sharon israely - Academia.edu (original) (raw)

Papers by sharon israely

Background/aim: Patients with stroke who are suffering from impaired reaching movement experience... more Background/aim: Patients with stroke who are suffering from impaired reaching movement experience insufficient spatial and temporal coordination, affecting upper limb functions and everyday life tasks. This study examines a new robot-assisted rehabilitation method for ameliorating arm reaching movements through velocity error enhancement training. The authors hypothesised that this robot-assisted rehabilitation training may encourage restoration of arm reaching abilities among poststroke hemiparesis patients. Methods: Several clinical and kinematic measures were used to evaluate outcomes. Subjects were assigned either to an experimental group that underwent 5-week treatments with error enhanced forces, or to a control group that received passive treatment. The control group undertook reaching tasks over the same period while they were connected to the robot but without it applying any error enhancement forces to their upper limb. The robotic system was programmed based on previous k...

Participants executed hand-reaching movements for 9 different target directions while monitored b... more Participants executed hand-reaching movements for 9 different target directions while monitored by surface EMG device, containing 8 electrodes that were attached to 8 muscles of the shoulder and arm. The direction of the targets were constant between different participants. The folder contains two subfolders, one of healthy individuals and the other of post-stroke individuals. Inside these folders there are 12 folders (Healthy) or 13 folders (post-stroke), each of which corresponds with individual. Each individual's dataset composed of 8 files of Maximum Voluntary Contraction (MVC) of muscles, and 9 or 6 "Target_XXX" files refer of hand-reaching movments for different directions. Each "Target" file contains signals of all the 8 muscles that were also measured by the MVC measurement. Target directions were similar for all individuals from both groups.

Advances in Experimental Medicine and Biology, 2020

Movement synergies, muscle co-contraction, and decreased motor drive to muscle agonists were sugg... more Movement synergies, muscle co-contraction, and decreased motor drive to muscle agonists were suggested to be major factors in motor impairments after stroke. The purpose of this study was to investigate the major muscle mechanisms contributing to motor impairment after stroke. Twelve healthy and 13 post-stroke patients participated in this observational study. Both groups participated in a single experimental session, performing hand pointing movements in multiple directions, during which EMG was assessed. Additionally, the patients underwent the Fugl-Meyer assessment. A set of features from the electromyography (EMG) signal and co-contraction ratios were used to compare the capacity to modulate the muscle activity between the two groups of participants. A correlation analysis was applied between the Euclidian distances of each target and the Fugl-Meyer scoring assessment in the post-stroke patients. We found that impaired modulation of muscle activity in post-stroke patients was characterized by significantly increased Euclidian distances between the EMG features of different target directions and by a higher variability between muscle activation compared to healthy subjects. Impaired capacity to modulate muscle activity significantly correlated with the impairment status. In conclusion, impaired motor performance post-stroke systematic disturbance in the control signal to limb muscles, which manifests as decreased capacity to modulate muscle activity, rather than co-contraction of muscle antagonists or stereotyped movement patterns.

Reviews in the Neurosciences, 2019

Individuals post-stroke sustain motor deficits years after the stroke. Despite recent advancement... more Individuals post-stroke sustain motor deficits years after the stroke. Despite recent advancements in the applications of non-invasive brain stimulation techniques and Deep Brain Stimulation in humans, there is a lack of evidence supporting their use for rehabilitation after brain lesions. Non-invasive brain stimulation is already in use for treating motor deficits in individuals with Parkinson’s disease and post-stroke. Deep Brain Stimulation has become an established treatment for individuals with movement disorders, such as Parkinson’s disease, essential tremor, epilepsy, cerebral palsy and dystonia. It has also been utilized for the treatment of Tourette’s syndrome, Alzheimer’s disease and neuropsychiatric conditions such as obsessive-compulsive disorder, major depression and anorexia nervosa. There exists growing scientific knowledge from animal studies supporting the use of Deep Brain Stimulation to enhance motor recovery after brain damage. Nevertheless, these results are cur...

Frontiers in computational neuroscience, 2018

A muscle synergies model was suggested to represent a simplifying motor control mechanism by the ... more A muscle synergies model was suggested to represent a simplifying motor control mechanism by the brainstem and spinal cord. The aim of the study was to investigate the feasibility of such control mechanisms in the rehabilitation of post-stroke individuals during the execution of hand-reaching movements in multiple directions, compared to non-stroke individuals. Twelve non-stroke and 13 post-stroke individuals participated in the study. Muscle synergies were extracted from EMG data that was recorded during hand reaching tasks, using the NMF algorithm. The optimal number of synergies was evaluated in both groups using the Variance Accounted For (VAF) and the Mean Squared Error (MSE). A cross validation procedure was carried out to define a representative set of synergies. The similarity index and the K-means algorithm were applied to validate the existence of such a set of synergies, but also to compare the modulation properties of synergies for different movement directions between g...

Advances in experimental medicine and biology, Jan 22, 2018

The purpose of this study was to investigate whether adaptive responses to error-augmentation for... more The purpose of this study was to investigate whether adaptive responses to error-augmentation force fields, would decrease the trajectory errors in hand-reaching movements in multiple directions in healthy individuals. The study was conducted, as a randomized controlled trial, in 41 healthy subjects. The study group trained on a 3D robotic system, applying error-augmenting forces on the hand during the execution of tasks. The control group carried out the same protocol in null-field conditions. A mixed-model ANOVA was implemented to investigate the interaction between groups and time, and changes in outcome measures within groups. The findings were that there was a significant interaction effect for group × time in terms of the magnitude of movement errors across game-sets. The trajectory error of the study group significantly decreased from 0.035 ± 0.013 m at baseline to 0.029 ± 0.011 m at a follow-up, which amounted to a 14.8% improvement. The degree of movement errors were not si...

IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society, Dec 1, 2017

Functional tasks of the upper extremity can be executed by a variety of muscular patterns, indepe... more Functional tasks of the upper extremity can be executed by a variety of muscular patterns, independent of the direction, speed and load of the task. This large number of degrees of freedom imposes a significant control burden on the CNS. Previous studies suggested that the human cortex synchronizes a discrete number of neural functional units within the brainstem and spinal cord, i.e. muscle synergies, by linearly combining them to execute a great repertoire of movements. Further exploring this control mechanism, we aim to study whether a single set of muscle synergies might be generalized to express movements in different directions. This was implemented by using a modified version of the non-negative matrix factorization algorithm on EMG data sets of the upper extremity of healthy people. Our twelve participants executed hand-reaching movements in multiple directions. Muscle synergies that were extracted from movements to the center of the reaching space could be generalized to sy...

Reviews in the neurosciences, Jan 5, 2018

Muscle synergies are proposed to function as motor primitives that are modulated by frontal brain... more Muscle synergies are proposed to function as motor primitives that are modulated by frontal brain areas to construct a large repertoire of movement. This paper reviews the history of the development of our current theoretical understanding of nervous system-based motor control mechanisms and more specifically the concept of muscle synergies. Computational models of muscle synergies, especially the nonnegative matrix factorization algorithm, are discussed with specific reference to the changes in synergy control post-central nervous system (CNS) lesions. An alternative approach for motor control is suggested, exploiting a combination of synergies control or flexible muscle control used for gross motor skills and for individualized finger movements. Rehabilitation approaches, either supporting or inhibiting the use of basic movement patterns, are discussed in the context of muscle synergies. Applications are discussed for the use of advanced technologies that can promote the recovery ...

Topics in Stroke Rehabilitation, 2016

Background: Evidence-based studies regarding deficits in handwriting performance relative to hand... more Background: Evidence-based studies regarding deficits in handwriting performance relative to hand reaching and grasping after a stroke are lacking. Objective: To evaluate the extent of damage to handwriting skills compared to arm reach and grasp task among post-stroke patients. Methods: Eighteen patients and 19 healthy subjects were recruited to this case-control study. Patients were evaluated 15.2 days (±6.5) after the stroke using a Computerized Penmanship Evaluation Tool, surface Electromyography and Fugl-Meyer assessment. This study compared motor deficits in hand reaching and grasping and in handwriting between stroke patients and healthy subjects. Damage to handwriting performance relative to hand reaching and grasping skills was also evaluated. Results: Significant differences were found between groups in handwriting performance (p < 0.05). The performance of the trapezius, biceps, and triceps muscles can predict 63.5% of the variance in the ability to write a short sentence (p < 0.023). Pen pressure can predict 74.9% of the hand motor performance from Fugl-Meyer assessment (p < 0.05). Handwriting was more damaged than was the pattern of activation of the proximal muscles of the shoulder and arm (p < 0.05). FM scores were highly, negatively correlated with the in-air writing time across tasks (r = −0.819, p < 0.004). Conclusions: This study confirms the clinical observation that dexterity skills are more damaged than are arm forward reach after a stroke. However, these differences in motor performance were not significant in mildly disabled patients, demonstrating the feasibility of handwriting rehabilitation in these patients. Therefore, we modestly recommend focusing on handwriting rehabilitation of the hemiparetic upper extremity in mildly impaired patients after a stroke.

Topics in Stroke Rehabilitation, 2016

Background: Improvement of motor performance is crucial in rehabilitation after a stroke. A new c... more Background: Improvement of motor performance is crucial in rehabilitation after a stroke. A new concept in motor learning and rehabilitation is error augmentation (EA): using erroneous sensory feedback to enhance adaptation to a new environment. However, the clinical efficacy of this method to enhance motor learning after a stroke needs to be evaluated. Objectives: To determine whether there is enough evidence-based knowledge to justify using the EA concept for upper extremity rehabilitation after a stroke over traditional rehabilitation methods. Methods: Two reviewers systematically searched the English-language literature in six databases: PubMed, Web of science, PEDro, CINAHL, Cochrane, and Scopus, using the key words: "error augmentation" or "error enhancement" or "negative viscosity" and "stroke" and "upper extremity." The studies were evaluated based on their main characteristics and methodology. Results:There is limited evidence about the effectiveness of this new method, as only eight studies, with limited methodological quality were found. The participants were usually in the chronic stage after the stroke. Two studies were randomized controlled trials, four used a crossover design, and two were pilot studies. Fugl-Meyer was the most common clinical outcome measure used to assess the effect of treatment. Three studies reported a significant improvement in the effects of EA training compared to control training, and two studies reported a significant treatment effect over time. Conclusions: Most of the studies reviewed have significant methodological drawbacks that resulted in equivocal results. Therefore, we recommend that additional randomized controlled trials, with larger sample sizes and acceptable protocols be conducted to determine the long-term efficacy of EA training.

SummaryCortical maps often undergo plastic changes during learning or in response to injury. In s... more SummaryCortical maps often undergo plastic changes during learning or in response to injury. In sensory areas, these changes are thought to be triggered by alterations in the pattern of converging inputs and a functional reassignment of the deprived cortical region. In the motor cortex, training on a task that engages distal effectors was shown to increase their cortical representation (as measured by response to intracortical microstimulation). However, this expansion could be a specific outcome of using a demanding dexterous task. We addressed this question by measuring the long-term changes in cortical maps of monkeys that were sequentially trained on two different tasks involving either proximal or distal joints. We found that motor cortical remodeling in adult monkeys was symmetric such that both distal and proximal movements can comparably alter motor maps in a fully reversible manner according to task demands. Further, we found that the change in mapping often included a swit...

International Journal of Therapy and Rehabilitation, 2014

Background/aim: Patients with stroke who are suffering from impaired reaching movement experience... more Background/aim: Patients with stroke who are suffering from impaired reaching movement experience insufficient spatial and temporal coordination, affecting upper limb functions and everyday life tasks. This study examines a new robot-assisted rehabilitation method for ameliorating arm reaching movements through velocity error enhancement training. The authors hypothesised that this robot-assisted rehabilitation training may encourage restoration of arm reaching abilities among post-stroke hemiparesis patients. Methods: Several clinical and kinematic measures were used to evaluate outcomes. Subjects were assigned either to an experimental group that underwent 5-week treatments with error enhanced forces, or to a control group that received passive treatment. The control group undertook reaching tasks over the same period while they were connected to the robot but without it applying any error enhancement forces to their upper limb. The robotic system was programmed based on previous kinematic data from hea...

Background/aim: Patients with stroke who are suffering from impaired reaching movement experience... more Background/aim: Patients with stroke who are suffering from impaired reaching movement experience insufficient spatial and temporal coordination, affecting upper limb functions and everyday life tasks. This study examines a new robot-assisted rehabilitation method for ameliorating arm reaching movements through velocity error enhancement training. The authors hypothesised that this robot-assisted rehabilitation training may encourage restoration of arm reaching abilities among poststroke hemiparesis patients. Methods: Several clinical and kinematic measures were used to evaluate outcomes. Subjects were assigned either to an experimental group that underwent 5-week treatments with error enhanced forces, or to a control group that received passive treatment. The control group undertook reaching tasks over the same period while they were connected to the robot but without it applying any error enhancement forces to their upper limb. The robotic system was programmed based on previous k...

Participants executed hand-reaching movements for 9 different target directions while monitored b... more Participants executed hand-reaching movements for 9 different target directions while monitored by surface EMG device, containing 8 electrodes that were attached to 8 muscles of the shoulder and arm. The direction of the targets were constant between different participants. The folder contains two subfolders, one of healthy individuals and the other of post-stroke individuals. Inside these folders there are 12 folders (Healthy) or 13 folders (post-stroke), each of which corresponds with individual. Each individual's dataset composed of 8 files of Maximum Voluntary Contraction (MVC) of muscles, and 9 or 6 "Target_XXX" files refer of hand-reaching movments for different directions. Each "Target" file contains signals of all the 8 muscles that were also measured by the MVC measurement. Target directions were similar for all individuals from both groups.

Advances in Experimental Medicine and Biology, 2020

Movement synergies, muscle co-contraction, and decreased motor drive to muscle agonists were sugg... more Movement synergies, muscle co-contraction, and decreased motor drive to muscle agonists were suggested to be major factors in motor impairments after stroke. The purpose of this study was to investigate the major muscle mechanisms contributing to motor impairment after stroke. Twelve healthy and 13 post-stroke patients participated in this observational study. Both groups participated in a single experimental session, performing hand pointing movements in multiple directions, during which EMG was assessed. Additionally, the patients underwent the Fugl-Meyer assessment. A set of features from the electromyography (EMG) signal and co-contraction ratios were used to compare the capacity to modulate the muscle activity between the two groups of participants. A correlation analysis was applied between the Euclidian distances of each target and the Fugl-Meyer scoring assessment in the post-stroke patients. We found that impaired modulation of muscle activity in post-stroke patients was characterized by significantly increased Euclidian distances between the EMG features of different target directions and by a higher variability between muscle activation compared to healthy subjects. Impaired capacity to modulate muscle activity significantly correlated with the impairment status. In conclusion, impaired motor performance post-stroke systematic disturbance in the control signal to limb muscles, which manifests as decreased capacity to modulate muscle activity, rather than co-contraction of muscle antagonists or stereotyped movement patterns.

Reviews in the Neurosciences, 2019

Individuals post-stroke sustain motor deficits years after the stroke. Despite recent advancement... more Individuals post-stroke sustain motor deficits years after the stroke. Despite recent advancements in the applications of non-invasive brain stimulation techniques and Deep Brain Stimulation in humans, there is a lack of evidence supporting their use for rehabilitation after brain lesions. Non-invasive brain stimulation is already in use for treating motor deficits in individuals with Parkinson’s disease and post-stroke. Deep Brain Stimulation has become an established treatment for individuals with movement disorders, such as Parkinson’s disease, essential tremor, epilepsy, cerebral palsy and dystonia. It has also been utilized for the treatment of Tourette’s syndrome, Alzheimer’s disease and neuropsychiatric conditions such as obsessive-compulsive disorder, major depression and anorexia nervosa. There exists growing scientific knowledge from animal studies supporting the use of Deep Brain Stimulation to enhance motor recovery after brain damage. Nevertheless, these results are cur...

Frontiers in computational neuroscience, 2018

A muscle synergies model was suggested to represent a simplifying motor control mechanism by the ... more A muscle synergies model was suggested to represent a simplifying motor control mechanism by the brainstem and spinal cord. The aim of the study was to investigate the feasibility of such control mechanisms in the rehabilitation of post-stroke individuals during the execution of hand-reaching movements in multiple directions, compared to non-stroke individuals. Twelve non-stroke and 13 post-stroke individuals participated in the study. Muscle synergies were extracted from EMG data that was recorded during hand reaching tasks, using the NMF algorithm. The optimal number of synergies was evaluated in both groups using the Variance Accounted For (VAF) and the Mean Squared Error (MSE). A cross validation procedure was carried out to define a representative set of synergies. The similarity index and the K-means algorithm were applied to validate the existence of such a set of synergies, but also to compare the modulation properties of synergies for different movement directions between g...

Advances in experimental medicine and biology, Jan 22, 2018

The purpose of this study was to investigate whether adaptive responses to error-augmentation for... more The purpose of this study was to investigate whether adaptive responses to error-augmentation force fields, would decrease the trajectory errors in hand-reaching movements in multiple directions in healthy individuals. The study was conducted, as a randomized controlled trial, in 41 healthy subjects. The study group trained on a 3D robotic system, applying error-augmenting forces on the hand during the execution of tasks. The control group carried out the same protocol in null-field conditions. A mixed-model ANOVA was implemented to investigate the interaction between groups and time, and changes in outcome measures within groups. The findings were that there was a significant interaction effect for group × time in terms of the magnitude of movement errors across game-sets. The trajectory error of the study group significantly decreased from 0.035 ± 0.013 m at baseline to 0.029 ± 0.011 m at a follow-up, which amounted to a 14.8% improvement. The degree of movement errors were not si...

IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society, Dec 1, 2017

Functional tasks of the upper extremity can be executed by a variety of muscular patterns, indepe... more Functional tasks of the upper extremity can be executed by a variety of muscular patterns, independent of the direction, speed and load of the task. This large number of degrees of freedom imposes a significant control burden on the CNS. Previous studies suggested that the human cortex synchronizes a discrete number of neural functional units within the brainstem and spinal cord, i.e. muscle synergies, by linearly combining them to execute a great repertoire of movements. Further exploring this control mechanism, we aim to study whether a single set of muscle synergies might be generalized to express movements in different directions. This was implemented by using a modified version of the non-negative matrix factorization algorithm on EMG data sets of the upper extremity of healthy people. Our twelve participants executed hand-reaching movements in multiple directions. Muscle synergies that were extracted from movements to the center of the reaching space could be generalized to sy...

Reviews in the neurosciences, Jan 5, 2018

Muscle synergies are proposed to function as motor primitives that are modulated by frontal brain... more Muscle synergies are proposed to function as motor primitives that are modulated by frontal brain areas to construct a large repertoire of movement. This paper reviews the history of the development of our current theoretical understanding of nervous system-based motor control mechanisms and more specifically the concept of muscle synergies. Computational models of muscle synergies, especially the nonnegative matrix factorization algorithm, are discussed with specific reference to the changes in synergy control post-central nervous system (CNS) lesions. An alternative approach for motor control is suggested, exploiting a combination of synergies control or flexible muscle control used for gross motor skills and for individualized finger movements. Rehabilitation approaches, either supporting or inhibiting the use of basic movement patterns, are discussed in the context of muscle synergies. Applications are discussed for the use of advanced technologies that can promote the recovery ...

Topics in Stroke Rehabilitation, 2016

Background: Evidence-based studies regarding deficits in handwriting performance relative to hand... more Background: Evidence-based studies regarding deficits in handwriting performance relative to hand reaching and grasping after a stroke are lacking. Objective: To evaluate the extent of damage to handwriting skills compared to arm reach and grasp task among post-stroke patients. Methods: Eighteen patients and 19 healthy subjects were recruited to this case-control study. Patients were evaluated 15.2 days (±6.5) after the stroke using a Computerized Penmanship Evaluation Tool, surface Electromyography and Fugl-Meyer assessment. This study compared motor deficits in hand reaching and grasping and in handwriting between stroke patients and healthy subjects. Damage to handwriting performance relative to hand reaching and grasping skills was also evaluated. Results: Significant differences were found between groups in handwriting performance (p < 0.05). The performance of the trapezius, biceps, and triceps muscles can predict 63.5% of the variance in the ability to write a short sentence (p < 0.023). Pen pressure can predict 74.9% of the hand motor performance from Fugl-Meyer assessment (p < 0.05). Handwriting was more damaged than was the pattern of activation of the proximal muscles of the shoulder and arm (p < 0.05). FM scores were highly, negatively correlated with the in-air writing time across tasks (r = −0.819, p < 0.004). Conclusions: This study confirms the clinical observation that dexterity skills are more damaged than are arm forward reach after a stroke. However, these differences in motor performance were not significant in mildly disabled patients, demonstrating the feasibility of handwriting rehabilitation in these patients. Therefore, we modestly recommend focusing on handwriting rehabilitation of the hemiparetic upper extremity in mildly impaired patients after a stroke.

Topics in Stroke Rehabilitation, 2016

Background: Improvement of motor performance is crucial in rehabilitation after a stroke. A new c... more Background: Improvement of motor performance is crucial in rehabilitation after a stroke. A new concept in motor learning and rehabilitation is error augmentation (EA): using erroneous sensory feedback to enhance adaptation to a new environment. However, the clinical efficacy of this method to enhance motor learning after a stroke needs to be evaluated. Objectives: To determine whether there is enough evidence-based knowledge to justify using the EA concept for upper extremity rehabilitation after a stroke over traditional rehabilitation methods. Methods: Two reviewers systematically searched the English-language literature in six databases: PubMed, Web of science, PEDro, CINAHL, Cochrane, and Scopus, using the key words: "error augmentation" or "error enhancement" or "negative viscosity" and "stroke" and "upper extremity." The studies were evaluated based on their main characteristics and methodology. Results:There is limited evidence about the effectiveness of this new method, as only eight studies, with limited methodological quality were found. The participants were usually in the chronic stage after the stroke. Two studies were randomized controlled trials, four used a crossover design, and two were pilot studies. Fugl-Meyer was the most common clinical outcome measure used to assess the effect of treatment. Three studies reported a significant improvement in the effects of EA training compared to control training, and two studies reported a significant treatment effect over time. Conclusions: Most of the studies reviewed have significant methodological drawbacks that resulted in equivocal results. Therefore, we recommend that additional randomized controlled trials, with larger sample sizes and acceptable protocols be conducted to determine the long-term efficacy of EA training.

SummaryCortical maps often undergo plastic changes during learning or in response to injury. In s... more SummaryCortical maps often undergo plastic changes during learning or in response to injury. In sensory areas, these changes are thought to be triggered by alterations in the pattern of converging inputs and a functional reassignment of the deprived cortical region. In the motor cortex, training on a task that engages distal effectors was shown to increase their cortical representation (as measured by response to intracortical microstimulation). However, this expansion could be a specific outcome of using a demanding dexterous task. We addressed this question by measuring the long-term changes in cortical maps of monkeys that were sequentially trained on two different tasks involving either proximal or distal joints. We found that motor cortical remodeling in adult monkeys was symmetric such that both distal and proximal movements can comparably alter motor maps in a fully reversible manner according to task demands. Further, we found that the change in mapping often included a swit...

International Journal of Therapy and Rehabilitation, 2014

Background/aim: Patients with stroke who are suffering from impaired reaching movement experience... more Background/aim: Patients with stroke who are suffering from impaired reaching movement experience insufficient spatial and temporal coordination, affecting upper limb functions and everyday life tasks. This study examines a new robot-assisted rehabilitation method for ameliorating arm reaching movements through velocity error enhancement training. The authors hypothesised that this robot-assisted rehabilitation training may encourage restoration of arm reaching abilities among post-stroke hemiparesis patients. Methods: Several clinical and kinematic measures were used to evaluate outcomes. Subjects were assigned either to an experimental group that underwent 5-week treatments with error enhanced forces, or to a control group that received passive treatment. The control group undertook reaching tasks over the same period while they were connected to the robot but without it applying any error enhancement forces to their upper limb. The robotic system was programmed based on previous kinematic data from hea...