Sub-second fluctuations in extracellular dopamine encode reward and punishment prediction errors in humans

In the mammalian brain, midbrain dopamine neuron activity is hypothesized to encode reward prediction errors that promote learning and guide behavior by causing rapid changes in dopamine levels in target brain regions. This hypothesis (and alternatives regarding dopamine’s role in punishment-learning) has limited direct evidence in humans. We report intracranial, sub-second measurements of dopamine release in human striatum measured while volunteers (i.e., patients undergoing deep brain stimulation (DBS) surgery) performed a probabilistic reward- and punishment-learning choice task designed to test whether dopamine release encodes only reward prediction errors or whether dopamine release may also encode adaptive punishment-learning signals. Results demonstrate that extracellular dopamine levels can encode both reward and punishment prediction errors, but may do so via by independent valence-specific pathways in the human brain. One-Sentence Summary Dopamine release encodes reward and punishment prediction errors via independent pathways in the human brain.