(A) Motion tracking of the left wrist, elbow, shoulder, and the headcap implant during reach and walk-and-reach movements for monkey K (left) and monkey L (right). Video-based markers are tracked in three dimensions and projected to a side-view. Trial-by-trial marker positions for the reach (red) and walk-and-reach (blue) movements to the mid-left targets are shown for a sampling frequency of 60 Hz, overlaid for multiple sessions (light-dark colors). (B) Small trial-to-trial variability of movement trajectories, even across sessions, demonstrates spatially well-structured and consistent behavior. For each trial and marker, the average Euclidean distance to the trial-averaged trajectory at corresponding times is shown (see Materials and methods). For reference, neighboring near targets were mounted at approximately 130 mm distance (dashed line) in this experiment. The MCT diameter is 75 mm. (C) Reconstructed 3-dimensional arm posture as function of time during reach and walk-and-reach movements based on the video motion capture separately for each monkey and session. The lines connect the marker (wrist to elbow to shoulder to headcap) for each marker position averaged across trials. Gray rectangles show target and start button MCTs. Pictures below show snapshots of characteristic postures during an example reach and walk-and-reach trial.