Figure 4.
Average baseline-normalized firing rate + 1 SEM (shading) for all adult and adolescent units, time-locked to task events during each of six sessions. The median taskwide firing rate for all adolescent units was 4.66 Hz, and all adult units was 5.18 Hz. Although slight, their corresponding firing-rate distributions were significantly different (rank-sum test, Z = 2.18, p = 0.03). This figure demonstrates that, in session 1 (adult, n = 47; adolescent, n = 60; first row), when the action–outcome association was not yet learned (Fig. 1c), there was little task-related activity to the cue (left), instrumental pokes (middle), or rewarded food-trough entries (right) in either group. By session 2 (adult, n = 59; adolescent, n = 60; second row), as animals learned at different rates and performed the task to varying extents, average OFC neural activity began to change around task events in both groups. From session 3 onward (session 3: adult, n = 49; adolescent, n = 64; session 4: adult, n = 46; adolescent, n = 67; session 5: adult, n = 41; adolescent, n = 72; session 6: adult, n = 48; adolescent, n = 62; third to sixth rows), average normalized neural activity settled into somewhat stable patterns in both age groups.