769 research outputs found
Tactile-STAR: A Novel Tactile STimulator And Recorder System for Evaluating and Improving Tactile Perception
Many neurological diseases impair the motor and somatosensory systems. While several different technologies are used in clinical practice to assess and improve motor functions, somatosensation is evaluated subjectively with qualitative clinical scales. Treatment of somatosensory deficits has received limited attention. To bridge the gap between the assessment and training of motor vs. somatosensory abilities, we designed, developed, and tested a novel, low-cost, two-component (bimanual) mechatronic system targeting tactile somatosensation: the Tactile-STAR—a tactile stimulator and recorder. The stimulator is an actuated pantograph structure driven by two servomotors, with an end-effector covered by a rubber material that can apply two different types of skin stimulation: brush and stretch. The stimulator has a modular design, and can be used to test the tactile perception in different parts of the body such as the hand, arm, leg, big toe, etc. The recorder is a passive pantograph that can measure hand motion using two potentiometers. The recorder can serve multiple purposes: participants can move its handle to match the direction and amplitude of the tactile stimulator, or they can use it as a master manipulator to control the tactile stimulator as a slave. Our ultimate goal is to assess and affect tactile acuity and somatosensory deficits. To demonstrate the feasibility of our novel system, we tested the Tactile-STAR with 16 healthy individuals and with three stroke survivors using the skin-brush stimulation. We verified that the system enables the mapping of tactile perception on the hand in both populations. We also tested the extent to which 30 min of training in healthy individuals led to an improvement of tactile perception. The results provide a first demonstration of the ability of this new system to characterize tactile perception in healthy individuals, as well as a quantification of the magnitude and pattern of tactile impairment in a small cohort of stroke survivors. The finding that short-term training with Tactile-STARcan improve the acuity of tactile perception in healthy individuals suggests that Tactile-STAR may have utility as a therapeutic intervention for somatosensory deficits
A robot-aided visuomotor wrist training induces gains in proprioceptive and movement accuracy in the contralateral wrist
Proprioceptive training is a neurorehabilitation approach known to improve proprioceptive acuity and motor performance of a joint/limb system. Here, we examined if such learning transfers to the contralateral joints. Using a robotic exoskeleton, 15 healthy, right-handed adults (18-35 years) trained a visuomotor task that required making increasingly small wrist movements challenging proprioceptive function. Wrist position sense just-noticeable-difference thresholds (JND) and spatial movement accuracy error (MAE) in a wrist-pointing task that was not trained were assessed before and immediately as well as 24 h after training. The main results are: first, training reduced JND thresholds (- 27%) and MAE (- 33%) in the trained right wrist. Sensory and motor gains were observable 24 h after training. Second, in the untrained left wrist, mean JND significantly decreased (- 32%) at posttest. However, at retention the effect was no longer significant. Third, motor error at the untrained wrist declined slowly. Gains were not significant at posttest, but MAE was significantly reduced (- 27%) at retention. This study provides first evidence that proprioceptive-focused visuomotor training can induce proprioceptive and motor gains not only in the trained joint but also in the contralateral, homologous joint. We discuss the possible neurophysiological mechanism behind such sensorimotor transfer and its implications for neurorehabilitation
Coupling Robot-aided assessment and surface electromyography to evaluate wrist and forearm muscles activity, muscle fatigue and its effect on proprioception
Sensorimotor functions and an intact neural control of muscles are essential for the effective
execution of movements during daily living tasks. However, despite the ability of human
sensorimotor system to cope with a great diversity of internal and external demands and
constraints, these mechanisms can be altered as a consequence of neurological disorders,
injuries or just due to excessive effort leading to muscle fatigue.
A precise assessment of both motor and sensory impairment is thus needed in order to provide
useful cues to monitor the progression of the disease in pathological populations or to prevent
injuries in case of workers.
In particular, considering muscle fatigue, an objective assessment of its manifestation may
be crucial when dealing with subjects with neuromuscular disorders for understanding how
specific disease features evolve over time or for testing the efficacy of a potential therapeutic
strategy. Indeed, muscle fatigue accounts for a significant portion of the disease burden in
populations with neuromuscular diseases but, despite its importance, a standardized, reliable
and objective method for fatigue measurement is lacking in clinical practice. The work
presented in this thesis investigates a practical solution through the use of a robotic task and
parameters extracted by surface electromyography signals.
Moreover, a similar approach that combines robot-mediated proprioception test and muscle
fatigue assessment has been developed and used in this thesis to objectively investigate the
influence of muscle fatigue on position sense.
Finally, the effect of posture on muscle activity, from a perspective of injuries prevention,
has been examined. Data on adults and children have been collected and quantitative and
objective information about muscle activity, muscle fatigue and joint sensitivity were obtained
gaining useful insight both in the clinical context and in the prevention of workplace injuries.
A novel method to assess muscle fatigue has been proposed together with the definition of an
easy readable indicator that can help clinicians in the assessment of the patient. As for the
impact of fatigue on the sensorimotor system, results obtained showed a decrease in wrist
proprioceptive acuity which led also to a decline in the performance of a simple tracing task. Regarding the adoption of different muscle strategies depending on postures, results showed
that muscle activity of forearm muscles was overall similar regardless from the postures
Consolidation of human somatosensory memory during motor learning
Abstract Sensorimotor learning is a bidirectional process associated with concurrent neuroplastic changes in the motor and somatosensory system. While motor memory consolidation and retention have been extensively studied during skill acquisition, little is known about the formation and consolidation of somatosensory memory associated with motor learning. Using a robotic exoskeleton, we tracked markers of somatosensory and motor learning while healthy participants trained to make goal-directed wrist reaching movements over five days and evaluated retention for up to 10 days after practice. Markers of somatosensory learning were changes in wrist position sense bias (systematic error) and precision (random error). The main results are as follows: First, somatosensory (proprioceptive) memory consolidation shows signs of cost savings with repeated sensorimotor training – the same feature is known for motor memory formation. Moreover, somatosensory learning generalized to untrained workspace. Second, somatosensory learning over days can be characterized as an early improvement in sensory precision and a later improvement in sensory bias. Third, the time course of learning gains in position sense acuity coincided with improvements in spatial movement accuracy. Finally, the gains of somatosensory learning were retained for several days. Improvements in position sense bias were still visible up to 3 days after the end of practice for the trained workspace positions, but decayed faster in the untrained workspace. Improvements in position sense precision were retained for up to 10 days and were workspace independent. The findings are consistent with the view that an internal model of somatosensory joint space is formed during motor learning
proprioceptive identification of joint position versus kinaesthetic movement reproduction
Abstract Regarding our voluntary control of movement, if identification of joint position, that is independent of the starting condition, is stronger than kinaesthetic movement reproduction, that implies knowledge of the starting position and movement's length for accuracy, is still a matter of debate in motor control theories and neuroscience. In the present study, we examined the mechanisms that individuals seem to prefer/adopt when they locate spatial positions and code the amplitude of movements. We implemented a joint position matching task on a wrist robotic device: this task consists in replicating (i.e. matching) a reference joint angle in the absence of vision and the proprioceptive acuity is given by the goodness of such matching. Two experiments were carried out by implementing two different versions of the task and performed by two groups of 15 healthy participants. In the first experiment, blindfolded subjects were asked to perform matching movements towards a fixed target position, experienced with passive movements that started from different positions and had different lengths. In the second experiment, blindfolded subjects were requested to accurately match target positions that had a different location in space but were passively shown through movements of the same length. We found a clear evidence for higher performances in terms of accuracy ( 0.42 ± 0.01 1 / ° ) and precision ( 0.43 ± 0.01 1 / ° ) in the first experiment, therefore in case of matching positions, rather than in the second where accuracy and precision were lower ( 0.36 ± 0.01 1 / ° and 0.35 ± 0.01 1 / ° respectively). These results suggested a preference for proprioceptive identification of joint position rather than kinaesthetic movement reproduction
Robot-aided assessment of wrist proprioception
Introduction: Impaired proprioception severely affects the control of gross and fine motor function. However, clinical assessment of proprioceptive deficits and its impact on motor function has been difficult to elucidate. Recent advances in haptic robotic interfaces designed for sensorimotor rehabilitation enabled the use of such devices for the assessment of proprioceptive function. Purpose: This study evaluated the feasibility of a wrist robot system to determine proprioceptive discrimination thresholds for two different DoFs of the wrist. Specifically, we sought to accomplish three aims: first, to establish data validity; second, to show that the system is sensitive to detect small differences in acuity; third, to establish test–retest reliability over repeated testing. Methodology: Eleven healthy adult subjects experienced two passive wrist movements and had to verbally indicate which movement had the larger amplitude. Based on a subject’s response data, a psychometric function was fitted and the wrist acuity threshold was established at the 75% correct response level. A subset of five subjects repeated the experimentation three times (T1, T2, and T3) to determine the test–retest reliability. Results: Mean threshold for wrist flexion was 2.15° ± 0.43° and 1.52° ± 0.36° for abduction. Encoder resolutions were 0.0075° (flexion–extension) and 0.0032° (abduction–adduction). Motor resolutions were 0.2°(flexion–extension) and 0.3° (abduction–adduction). Reliability coefficients were rT2-T1 = 0.986 and rT3-T2 = 0.971. Conclusion: We currently lack established norm data on the proprioceptive acuity of the wrist to establish direct validity. However, the magnitude of our reported thresholds is physiological, plausible, and well in line with available threshold data obtained at the elbow joint. Moreover, system has high resolution and is sensitive enough to detect small differences in acuity. Finally, the system produces reliable data over repeated testing
Understanding motor control in humans to improve rehabilitation robots
Recent reviews highlighted the limited results of robotic rehabilitation and the low quality of evidences in this field. Despite the worldwide presence of several robotic infrastructures, there is still a lack of knowledge about the capabilities of robotic training effect on the neural control of movement. To fill this gap, a step back to motor neuroscience is needed: the understanding how the brain works in the generation of movements, how it adapts to changes and how it acquires new motor skills is fundamental. This is the rationale behind my PhD project and the contents of this thesis: all the studies included in fact examined changes in motor control due to different destabilizing conditions, ranging from external perturbations, to self-generated disturbances, to pathological conditions. Data on healthy and impaired adults have been collected and quantitative and objective information about kinematics, dynamics, performance and learning were obtained for the investigation of motor control and skill learning. Results on subjects with cervical dystonia show how important assessment is: possibly adequate treatments are missing because the physiological and pathological mechanisms underlying sensorimotor control are not routinely addressed in clinical practice. These results showed how sensory function is crucial for motor control. The relevance of proprioception in motor control and learning is evident also in a second study. This study, performed on healthy subjects, showed that stiffness control is associated with worse robustness to external perturbations and worse learning, which can be attributed to the lower sensitiveness while moving or co-activating. On the other hand, we found that the combination of higher reliance on proprioception with \u201cdisturbance training\u201d is able to lead to a better learning and better robustness. This is in line with recent findings showing that variability may facilitate learning and thus can be exploited for sensorimotor recovery. Based on these results, in a third study, we asked participants to use the more robust and efficient strategy in order to investigate the control policies used to reject disturbances. We found that control is non-linear and we associated this non-linearity with intermittent control. As the name says, intermittent control is characterized by open loop intervals, in which movements are not actively controlled. We exploited the intermittent control paradigm for other two modeling studies. In these studies we have shown how robust is this model, evaluating it in two complex situations, the coordination of two joints for postural balance and the coordination of two different balancing tasks. It is an intriguing issue, to be addressed in future studies, to consider how learning affects intermittency and how this can be exploited to enhance learning or recovery. The approach, that can exploit the results of this thesis, is the computational neurorehabilitation, which mathematically models the mechanisms underlying the rehabilitation process, with the aim of optimizing the individual treatment of patients. Integrating models of sensorimotor control during robotic neurorehabilitation, might lead to robots that are fully adaptable to the level of impairment of the patient and able to change their behavior accordingly to the patient\u2019s intention. This is one of the goals for the development of rehabilitation robotics and in particular of Wristbot, our robot for wrist rehabilitation: combining proper assessment and training protocols, based on motor control paradigms, will maximize robotic rehabilitation effects
Comparison of Upper Limb Proprioception in Chronic Mechanical Neck Pain Patients with Age-Sex Matched Healthy Normals
Purpose: Primarily to compare the Upper Limb Proprioception in Chronic Mechanical Neck Pain Patients to Age - Sex Matched Normals.
Method: 30 women, 19- 30 years of age were assessed via a digital inclinometer for repositioning error for shoulder, elbow and wrist joints.
Results: It was found that there was a difference in upper Limb Proprioception in Chronic Mechanical Neck Pain patients as compared to age sex matched normal individuals. Conclusion: On comparison, individuals with Chronic Mechanical Neck Pain had a statistically significant difference in the shoulder and wrist proprioception as compared to age matched Normals
Investigating the Effects of Subclinical Neck Pain, Cervical Treatment, and Neck Muscle Fatigue on Wrist Joint Position Sense
The purpose of this work was to evaluate the effects of neck pain, cervical treatment, and neck muscle fatigue on joint position sense of the wrist. 12 healthy participants and 12 participants with chronic subclinical neck pain were recruited. Participants took part in two sessions, separated by 48 hours. On the first day, participants preformed two wrist proprioception sessions using a haptic robotic device separated by an isometric cervical extensor fatigue protocol. On the second day participants performed an additional two proprioception sessions, this time separated either by a neck treatment (pain group) or 20 minutes of rest (control group). Each session consisted of 12 trials; 6 in wrist flexion and 6 in wrist extension. Matching error, error bias and variability were measured for each trial. Kinematic data for each trial was recorded from the robotic device and analyzed. Results showed significantly higher error scores for the pain group when compared to the control group at baseline (p=<0.05). Joint position error scores increased significantly in the control group after the fatigue protocol (p= <0.05). Error scores for the pain group decreased significantly after a single treatment session (p= <0.05). This study confirms that altered afferent input from the neck (due to pain and/or fatigue) can influence wrist joint position sense (JPS). Furthermore, the results suggest that a single treatment can improve wrist JPS accuracy
Does visual experience influence arm proprioception and its lateralization? Evidence from passive matching performance in congenitally-blind and sighted adults
In humans, body segments' position and movement can be estimated from
multiple senses such as vision and proprioception. It has been suggested that
vision and proprioception can influence each other and that upper-limb
proprioception is asymmetrical, with proprioception of the non-dominant arm
being more accurate and/or precise than proprioception of the dominant arm.
However, the mechanisms underlying the lateralization of proprioceptive
perception are not yet understood. Here we tested the hypothesis that early
visual experience influences the lateralization of arm proprioceptive
perception by comparing 8 congenitally-blind and 8 matched, sighted
right-handed adults. Their proprioceptive perception was assessed at the elbow
and wrist joints of both arms using an ipsilateral passive matching task.
Results support and extend the view that proprioceptive precision is better at
the non-dominant arm for blindfolded sighted individuals. While this finding
was rather systematic across sighted individuals, proprioceptive precision of
congenitally-blind individuals was not lateralized as systematically,
suggesting that lack of visual experience during ontogenesis influences the
lateralization of arm proprioception
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