Figure 3. Sustained firing rate during the expectation period is modulated by previous reward outcome.

(A) Activity raster plots from a representative neuron, separated according to previous trial outcome: negative (−$10, top), neutral ($0, middle) and positive (+$10), bottom during the expectation period prior between patient choice (t=−3000ms) and reward reveal outcome (t=0). (B) Firing rate during the expectation period split by previous reward outcome, averaged across trials. The sustained firing rate was significantly greater in trials following positive outcome than in trials following negative outcomes (p < 0.05, paired t-test) and neutral outcomes (p<0.01, paired t-test). (C-D) as (A-B), for a second neuron that only showed differences between negative (−$10) and positive (+$10) previous outcomes.