Adaptation of eye and hand movements to target displacements of different size

Previous work has documented that the direction of eye and hand movements can be adaptively modified using the double-step paradigm. Here we report that both motor systems adapt not only to small direction steps (5° gaze angle) but also to large ones (28° gaze angle). However, the magnitude of adaptation did not increase with step size, and the relative magnitude of adaptation therefore decreased from 67% with small steps to 15% with large steps. This decreasing efficiency of adaptation may reflect the participation of directionally selective neural circuits in double-step adaptation

Path control: a method for patient-cooperative robot-aided gait rehabilitation

Gait rehabilitation robots are of increasing importance in neurorehabilitation. Conventional devices are often criticized because they are limited to reproducing predefined movement patterns. Research on patient-cooperative control strategies aims at improving robotic behavior. Robots should support patients only as much as needed and stimulate them to produce maximal voluntary efforts. This paper presents a patient-cooperative strategy that allows patients to influence the timing of their leg movements along a physiologically meaningful path. In this "path control" strategy, compliant virtual walls keep the patient's legs within a "tunnel" around the desired spatial path. Additional supportive torques enable patients to move along the path with reduced effort. Graphical feedback provides visual training instructions. The path control strategy was evaluated with 10 healthy subjects and 15 subjects with incomplete spinal cord injury. The spatio-temporal characteristics of recorded kinematic data showed that subjects walked with larger temporal variability with the new strategy. Electromyographic data indicated that subjects were training more actively. A majority of iSCI subjects was able to actively control their gait timing. Thus, the strategy allows patients to train walking while being helped rather than controlled by the robot

A bio-inspired robotic test bench for repeatable and safe testing of rehabilitation robots

The development of new algorithms for controlling rehabilitation robots requires iterative testing prior experimentation with humans. Experiments in humans-especially in humans with physical impairments-pose several challenges regarding safety and repeatability of the testing conditions. To address this problem we propose the use of a test bench that uses a bio-inspired model of a human leg implemented on the leg orthosis of a robotic gait trainer. The model consists of a feedback controller, used to simulate muscle-Tendon visco-elastic properties and spinal reflexes, and a feedforward stage simulating motor commands from higher brain centers. Abnormal limb neuro-mechanics, such as weakness or spastic-like behavior can then be simulated and tested against newly developed robotic algorithms. In this study, such bio-inspired robotic test bench was used to evaluate the performance of an algorithm for the assessment of the walking function (RAGA, Robot-Aided Gait Assessment). We hypothesized that the RAGA software is able to identify the level of simulated impairment and to localize in which phase of the gait cycle the impairment is more evident. Therefore, we simulated different levels and types of impairments at three walking speeds and evaluated the outcome measures of the RAGA algorithm. We could confirm that the RAGA was able to identify different levels of simulated impairment correctly and to provide useful insights into gait dynamics. Moreover, we determined how increasing walking speeds can cause a positive offset in the outcome measures. We believe that this test bench represents a very useful and versatile tool that can be applied for testing novel training and assessment strategies implemented in rehabilitation robots

Technology of the robotic gait orthosis Lokomat

Rehabilitation robots allow for a longer and more intensive locomotor training than that achieved by conventional therapies. Robot-assisted treadmill training also offers the ability to provide objective feedback within one training session and to monitor functional improvements over time. This article provides an overview of the technical approach for one of these systems known as “Lokomat” including new features such as hip ab/adduction actuation, cooperative control strategies, assessment tools, and augmented feedback. These special technical functions may be capable of further enhancing training quality, training intensity, and patient participation

Locomotor training in subjects with sensori-motor deficits: An overview of the robotic gait orthosis lokomat

It is known that improvement in walking function can be achieved in patients suffering a movement disorder after stroke or spinal cord injury by providing intensive locomotor training. Rehabilitation robots allow for a longer and more intensive training than that achieved by conventional therapies. Robot assisted treadmill training also offers the ability to provide objective feedback within one training session and to monitor functional improvements over time. This article provides an overview of the technical features and reports the clinical data available for one of these systems known as "Lokomat". First, background information is given for the neural mechanisms of gait recovery. The basic technical approach of the Lokomat system is then described. Furthermore, new features are introduced including cooperative control strategies, assessment tools and augmented feedback. These features may be capable of further enhancing training intensity and patient participation. Findings from clinical studies are presented covering the feasibility as well as efficacy of Lokomat assisted treadmill training

Rightward Biases during Bimanual Reaching

Two experiments were carried out to investigate whether attention is biased toward the right hand of right handers during bimanual coordination (Peters 1981). A novel discontinuous double-step reaching task was developed, where right-handed participants executed a bimanual reach followed by a left or right hand unimanual reach. Asymmetries in the downtime between the bimanual and unimanual reach portions (the refractory period) were used to infer the direction of attention. A shorter right hand refractory period was found in the first experiment, indicating a rightward bias in attention. In a second experiment, shifting the focus of attention during the bimanual portion of the reach altered the direction and magnitude of the asymmetry in a way consistent with the attentional bias hypothesis. The role of attention during bimanual reaching, and a further programme of experimental work aimed at clarifying the nature of these rightward biases during discrete bimanual coordination is discussed