Fig. 1

A cortico-basal ganglia network signals reward uncertainty. a ACC–icbDS–Pal network. Lucifer yellow was injected in icbDS (middle, black area). Retrogradely labeled cell bodies (gray) were found in ACC (top; inset) and Pal (bottom). Anterogradely labeled fibers (orange area) were found in Pal (bottom; inset). ic: internal capsule, Cd: caudate nucleus, Pu: putamen, dACC: dorsal ACC, Pal: pallidum, vACC: ventral ACC, ac: anterior commissure, GPe: globus pallidus external segment, VP: ventral pallidum. Text indicates the plane’s anterior-posterior position relative to the midline anterior commissure. Scale bar: 2 mm. b Reconstruction of recording sites. Circles indicate locations of neurons that responded to uncertainty with significant excitation (black) or inhibition (white). Structures are shown in the coronal plane. Neurons are projected onto the nearest shown plane; text indicates the range of neuron locations. c Example neurons in each area. The neurons have excitatory or inhibitory ramping activity up to the time of uncertain reward: strongest for highly uncertain rewards (blue, 50%), strong for intermediately uncertain rewards (turquoise colors, 25 and 75%), and weak for certain outcomes (black, 100%; gray, 0%). Top: spike times (dots) on each trial (rows). Bottom: smoothed firing rates. d Population average normalized activity of uncertainty coding neurons in each area. Shaded areas are ± 1 SE. Arrow and text indicate latency of uncertainty coding. Gray area below x-axis is the pre-outcome analysis window. e Population average pre-outcome normalized activity is well fitted with a second-order polynomial function of reward probability (gray lines; shaded areas are ± 1 bootstrap SE) showing the inverted-U relationship with reward probability expected for uncertainty coding. f Graded coding of reward uncertainty. Histograms show each neuron’s difference in normalized activity between CSs with high (50%) vs. intermediate (25, 75%) uncertainty. Colored neurons have significantly differential activity: more normalized activity for high uncertainty (blue) or intermediate uncertainty (turquoise). *** indicates more neurons than expected by chance (p ≤ 0.001, binomial test). Arrows indicate means of all neurons (open arrow) and all neurons with significant differential activity (filled arrows); **, *** indicate the significance of their difference from zero, p < 0.01, 0.001 (signed-rank tests)