Motivation influences our daily lives in numerous ways, from major decisions like changing careers to simpler choices like switching TV channels. Our actions are often driven by what we find motivating and rewarding.
In a recent study featured in PNAS, researchers from Nagoya University in Japan have pinpointed neurons that produce the chemical orexin as key players in food-reward motivation in rats.
Located in the brain’s hypothalamus, these neurons have been previously associated with wakefulness, energy expenditure, and motivation. The researchers aimed to delve deeper into the connection between these neurons and motivation.
“A potential mechanism for translating expectations into sustained action.”
– Neuroscientist Hiroyuki Mizoguchi
Their experiments revealed the moment-to-moment influence of orexin and its role in determining whether a reward is worth the effort, a critical aspect of motivation.
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The researchers noted that orexin activities are closely tied to the motivational process in rats, with dynamic changes in neuron activation potentially influencing reward-seeking behavior based on reward prediction. The response of orexin neurons varies with the degree of effort, indicating expectations for incentives relative to one’s efforts.
By genetically modifying the activity of orexin-producing neurons, the researchers found that rats worked harder for food rewards when these neurons were activated, but gave up more quickly when they were inhibited.
Additionally, real-time monitoring showed increased orexin activity before the rats received a reward and decreased activity afterward. Orexin activity remained high when a reward was expected but not received.
The more effort rats exerted for a reward, the stronger the orexin neuron activity, suggesting it could serve as a marker for the effort involved in pursuing an expected reward.
“Our study demonstrated significant changes in orexin neuron activity depending on expected rewards and the effort required, suggesting a potential mechanism for translating expectations into sustained action,” says neuroscientist Hiroyuki Mizoguchi from Nagoya University.
Further tests showed that controlling orexin neuron activity could influence motivation. Reducing activity appeared to decrease motivation, while increasing it did not boost motivation significantly. These neurons might maintain motivation at a baseline level rather than working like a volume dial.
“Therefore, orexin is crucial for linking predicted expectations with motivated behavior,” write the researchers. “Moreover, optimization of orexin activity is necessary to overcome difficulties during motivated behaviors.”
Although these findings need to be applied to the human brain, humans also possess an orexin system. This raises important questions for future research on task commitment and perseverance.
Motivation issues are associated with mental disorders such as depression and addiction. Understanding orexin’s role in the brain could improve treatments for these conditions. However, more research is needed to explore the brain circuits connected to orexin neurons to uncover the natural sequence of events that activate or deactivate them.
Related: One Brain Chemical May Be Key to Breaking a Habit, Study Finds
As motivation is a key driver of behavior, any new insights into its mechanisms could have far-reaching implications. “A better and further understanding of orexinergic mechanisms underlying motivated behaviors would provide insights into the ways that motivation can be developed, and the disorders can be overcome,” write the researchers.
The research is published in Proceedings of the National Academy of Sciences.
This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
