Figure 8

Programmed and experienced delays to reinforcement. H-lesioned rats experienced slightly shorter response-delivery delays (the delay between the most recent lever press and pellet delivery) than shams, and slightly shorter response-collection delays (the delay between the most recent lever press and pellet collection). (a) Mean experienced response-delivery delays (one value calculated per subject). When the programmed delay was 0 s, reinforcers were delivered immediately so no data are shown. H-lesioned rats experienced shorter response-delivery delays when the programmed delay was 10 s (* p = .012) or 20 s (** p = .009). (b) Mean experienced response-collection delays (one value calculated per subject). H-lesioned rats experienced slightly shorter delays overall (* p = .047, main effect of lesion), but the experienced delays did not differ significantly at any given programmed delay. (c) Distribution of experienced response-delivery delays. All experienced delays for a given subject were aggregated across all sessions, and the proportion falling into different 2-s ranges were calculated to give one value per range per subject; the graphs show means ± SEMs of these values. The interval notation '[a, b)' indicates that a given delay x falls in the range a ≤ x <b. H-lesioned rats experienced slightly fewer long delays and slightly more short delays in the 10 s condition (p = .019) and in the 20 s condition (p = .014). (d) Distribution of experienced response-collection delays, displayed in the same manner as (c). There were no differences in the distribution of delays experienced by H-lesioned and sham rats in the 0 s condition. In the 10 s condition, H-lesioned rats experienced a slightly lower proportion of long delays and a slightly higher proportion of short delays (p = .009), and similarly in the 20 s condition (p = .001).