The cells, located in the lateral habenula – a small region deep in the brain often described as the “anti-reward centre” – were observed in mice during experiments where expected sugar rewards were withheld.
These neurons remained mostly inactive when rewards arrived as expected but became highly active when expectations were not met, effectively acting as a “disappointment signal.” Researchers say the cells activate specifically when reality falls short of expectations.
Interestingly, the same neurons did not respond strongly to unpleasant stimuli such as mild shocks or sudden disturbances, suggesting they are specialised for detecting unmet expectations rather than general negative experiences. This aligns with broader research showing the brain distinguishes between different types of “prediction errors” when outcomes differ from expectations.
The discovery could have important implications for understanding conditions such as depression and addiction, where the brain’s reward system does not function normally. Scientists hope that targeting these specific cells may eventually lead to more precise treatments with fewer side effects.
The study was published in Current Biology.
