The decay of motor adaptation to novel movement dynamics reveals an asymmetry in the stability of motion state-dependent learning
Fig 2
Adaptation and subsequent decay for training in position- and velocity -dependent force-fields (A). Comparison of the adaptation coefficients during position (pFF, blue curve) and velocity-dependent force-field training (vFF, red curve). Each point during the adaptation period is the average adaptation coefficient across subjects for windows of 10 or 15 trials. During the decay period, the points are average across all subjects for each trial. The start of the decay period is shown as a vertical dashed line. Shaded areas show standard error. (B) Normalized decay for pFF and vFF training. The adaptation coefficients were scaled with respect to the first coefficient in the decay period, with the first point rescaled to a value of 1.0. Bar graphs show the average adaptation across subjects for early and late epochs of the decay, represented by the shaded areas. Error bars are standard error. (C and D) Temporal force profiles during adaptation and decay for pFF and vFF training. Top panel shows the evolution of the force patterns in the early and late stages of adaptation, while the bottom panel shows the changes in early and late stages of the decay period. The average force across all subjects is shown by a gray trace. The contribution of position and velocity to the force profile is represented by the blue and pink dashed lines. The combination of the position and velocity contribution is shown by a black dashed line, and approximates actual exerted forces. The R2 value from the regression between actual (thick gray trace) and combined position-velocity fit (black dashed trace) is provided in the top left of each panel.