- •1-Hz repetitive transcranial magnetic stimulation with rehabilitation immediately after botulinum toxin type A injection in a stroke patient.
- •The spasticity, motor function, and usefulness of the paretic hand improved.
- •This is a possibility of shortening the intervention period of combined therapy.
Posts Tagged paretic hand
[Abstract] Upper Limb Three-Dimensional Reachable Workspace Analysis Using the Kinect Sensor in Hemiplegic Stroke Patients
A reachable workspace evaluation using the Kinect sensor was previously introduced as a novel upper limb outcome measure in neuromuscular and musculoskeletal conditions. This study investigated its usefulness in hemiplegic stroke patients.
Forty-one patients with hemiplegic stroke were included. Kinect-based reachable workspace analysis was performed on both paretic and nonparetic sides. Upper limb impairment was measured using the Fugl-Meyer Assessment and the Motricity Index on the paretic side. Disability was assessed using the shortened Disabilities of the Arm, Shoulder, and Hand questionnaire. Correlations between the relative surface areas, impairment scores, and disability were analyzed.
Quadrants 1, 3, and 4 as well as the total relative surface area of the paretic side were significantly reduced compared with the nonparetic side. The total relative surface area of the paretic side correlated with the Fugl-Meyer Assessment scores, the Motricity Index for Upper Extremity, and the Disabilities of the Arm, Shoulder, and Hand questionnaire score. Furthermore, quadrant 3 was the most important determinant of upper limb impairment and disability.
A reachable workspace (a sensor-based measure that can be obtained relatively quickly and unobtrusively) could be a useful and alternative outcome measure for upper limb in hemiplegic stroke patients.
Purpose: Precise control of a car steering wheel requires adequate motor capability. Deficits in grip strength and force control after stroke could influence the ability steer a car. Our study aimed to determine the impact of stroke on car steering and identify the relative contribution of grip strength and grip force control to steering performance.
Methods: Twelve chronic stroke survivors and 12 controls performed three gripping tasks with each hand: maximum voluntary contraction, dynamic force tracking, and steering a car on a winding road in a simulated driving environment. We quantified grip strength, grip force variability, and deviation of the car from the center of the lane.
Results: The paretic hand exhibited reduced grip strength, increased grip force variability, and increased lane deviation compared with the non-dominant hand in controls. Grip force variability, but not grip strength, significantly predicted (R2 = 0.49, p < 0.05) lane deviation with the paretic hand.
Conclusion: Stroke impairs the steering ability of the paretic hand. Although grip strength and force control of the paretic hand are diminished after stroke, only grip force control predicts steering accuracy. Deficits in grip force control after stroke contribute to functional limitations in performing skilled tasks with the paretic hand.
- Implications for rehabilitation
Driving is an important goal for independent mobility after stroke that requires motor capability to manipulate hand and foot controls.
Two prominent stroke-related motor impairments that may impact precise car steering are reduced grip strength and grip force control.
In individuals with mild-moderate impairments, deficits in grip force modulation rather than grip strength contribute to compromised steering performance with the paretic hand.
We recommend that driving rehabilitation should consider re-educating grip force modulation for successful driving outcomes post stroke.
Motus Nova is expanding its list of partner hospitals and clinics using its FDA-approved robotic stroke therapy system. It also plans to introduce its system to the consumer market for home use in Q3 2019.
Twenty-five hospitals in the Atlanta area within Emory Healthcare, the Grady Health System, and the Wellstar Health System are now using the Motus Nova rehabilitation therapy system, which is designed to use Artificial Intelligence (AI) to accelerate recovery from neurological injuries such as strokes.
The system features a Hand Mentor and Foot Mentor, which are sleeve-like robots that fit over a stroke survivor’s impaired hand or foot. Equipped with an active-assist air muscle and a suite of sensors and accelerometers, they provide clinically appropriate assistance and resistance while individual’s perform the needed therapeutic exercises.
A touchscreen console provides goal-directed biofeedback through interactive games—which Motus Nova calls “theratainment”—that make the tedious process of neuro rehab engaging and fun.
“It’s a system that has proven to be a valuable partner to stroke therapy professionals, where it complements skilled clinical care by augmenting the repetitive rehabilitation requirements of stroke recovery and freeing the clinician to do more nuanced care and assessment,” says Nick Housley, director of clinical research for Atlanta-based Motus Nova, in a media release.
“And while we continue to fill orders for the system to support therapy in the clinic and hospital, we also are looking to use our system to fill the gap patients often experience in receiving the needed therapy once they go home.”
Clinical studies show that neuroplasticity begins after approximately many 10’s to 100’s of hours of active guided rehab. The healing process can take months or years, and sometimes the individuals might never fully recover. Yet the typical regimen for stroke survivors is only two to three hours of outpatient therapy per week for a period of three to four months.
“These constraints were instituted by the Centers for Medicare & Medicaid Services (CMS) in determining Medicare reimbursement without a full understanding of the appropriate dosing required for stroke recovery, and many private insurers have adopted the policy, as well,” states David Wu, Motus Nova’s CEO.
Motus Nova plans to offer a more practical model, the release continues.
“By making the system available for home use at a reasonable weekly rate as long as the patient needs it, the individual can perform therapy anytime,” Wu adds. “A higher dosage of therapy can be achieved without the inconvenience of scheduling appointments with therapists or traveling to and from a clinic, and without the high cost of going to an outpatient center every time the individual wants to do therapy.”
While the system gathers data about individual performance, AI tailors the regimen to maximize user gains, discover new approaches, minimize side effects and help the stroke survivor realize his or her full potential more quickly.
“By optimizing factors such as frequency, intensity, difficulty, encouragement, and motivation, the AI system builds a personalized medicine plan uniquely tailored to each individual user of the system,” Housley comments.
“Our system is durable, too, proven in clinical trials to deliver an engaging physical therapy experience over thousands of repetitions. We look forward to making it available on a much wider scale in the coming months.”
[Source(s): Motus Nova, PR Newswire]
[ARTICLE] A pilot study into reaching performance after severe to moderate stroke using upper arm support – Full Text
Stroke effects millions of people each year and can have a significant impact on the ability to use the impaired arm and hand. One of the results of stroke is the development of an abnormal shoulder-elbow flexion synergy, where lifting the arm can cause the elbow, wrist, and finger flexors to involuntarily contract, reducing the ability to reach with the arm and hand opening. This study explored the effect of using support at the upper arm to improve hand and arm reaching performance. Nine participants were studied while performing a virtual reaching task under three conditions: while the weight of their impaired arm was supported by a robot arm, while unsupported, and while using their non-impaired arm. Most subjects exhibited faster and more accurate reaching while supported compared to unsupported. For the subjects who could voluntarily open their hand, most were able to more swiftly open their hand when using upper arm support. In many cases, performance with support was not statistically different than the unaffected arm and hand. Muscle activity of the impaired limb with upper arm support showed decreased effort to lift the arm and reduced biceps activity in most subjects, pointing to a reduction in the abnormal flexion synergy while using upper arm support. While arm support can help to reduce the activation of abnormal synergies, weakness resulting from hemiparesis remains an issue impacting performance. Future systems will need to address both of these causes of disability to more fully restore function after stroke.
Stroke is a common occurrence in the U.S.; Approximately 795,000 Americans suffer a stroke every year . It is the third leading cause of death and one of the main causes of disability. There are currently 7,000,000 chronic stroke survivors over 20 years old in the U.S., representing about 3% of the general population . In the veteran community, over 5,000 veterans are hospitalized each year due to ischemic stroke, with those patients accounting for over 10% of the case load and costing more than three times the overall average . Recent studies have shown that there is a significantly increased risk of stroke in people who have suffered traumatic brain injuries (TBIs) [3,4] and in patients with Post Traumatic Stress Disorder (PTSD) who are often on potent antipsychotic medications . With these conditions being seen in remarkably greater numbers in the current military engagements compared to previous combat actions, there exists the likelihood of the VA seeing progressively more stroke survivors [6,7].
There are many potential effects of a stroke, depending on where in the brain the event occurred. Approximately 50% of stroke survivors over age 64 have some hemiparesis affecting control of the arm and hand  with the vast majority (88.4%) not regaining complete function . Moderate to severe hemiparesis can have a significant impact upon many common activities of daily living (ADLs), resulting in significant dependence on caregivers. In particular, upper limb hemiparesis, which occurs in approximately 26% of stroke survivors , negatively impacts bimanual tasks, such as opening containers, cutting food, and holding open a bag such as a wallet or grocery bag. In addition to hemiparesis, stroke survivors can also develop abnormal muscle synergies where voluntary effort to contract the muscle or group of muscles needed to execute a task causes other muscles not normally involved in the task to involuntarily contract, resulting in loss of control or coordination during certain movements [9–14].
One common abnormal synergy is the shoulder-elbow flexion synergy where the elbow, wrist, and fingers flex involuntarily when the patient abducts or raises the shoulder–resulting in a loss of reach area and difficulty performing ADLs. The magnitude of this effect is related to the amount of effort the individual exerts. Abnormal synergy does not occur if the arm is manually lifted by an outside force (e.g. by a therapist or assistive device). However, when the individual lifts their arm voluntarily, the synergy is activated, with increasing amounts of shoulder abduction torque resulting in greater elbow, wrist, and finger flexion torque, which reduces the overall reach volume of the arm [9,12].
In studies of individuals with stroke, providing gravity compensation at the forearm has allowed participants to access a greater range of motion. In the case of stroke this is the result of reducing abnormal muscle synergies [9,15], and allowing for retained voluntary control to be more effective.
One way to provide this type of support is to use a mechanical assistance device. Over the years, a number of robots intended for post-stroke rehabilitation of the upper extremity have been developed for both therapy and to assist daily function. Notable examples of therapy devices include the ARMin [16–18] and RUPERT [19,20]. The MIT MANUS robot has been clinically evaluated and has shown statistically significant although functionally modest results in rehabilitation and motor re-learning . While these previous devices were lab-based robots intended for therapy, a number of robotic devices for assisting arm function as a form of “force prosthesis” have been developed that range from devices to support the arm against gravity [22–26] to full arm, powered exoskeletons [27,28]. The primary drawback to these machines is that due to the force requirements and the kinematics of applying force assistance at the end of the forearm, they tend to be large and are required to be mounted to a user’s wheelchair or other rigid structure . While some stroke patients are limited in terms of walking mobility, a large number are ambulatory and do not require a wheelchair, and hence are not interested in using these large, primarily lab-based mechanical devices to assist in their daily activities. For these users, a different solution is needed.
Thus far, all of the devices in clinical use attempt to reduce abnormal muscle synergy by providing gravity assistance at the forearm, but support at the upper arm, between the shoulder and elbow, has not been explored. This work investigates the hypothesis that upper arm support can assist shoulder abduction by producing gravity compensation for the affected limb and improve reaching capacity.
To explore the impact of upper arm support on improving reaching and hand opening, research participants were asked to perform directed reaching tasks in a virtual reality environment. This was done over three conditions, 1) with their impaired arm while supported, 2) with the impaired arm without support, and 3) with their unaffected arm as a “gold standard” for comparison.
For this work, nine people who have suffered a severe to moderate stroke (Table 1) were recruited through the stroke research programs in cooperation with clinicians at the Louis Stokes Cleveland DVA Medical Center (LSCDVAMC). Inclusion criteria consisted of: 1) being greater than 6 months post-stroke, 2) age between 20 and 80 years old, 3) having paresis confined to one side of the body with upper limb motor impairment, and 4) presenting moderate to severe impairment (Fugl-Meyer upper limb assessment between 15 and 47) including a reduced reach volume and reduced voluntary extension of the joints of the affected arm. Criteria for excluding participants was: 1) having substantial pain in the impaired limb, 2) having sensory impairment of the affected limb, 3) having visual deficits beyond those that can be corrected with corrective lenses, 4) being unable to perceive or visually track objects shown on a computer screen, 5) exhibiting cognitive impairment that would preclude the individual from following simple instructions similar to those common to standard of care therapy practices, and 6) having apraxia or significant neglect of the impaired limb. All subjects were able to give written Informed Consent and all research protocols were approved by the Louis Stokes Cleveland Department of Veterans Affairs Medical Center Institutional Review Board, IRB #16050-H37. Prior to any reaching experiments, participants were screened using the Mini Mental State Exam to verify that they were cognitively capable of both providing Informed Consent as well as able to follow basic instructions.
[ARTICLE] Feasibility of the UR5 Industrial Robot for Robotic Rehabilitation of the Upper Limbs After Stroke – Full Text PDF
Robot-assisted therapy is an emerging form of
rehabilitation treatment for motor recovery of the upper limbs
after neurological injuries such as stroke or spinal cord injury.
Robotic rehabilitation devices have the potential to reduce the
physical strain put on therapists due to the high-effort oneto-one
interactions between the therapist and patient involving
repetitive high-intensity movements to restore arm and
hand functions. Numerous custom robotic devices have been
developed in recent years to aid in physical rehabilitation
of stroke patients, but most commercially available systems
are high-cost devices because of low production volumes and
high development costs. In this paper, we analyse the safety
and functionality of the UR5 collaborative industrial robot
from Universal Robots equipped with an external force/torque
sensor in a real-time control system for typical rehabilitation
exercises. The aim of the paper is to show that a new class
of general-purpose industrial robots designed for human-robot
collaboration may prove a viable alternative to custom designs.
Experiments show that robotic rehabilitation of the upper
limbs using a standard industrial robot manipulator UR5
may be feasible. Results have the potential to reduce costs
and complexity for robotic rehabilitation devices, and thus
make robotic rehabilitation more affordable as a high-quality
therapeutic treatment for more patients.
[Abstract] Combined effects of botulinum toxin type A and repetitive transcranial magnetic stimulation with intensive motor training immediately after injection in a patient with chronic stroke: A case report
Single case report.
A previous study clarified that spasticity and motor function were improved by combined treatment with botulinum toxin type A (BTX) injection and 1-Hz repetitive transcranial magnetic stimulation (rTMS) with intensive motor training at 4 weeks after injection. However, it is not clear whether 1-Hz rTMS with intensive motor training immediately after BTX injection also improves spasticity and motor function in stroke patients.
Purpose of the Case Report
The purpose of this case report is to test the short- and long-term effects of BTX injection and rTMS with intensive motor training on the spasticity, motor function, and usefulness of the paretic hand in a stroke patient.
A 64-year-old male, who suffered from a right cerebral hemorrhage 53 months previously, participated in the present study. BTX was injected into the spastic muscles of the affected upper limb. He then received the new protocol for a total of 24 sessions. The Modified Ashworth Scale (MAS), Fugl-Meyer Assessment (FMA), and Motor Activity Log, consisting of the amount of use and quality of movement scales, were assessed before and immediately after BTX injection, at discharge, and monthly for up to 5 months after discharge.
For the short-term effects of the therapy, the MAS scores of the elbow and wrist, FMA score, and quality of movement score improved. For the long-term effects of the therapy, the MAS score of the fingers, FMA score, and amount of use score improved for up to 5 months after discharge.
The present case report showed the improvement of all assessments performed in the short and/or long term and suggest the possibility of shortening the intervention period of combined therapy of BTX and rTMS with intensive motor training.
via Combined effects of botulinum toxin type A and repetitive transcranial magnetic stimulation with intensive motor training immediately after injection in a patient with chronic stroke: A case report – Journal of Hand Therapy
[ARTICLE] Brain-actuated functional electrical stimulation elicits lasting arm motor recovery after stroke – Full Text
Brain-computer interfaces (BCI) are used in stroke rehabilitation to translate brain signals into intended movements of the paralyzed limb. However, the efficacy and mechanisms of BCI-based therapies remain unclear. Here we show that BCI coupled to functional electrical stimulation (FES) elicits significant, clinically relevant, and lasting motor recovery in chronic stroke survivors more effectively than sham FES. Such recovery is associated to quantitative signatures of functional neuroplasticity. BCI patients exhibit a significant functional recovery after the intervention, which remains 6–12 months after the end of therapy. Electroencephalography analysis pinpoints significant differences in favor of the BCI group, mainly consisting in an increase in functional connectivity between motor areas in the affected hemisphere. This increase is significantly correlated with functional improvement. Results illustrate how a BCI–FES therapy can drive significant functional recovery and purposeful plasticity thanks to contingent activation of body natural efferent and afferent pathways.
Despite considerable efforts over the last decades, the quest for novel treatments for arm functional recovery after stroke remains a priority1. Synergistic efforts in neural engineering and restoration medicine are demonstrating how neuroprosthetic approaches can control devices and ultimately restore body function2,3,4,5,6,7. In particular, non-invasive brain-computer interfaces (BCI) are reaching their technological maturity8,9 and translate neural activity into meaningful outputs that might drive activity-dependent neuroplasticity and functional motor recovery10,11,12. BCI implies learning to modify the neuronal activity through progressive practice with contingent feedback and reward —sharing its neurobiological basis with rehabilitation13.
Most attempts to use non-invasive BCI systems for upper limb rehabilitation after stroke have coupled them with other interventions, although not all trials reported clinical benefits. The majority of these studies are case reports of patients who operated a BCI to control either rehabilitation robots14,15,16,17,18,19 or functional electrical stimulation (FES)20,21,22,23. A few works have described changes in functional magnetic resonance imaging (fMRI) that correlate with motor improvements17,18,22.
Recent controlled trials have shown the potential benefit of BCI-based therapies24,25,26,27. Pichiorri et al.26recruited 28 subacute patients and studied the efficacy of motor imagery with or without BCI support via visual feedback, reporting a significant and clinically relevant functional recovery for the BCI group. As a step forward in the design of multimodal interventions, BCI-aided robotic therapies yielded significantly greater motor gains than robotic therapies alone24,25,27. In the first study, involving 30 chronic patients24, only the BCI group exhibited a functional improvement. In the second study, involving 14 subacute and chronic patients, both groups improved, probably reflecting the larger variance in subacute patients’ recovery and a milder disability25. The last study27 showed that in a mixed population of 74 subacute and chronic patients, the percentage of patients who achieved minimally clinical important difference in upper limb functionality was higher in the BCI group. The effect in favor of the BCI group was only evident in the sub-population of chronic patients. Moreover, the conclusions of this study are limited due to differences between experimental and control groups prior to the intervention, such as number of patients and FMA-UE scores, which were always in favor of the BCI group.
In spite of promising results achieved so far, BCI-based stroke rehabilitation is still a young field where different works report variable clinical outcomes. Furthermore, the efficacy and mechanisms of BCI-based therapies remain largely unclear. We hypothesize that, for BCI to boost beneficial functional activity-dependent plasticity able to attain clinically important outcomes, the basic premise is contingency between suitable motor-related cortical activity and rich afferent feedback. Our approach is designed to deliver associated contingent feedback that is not only functionally meaningful (e.g., via virtual reality or passive movement of the paretic limb by a robot), but also tailored to reorganize the targeted neural circuits by providing rich sensory inputs via the natural afferent pathways28, so as to activate all spare components of the central nervous system involved in motor control. FES fulfills these two properties of feedback contingent on appropriate patterns of neural activity; it elicits functional movements and conveys proprioceptive and somatosensory information, in particular via massive recruitment of Golgi tendon organs and muscle spindle feedback circuits. Moreover, several studies suggest that FES has an impact on cortical excitability29,30.
To test our hypothesis, this study assessed whether BCI-actuated FES therapy targeting the extension of the affected hand (BCI–FES) could yield stronger and clinically relevant functional recovery than sham-FES therapy for chronic stroke patients with a moderate-to-severe disability, and whether signatures of functional neuroplasticity would be associated with motor improvement. Whenever the BCI decoded a hand-extension attempt, it activated FES of the extensor digitorum communis muscle that elicited a full extension of the wrist and fingers. Patients in the sham-FES group wore identical hardware and received identical instructions as BCI–FES patients, but FES was delivered randomly and not driven by neural activity.
As hypothesized, our results confirm that only the BCI group exhibit a significant functional recovery after the intervention, which is retained 6–12 months after the end of therapy. Besides the main clinical findings, we have also attempted to shed light on possible mechanisms underlying the proposed intervention. Specifically, electroencephalography (EEG) imaging pinpoint significant differences in favor of the BCI group, mainly an increase in functional connectivity between motor areas in the affected hemisphere. This increase is significantly correlated with functional improvement. Furthermore, analysis of the therapeutic sessions substantiates that contingency between motor-related brain activity and FES occurs only in the BCI group and contingency-based metrics correlate with the functional improvement and increase in functional connectivity, suggesting that our BCI intervention might have promoted activity-dependent plasticity.[…]
Objectives: Mirror therapy is a unique treatment with a touch of modality that is purported to improve the motor function of the affected limb in individuals with hemiplegia. Previous studies have focused on the neuro-physiological factors underlying the mechanism of the clinical effect of this technique. The present study aims to understand the mechanism using the rehabilitation method and neuro-occupation model as well as analyze the effects of mirror therapy on the upper limb function of subjects with spastic hemiplegic cerebral palsy.
Methods: Single subject design known as withdrawal design was used by a convenience sample of four subjects. The study involved three observational phases known as baseline, treatment, and withdrawal phases that took place during a 10 week period. The study contained a home-based mirror therapy protocol whereby the participants were instructed to do some exercises on a daily basis. The improvement of the hand function of the hemiplegic side was examined by Box and Block test along with two more activities including Threading Beads and Stacking Rings.
Results: The ability to perform the Box and Block test, Threading Beads, and Stacking Rings tended to remain steady in the baseline phase, whereas there was a noticeable improvement during the treatment phase and a decline in the withdrawal phase.
Discussion: From the perspective of visual feedback neuro-occupation model, it could be hypothesized that alterations to the sensory system caused by the mirror reflection of non affected hand may have led to the destabilization of the sensory cortices that changed the participants’ intention, meaning, and perception, thereby improving the subject’s motor control.
[Poster] Exploration of the Factors That Influence Spontaneous Bimanual Arm Use After Stroke: Implications for Clinical Rehabilitation
After a stroke, returning to activities of daily living requires the use of the two hands together for bimanual tasks, such as cutting bread, buttoning a shirt etc. Here, we sought to first, identify spontaneous volitional arm use patterns adopted for two distinct bimanual tasks, and, next, determine if and to what extent the degree of impairment, side of stroke, task demands, self-reported confidence, and single-limb (paretic and non-paretic) measures of functional performance can predict the observed task use patterns.
Fifty pre-morbidly right-handed stroke survivors (Upper Extremity Fugl-Meyer, UEFM 42±10, 25 right-hemiparesis, RHP) performed 2 bimanual tasks (letter-envelope and photo-album) without explicit instructions. Arm use patterns were classified by: 1) whether one or both arms were used, and 2) the nature of paretic arm use. Logistic regression and receiver-operator characteristics (AUC) were used to examine the influence of impairment (UEFM, more severe < 41, less severe ≥ 41), side of lesion, task demand, self-reported confidence (CAHM), and single-limb functional performances (paretic and non-paretic log-transformed distal component time-scores of Wolf Motor Function test, ln-WMFT) on bimanual arm use. Those more severely impaired and LHP were less likely to choose a bimanual strategy for either task (β = 14.64, p<0.001). For the photo-album task, probability of bimanual use was greater for RHP than LHP group, especially in less impaired; whereas, for the letter-envelope task, probability of use for RHP > LHP only in the more impaired (β = -1.45, p< 0.001). LHP, but not RHP, who reported greater confidence in the use of the paretic arm were more likely to use a bimanual strategy (ρ > 0.34, p<0.05). Finally, paretic arm ln-WMFT was a fair predictor of use patterns for both LHP (AUC = 0.79) and RHP (AUC = 0.80) groups, while the non-paretic arm time-score was a good predictor of use patterns only for the RHP (AUC = 0.85), but not the LHP group (AUC = 0.55).
Taken together, spontaneous bimanual arm use is modified by impairment, task demands, confidence in paretic arm, and non-paretic arm function, but the effect depends on the side of stroke. Thus, consideration of side of lesion is important when developing interventions to improve bimanual arm use.
[ARTICLE] Study of Repetitive Movements Induced Oscillatory Activities in Healthy Subjects and Chronic Stroke Patients – Full Text
Repetitive movements at a constant rate require the integration of internal time counting and motor neural networks. Previous studies have proved that humans can follow short durations automatically (automatic timing) but require more cognitive efforts to track or estimate long durations. In this study, we studied sensorimotor oscillatory activities in healthy subjects and chronic stroke patients when subjects were performing repetitive finger movements. We found the movement-modulated changes in alpha and beta oscillatory activities were decreased with the increase of movement rates in finger lifting of healthy subjects and the non-paretic hands in stroke patients, whereas no difference was found in the paretic-hand movements at different movement rates in stroke patients. The significant difference in oscillatory activities between movements of non-paretic hands and paretic hands could imply the requirement of higher cognitive efforts to perform fast repetitive movements in paretic hands. The sensorimotor oscillatory response in fast repetitive movements could be a possible indicator to probe the recovery of motor function in stroke patients.
Timing in the brain has its important role in many aspects, such as speech perception, speech production, reading, attention, memory, cognitive processing, decision-making, and motor coordination1. Especially, internal time counting is crucial for motor control in our daily life activities. The processing of time estimation for movements has been studied in many literatures2. Morillon et al. postulated the time estimation in human motor system as a dual system, which can track a short duration automatically (automatic timing) but requires more cognitive demands to track a long duration by a so-called default mode network (DMN)3. Poppel E. studied the capability of time estimation in a stimulus reproduction task from 0.5 s to 7 s, and found movements become temporally irregular for inter-movement interval (IMI) above 3 s which indicated precisely control of movements with IMIs longer than 3 s is not possible4. Though these literatures have shown great difference between movements in short and long durations in healthy subjects, nevertheless, the study of brain responses induced by rapid movements in patients with motor neurological disorder was seldom reported.
Several imaging modalities have been developed to quantify motor response in human brain, including EEG, MEG, fMRI, TMS, etc.5,6. The EEG, which is the tool used most widely, has the advantages of low-cost, easy preparation, and its superiority of high temporal resolution to measure fast changes of neural oscillatory activities. Neural oscillatory activities in human brain can be either phase-locked or non-phase-locked reactive to external or internal stimuli. These oscillatory activities usually exist in specific frequency bands and spatial locations. Event-related non-phase-locked neural activities represent power changes, either enhanced or suppressed relative to baseline activities. The power changes in event-related activities can be caused by the decrease or increase in synchrony of the underlying activated neuronal populations. Pfurtscheller et al.7 studied the Mu-rhythm changes in discrete voluntary finger movements, and found oscillatory activities were suppressed, started about 1.5 s preceding movement onsets, followed by post-movement power rebound, occurred around 0.7 s~1 s after movement offsets7. The power suppression was referred to as event-related desynchronization (ERD), reflecting the motor planning and preparation of initialization a movement, whereas the post-movement power rebound was referred to as event-related synchronization (ERS), indicating the motor inhibition or idling of motor neural network. Other EEG techniques, such as temporal-spectral evolution (TSE)8, amplitude modulation (AM)9, autoregression model method (AR)10, etc., were also developed to quantify task-specific brain oscillatory activity. These signal processing tools enable researchers to quantify the neural activities under different experimental manipulations and provide evidences for diagnosing clinical neurological diseases11,12,13.
The difference of brain oscillatory activities between healthy and stroke patients has been investigated in some studies. Rossiter et al. studied the movement-related beta desynchronization (MRBD) in healthy and middle cerebral artery (MCA) stroke patients14. They found reduced MRBD when patients were performing visually-cued grip task with their affected hand, compared to the MRBD obtained from healthy subjects. Giaquinto et al. followed up the changes of resting EEG in different frequency bands over six months in MCA stroke patients15, and they observed the amplitudes of movement-related Mu – rhythm improved significantly in the first three months and reached stable states in six months after stroke. Tecchio et al. studied the rhythmic brain activity at resting states in mono-hemispheric MCA stoke patients16. They found both the values of spectral power in affected and unaffected hemispheres were increased over Rolandic areas. Stepien et al. studied alpha ERD in stroke patients with cortical and subcortical lesions in performing a visually-cued button press task17. They found suppressed ERD in affected hemisphere when moving paretic hand, while no suppression in alpha ERD was found in the affected hemisphere when moving non-paretic hand. These studies measured oscillatory activities of sensorimotor Mu rhythm in visual selection task or slow self-paced voluntary movement (IMI ≥ 7 s). Oscillatory activity induced by fast repetitive movement in stroke patient was not studied. Since fast simple movement has been reported to have strong coupled connections among motor-related cortices18, study of cortical oscillatory activity in rapid simple movements could be crucial for the understanding of motor function in stroke patients.
Fast repetitive movement with short IMI recruits several motor-related areas in human brain, including primary motor cortex (M1), premotor cortex, supplementary motor cortex, cingulate cortex, basal ganglia, and thalamus19. Studies in healthy subjects have shown clear difference between the oscillatory activities induced by slow and fast repetitive movements. Wu et al. recorded the post-movement beta rebound (PMBD) in healthy subjects and observed that the PMBD was suppressed with the decrease of IMI in repetitive finger-lifting movements19. Erbil and Ungan19 investigated EEG alpha and beta oscillatory activities in repetitive extension-flexion finger movements over rolandic regions. Sustained suppression in Mu rhythm was observed during continuous movements which indicated that continuous movements are conducted through neural processing distinct from discrete movements. Bortoletto and Cunnington measured the fMRI responses of repetitive movements, and compared the results with another two finger movements with highly cognitive demands, one was a complicated sequencing task and the other was a timing task20. They found neural activities in lateral prefrontal regions were participated differently in the three tasks, owing to the different levels of cognitive efforts involved in the three tasks. In this study, we aimed to study the oscillatory activities induced by simple repetitive movements in healthy subjects and chronic stroke patients. The difference of oscillatory activities between stroke patients and healthy subjects might be a potential feature to evaluate the recovery of motor function in stroke patients.[…]