Figure 5.

Properties of voluntary reaching movements and associated muscle activity in experiment 2

(A) Hand paths displayed by a representative participant (mean ± SD in the x-direction) when encountering random disturbances.

(B) Group mean and SE hand paths in each phase of the experiment. Gray dots represent the averaged pointwise SD in the x-direction displayed by individual participants in each phase of the experiment. Colored diamonds represent the group mean.

(C) Mean and SE forward velocities of the same exemplar participant as in (A). Forward velocities of the low and high variability conditions are based on trials where participants encountered the random disturbances. The data are aligned with movement onset (t = 0 ms).

(D) Group mean and SE forward velocities. Data are plotted in the same format as (C). Gray dots show the peak forward velocity for each participant. The colored diamonds indicate the group averages in each phase of the experiment.

(E) Mean and SE elbow flexor (brachioradialis & biceps) muscle activity of the same exemplar participant as in (A). Note that we display the muscle activity of unperturbed reaching movements across all experimental phases to avoid reflexive increases in muscle responses elicited by the random disturbances. Shaded gray area indicates the muscle activity associated with the planning and initiation of voluntary reaching movements (−100 to 100 ms aligned with movement onset). Note that we smoothed the muscle activity traces using a 10 sample (10 ms), zero-delay moving average for display purposes.

(F) Group mean and SE elbow flexor muscle activity are shown in each phase of the experiment. The data are plotted in the same format as (E). Gray dots represent the means of the elbow flexor muscle activity. Colored diamonds indicate the group means in each phase of the experiment.

(G and H) Elbow extensor (triceps lateralis & triceps longus) muscle activity is displayed following the same layout as (E) and (F).

Statistically significant effects are highlighted with %-changes in the outcome variable.

See also Figure S1.