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Sep 14, 2022·edited Sep 14, 2022

"Any neuroscience article will tell you that the “reward center” of the brain - the nucleus accumbens - monitors actual reward minus predicted reward."

This claim is way too strong.

What is correct:

Reward Prediction Error (RPE) is one of the main theories on what the reward center (nucleus accumbens NAc) does. There are many situations and experiments in which this explanation fits nicely.

What is also correct:

There are many situations in which RPE does *not* fit nicely. The discussion on what the reward center really does is far from settled.

I can highly recommend the paper "Dopamine release in the nucleus accumbens core signals perceived saliency" by Kutlu et al. from last year for a different opinion. It's really well written and contains great experiments. The authors suggest that the reward center does not represent RPE, but saliency. They summarize their work with the following four points:

- NAc core dopamine only mimics reward prediction error in select reward contexts

- RPE does not model dopamine release during negative reinforcement

- Dopamine signaling in the NAc core does not support valence-free prediction error

- NAc core dopamine tracks valence-free perceived saliency in all conditions

This paper will not be the end of the debate. But RPE is not the end of the debate either.

UPDATE: After reading the full post (great post!), I really have to find some time to re-read the study by Kutlu et al., put it next to the post, and see how the post aligns with their experiments. The result might be quite interesting.

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