Fig. 4.

Changes in correlated activity in OFC during intertrial intervals in the early (white bars) and late (black bars) phases of precriterion training, during postcriterion performance (gray bars), and after reversal (striped bars). A, Correlated activity at short latency (within 2 msec of a spike in the reference cell) increased significantly during initial training (F_(2,498) = 13.0; p< 0.001). Post hoc comparisons revealed no significant difference between the early and late phases of precriterion training (p = 0.183). However, correlated activity in the postcriterion phase differed significantly from each of the precriterion phases (p < 0.001 andp = 0.003 for early and late, respectively). A separate analysis of neuron pairs recorded during reversals revealed that efficacy of correlated firing within the short latency interval increased further after reversal (F_(1,140) = 14.5; p< 0.001). B, Correlated activity at longer latency (2–10 msec after a spike in the reference cell) also increased significantly during initial training (F_(2,498) = 90.1; p< 0.001). Efficacy in OFC differed between the early and late precriterion phases (p = 0.0386), and a significant increase in the postcriterion phase was also evident compared with each of the precriterion phases (p < 0.001 for both comparisons). Efficacy of correlated firing within the longer latency interval increased further after reversal (F_(1,140) = 58.3; p < 0.001). C, Activity in cell pairs with correlated activity in OFC. Average firing rate is shown for both neurons within each pair that was included in the analyses presented in A and B. Note the difference in both pattern and magnitude between the minimal changes in activity and the changes in correlated firing across the training phases.