeared in WIRED en Español and has been translated from Spanish.
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