4 min readAug 7, 2026 12:02 PM IST
Scientists have identified a group of brain cells that appear to play a key role in helping people stay motivated when achieving a goal becomes increasingly difficult. The discovery could improve understanding of why motivation declines in conditions such as depression, attention deficit hyperactivity disorder (ADHD), and addiction, where sustaining goal-directed behaviour is often a major challenge.
The study, published in the Proceedings of the National Academy of Sciences (PNAS), was led by researchers at Nagoya University, Japan. It found that orexin neurons, brain cells best known for regulating sleep, appetite, and energy balance, also help translate the expectation of a reward into the determination needed to continue working for it.
Why motivation matters
Motivation allows people to persist even when tasks become more demanding or rewards are delayed. While reduced motivation is a common symptom of several psychiatric and neurological disorders, scientists have not fully understood the brain mechanisms underlying goal-directed behaviour.
The research team, led by Associate Professor Hiroyuki Mizoguchi and Professor Emeritus Kiyofumi Yamada, investigated whether orexin neurons contribute directly to motivation.
Previous studies had hinted at such a role, but evidence remained limited because selectively targeting these neurons in laboratory rats had been technically difficult.
Genetically modified rats helped unlock the mystery
To overcome this challenge, the researchers developed genetically engineered “orexin-Cre” rats, thereby enabling precise manipulation of orexin-producing neurons.
Unlike mice, which are commonly used in neuroscience experiments, rats have stronger learning abilities and are considered better suited for complex behavioural tasks involving motivation.
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The team then examined how manipulating orexin neuron activity affected the animals’ willingness to work for food rewards.
Measuring how hard animals would work
Researchers used a behavioural experiment known as a progressive ratio test, in which rats had to perform an increasing number of touchscreen responses to receive each successive food reward.
The point at which an animal stopped trying, known as the breakpoint, served as a measure of its motivation.
When scientists activated orexin neurons using chemogenetics, the rats continued working for longer and reached significantly higher breakpoints, indicating stronger motivation.
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In contrast, rats whose orexin neurons had been selectively destroyed gave up much sooner and showed substantially lower breakpoints, suggesting their motivation had declined.
Brain activity tracked reward expectation
To understand what these neurons were doing during the task, researchers monitored their activity in real time using fibre photometry, a technique that records activity in specific groups of neurons while animals behave naturally.
They found that orexin neuron activity increased as rats anticipated receiving a reward but dropped once the food was delivered.
Interestingly, when an expected reward failed to appear, activity remained elevated.
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The neurons also became progressively more active as the amount of work required to earn the reward increased.
According to the researchers, this suggests orexin neurons help connect reward expectation with the effort needed to obtain it, enabling sustained motivation despite growing challenges.
Blocking the neurons weakened motivation
The team also used optogenetics, a technique that uses light to precisely control neurons, to determine whether orexin activity directly influenced behaviour.
When researchers temporarily suppressed orexin neurons at the moment rats expected a reward, the animals became noticeably less motivated. They took longer to complete tasks and abandoned them earlier.
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However, increasing orexin neuron activity above normal levels did not make the rats work any harder.
The findings indicate that while orexin neurons are necessary for maintaining motivation, simply boosting their activity beyond natural levels may not produce additional motivation.
Researchers say the result suggests motivation depends not only on how active these neurons are, but also on when and how they are activated within broader brain networks.
Potential implications for mental health
The researchers believe their findings could help explain motivational problems seen in disorders such as depression, ADHD, and substance addiction.
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Future research will investigate the wider brain circuits connected to orexin neurons and explore whether manipulating these pathways could eventually lead to new treatments for disorders characterised by reduced motivation and impaired goal-directed behaviour.
