Error Enhancement of the Velocity Component

Error Enhancement of the Velocity Component in the Course of Stroke Patients' Reaching Movements - A Pilot Study

The purpose of this pilot study was to explore the impact of enhancement of the velocity component error in the course of reaching movements of the impaired/hemiparetic limb in an acute stroke subject. We hypothesized that the method would shift velocity profiles toward the optimal, resulting in a reduction in error. A prototype robot. This robotic device system has a two-dimensional motor, basic measurement capacities, and a robotic arm which is engaged to the subject's upper-limb in a sitting position. The enhancement of the velocity component error would shift velocity profiles toward the optimal, resulting in a reduction in error.

The wrist of the subject is connected to the robotic arm by a strip which supports the arm but allows free movements of the wrist. This configuration allows subjects with impaired grasping ability to use the system. A bio-feedback system enables the subject to perform various functional motor tasks that are presented on the screen in front of him. The system's sensors detect motor errors or deviations from an optimal/proper movement trajectory or velocity profile. Any deviation in direction, velocity, acceleration or necessary force from the optimal trajectory results in applied robotic forces that enhance such errors/deviations. The sensors and the applied forces all work and compute in real time, so that the force measurements and the applied force are updated to the executed movement.

Training of the upper extremity, using a robotic devise with error enhanced forces and traditional therapy.

Training of the upper extremity, using a robotic devise without forces applied and traditional therapy.

Patients underwent upper extremity robotic training with the error enhancement effect. Training have focused on hand reaching movements in varity of directions and range of motions.

Patients underwent upper extremity robotic training without the error enhancement effect. Training have focused on hand reaching movements in varity of directions and range of motions.

While reaching, people have typical movement pattern of trajectory, moving the end-effector (hand) in straight line. The abnormal motor control after a stroke may cause these patients to deviate from this pattern. Our robotic device enabled us to measure the magnitude of the deviation from the optimal profile of healthy people. This was followed by a calculation of the average error the paricipants made in each treatment session. So we finally recieved a score of the average magnitude of trajectory error the participants made through a treatment session. Each treatment seesoin composed of about 100 reaching movements. The outcome measure expresses the change in the movement error from T1 to T2.

The outcome was assessed at the begining of the rehabilitation (T1) and about 5 weeks later at the end of rehabilitation (T2).

The Fugl-Meyer assessment score (FM) is a zero (disabaled function) to 66 points (high level of function) scale that evaluates the level of the motor impairment of the upper extremity, in stroke patients.

The measured assessed at the begining of the rehabilitation (T1) and about 5 weeks later at the end of the rehabilitation (T2).

Inclusion Criteria: Single stroke Two to three weeks post Stroke Able to understand simple commands Able to perform some reaching movements with the affected arm. No other neurological, neuromuscular, orthopedic disorders and visual deficit Exclusion Criteria: Perceptual, apraxic, or major cognitive deficits, Shoulder joint subluxation or pain in the upper-limb, and Spasticity > 1 (single muscle Modified Ashworth Scale).

Givon-Mayo R, Simons E, Ohry A, Karpin H, Israely S, Carmeli E. A preliminary investigation of error enhancement of the velocity component in stroke patients' reaching movements. International Journal of Therapy and Rehabilitation. 2014;21(4):160-168.