Posts Tagged Transcranial magnetic stimulation

[ARTICLE] Evidence of Neuroplasticity: A Robotic Hand Exoskeleton Study for Post-Stroke Rehabilitation – Full Text PDF

Abstract

Background: A novel electromechanical robotic-exoskeleton was designed in-house for rehabilitation of wrist joint and Metacarpophalangeal (MCP) joint.

Objective: The objective was to compare the rehabilitation effectiveness (clinical-scales and neurophysiological-measures) of robotic-therapy training-sessions with dose-matched control in patients with stroke.

Methods: An observational pilot study was designed with patients within 2 years of chronicity. Patients received an intervention of 20 sessions of 45-minutes each, five days a week for four-weeks) in Robotic-therapy Group (RG) (n=12) and conventional upper-limb rehabilitation in Control-Group (CG) (n=11). Clinical-scales– Modified Ashworth Scale, Active Range of Motion, Barthel-Index, Brunstrom-stage and Fugl-Meyer scale (Shoulder/Elbow and Wrist/Hand component), and neurophysiological-measures of cortical-excitability (using Transcranial Magnetic Stimulation) –Motor Evoked Potential and Resting Motor-threshold, were acquired pre and post-therapy.

Results: RG and CG showed significant improvement in all clinical motor-outcomes (p<0.05) except Modified Ashworth Scale in CG. RG showed significantly higher improvement over CG in Modified Ashworth Scale, Active Range of Motion and Fugl-Meyer (FM) scale and FM Wrist-/Hand component) (p<0.05). Increase in cortical-excitability in ipsilesional-hemisphere was found to be statistically significant in RG over CG, as indexed by decrease in Resting Motor-Threshold and increase in amplitude of Motor Evoked Potential (p<0.05). No significant changes were shown by the contralesional-hemisphere. Interhemispheric RMT-asymmetry evidenced significant changes in RG over CG (p<0.05) indicating increased cortical-excitability in ipsilesional-hemisphere along with interhemispheric changes.

Conclusion: Neurophysiological-changes in RG could be most likely a consequence of plastic-reorganization and use-dependent plasticity. Robotic-exoskeleton training could significantly improve motor-outcomes and cortical-excitability in patients with stroke.


1. Introduction

Stroke is one of the leading causes of mortality and morbidity worldwide (1). The ability to actively initiate extension movements at wrist and fingers against flexor-hypertonia is one of the key indicators of motor recovery (2),(3). Regaining hand-function and Activities of daily-living (ADL) is particularly impervious to therapy or rehabilitation pertaining to the complexity of motor-control needed for distal-joints (4). Conventional rehabilitation-therapy is time taking, labour-intensive and subjective, which with high clinical-load and absence of skilled resources gets difficult for the present medical and healthcare-system to provide appropriate or effective rehabilitation services (5).

Although rehabilitation with neuro-rehabilitation robots has shown encouraging clinical-results (5, 6, 15, 7–14), it is currently limited to a very few hospitals and not widely used because of associated high-cost and an infrastructural-requirement to station, size, complexity, set-up time, safety and usability restricting its success (16),(17),(18). Rehabilitation-strategies need to take into account the multifaceted nature of disability, which itself changes with time elapsed post-stroke and address with a multimodal-approach. Hence, the device needs to be flexible enough to accommodate a large patient-population. An effective rehabilitation device for hand should be able to facilitate a specific pattern of movements mirroring complex inter-joint coordination of hand with a patient-specific impairment, currently not integrated by the available devices.

In our previous work, we designed a robotic-hand exoskeleton for rehabilitation of the wrist and MCP (Metcarpo-phallengeal) joint, to synchronize wrist-extension with finger-flexion and wrist-flexion with finger-extension, mimicking ADL (19). With simple and easy-to-operate exoskeleton for low-resource settings, the exoskeleton targets spasticity through a synergy-based rehabilitation approach while also maintaining patient-initiated therapy through residual muscle-activity for maximizing voluntary effort. The lightweight and portable device has shown evidence of improvement in quantitative motor clinical-outcomes in patients with chronic stroke (19).

The aim of the present study was twofold. The first objective was to assess the clinical effectiveness of the novel robotic-exoskeleton device (19) and the second is comparison of its clinical-effectiveness with conventional upper-limb rehabilitation. We hypothesized that the exoskeleton could show higher improvement of distal-function and cortical-excitability in patients with stroke as compared to conventional-rehabilitation.[…]

Continue —-> https://www.researchsquare.com/article/rs-67841/v1

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[Abstract] Effects of transcranial magnetic stimulation on the performance of the activities of daily living and attention function after stroke: a randomized controlled trial

We aimed to interrogate the effects of transcranial magnetic stimulation (TMS) on the performance in activities of daily living (ADL) and attention function after stroke.

Randomized controlled trial.

Inpatient rehabilitation hospital.

We randomized 62 stroke patients with attention dysfunction who were randomly assigned into two groups, and two dropped out from each group. The TMS group (n = 29) and a sham group (n = 29), whose mean (SD) was 58.12 (6.72) years. A total of 33 (56.9%) patients had right hemisphere lesion while the rest 25 (43.1%) patients had left hemisphere lesion.

Patients in the TMS group received 10 Hz, 700 pulses of TMS, while those in the sham group received sham TMS for four weeks. All the participants underwent comprehensive cognitive training.

At baseline, and end of the four-week treatment, the performance in the activities of daily living was assessed by Functional Independence Measure (FIM). On the other side, attention dysfunction was screened by Mini-Mental State Examination (MMSE), while the attention function was assessed by the Trail Making Test-A (TMT-A), Digit Symbol Test (DST) and Digital Span Test (DS).

Our data showed a significant difference in the post-treatment gains in motor of Functional Independence Measure (13.00 SD 1.69 vs 4.21 SD 2.96), cognition of Functional Independence Measure (4.69 SD 1.56 vs 1.52 SD 1.02), total of Functional Independence Measure (17.69 SD 2.36 vs 5.72 SD 3.12), Mini-Mental State Examination (3.07 SD 1.36 vs 1.21 SD 0.62), time taken in Trail Making Test-A (96.67 SD 25.18 vs 44.28 SD 19.45), errors number in Trail Making Test-A (2.72 SD 1.03 vs 0.86 SD 1.03), Digit Symbol Test (3.76 SD 1.09 vs 0.76 SD 0.87) or Digital Span Test (1.69 SD 0.54 vs 0.90 SD 0.72) between the TMS group and the sham group (P < 0.05).

Taken together, we demonstrate that TMS improves the performance in the activities of daily living and attention function in patients with stroke.

via Effects of transcranial magnetic stimulation on the performance of the activities of daily living and attention function after stroke: a randomized controlled trial – Yuanwen Liu, Mingyu Yin, Jing Luo, Li Huang, Shuxian Zhang, Cuihuan Pan, Xiquan Hu, 2020

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[ARTICLE] A new electromechanical trainer for sensorimotor rehabilitation of paralysed fingers: A case series in chronic and acute stroke patients – Full Text

Abstract

Background

The functional outcome after stroke is improved by more intensive or sustained therapy. When the affected hand has no functional movement, therapy is mainly passive movements. A novel device for repeating controlled passive movements of paralysed fingers has been developed, which will allow therapists to concentrate on more complicated tasks. A powered cam shaft moves the four fingers in a physiological range of movement.

Methods

After refining the training protocol in 2 chronic patients, 8 sub-acute stroke patients were randomised to receive additional therapy with the Finger Trainer for 20 min every work day for four weeks, or the same duration of bimanual group therapy, in addition to their usual rehabilitation.

Results

In the chronic patients, there was a sustained reduction in finger and wrist spasticity, but there was no improvement in active movements. In the subacute patients, mean distal Fugl-Meyer score (0–30) increased in the control group from 1.25 to 2.75 (ns) and 0.75 to 6.75 in the treatment group (p < .05). Median Modified Ashworth score increased 0/5 to 2/5 in the control group, but not in the treatment group, 0 to 0. Only one patient, in the treatment group, regained function of the affected hand. No side effects occurred.

Conclusion

Treatment with the Finger Trainer was well tolerated in sub-acute & chronic stroke patients, whose abnormal muscle tone improved. In sub-acute stroke patients, the Finger Trainer group showed small improvements in active movement and avoided the increase in tone seen in the control group. This series was too small to demonstrate any effect on functional outcome however.

Introduction

The annual stroke incidence is approximately 180 patients per 100,000 inhabitants in the industrialized world. About 30% of the surviving patients suffer from a severe upper limb paresis with a non functional hand. The prognosis for regaining meaningful hand activity six months after stroke onset is poor [1]: this may partly be because current rehabilitation practice puts more emphasis on the compensatory use of the non-affected upper extremity [2].

Powered machines which can allow prolonged repetition of a controlled movement are a promising way of increasing the intensity of rehabilitation after stroke. Several devices, to treat wrist, elbow & shoulder movements, have been developed since the pioneering MIT-Manus in the early 1990s [3]. Randomized controlled trials show a convincing beneficial effect of robot-assisted upper limb treatment on the impairment of severely affected stroke patients [49].

There are fewer clinical reports of machine-assisted movement of paralysed fingers. The Rutgers Hand Masters I and II use pistons mounted inside the palm to move the fingers, with virtual reality to improve motivation. Chronic stroke patients improved range of motion, motor control and speed of the paretic fingers over several weeks of training, and the benefits were retained at follow-up [1011].

With the Howard Hand Robot, pistons assist with patient initiated grasping and releasing movements around virtual or real objects. In moderately affected chronic stroke subjects, upper limb motor functions improved, and functional MRI revealed increased sensorimotor cortex activation during the grasping task which was not seen during a non-practiced task, supination/pronation [12].

Fischer et al assisted the finger extension of mildly affected stroke patients with the help of a powered orthosis. Following six weeks of training in reach-to-grasp of virtual and actual objects, patients’ active motor performance had shown a moderate improvement [13].

The treatment of the plegic fingers after stroke is pertinent given their large cortical representation, the presumed competition between proximal and distal limb segments for plastic brain territory [14], and recent results from the MIT-group promoting earlier active treatment of distal limb [15]. Further, paresis-related immobilization seems to contribute to the development of long-term disabling finger flexor spasticity [16].

We have designed an electromechanical Finger Trainer to move individual fingers in a physiological range of movement. This article describes the device and reports its use in a small number of chronic and acute stroke patients with completely paralysed hands.

Device

The Finger Trainer, Reha-Digit, (figure 1) consists of four, mutually independent plastic rolls, each fixed eccentrically to the powered axle of the device, forming a cam-shaft. Each finger-roll can be repositioned & secured by turning a knob on the main axle, on the other end from the motor, to fit the size & range of movement of each individual finger.

Figure 1
figure1

The Finger Trainer, “Reha-Digit”, without a patient (left), and a left-hemiparetic patient practicing with the device (right).

The surface of each finger roll is concave, forming a gutter to maximise the contact area between finger & roll. Two smaller locking rollers, also concave, hold each finger against the larger finger roll. Each pair of locking rollers moves orthogonally to the axis of the finger roll, and an elastic spring pulls each pair of locking rollers towards the finger roller. These can be lifted out of the way when first positioning the hand & fingers in the device.

A spacing bar, parallel to the drive axle, holds the hand in the optimal position: a thumb stop may be used to provide additional stability. This can be moved to either side, to accommodate either the left or right hand. There are emergency-stop switches at each end of the spacing bar. The forearm can be stabilised at the correct angle & height on a gutter support.

A 24 V DC motor rotates the drive axle up to 30 times a minute through a clutch mechanism, which allows the axle to stop rotating if the hand goes into a powerful spasm. A vibration engine, situated under the base plate, provides small amplitude (2 mm) stimulation at a frequency which can be set between 0 to 30 Hz, by turning a knob. The device’s weight is 7 kg, and its dimensions are 35 cm × 24 cm × 22 cm.[…]

Continue —->  A new electromechanical trainer for sensorimotor rehabilitation of paralysed fingers: A case series in chronic and acute stroke patients | Journal of NeuroEngineering and Rehabilitation | Full Text

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[Abstract] Roles of Lesioned and Nonlesioned Hemispheres in Reaching Performance Poststroke

Background. Severe poststroke arm impairment is associated with greater activation of the nonlesioned hemisphere during movement of the affected arm. The circumstances under which this activation may be adaptive or maladaptive remain unclear.

Objective. To identify the functional relevance of key lesioned and nonlesioned hemisphere motor areas to reaching performance in patients with mild versus severe arm impairment.

Methods. A total of 20 participants with chronic stroke performed a reaching response time task with their affected arm. During the reaction time period, a transient magnetic stimulus was applied over the primary (M1) or dorsal premotor cortex (PMd) of either hemisphere, and the effect of the perturbation on movement time (MT) was calculated.

Results. For perturbation of the nonlesioned hemisphere, there was a significant interaction effect of Site of perturbation (PMd vs M1) by Group (mild vs severe; P < .001). Perturbation of PMd had a greater effect on MT in the severe versus the mild group. This effect was not observed with perturbation of M1. For perturbation of the lesioned hemisphere, there was a main effect of site of perturbation (P < .05), with perturbation of M1 having a greater effect on MT than PMd.

Conclusions. These results demonstrate that, in the context of reaching movements, the role of the nonlesioned hemisphere depends on both impairment severity and the specific site that is targeted. A deeper understanding of these individual-, task-, and site-specific factors is essential for advancing the potential usefulness of neuromodulation to enhance poststroke motor recovery.

  

via Roles of Lesioned and Nonlesioned Hemispheres in Reaching Performance Poststroke – Rachael M. Harrington, Evan Chan, Amanda K. Rounds, Clinton J. Wutzke, Alexander W. Dromerick, Peter E. Turkeltaub, Michelle L. Harris-Love,

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[VIDEO] Harnessing the Power of Neuroplasticity: The Nuts and Bolts of Better Brains – YouTube

What if your brain at 77 were as plastic as it was at 7? What if you could learn Mandarin with the ease of a toddler or play Rachmaninoff without breaking a sweat? A growing understanding of neuroplasticity suggests these fantasies could one day become reality. Neuroplasticity may also be the key to solving diseases like Alzheimer’s, depression, and autism. In this program, leading neuroscientists discuss their most recent findings and both the tantalizing possibilities and pitfalls for our future cognitive selves.

PARTICIPANTS: Alvaro Pascual-Leone, Nim Tottenham, Carla Shatz

MODERATOR: Guy McKhann

MORE INFO ABOUT THE PROGRAM AND PARTICIPANTS: https://www.worldsciencefestival.com/…

This program is part of the BIG IDEAS SERIES, made possible with support from the JOHN TEMPLETON FOUNDATION.

TOPICS: – Opening film 00:07 – What is neuroplasticity? 03:53 – Participant introductions 04:21 – Structure of the brain 05:21 – Is the brain fundamentally unwired at the start? 07:02 – Why does the process of human brain development seem inefficient? 08:30 – Balancing stability and plasticity 10:43 – Critical periods of brain development 13:01 – Extended human childhood development compared to other animals 14:54 – Stability and. plasticity in the visual system 17:37 – Reopening the visual system 25:13 – Pros and cons of brain plasticity vs. stability 27:28 – Plasticity in the autistic brain 29:55 – What is Transcranial magnetic stimulation (TMS) 31:25 – Phases of emotional development 33:10 – Schizophrenia and plasticity 37:40 – Recovery from brain injury 40:24 – Modern rehabilitation techniques 47:21 – Holy grail of Neuroscience 50:12 – Enhancing memory performance as we age 53:37 – Regulating emotions 57:19

PROGRAM CREDITS: – Produced by Nils Kongshaug – Associate Produced by Christine Driscoll – Opening film written / produced by Vin Liota – Music provided by APM – Additional images and footage provided by: Getty Images, Shutterstock, Videoblocks

This program was recorded live at the 2018 World Science Festival and has been edited and condensed for YouTube.

via Harnessing the Power of Neuroplasticity: The Nuts and Bolts of Better Brains – YouTube

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[BLOG POST] tES vs. TMS: pros and cons of the two techniques

tms-vs-tes

At Neuroelectrics, we believe in the advantages and effectiveness of transcranial electric stimulation (tES) in treating numerous brain diseases. Yet, despite the increasing number of tES publications per year, the lion’s share in the market of non-invasive brain stimulation technologies is still played by transcranial magnetic stimulation (TMS), likely because TMS received US-FDA approval in 2008 whereas tES has not yet.

Does this mean TMS is more effective? Well, it’s not quite fair to say so, considering TMS studies started at least 10 years earlier than those of tES. Therefore, there are several more clinical trials proving TMS efficacy.

However, the two techniques are close relatives: you can think of TMS as the elderly, stiff and sturdy brother, and tES as the younger, more flexible and easy-going one.
In this blogpost, we’ll go over the roots of their differences and see when and why you might prefer one over the other.

[E-fields patterns and biophysical substrates]

At a fundamental level, the two techniques rely on different physics and induce distinct patterns of electric fields (E-field) on the cortex, acting on a different neural substrate.

TMS is based on electromagnetic induction: a large magnetic coil is placed just a few centimetres above the scalp to stimulate over a specific cortical area. When the operator launches the electric pulse, vast amounts of current flows suddenly through the coil and creates a magnetic field around it, which varies rapidly in time. This changing magnetic field induces a very short (order of 1ms), highly localized (figure 1), super-threshold (order of 100V/m) E-field in the cortex. The E-field maximum is reached on the gyrus right under the coil, and the orientation is mostly parallel to the cortical surface.
The most sensitive cells to an E-field with such characteristics are interneurons and collaterals of pyramidal cells aligned tangentially to the cortical surface, which are automatically triggered to fire.

Instead, tES operates in the (quasi-)static regime, as only a small amount of direct current (DC) or low frequency alternating current (AC) is applied through electrodes placed directly on the scalp. The temporal resolution of the technique is low because the neuromodulatory effects begins a few seconds after the start of stimulation. Moreover, the E-field generated is much weaker (order of 0.1V/m) and less focalized (although the focality can be improved by using multichannel montages, it remains much lower than TMS E-field). Depending on the electrodes’ geometry, the maxima can occur on the gyri at the edges of the electrodes or between them. The overall orientation of the E-field is normal to the cortical surface, which indicates that tES probably influences layer V pyramidal neurons, as they are mostly perpendicular to the cortex.

Given the low, subthreshold intensity, the tES E-field cannot cause neural firing, but it is able to modulate the firing rate, facilitating or inhibiting the activation of pyramidal cells.

[Devices]

Other important differences concerning system setup.

TMS technology is more complex and cumbersome. The cost of the whole equipment is between 50-100k USD or Euros. This includes a wall-powered and heavy stimulator about the size of a fridge, a coil connected to the stimulator by a high-voltage cable, a mechanical arm to hold it in place, and a neuro-navigation system to accurately place the coil over the target brain region. The coil hangs suspended over the head of the patient, and since the strength of the effects depends on the coil-cortex distance, it’s crucial to keep it at the specific distance. For this, during the treatment session, the patient must sit still in a specially designed chair, with positioning frames around the chin and forehead.

On the contrary, tES is much cheaper and effortless: the cost is between an average of 6-30k USD/Euros, and the whole setup fits a shoe box. The stimulator can be as small as a mobile phone, light/portable, and almost always battery powered. The electrodes are directly in contact with the scalp, held in place by a rubber band or a neoprene cap. This way, the patient can move and even walk during the stimulation session.

[Applications]

Despite the underlying differences, TMS and tES are both quite versatile tools for treatment and research, and they offer similar options.

In research settings, you can leverage on TMS’ high spatial and temporal resolution to study how brain networks dynamically operate. In this context, TMS is usually performed online (during task performance) by applying one pulse at the onset of a stimulus (single-pulse TMS), or two pulses over separate regions which are interconnected (paired-pulses TMS). But tES too allows one to study the causal link between cortical areas. For instance, with tACS, one can simultaneously apply oscillatory currents over distinct regions at the same frequency but with different phases to promote or hamper the synchronization of functional networks.

Clinical applications of brain stimulation techniques instead tend to focus more on long-term effects, promoting network neuroplasticity that can outlast the period of stimulation.
In this case, TMS is usually ran in the repetitive mode (rTMS), which consists in multiple pulses within just microseconds. Frequency lower than 1Hz has been linked to long term depression (LTD), whereas frequency above 5Hz to long term potentiation (LTP). Similar outcomes can be achieved with tCS using either tDCS anodal or cathodal stimulation, which has been shown promoting and inhibiting synaptic activation, respectively.

The side effects of both techniques are quite moderate – with one important exception. While tES can induce only mild and temporary itching, tingling, and skin reddening when done properly, TMS might cause mild headaches, facial twitching, seizures in extreme cases.

For both TMS and tES, medical treatment must be performed mostly in clinical settings, which means you will have to find a clinician who provides these services in their clinic. However, one of the strengths of tES is the possibility to perform stimulation telemedically (under the remote guidance of a clinicians) via home-treatment. This is important as it will boost therapeutic effects for pathologies such as motor rehabilitation, depression, Alzheimer’s disease, etc in the comfort of one’s home. And it has been shown that the number of sessions modulates the length of the long-term plastic effects.

Interested in home-application of tCS? Check our home-kit here.

tes-vs-tms

Figure 1 Distribution of the E-field magnitude on the GM surface (left) and on a midsagittal slice (right) during TMS (A,C) and tDCS  with 35cm2 rectangular sponges (B, D). E-field magnitude is in V/m. Courtesy of Salvador et. al. 2015

[REFERENCES]

Polanía R, Nitsche M.A., Ruff C., Studying and modifying brain function with non-invasive brain stimulation, Nat. neurosci., 21:174–187 (2018)

Dayan E., Censor N., Buch E.R., Sandrini M, Cohen L.G., Noninvasive brain stimulation: from physiology to network dynamics and back, Nat. Neurosci., 16:838–844 (2013)

Salvador R., Wenger C., Miranda P.C. Investigating the cortical regions involved in MEP modulation in tDCS, Front. Cell. Neurosci. 9:405 (2015)

thebrainstimulator.net/brain-stimulation-comparison/caputron.com/pages/tms-vs-tdcs

 

via tES vs. TMS: pros and cons of the two techniques – Blog Neuroelectrics

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[Abstract] The effects of a robot-assisted arm training plus hand functional electrical stimulation on recovery after stroke: a randomized clinical trial

Abstract

Objective

To compare the effects of unilateral, proximal arm robot-assisted therapy combined with hand functional electrical stimulation to intensive conventional therapy for restoring arm function in subacute stroke survivors.

Design

This was a single blinded, randomized controlled trial.

Setting

Inpatient Rehabilitation University Hospital.

Participants

Forty patients diagnosed with ischemic stroke (time since stroke <8 weeks) and upper limb impairment were enrolled.

Interventions

Participants randomized to the experimental group received 30 sessions (5 sessions/week) of robot-assisted arm therapy and hand functional electrical stimulation (RAT + FES). Participants randomized to the control group received a time-matched intensive conventional therapy (ICT).

Main outcome measures

The primary outcome was arm motor recovery measured with the Fugl-Meyer Motor Assessment. Secondary outcomes included motor function, arm spasticity and activities of daily living. Measurements were performed at baseline, after 3 weeks, at the end of treatment and at 6-month follow-up. Presence of motor evoked potentials (MEPs) was also measured at baseline.

Results

Both groups significantly improved all outcome measures except for spasticity without differences between groups. Patients with moderate impairment and presence of MEPs who underwent early rehabilitation (<30 days post stroke) demonstrated the greatest clinical improvements.

Conclusions

A robot-assisted arm training plus hand functional electrical stimulation was no more effective than intensive conventional arm training. However, at the same level of arm impairment and corticospinal tract integrity, it induced a higher level of arm recovery.

 

via The effects of a robot-assisted arm training plus hand functional electrical stimulation on recovery after stroke: a randomized clinical trial – ScienceDirect

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[WEB SITE] Depression Overview: Emotional Symptoms, Physical Signs, and More – WebMD

via Depression Overview: Emotional Symptoms, Physical Signs, and More

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[Abstract] Role of Interhemispheric Cortical Interactions in Poststroke Motor Function

Background/Objective. We investigated interhemispheric interactions in stroke survivors by measuring transcranial magnetic stimulation (TMS)–evoked cortical coherence. We tested the effect of TMS on interhemispheric coherence during rest and active muscle contraction and compared coherence in stroke and older adults. We evaluated the relationships between interhemispheric coherence, paretic motor function, and the ipsilateral cortical silent period (iSP).

Methods. Participants with (n = 19) and without (n = 14) chronic stroke either rested or maintained a contraction of the ipsilateral hand muscle during simultaneous recordings of evoked responses to TMS of the ipsilesional/nondominant (i/ndM1) and contralesional/dominant (c/dM1) primary motor cortex with EEG and in the hand muscle with EMG. We calculated pre- and post-TMS interhemispheric beta coherence (15-30 Hz) between motor areas in both conditions and the iSP duration during the active condition.

Results. During active i/ndM1 TMS, interhemispheric coherence increased immediately following TMS in controls but not in stroke. Coherence during active cM1 TMS was greater than iM1 TMS in the stroke group. Coherence during active iM1 TMS was less in stroke participants and was negatively associated with measures of paretic arm motor function. Paretic iSP was longer compared with controls and negatively associated with clinical measures of manual dexterity. There was no relationship between coherence and. iSP for either group. No within- or between-group differences in coherence were observed at rest.

Conclusions. TMS-evoked cortical coherence during hand muscle activation can index interhemispheric interactions associated with poststroke motor function and potentially offer new insights into neural mechanisms influencing functional recovery.

 

via Role of Interhemispheric Cortical Interactions in Poststroke Motor Function – Jacqueline A. Palmer, Lewis A. Wheaton, Whitney A. Gray, Mary Alice Saltão da Silva, Steven L. Wolf, Michael R. Borich, 2019

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[Abstract] Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials

Background. After stroke, recovery of movement in proximal and distal upper extremity (UE) muscles appears to follow different time courses, suggesting differences in their neural substrates.

Objective. We sought to determine if presence or absence of motor evoked potentials (MEPs) differentially influences recovery of volitional contraction and strength in an arm muscle versus an intrinsic hand muscle. We also related MEP status to recovery of proximal and distal interjoint coordination and movement fractionation, as measured by the Fugl-Meyer Assessment (FMA).

Methods. In 45 subjects in the year following ischemic stroke, we tracked the relationship between corticospinal tract (CST) integrity and behavioral recovery in the biceps (BIC) and first dorsal interosseous (FDI) muscle. We used transcranial magnetic stimulation to probe CST integrity, indicated by MEPs, in BIC and FDI. We used electromyography, dynamometry, and UE FMA subscores to assess muscle-specific contraction, strength, and inter-joint coordination, respectively.

Results. Presence of MEPs resulted in higher likelihood of muscle contraction, greater strength, and higher FMA scores. Without MEPs, BICs could more often volitionally contract, were less weak, and had steeper strength recovery curves than FDIs; in contrast, FMA recovery curves plateaued below normal levels for both the arm and hand.

Conclusions. There are shared and separate substrates for paretic UE recovery. CST integrity is necessary for interjoint coordination in both segments and for overall recovery. In its absence, alternative pathways may assist recovery of volitional contraction and strength, particularly in BIC. These findings suggest that more targeted approaches might be needed to optimize UE recovery.

 

via Differential Poststroke Motor Recovery in an Arm Versus Hand Muscle in the Absence of Motor Evoked Potentials – Heidi M. Schambra, Jing Xu, Meret Branscheidt, Martin Lindquist, Jasim Uddin, Levke Steiner, Benjamin Hertler, Nathan Kim, Jessica Berard, Michelle D. Harran, Juan C. Cortes, Tomoko Kitago, Andreas Luft, John W. Krakauer, Pablo A. Celnik, 2019

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