Fig. 6: Infusions in PPC during surebet value change and free choice.

a, Schematic showing that changing the surebet magnitude is equivalent to shifting the choice boundary. The data points were simulated from a risk-neutral agent using the three-agent model (ρ = 1, σ = 3, ω_rational = 1). A smaller surebet magnitude (light blue) horizontally shifts the psychometric curve leftwards; a larger surebet magnitude (dark blue) shifts the curve rightwards. The frequency-to-lottery mapping remains the same. b, Changing surebet magnitude from 6.8 to 3 shifted choices leftwards in one example animal. Combined trials from six sessions before the change are shown in gray, after the change shown in blue. One three-agent model was fit to all the trials, and the parameters were used for ribbon extrapolation (n = 547 trials for surebet magnitude is 6.8; n = 585 trials for surebet magnitude is 3; the circles with error bars are the mean and 95% binomial CIs). c, Same as b but with 0.6 μg per side bilateral PPC infusion, performed on the day of surebet change (from 3 to 6.8—n = 585 trials for surebet value is 3; n = 503 trials for surebet value is 6.8; the circles with error bars are the mean and 95% binomial CIs). d, The three-agent mixture model predicts the shifts in behavior well. One model was fit using all the sessions containing various surebet magnitudes for each animal. On the x axis is the predicted shift in probability choosing lottery: the difference in P(Choose Lottery) between model prediction using the new surebet magnitude and the session just before that change. On the y axis is the actual shift in P(Choose Lottery): the difference in P(Choose Lottery) between the first session of a surebet change and the session before that change. Sessions with just surebet change are in blue (n = 21, 4 animals); sessions with both surebet change and 0.6 μg per side bilateral PPC infusions are in gold (n = 8). There is a strong correlation between predicted and actual shift (Pearson’s correlation, r = 0.905, P = 1.6 × 10⁻¹¹), and this relationship is significantly different between shifts where PPC was silenced and control shifts (LR test, χ²(2, 29) = 7.44, P = 6.4 × 10⁻³). e, Schematic of the free trials. After fixation at the center port accompanied by a neutral tone, the animal was free to choose the left or right port, both illuminated in blue LEDs. Choosing either port resulted in a reward twice the magnitude of surebet. The free trials were randomly interleaved with the forced and choice trials. f, Unilateral PPC infusions (0.6 μg) led to a significant ipsilateral bias toward the side of infusion. This panel shows % ipsilateral bias: (∑choose_infusion_side − ∑choose_other_side) / ∑total_choices, when the side of infusions was chosen to be the opposite to the animalsʼ preferred side. % ipsilateral bias was computed using free trials from the previous three sessions, the infusion session and the following three sessions for six subjects. g, Left: unilateral PPC infusions generated a significant 52 ± 16% (t(5) = 3.09, P = 0.027, mean ± s.e. across rats, n = 6, two-sided) change in % ipsilateral bias on free trials compared to control sessions (three pre-infusion sessions). For the choice trials from the same sessions, the change in % ipsilateral bias was not significant (15 ± 8%, t(5) = 1.92, P = 0.11, mean ± s.e. across rats, n = 6, two-sided). Right: performance on the choice trials was not affected. Control sessions from the three pre-infusion sessions (n = 65 sessions, 6 rats) are in gray; 0.6 μg left PPC infusions (n = 5 sessions) are in blue; and 0.6 μg right PPC infusions (n = 6 sessions) are in orange.