PMC3819641_01
Motor-training. Four targets "center-out" task (A) with an example of a trajectory and some assisted-force-feedback vectors (orange arrows); physical representation (B) of the reaching task. The trajectory is shown for clarity, but during the motor task was never present.
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F1
E, S, and W) target positions was randomly selected in each trial for the ME (see Figure 1). Each target was represented by a white square of 18 mm. The patient was asked to move the cursor, controlling the end-effector from the center to the target in a pre-defined time window (0.5/0.7 s) and to perform the task as accurate as possible (see Figures 1 and 2).
Experimental procedure. Timing of self-paced trials with and without assisted-force-feedback (the force applied to the robotic arm was continuously updated every 16 ms). A self-paced trials starts by entering the center box, after 1.5 s a target appears (one out of four possible directions), thus the user plans the movement execution and initiates the movement toward the target; as soon as the target was reached (i.e., at the end of the trial) both visual and auditory feedback inform the user about the task completion; then the user comes back to the center position to start another trial. During BMI-training an assisted-force-feedback was provided according to the algorithm explained in Section "On-Line BMI Assisted-Force-Feedback."
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F2
The patient was asked to move the cursor, controlling the end-effector from the center to the target in a pre-defined time window (0.5/0.7 s) and to perform the task as accurate as possible (see Figures 1 and 2). Table 1). The MEM analysis window started 0.5 s before a movement interval onset, continued through this interval as a sliding window with steps of four samples to replicate the on-line settings (see Figure 2), and ended 0.5 s before a valid interval offset. This external program, referred as "robotic interface," is characterized by two concurrent processes: the first one controls the robotic arm and performs kinematic measurements (servo-loop rate equal to 1000 Hz); the second one handles the graphic interface adjusting the cursor position and scheduling each trial phase according to the timing of the task (see Figure 2).
Experimental protocol. Interval between blocks consisted of 2 days.
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F3
The robot training was performed on both healthy and paretic arms in daily sessions during 2 weeks, 3 days a week, resulting in 18 runs for each arm (see Figure 3). This configuration remained unchanged during on-line feedback BMI-training (see Figure 3).