Figure 5.

Extinction of reward-predicting stimulus removes small dopamine activation to conditioned inhibitor. a, Extinction training (top to bottom). Licking and neuronal responses to stimulus A- subsided gradually. Bin width = 10 msec. b, Average population responses in 23 dopamine neurons to A-, AX-, and X- were abolished after extinction of A. Responses to free reward were preserved in the same neurons (bottom). Trial types with conditioned stimuli alternated semirandomly and were separated for display. Control stimuli B-, BY-, and Y- continued to not elicit any responses (data not shown). c, Preserved conditioned behavioral inhibition after extinction of reward-predicting stimulus, as evidenced by adding the established conditioned inhibitor X- to the established reward-predicting stimulus C+ (summation test). Animals licked in initial CY- trials, indicating reward prediction but not yet conditioned inhibition (bottom).