The same center-out-and-back task was run on 280 sessions across monkeys L and J, spanning at least 16 months for each monkey. Although additional experiments (using different control algorithms and behavioral tasks) may have been run on these experimental days, at least 200 trials of center-out-and-back with the ReFIT-KF control algorithm were tested. On most experimental days, the task difficulty was greater than that shown in Figure 1 and Supplementary Table 1. For the experiments documented in Figure 1, the task difficulty was selected so that the monkey could successfully complete the task with the lower quality of control afforded by the Velocity-KF algorithm.
The Fitts’ law calculation is used to provide a metric that normalizes across task difficulty. For reference, monkey L was implanted on 01/22/2008 and monkey J was implanted on 08/24/2009. Data for monkey L were collected on 182 sessions over 29 months (from 24 to 53 months post-implantation). Data for monkey J were collected on 98 sessions over 16 months (from 5 to 21 months post-implantation). Each open square and circle in Figure 2 corresponds to a single experimental day on which the index of difficulty was 1.32 (4 cm targets at 8 cm from center) and throughput was calculated from at least 40 trials of center-out to either a vertical or horizontal target. All experiments from the timespans indicated that match these criteria were included, except for days on which other experiments may have impacted animal behavior. Regression lines were fit for data from each monkey using least square regression and p-values were calculated using an ANOVA for linear regression models.