No one likes to do something they find unpleasant. Who among us hasn’t put off icky things such as a tedious work assignment, a fridge deep clean or a difficult conversation? The reason why someone just can’t seem to get started isn’t a mere failure of willpower: it is rooted in neurobiology.
In a new paper published in Current Biology, researchers describe a circuit in the brains of macaque monkeys that appears to function as a “motivation brake,” a finding that could offer clues to why people hesitate in making certain decisions.
“We were able to causally link a specific brain pathway to a ‘brake’ on motivation when individuals face unpleasant tasks in daily life,” says Ken-ichi Amemori, an associate professor at the Institute for the Advanced Study of Human Biology at Kyoto University and a co-author of the study.
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In the study, researchers presented macaques with tasks: the monkeys would either get a reward at the end of the task or a reward plus a puff of air on their face. As one might expect, the monkeys took longer to do the task when it meant getting the uncomfortable puff of air.
Then, using a technique called chemogenetics, whereby scientists can use drugs to control specific brain cells, the researchers suppressed a circuit between two brain regions called the ventral striatum and the ventral pallidum—both are known to be involved in motivation.
Once the circuit’s activity was tamped down, the monkeys were less hesitant to act on the task even if they knew the air puff was coming. In other words, the “brake” appeared to have been eased off.
“We hope that understanding this neural mechanism will help advance our understanding of motivation in stressful modern societies,” Amemori says.
He and his team hope the findings could one day inform treatments for psychiatric conditions that involve motivation such as schizophrenia and depression. He also notes, however, that interventions designed to weaken the “brake” should be approached with caution in case they might instead promote the opposite—unsafe risk-taking.
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