Psiche Giannoni

Self-adaptive robot training of stroke survivors for continuous tracking movements

BackgroundAlthough robot therapy is progressively becoming an accepted method of treatment for stroke survivors, few studies have investigated how to adapt the robot/subject interaction forces in an automatic way. The paper is a feasibility study of a novel self-adaptive robot controller to be applied with continuous tracking movements.MethodsThe haptic robot Braccio di Ferro is used, in relation with a tracking task. The proposed control architecture is based on three main modules: 1) a force field generator that combines a non linear attractive field and a viscous field; 2) a performance evaluation module; 3) an adaptive controller. The first module operates in a continuous time fashion; the other two modules operate in an intermittent way and are triggered at the end of the current block of trials. The controller progressively decreases the gain of the force field, within a session, but operates in a non monotonic way between sessions: it remembers the minimum gain achieved in a session and propagates it to the next one, which starts with a block whose gain is greater than the previous one. The initial assistance gains are chosen according to a minimal assistance strategy. The scheme can also be applied with closed eyes in order to enhance the role of proprioception in learning and control.ResultsThe preliminary results with a small group of patients (10 chronic hemiplegic subjects) show that the scheme is robust and promotes a statistically significant improvement in performance indicators as well as a recalibration of the visual and proprioceptive channels. The results confirm that the minimally assistive, self-adaptive strategy is well tolerated by severely impaired subjects and is beneficial also for less severe patients.ConclusionsThe experiments provide detailed information about the stability and robustness of the adaptive controller of robot assistance that could be quite relevant for the design of future large scale controlled clinical trials. Moreover, the study suggests that including continuous movement in the repertoire of training is acceptable also by rather severely impaired subjects and confirms the stabilizing effect of alternating vision/no vision trials already found in previous studies.

Minimally assistive robot training for proprioception enhancement

In stroke survivors, motor impairment is frequently associated with degraded proprioceptive and/or somatosensory functions. Here we address the question of how to use robots to improve proprioception in these patients. We used an ‘assist-as-needed’ protocol, in which robot assistance was kept to a minimum and was continuously adjusted during exercise. To specifically train proprioceptive functions, we alternated blocks of trials with and without vision. A total of nine chronic stroke survivors participated in the study, which consisted of a total of ten 1-h exercise sessions. We used a linear mixed-effects statistical model to account for the effects of exercise, vision and the degree of assistance on the overall performance, and to capture both the systematic effects and the individual variations. Although there was not always a complete recovery of autonomous movements, all subjects exhibited an increased amount of voluntary control. Moreover, training with closed eyes appeared to be beneficial for patients with abnormal proprioception. Our results indicate that training by alternating vision and no-vision blocks may improve the ability to use proprioception as well as the ability to integrate it with vision. We suggest that the approach may be useful in the more general case of motor skill acquisition, in which enhancing proprioception may improve the ability to physically interact with the external world.

Wrist Rehabilitation in Chronic Stroke Patients by Means of Adaptive, Progressive Robot-Aided Therapy

Despite distal arm impairment after brain injury is an extremely disabling consequence of neurological damage, most studies on robotic therapy are mainly focused on recovery of proximal upper limb motor functions, routing the major efforts in rehabilitation to shoulder and elbow joints. In the present study we developed a novel therapeutic protocol aimed at restoring wrist functionality in chronic stroke patients. A haptic three DoFs (degrees of freedom) robot has been used to quantify motor impairment and assist wrist and forearm articular movements: flexion/extension (FE), abduction/adduction (AA), pronation/supination (PS). This preliminary study involved nine stroke patients, from a mild to severe level of impairment. Therapy consisted in ten 1-hour sessions over a period of five weeks. The novelty of the approach was the adaptive control scheme which trained wrist movements with slow oscillatory patterns of small amplitude and progressively increasing bias, in order to maximize the recovery of the active range of motion. The primary outcome was a change in the active RoM (range of motion) for each DoF and a change of motor function, as measured by the Fugl-Meyer assessment of arm physical performance after stroke (FMA). The secondary outcome was the score on the Wolf Motor Function Test (WOLF). The FMA score reported a significant improvement (average of 9.33±1.89 points), revealing a reduction of the upper extremity motor impairment over the sessions; moreover, a detailed component analysis of the score hinted at some degree of motor recovery transfer from the distal, trained parts of the arm to the proximal untrained parts. WOLF showed an improvement of 8.31±2.77 points, highlighting an increase in functional capability for the whole arm. The active RoM displayed a remarkable improvement. Moreover, a three-months follow up assessment reported long lasting benefits in both distal and proximal arm functionalities. The experimental results of this preliminary clinical study provide enough empirical evidence for introducing the novel progressive, adaptive, gentle robotic assistance of wrist movements in the clinical practice, consolidating the evaluation of its efficacy by means of a controlled clinical trial.

Bilateral robot therapy based on haptics and reinforcement learning: Feasibility study of a new concept for treatment of patients after stroke.

OBJECTIVE To carry out a preliminary feasibility study of a new concept of robot therapy for severely impaired patients after stroke. DESIGN A haptic manipulandum connected to a bar that can rotate freely while providing a measure of the rotation angle. The controller combines a bilateral reaching task with the task of balancing the action of the 2 arms. Reinforcement is given to the subject in 2 forms: audio-visual and haptic by means of adaptable force fields. PATIENTS Four highly paretic patients with chronic stroke (Fugl-Meyer score less than 15). METHODS The training cycle consisted of 5 sessions over a period of 2 weeks. Each session (45 min) was divided in blocks of 10 pairs of forward/backward movements. Performance was determined by evaluating the number of successful movements per session, the session-by-session decrease in the assistive field, the mean reaching time, and the mean stopping field. RESULTS All subjects could understand the task, appreciated it and improved their performance during training. The reaching movements became smoother and quicker; balance errors and the magnitude of the resisting field were consistently reduced. CONCLUSION Bilateral robot therapy is a promising technique, provided that it self-adapts to the patients performance. Formal clinical trials should address this point.

Desirable features of a “humanoid” robot-therapist

In relation with a recent Cochrane review, the paper discusses desirable features of a “humanoid” robot-therapist: 1) high mechanical compliance, 2) large range of force, 3) minimum assistance level, 4) soft haptic interaction for proprioceptive awareness, 5) adaptative assistance properties. It also proposes a framework for addressing optimal assistance and learning paradigms in view of a consensus in the community of rehabilitation engineers about shared principles and common standards.

Proprioceptive Bimanual Test in Intrinsic and Extrinsic Coordinates

Is there any difference between matching the position of the hands by asking the subjects to move them to the same spatial location or to mirror-symmetric locations with respect to the body midline? If the motion of the hands were planned in the extrinsic space, the mirror-symmetric task would imply an additional challenge, because we would need to flip the coordinates of the target on the other side of the workspace. Conversely, if the planning were done in intrinsic coordinates, in order to move both hands to the same spot in the workspace, we should compute different joint angles for each arm. Even if both representations were available to the subjects, the two tasks might lead to different results, providing some cue on the organization of the “body schema”. In order to answer such questions, the middle fingertip of the non-dominant hand of a population of healthy subjects was passively moved by a manipulandum to 20 different target locations. Subjects matched these positions with the middle fingertip of their dominant hand. For most subjects, the matching accuracy was higher in the extrinsic modality both in terms of systematic error and variability, even for the target locations in which the configuration of the arms was the same for both modalities. This suggests that the matching performance of the subjects could be determined not only by proprioceptive information but also by the cognitive representation of the task: expressing the goal as reaching for the physical location of the hand in space is apparently more effective than requiring to match the proprioceptive representation of joint angles.

Impedance-controlled, minimally-assistive robotic training of severely impaired hemiparetic patients

The paper describes a pilot study in the robotic training of severely impaired hemiparetic patients. It provides arguments in favor of impedance control, with a backdrivable manipulandum characterized by a very low level of the intrinsic mechanical impedance, and proposes a method of minimally assistive robotic training that focuses on outward reaching movements of large amplitude. This type of training is well accepted by the patients and appears to help them decrease the dominating flexion patterns that characterize their pathology

Testing proprioception in intrinsic and extrinsic coordinate systems: is there a difference?

An intact position sense is considered important for neuromotor recovery, but the available methods and protocols for its assessment are still limited. In the clinical practice it is generally tested trough a bimanual position matching test, that consists of replicating with one arm the angular positions of the other arm in space (intrinsic coordinates matching). However, the same test could be carried out by matching the hand location in space (extrinsic coordinates matching). Is there any difference between the procedures that may be relevant to the evaluation of position sense deficits? In this study we compared the performance of eight right handed subjects and two stroke survivors with left hemiparesis performing the test in the two conditions. A robotic manipulandum passively moved the left arm of the participants in twenty-four positions in the workspace. Subjects had to match the left arm position with their right arm either in intrinsic or extrinsic coordinates. The results show that all the subjects (impaired and controls) performed better when using the extrinsic paradigm.

Training the Unimpaired Arm Improves the Motion of the Impaired Arm and the Sitting Balance in Chronic Stroke Survivors

Robot-assisted rehabilitation of stroke survivors mainly focuses on the impaired side of the body while the role of the unimpaired side in the recovery after stroke is still controversial. The goal of this study is to investigate the influence on sitting balance and paretic arm functions of a training protocol based on movements of the unimpaired arm. Sixteen chronic stroke survivors underwent nineteen training sessions, in which they performed active movements with the unimpaired arm supported by a passive exoskeleton. Performance of the trunk and upper limbs was evaluated before treatment, after treatment and at six months follow up with clinical scales and an instrumented evaluation. A reaching test executed with the exoskeleton was used to assess changes in performance of both arms. The treatment based on the unimpaired arm’s movements executed with a correct body posture led to benefits in control of the trunk and of both the trained and the untrained arm. The amount of impaired arm improvement in the Fugl-Meyer score was comparable to the outcome of robotic treatments focused directly on this arm. Our results highlight the importance of taking into account all body schema in the rehabilitation robotic program, instead of focusing only on the impaired side of the body.

Training stroke patients with continuous tracking movements: Evaluating the improvement of voluntary control

We report on a pilot study of robot therapy with stroke patients. Patients were requested to track a continuously moving target according to a figure-of-eight. Assistance was provided by an attractive force field, whose magnitude was regulated according to a principle of minimal assistance and a principle of consolidation of the learned memory trace. From the analysis of the assistive forces, we show that subjects improve their degree of voluntary control.