Reintroduction of Vibration. On day 3, during the last block of the study, sequence-specific learning improvements in tracking that were demonstrated by the AV group at the retention test when vibration was removed were masked by the re-introduction of vibration. That is, performance on random and sequence epochs were similar as shown by the lack of difference (low change score) between random and repeated sequence tracking error for the AV group. In contrast, CTL participants maintained sequence-specific improvement that was seen in no-vibration retention testing. Larger change in RMSE denotes greater performance difference between the sequence than the random epoch.