Figure 5.

Changes in TAN activity when expected rewards were omitted in unrewarded trials. A, Comparison of magnitudes of changes in activity following the omission of reward as a function of reward probability. Results are pooled for the two monkeys. Numbers of values at p = 0.75, 0.5, and 0.25 for neurons showing a decrease in activity after reward omission are 17, 22, and 9, respectively (left); for neurons showing an increase in activity after reward omission, 16, 24, and 12, respectively (right). Values are given as means ± SEM. r, Correlation coefficient. B, Population activities for TANs responding to reward omission. Neurons were separated into two groups according to the direction of their response to no reward, namely increase or decrease in activity. Same numbers of neurons as in A. Vertical scale denotes impulses/s.