Scientists discover the brain cells that keep you motivated
A group of brain cells called orexin neurons appears to help us keep working when reaching a reward becomes increasingly difficult. Blocking their activity weakened motivation in rats, pointing to a possible new target for understanding why people sometimes struggle to sustain goal-directed behavior.
Researchers at Nagoya University in Japan have identified a brain mechanism that may help explain why people maintain motivation despite increasingly demanding challenges. Their study, published in the Proceedings of the National Academy of Sciences, found that orexin neurons play a crucial role in sustaining and regulating motivated behavior.
Loss of motivation is common in conditions such as depression, addiction, and ADHD, although the brain processes contributing to these difficulties are not fully understood. The team led by Hiroyuki Mizoguchi and Kiyofumi Yamada focused on orexin neurons, which control vital functions like sleep, appetite, and energy expenditure.
Previous research suggested orexin neurons might affect motivation, but their specific contribution remained uncertain. To investigate, the scientists used genetically modified orexin-Cre rats to selectively target and manipulate orexin-producing neurons. They first activated orexin neurons using chemogenetics and measured the animals' performance in a progressive ratio test, where the number of required touches increased with each food reward.
Rats with activated orexin neurons reached higher breakpoints, indicating stronger motivation. Conversely, rats with degenerated orexin neurons showed weaker motivation. The researchers also monitored orexin neuron activity in real time with fiber photometry. Activity increased during reward anticipation, fell after delivery, and remained high when an expected reward didn't appear.
This pattern suggests the brain links reward expectations with required effort. Optogenetics revealed that suppressing orexin neuron activity reduced motivated behavior, while increasing activity didn't boost motivation further. Mizoguchi concluded that orexin neurons help maintain motivated behavior but additional research is needed to understand why effects vary and how factors like activity patterns influence outcomes. The study could lead to new treatments for motivational deficits.
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