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Many survivors of stroke have persistent somatosensory deficits on the contralesional side of their body. Non-invasive supplemental feedback of limb movement could enhance the accuracy and efficiency of actions involving the upper extremity, potentially improving quality of life after stroke. In this proof-of-concept study, we evaluated the feasibility and the immediate effects of providing supplemental kinesthetic feedback to stroke survivors, performing goal-directed actions with the contralesional arm. Three survivors of stroke in the chronic stage of recovery participated in experimental sessions wherein they performed reaching and stabilization tasks with the contralesional arm under different combinations of visual and vibrotactile feedback, which was induced on the ipsilesional arm. Movement kinematics were encoded by a vibrotactile feedback interface in two ways: state feedback—an optimal combination of hand position and velocity, and error feedback—the difference between the actual hand position and its instantaneous target. In each session we evaluated the feedback encoding scheme’s immediate objective utility for improving motor performance as well as its perceived usefulness. All three participants improved their stabilization performance using at least one of the feedback encoding schemes within just one experimental session. Two of the participants also improved reaching performance with one or the other of the encoding schemes. Although the observed beneficial effects were modest in each participant, these preliminary findings show that supplemental vibrotactile kinesthetic feedback can be readily interpreted and exploited to improve reaching and object stabilizing actions performed with the contralesional arm after stroke. These short-term training results motivate a longer multisession training study using personalized vibrotactile feedback as a means to improve the accuracy and efficacy of contralesional arm actions after stroke.

Stroke often impairs the control of the contralesional arm, thus most survivors rely on the ipsilesional arm to perform daily living activities that require an efficient control of movements and forces. Whereas the ipsilesional arm is often called ‘unaffected’ or ‘unimpaired’, several studies suggested that during dynamic tasks its kinematics and joint torques are altered. Is stroke also affecting the ability of the ipsilesional arm to produce isometric force, as when pushing or pulling a handle? Here, we address this question by analyzing behavioral performance and muscles’ activity when subjects applied an isometric force of 10 N in eight coplanar directions. We found that stroke affected the ability to apply well-controlled isometric forces with the ipsilesional arm, although to a minor extent compared to the contralesional arm. The spinal maps, the analysis of single muscle activities and the organization of muscle synergies highlighted that this effect was mainly associated with abnormal activity of proximal muscles with respect to matched controls, especially when pushing or pulling in lateral directions.

Background and Objectives: The number of preterm babies is steadily growing world-wide and these neonates are at risk of neuro-motor-cognitive deficits. The observation of spontaneous movements in the first three months of age is known to predict such risk. However, the analysis by specifically trained physiotherapists is not suited for the clinical routine, motivating the development of simple computerized video analysis systems, integrated with a well-structured Biobank to make available for preterm babies a growing service with diagnostic, prognostic and epidemiological purposes. Methods: MIMAS (Markerless Infant Movement Analysis System) is a simple, low-cost system of video analysis of spontaneous movements of newborns in their natural environment, based on a single standard RGB camera, without markers attached to the body. The original videos are transformed into binarized sequences highlighting the silhouette of the baby, in order to minimize the illumination effects and increase the robustness of the analysis; such sequences are then coded by a large set of parameters (39) related to the spatial and spectral changes of the silhouette. The parameter vectors of each baby were stored in the Biobank together with related clinical information. Results: The preliminary test of the system was carried out at the Gaslini Pediatric Hospital in Genoa, where 46 preterm (PT) and 21 full-term (FT) babies (as controls) were recorded at birth (T0) and 8-12 weeks thereafter (T1). A simple statistical analysis of the data showed that the coded parameters are sensitive to the degree of maturation of the newborns (comparing T0 with T1, for both PT and FT babies), and to the conditions at birth (PT vs. FT at T0), whereas this difference tends to vanish at T1. Moreover, the coding method seems also able to detect the few ‘abnormal’ preterm babies in the PT populations that were analyzed as specific case studies. Conclusions: Preliminary results motivate the adoption of this tool in clinical practice allowing for a systematic accumulation of cases in the Biobank, thus for improving the accuracy of data analysis performed by MIMAS and ultimately allowing the adoption of data mining techniques.

The development of an easy to implement, quantitative measure to examine vibration perception would be useful for future application in clinical settings. Vibration sense in the lower limb of younger and older adults was examined using the method of constant stimuli and the two-alternative forced choice paradigm. The focus of this experiment was to determine an appropriate stimulation site on the lower limb (tendon versus bone) to assess vibration threshold and to determine if the left and right legs have varying thresholds. Discrimination thresholds obtained at two stimulation sites in the left and right lower limbs showed differences in vibration threshold across the two ages groups, but not across sides of the body nor between stimulation sites within each limb. Overall, the method of constant stimuli can be implemented simply, reliably, and with minimal time. It can also easily be implemented with low-cost technology. Therefore, it could be a good candidate method to assess the presence of specific deep sensitivity deficits in clinical practice, particularly in populations likely to show the onset of sensory deficits.

The integrity of muscle synergies patterns has been proposed as a physiological marker of cortical damage but how to modify and train muscle synergies to relearn movement is still an open question. Here we present our recent results about the modifications that the forces induced by robots can cause on upper limb muscle synergies after stroke. Our results show that a single exposure to forces provided by a robotic device can impact muscle synergies activation. Moreover, a prolonged robot-aided motor training can promote an enduring longitudinal reorganization of upper limb muscle synergies. Finally, we discuss the application of muscle synergies in neurorehabilitation to both assess the effectiveness of treatments and design novel protocols.

Background: Gait re-education is a primary rehabilitation goal after stroke. In the last decades, robots with different mechanical structures have been extensively used in the clinical practice for gait training of stroke survivors. However, the effectiveness of robotic training is still controversial, especially for chronic subjects. In this study, we investigated the short-term effects of gait training assisted by an endpoint robot in a population of chronic stroke survivors. Methods: Subjects were evaluated before and after training with clinical scales and instrumented gait analysis. Our primary outcome indicator was the walking speed. Next, we investigated the changes in kinetic and kinematic gait patterns as well as the intersegmental coordination at the level of the lower limbs. Results: Most subjects improved their speed in over-ground walking, by modifying the temporal more than the spatial gait parameters. These changes led to an improvement in the ankle power for both sides and to a slight reduction of the inclination of the pelvis during the swing phase, mainly due to a decreased knee flexion and an increased hip extension on the unimpaired leg. Conclusions: These results indicate that the proposed training induced mainly a functional change rather than an improvement of the quality of gait.Implication for RehabilitationGait re-education is a primary goal in stroke rehabilitation.Nowadays several robotic devices for gait rehabilitation are used in the clinical practice, but their effectiveness is controversial, especially for chronic survivors.After a 20-session training with an endpoint robot the chronic stroke survivors showed an improvement in overground gait speed.The increased gait speed was mainly due to functional changes of the temporal parameters and of the kinetic variables at the level of both ankle joints, as well as to a reduction of compensatory strategies observable in the unimpaired side. Gait re-education is a primary goal in stroke rehabilitation. Nowadays several robotic devices for gait rehabilitation are used in the clinical practice, but their effectiveness is controversial, especially for chronic survivors. After a 20-session training with an endpoint robot the chronic stroke survivors showed an improvement in overground gait speed. The increased gait speed was mainly due to functional changes of the temporal parameters and of the kinetic variables at the level of both ankle joints, as well as to a reduction of compensatory strategies observable in the unimpaired side.

The body-machine interfaces (BMIs) map the subjects' movements into the low dimensional control space of external devices to reach assistive and/or rehabilitative goals. This work is a first proof of concept of this kind of BMI as tool for rehabilitation after stroke. We designed an exercise to improve the control of selective movements of the pelvis in stroke survivors, increasing the ability to decouple the motion in the sagittal and frontal planes and decreasing compensatory adjustments at the shoulder girdle. A Kinect sensor recorded the movements of the subjects. Subjects played different games by controlling the vertical and horizontal motion of a cursor on a screen with respectively the lateral tilt and the ante/retroversion of their pelvis. We monitored also the degrees of freedom not directly involved in cursor control, thus subjects could complete the task only with a correct posture. Our preliminary results highlight significant improvement not only in cursor control, but also in the Trunk Impairment Scale (TIS) and in the Five Times Sit to Stand Test (5xSST).

This paper presents a pilot, proof-of-concept study of robot arm therapy (RT) with a treatment protocol specifically designed for severe hemiparetic patients and integrated with a suitable performance measurement protocol. The robot is a planar haptic manipulandum, with low inertia, low friction and impedance control. The task is reaching, with targets arranged in the horizontal plane, in such a way to induce full extension of the arm. Targets are represented haptically, by means of an attractive force field applied by the manipulandum, and visually, by means of circles on a computer screen. The force field is smoothly activated until it reaches a preset intensity that is maintained until the target is reached. Such level of assistance is selected initially as the minimum level that allows each patient to fulfill the task. In each training session, two blocks of trials are alternated (with open and closed eyes, respectively). In the course of training, the level of assistance is reduced as performance improves. Functional recovery is evaluated by processing the kinematic measurements in order to express in quantitative terms the smoothness of the targeting movements. In particular, we defined four performance indicators or outcome measures: (1) the mean speed of the movements; (2) the number of sub-movements in which reaching is decomposed, (3) the remaining error after the first sub-movement, (4) the relative time of the first sub-movement with respect to the total reaching time. For these indicators we identified a measurement scale from the performance of a population of normal subjects performing the same task. The statistical analysis of the responses shows that the proposed protocol is capable to induce significant improvements in all the patients and the performance indicators are sufficiently stable to be chosen as candidates of future adaptive RT protocols in which the training and measurement protocols are designed in an integrated way.

Objective: To carry out a proof of concept study for integrating robot therapy with physiotherapy in the treatment of stroke patients. Design: A simple and `gentle' paradigm of robot—patient interaction was designed in order to foster the re-emergence of smooth, active control patterns in coordinated shoulder/elbow reaching movements. A haptic robot was programmed according to a strategy of minimal, progressively reduced assistance, with a double representation of targets: (i) visual (circles on a screen) and (ii) haptic (robot-generated force fields). The protocol included trials with and without vision, in order to emphasize the role of proprioceptive feedback. The training paradigm included 10 sessions and more than 5000 movements. Subjects: Ten chronic, hemiparetic subjects; four controls provided reference values for the performance measurements. Outcome measures: Four performance indicators (derived from the analysis of the reaching trajectories); clinical/functional measures (Fugl-Meyer and Ashworth scales). Results: After robot therapy reaching movements became faster and smoother. The performance in the no-vision trials was at least as good as in the vision trials. The Fugl-Meyer arm scores also increased significantly and remained approximately constant at follow-up; the Ashworth scores did not change. Conclusion: In spite of its simplicity, a limited number of `gentle' robot therapy sessions appear to be beneficial, even for severely impaired patients, although no firm conclusion can be drawn at this point. However, the study provides support material for the careful design of controlled clinical trials and for a better integration with physiotherapy.

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.

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.

Gait re-education is a primary rehabilitation goal after stroke. In this study, we used instrumented gait analysis for evaluating the outcomes of gait training assisted by an endpoint robot in a population of six chronic stroke survivors. The preliminary results, based on spatial-temporal and kinematic analysis, suggest that (a) self-placed walking speed increases, with an improvement of both length and duration of the stride, (b) balance increases during standing and walking, (c) the non-affected side becomes less involved in attempting to correct for the deficiencies of the affected side, thus reducing the importance of compensatory strategies.

Stroke survivors strongly rely on visual feedback to control their movements, since segmental reflexes are characterized by an inherent hyper-excitability. To test the effect of visual feedback on the modulation of arm stability we estimated the stiffness of the paretic arm in nine stroke survivors during robot mediated therapy, where subjects trained with and without vision. While several studies found a negligible effect in unimpaired individuals, our results highlighted a marked reduction of stroke survivors' arm stiffness in absence of visual feedback.

Spasticity and muscular hypertonus are frequently found in stroke survivors and may have a significant effect on functional impairment. These abnormal neuro-muscular properties, which are quantifiable by the net impedance of the hand, have a direct consequence on arm mechanics and are likely to produce anomalous motor paths. Literature studies quantifying limb impedance in stroke survivors have focused on multijoint static tasks and single joint movements. Despite this research, little is known about the role of sensory motor integration in post-stroke impedance modulation. The present study elucidates this role by integrating an evaluation of arm impedance into a robotically mediated therapy protocol. Our analysis had three specific objectives: 1) obtaining a reliable measure for the mechanical proprieties of the upper limb during robotic therapy; 2) investigating the effects of robot-assisted training and visual feedback on arm stiffness and viscosity; 3) determining if the stiffness measure and its relationship with either training or visual feedback depend on arm position, speed, and level of assistance. This work demonstrates that the performance improvements produced by minimally assistive robot training are associated with decreased viscosity and stiffness in stroke survivors' paretic arm and that these mechanical impedance components are partially modulated by visual feedback.

Background Although 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. Methods The 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. Results The 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. Conclusions The 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.

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.

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 patient's performance. Formal clinical trials should address this point.

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.

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.

Robot therapy seems promising with stroke survivors, but it is unclear which exercises are most effective, and whether other pathologies may benefit from this technique. In general, exercises should exploit the adaptive nature of the nervous system, even in chronic patients. Ideally, exercise should involve multiple sensory modalities and, to promote active subject participation, the level of assistance should be kept to a minimum. Moreover, exercises should be tailored to the different degrees of impairment, and should adapt to changing performance. To this end, we designed three tasks: (i) a hitting task, aimed at improving the ability to perform extension movements; (ii) a tracking task, aimed at improving visuo-motor control; and (iii) a bimanual task, aimed at fostering inter-limb coordination. All exercises are conducted on a planar manipulandum with two degrees of freedom, and involve alternating blocks of exercises performed with and without vision. The degree of assistance is kept to a minimum, and adjusted to the changing subject's performance. All three exercises were tested on chronic stroke survivors with different levels of impairment. During the course of each exercise, movements became faster, smoother, more precise, and required decreasing levels of assistive force. These results point to the potential benefit of that assist-as-needed training with a proprioceptive component in a variety of clinical conditions.

This paper presents the design, and performance of a high fidelity three degree-of-freedom wrist exoskeleton robot, for neuroscience study, training and rehabilitation. The IIT-Wrist is intended to provide kinesthetic feedback during the training of motor skills or rehabilitation of reaching movements. Motivation for such applications is based on findings that show robot-assisted physical therapy aids in the rehabilitation process following neurological injuriesIn the present paper the IIT-Wrist haptic robot is described in terms of kinematics and haptics features to meet specific requirements for a safety human.machine interaction. In relation with a feasibility study in the field of robot therapy a preliminary training of stroke patient was perfrormed. The task consisted in tracking a target using one degree of freedom at time: Flexion/Extension, Adduction/Abduction, Pronation/Supination separately. The target motion is harmonic and tracking is aided by a suitable force field. The preliminary study with three patients shows the stability and the efficacy of the control scheme.

Background In the last two decades robot training in neuromotor rehabilitation was mainly focused on shoulder-elbow movements. Few devices were designed and clinically tested for training coordinated movements of the wrist, which are crucial for achieving even the basic level of motor competence that is necessary for carrying out ADLs (activities of daily life). Moreover, most systems of robot therapy use point-to-point reaching movements which tend to emphasize the pathological tendency of stroke patients to break down goal-directed movements into a number of jerky sub-movements. For this reason we designed a wrist robot with a range of motion comparable to that of normal subjects and implemented a self-adapting training protocol for tracking smoothly moving targets in order to facilitate the emergence of smoothness in the motor control patterns and maximize the recovery of the normal RoM (range of motion) of the different DoFs (degrees of Freedom). Methods The IIT-wrist robot is a 3 DoFs light exoskeleton device, with direct-drive of each DoF and a human-like range of motion for Flexion/Extension (FE), Abduction/Adduction (AA) and Pronation/Supination (PS). Subjects were asked to track a variable-frequency oscillating target using only one wrist DoF at time, in such a way to carry out a progressive splinting therapy. The RoM of each DoF was angularly scanned in a staircase-like fashion, from the "easier" to the "more difficult" angular position. An Adaptive Controller evaluated online performance parameters and modulated both the assistance and the difficulty of the task in order to facilitate smoother and more precise motor command patterns. Results Three stroke subjects volunteered to participate in a preliminary test session aimed at verify the acceptability of the device and the feasibility of the designed protocol. All of them were able to perform the required task. The wrist active RoM of motion was evaluated for each patient at the beginning and at the end of the test therapy session and the results suggest a positive trend. Conclusion The positive outcomes of the preliminary tests motivate the planning of a clinical trial and provide experimental evidence for defining appropriate inclusion/exclusion criteria.