Figure 2.

Delayed reward and preemptive checking in SD rats (n = 5). A, With delayed reward, the SWD burst could be any length ≥3 s (in this example, the length was 3 s) but had to be voluntarily terminated with 3 s of no SWD (magenta, pre) before the pellet was delivered, to avoid stimulus-induced blocking. Checking of the reward tube was detected by interruption of a photodiode (blue trace). B, Histogram, computed across rats, of first checks (the initial interruption of the photodiode after SWD termination), during SWDs, following SWDs but before pellet delivery (pre, arrow), 3 s period following pellet delivery (post), and the beginning of the interburst interval (IBI). Most first checks were preemptive, before the pellet was delivered. C, The average rate of checking was higher during the prereward and postreward periods than during either SWD or interburst interval. Results shown as mean ± SEM.