During all rehabilitative training sessions throughout the study, an adaptive reward threshold was used to scale the difficulty of the task. Reward threshold was based on the median of the ten antecedent trials and capped at 120 g, thus rats received a food reward on a given trial if their pull force exceeded the best 50% of 10 most recent trials or 120 g (Ganzer et al., 2016a), (Meyers et al., 2017). This adaptive reward threshold was for all subjects at all times throughout the study. The reward threshold is shown as a green line in all panels and in Videos 1–5. An independent adaptive stimulation threshold specific to each CLV group was used to determine stimulation delivery during rehabilitative training (described in detail below). Adaptive stimulation thresholds are shown as a red line in the panels below. (A) In the Top 20% CLV group, the stimulation threshold was scaled such that VNS was delivered on trials in which pull force exceeded the top quintile of the peak pull force from the previous 10 trials. Circles represents the peak force of each individual trial during a rehabilitative training session. Green filled circles indicate the successful trials in which pull force exceeded the reward threshold. Green circles with a red border indicate trials on which VNS was delivered (the top 20% of trials). White circles indicate trials in which peak force did not exceed the reward threshold. A one minute representative segment of trials (marked with a dashed box) is shown in panel B. (B) The green vertical line represents the time in which the reward threshold is crossed. The dashed red vertical line indicates the timing of VNS delivery. Stimulation began after pull force crossed the stimulation threshold, resulting in a short difference between the closest successful trial and VNS (Δt) of 0.2 s. (C) This panel depicts pull force and VNS timing on an example stimulated trial (denoted with a black box in panel B). Note that the train of VNS (horizontal red lines) occurs coincident with crossing the red stimulation threshold and shortly after pull force exceeds the green success threshold. (D) A subset of rats received Delayed Top 20% CLV. In this configuration, VNS was still delivered on trials in which pull force exceeded the top 20% of the previous ten trials, but stimulation was delayed until the end of the 2 s trial window as shown in E and F. (E,F) This delay resulted in an average Δt of 1.4 s between the most successful trials and VNS. (G) In the Bottom 20% CLV group, the stimulation threshold was set such that VNS was delivered at the end of the trial window if pull force did not exceed the lowest quintile of the peak force of the 10 previous trials. White circles with a red border indicate trials on which VNS was delivered (the bottom 20% of trials). (H,I) Stimulation was delivered at the end of the 2 s trial window if the stimulation threshold was not exceeded, resulting in an average Δt of 25 s between the most successful trials and VNS. (J) For rats in the Top 50% CLV groups, the stimulation threshold was set such that VNS was delivered on trials in which pull force exceeded the median peak force of the previous ten trials or exceeded 120 g. (K,L) Stimulation began immediately (~50 ms) after pull force crossed the stimulation threshold.