Figure 3. Striatal U+ neurons are sensitive to the level of reward uncertainty.

(a) Responses of a single uncertainty selective (U+) neuron to the presentation of 10 fractal objects associated with certain and uncertain predictions of juice reward. (b) Average responses of 20 U+ neurons in the reward-probability block (left) and reward amount block (right). (c) Average normalized responses of 20 U+ neurons for probability (red) and amount (black) CSs. Asterisks indicate differences between CSs (**P<0.01; *P<0.025; paired sign-rank test). The inset shows the single neuron's CS responses for different reward predictions in the reward-probability block (normalized to the maximum CS response; from 0 to 1). Numbers above the inset indicate the number of cells that exhibited the greatest response for 25, 50 or 75% CSs; 60% of the neurons exhibited greatest response for 50% reward CS.