Scientists Discover Brain Cells Acting as 'Frustration Meter'

Scientists in the United States have pinpointed a cluster of brain cells that function as a "frustration meter," detecting when reality does not meet expectations. Published in the journal Current Biology, researchers from the University of Oregon describe a specific set of neurons in the brains of mice that become active when the animal expects a reward but receives a smaller amount or none at all. This suggests that the feeling of disappointment is not merely a subjective experience but something that specific brain cells detect and record.

The mapping of these cells could pave the way for novel drug treatments for neuropsychiatric disorders, including depression and addiction, according to Emily Sylvester, an associate professor of biology at the University of Oregon and lead author of the study. "When you study a neuropsychiatric illness, you need to know which 'buttons' to adjust to restore function. If we know that a specific type of cell is affected in depression, we can design drugs that target precisely that cell, avoiding parallel effects on other systems," Sylvester explained.

The research team studied a small and evolutionarily ancient structure deep within the brain, the lateral habenula. Previous research had indicated that this area activates during unexpectedly negative events, such as the absence of an anticipated reward, and has been informally labeled the brain's "anti-reward center." While scientists had previously described the type of cell Sylvester's lab studied, they lacked direct access to it. Sylvester's team discovered these neurons by chance while investigating a neighboring brain region. During an experiment, they observed signals from cells that appeared every time a mouse expected a reward but did not receive it.

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When you study a neuropsychiatric illness, you need to know which 'buttons' to adjust to restore function. If we know that a specific type of cell is affected in depression, we can design drugs that target precisely that cell, avoiding parallel effects on other systems.

This observation sparked the study, where Sylvester and her colleagues recorded the neural activity of mice trained to touch a lit port, anticipating a sugar water reward. When the quantity was reduced or absent, the neurons' activity increased proportionally to the degree of disappointment. "It's as if we can see from the neurons' activity whether they received one, two, or three doses of sugar water when they were expecting five," Sylvester stated. "The neurons essentially function as a reliable counter of the difference between expectation and outcome."

The researchers found that these specific neurons do not respond to all negative stimuli, such as sudden discomfort. This indicates they are specialized for the disappointment of an expected reward, rather than general "negativity." Kana Suzuki, a doctoral student and co-lead author of the study, emphasized that...

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It's as if we can see from the neurons' activity whether they received one, two, or three doses of sugar water when they were expecting five. The neurons essentially function as a reliable counter of the difference between expectation and outcome.