A new study published in Current Biology by a team of researchers led by Jung-min Oh and Ken-ichi Amemori revealed the brain mechanism that regulates our ability to act in adverse conditions. The driving force behind the work was to answer why there is we block when faced with a difficult taskeven if we aspire to the final prize. It’s easy to take action when everything is going well, but finding the push to start when there are obstacles or risks is a challenge neurological process completely different. The research, conducted on macaques, identified a specific circuit, the pathway connecting the ventral striatum (VS) to the ventral pallidum (VP), which acts as a behavioral “brake”. when the environment presents threats or high costs. By deactivating this brake, it is possible to restore motivation without altering the perception of risk: the brain is no longer paralyzed by the presence of the threat and carries out the action to obtain the final reward.
The study on the neural “brake” that causes lack of motivation
The heart of the discovery, explained in the study published on Current Biologyresides in distinction between the desire for a reward and the actual ability to initiate the action necessary to obtain it, especially when there is a price to pay. For example, choosing to get up early in the morning to train, knowing that physical activity is good for our health, but at the cost of abandoning the warm embrace of our bed. To study this phenomenon, the researchers trained macaque monkeys in two distinct decision-making tasks: a task based only on rewards, and a more complex task in which the animals had to decide whether to accept an offer that combined a reward (juice) with an unpleasant stimulus (an annoying breath of air on the face).
Under normal conditions, the presence of any negative feedback tends to suppress motivationoften leading individuals to not start the task at all. Using an advanced technique called chemogenetics, which allows reversible silencing of specific neurons, the team selectively inhibited the pathway from the ventral striatum (VS) to the ventral pallidum (VP). The results were surprising: inhibition of this circuit restored the animals’ motivation specifically in the aversive task. When the VS-VP circuit was “off,” the monkeys stopped hesitating and began the task with the unpleasant stimulus much more frequently. Recordings of neuronal activity confirmed that, normally, the neurons of the VS they activate rapidly in response to negative contexts e inhibit the VPeffectively blocking the initiative. Therefore, removing this inhibition allows the “engine” of the action (the VP) to function freely even in the presence of difficulties.
Restart the engine of action
A crucial aspect that emerged from the study is that the restoration of motivation is not due to a distortion of reality or an inability to evaluate danger. Even under the effect of chemogenetic inhibition, the animals continued to perfectly distinguish the advantageous offers from the disadvantageous ones and they showed no altered preferences. In other words, it’s not that the “blow of air” was more pleasant or less scary; simply, the brain no longer let that negative perspective paralyze the initiation of action.
This distinction is critical because it separates “goal evaluation” processes from “behavioral initiation” processes. The study demonstrated that the VS-VP pathway specifically regulates the effort and will to get startedregardless of how good the final prize is. Analyzing the history of attempts, the researchers noticed that this circuit is particularly sensitive to recent failures: normally, a previous error tends to discourage the next attempt, but by suppressing the VS-VP pathway, this tendency to “give up” after a failure it came attenuated.
