Co-contraction Of Antagonist Muscles Research Articles

Changes in Muscle Activation and Joint Motion During Walking After Transtibial Amputation with Sensory Feedback from Spinal Cord Stimulation: A Case Study.

The goal of this study was to examine the effects of spinal cord stimulation (SCS) on muscle activity during walking after lower-limb amputation. Amputation results in a loss of sensory feedback and alterations in gait biomechanics, including co-contractions of antagonist muscles about the knee and ankle, and reduced pelvic obliquity range-of-motion and pelvic drop. SCS can restore sensation in the missing limb, but its effects on muscle activation and gait biomechanics have not been studied in people with lower-limb amputation. This case study included a participant with transtibial amputation who was implanted percutaneously with SCS electrodes over the lumbosacral enlargement for 84 days. SCS was used during in-lab experiments to provide somatosensory feedback from the missing limb, relaying a sense of plantar pressure when the prosthesis was in the stance phase of the gait cycle. We used electromyography (EMG) to record muscle activity from the residual and intact limbs, and 3D motion capture to measure pelvic obliquity. EMG signals were recorded during walking with and without SCS at early and late time points across the implant duration. During walking, co-contraction of knee antagonist muscles was reduced following multiple sessions of SCS-mediated sensory restoration. Additionally, the activation of the hip abductor (tensor fasciae latae) muscle increased activity during gait with SCS-mediated sensory restoration, which corresponded to an increase in pelvic obliquity range-of-motion and pelvic drop, towards normal. Restoring sensation in the missing limb using SCS modulated muscle activity during walking leading to improved coordination and pelvic motion in an individual with lower-limb amputation.

Peripheral nerve injury induces dystonia-like movements and dysregulation in the energy metabolism: A multi-omics descriptive study in Thap1+/- mice.

DYT-THAP1 dystonia is a monogenetic form of dystonia, a movement disorder characterized by the involuntary co-contraction of agonistic and antagonistic muscles. The disease is caused by mutations in the THAP1 gene, although the precise mechanisms by which these mutations contribute to the pathophysiology of dystonia remain unclear. The incomplete penetrance of DYT-THAP1 dystonia, estimated at 40 to 60 %, suggests that an environmental trigger may be required for the manifestation of the disease in genetically predisposed individuals. To investigate the gene-environment interaction in the development of dystonic features, we performed a sciatic nerve crush injury in a genetically predisposed DYT-THAP1 heterozygous knockout mouse model (Thap1+/-). We employed a multi-omic assessment to study the pathophysiological pathways underlying the disease. Phenotypic analysis using an unbiased deep learning algorithm revealed that nerve-injured Thap1+/- mice exhibited significantly more dystonia like movements (DLM) over the course of the 12-week experiment compared to naive Thap1+/- mice. In contrast, nerve-injured wildtype (wt) mice only showed a significant increase in DLM compared to their naive counterpart during the first weeks after injury. Furthermore, at week 11 after nerve crush, nerve-injured Thap1+/- mice displayed significantly more DLM than nerve-injured wt counterparts. Multi-omic analysis of the cerebellum, striatum and cortex in nerve-injured Thap1+/- mice revealed differences that are indicative of an altered energy metabolism compared to naive Thap1+/- and nerve-injured wt animals. These findings suggest that aberrant energy metabolism in brain regions relevant to dystonia may underlie the dystonic phenotype observed in nerve injured Thap1+/- mice.

Surface Electromyography for the Diagnosis of Tremor Syndrome: A Study of 97 Patients.

Tremor is one of the most frequent movement disorders encountered in clinical practice with heterogeneous phenomenology and etiology. Surface electromyography (SEMG) is a noninvasive and reproducible test that can diagnose tremor syndromes. In this retrospective study, the clinical and electrophysiologic records of 97 consecutive patients with tremor syndromes who visited our movement disorder clinic between January 2023 and March 2024 were examined. In our study, 28.8% (n = 28) of patients were of essential tremor (ET) syndrome. SEMG of ET syndrome patients showed synchronous bursts in 71.4% (n = 20), alternating bursts in 10.7% (n = 3), synchronous bursts with co-contraction of agonist and antagonist muscles in 10.7% (n = 3), and both synchronous and alternating bursts in 3.6% (n = 1) of patients. Tremor-ataxia syndrome formed 21.6% (n = 21) of our study population, with 71.4% (n = 15) of patients showing synchronous bursts and co-contraction and 28.6% (n = 6) patients having alternating bursts. Moreover, 12.3% (n = 12) patients were of parkinsonian tremor, of whom alternating bursts were present in 75% (n = 9) and synchronous bursts with co-contraction were present in 25% (n = 3) of patients. In addition, 11.3% (n = 11) of patients had dystonic tremor (DT), of whom 81.8% (n = 9) had synchronous bursts and co-contraction and 18.2% (n = 2) had alternating bursts. Synchronous bursts with co-contraction suggestive of DT were observed in most patients with tremor-ataxia syndrome and a small number of patients with ET syndrome. Our data suggests that SEMG helps differentiate these two clinical syndromes, which is difficult in a clinical setting.

The effectiveness of massage on pain, external knee adduction moment, and muscle Co-contraction in individuals with medial compartment knee osteoarthritis

BackgroundThe pain, external knee adduction moment (EKAM), and muscle co-contraction are increased in knee osteoarthritis (KOA). Massage therapy decreases pain in KOA, yet KOA is a mechanical disease and biomechanical changes need to be investigated as well. Therefore, the current study aims to investigate the effectiveness of massage on these outcomes in individuals with medial KOA. MethodsA cohort of fifteen participants with confirmed medial compartment KOA (2 males, 13 females, age: 61.33 (6.16) years; height: 1.62 (0.06) m; mass: 65.39 (4.04) kg; BMI: 24.74 (4.04) kg/m2) was given a six-week massage. Outcomes assessed pre- and post-intervention were: Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores, temporal-spatial variables, knee joint kinematics and kinetics in sagittal, frontal, and transverse planes, vertical ground reaction force (GRF), and knee antagonist muscle co-contraction during gait. The paired t-test were used for statistical analysis. ResultsFifteen participants completed the study. Significant improvements were observed in WOMAC scores (pain, stiffness, function, and total), walking speed, step length, 1st peak GRF, sagittal plane knee joint range of motion during stance, and medial muscle co-contraction in early and mid-stance (p < 0.05). However, no significant change was found in EKAM and knee adduction angular impulse (KAAI) (p > 0.05). ConclusionMassage therapy, as a stand-alone treatment, reduces pain, improves function, and decreases medial muscle co-contraction in individuals with medial KOA. Although EKAM did not change, the results suggest a reduction in medial muscle co-contraction might be a mechanism by which pain is improved.

Multi-session transcutaneous spinal cord stimulation prevents chloride homeostasis imbalance and the development of hyperreflexia after spinal cord injury in rat

Spasticity is a complex and multidimensional disorder that impacts nearly 75% of individuals with spinal cord injury (SCI) and currently lacks adequate treatment options. This sensorimotor condition is burdensome as hyperexcitability of reflex pathways result in exacerbated reflex responses, co-contractions of antagonistic muscles, and involuntary movements. Transcutaneous spinal cord stimulation (tSCS) has become a popular tool in the human SCI research field. The likeliness for this intervention to be successful as a noninvasive anti-spastic therapy after SCI is suggested by a mild and transitory improvement in spastic symptoms following a single stimulation session, but it remains to be determined if repeated tSCS over the course of weeks can produce more profound effects. Despite its popularity, the neuroplasticity induced by tSCS also remains widely unexplored, particularly due to the lack of suitable animal models to investigate this intervention. Thus, the basis of this work was to use tSCS over multiple sessions (multi-session tSCS) in a rat model to target spasticity after SCI and identify the long-term physiological improvements and anatomical neuroplasticity occurring in the spinal cord. Here, we show that multi-session tSCS in rats with an incomplete (severe T9 contusion) SCI (1) decreases hyperreflexia, (2) increases the low frequency-dependent modulation of the H-reflex, (3) prevents potassium-chloride cotransporter isoform 2 (KCC2) membrane downregulation in lumbar motoneurons, and (4) generally augments motor output, i.e., EMG amplitude in response to single pulses of tSCS, particularly in extensor muscles. Together, this work displays that multi-session tSCS can target and diminish spasticity after SCI as an alternative to pharmacological interventions and begins to highlight the underlying neuroplasticity contributing to its success in improving functional recovery.

Functional electrical stimulation therapy for upper extremity rehabilitation following spinal cord injury: a pilot study.

Pilot study. To examine if functional electrical stimulation therapy (FEST) improves neuromuscular factors underlying upper limb function in individuals with SCI. A tertiary spinal cord rehabilitation center specialized in spinal cord injury care in Canada. We examined 29 muscles from 4 individuals living with chronic, cervical, and incomplete SCI. The analysis was focused on the changes in muscle activation, as well as on how the treatment could change the ability to control a given muscle or on how multiple muscles would be coordinated during volitional efforts. There was evidence of gains in muscle strength, activation, and median frequency after the FEST. Gains in muscle activation indicated the activation of a greater number of motor units and gains in muscle median frequency the involvement of higher threshold, faster motor units. In some individuals, these changes were smaller but accompanied by increased control over muscle contraction, evident in a greater ability to sustain a volitional contraction, reduce the co-contraction of antagonist muscles, and provide cortical drive. FEST increases muscle strength and activation. Enhanced control of muscle contraction, reduced co-contraction of antagonist muscles, and a greater presence of cortical drive were some of the findings supporting the effects of FEST at the sensory-motor integration level.

Treatment of writer’s cramp based on current pathophysiological concepts

Task specific dystonia belongs to the group of focal dystonias. They are debilitating movement disorders that present with co-contraction of antagonist muscles during a specific task. The most common one is writer’s cramp. Botulinum toxin is the symptomatic standard treatment. Its response rate is 50% after 1 year, and the overall efficacy limited due to unwanted weakness in not injected muscles. The pathophysiology of writer’s cramp remains unclear, but genetic and additional environmental causes have been proposed. A possible underlying mechanism may be maladaptive reorganization in the sensorimotor cortex. Based on this background alternative treatment strategies were developed such as several different sensory and motor training programs that have been applied to reverse these brain abnormalities. In some studies, sensory and motor training were combined and adjunct with fitness exercises. They were conducted either as an outpatient setting or were established home based. Clinical outcome was measured with different clinical scales such as the writer’s cramp rating scale, the arm dystonia rating scale or the Burke, Fahn Marsden Scale. For objective assessment, kinematic handwriting parameters were analyzed. Functional or structural changes of the sensorimotor cortex were estimated using functional magnetic tomography, magnetencephalography and voxel-based morphometry. The results of these training programs were promising; however, one drawback is that the number of patients studied were small and the programs were not controlled since it is difficult to establish a control training to conduct a randomized controlled study.

Dystonias: Clinical Recognition and the Role of Additional Diagnostic Testing.

Dystonia is the third most common movement disorder, characterized by abnormal, frequently twisting postures related to co-contraction of agonist and antagonist muscles. Diagnosis is challenging. We provide a comprehensive appraisal of the epidemiology and an approach to the phenomenology and classification of dystonia, based on the clinical characteristics and underlying etiology of dystonia syndromes. We discuss the features of common idiopathic and genetic forms of dystonia, diagnostic challenges, and dystonia mimics. Appropriate workup is based on the age of symptom onset, rate of progression, whether dystonia is isolated or combined with another movement disorder or complex neurological and other organ system features. Based on these features, we discuss when imaging and genetic should be considered. We discuss the multidisciplinary treatment of dystonia, including rehabilitation and treatment principles according to the etiology, including when pathogenesis-direct treatment is available, oral pharmacological therapy, chemodenervation with botulinum toxin injections, deep brain stimulation and other surgical therapies, and future directions.

Estimation of muscle activities with co-contractions of antagonist muscles

Estimation of muscle activities with co-contractions of antagonist muscles

Abnormal movements "Motare" in Kyudo have the characteristics of task-specific focal dystonia

Among the abnormal kyudo movements ("yips"), "motare" is the inability to release the arrow at the intended timing if aiming the target. We hypothesized that "motare" is a task-specific focal dystonia (TSFD). We interviewed three participants with "motare," three participants with "hayake", and three controls without "motare" nor "hayake". Moreover, we conducted a surface electromyography (sEMG) examination and found that "motare" was characterized by stereotypy, sensory tricks, and morning benefit; however, these findings were not observed in "hayake". Abnormal co-contraction of the upper extremity antagonist muscles was observed in one of the three "motare" participants. Overall, these findings suggest that "motare" have the characteristics of TSFD not previously reported.

Locomotor resilience through load-dependent modulation of muscle co-contraction

Terrestrial locomotor behavior in variable environments requires resilience to sudden changes in substrate properties. For example, walking animals can adjust to substantial changes in slope and corresponding changes in load distribution among legs. In insects, slope-dependent adjustments have mainly been examined under steady-state conditions, whereas the transition dynamics have been largely neglected. In a previous study, we showed that steady-state adjustments of stick insects to ±45deg slopes involve substantial changes in joint torques and muscle activity with only minor changes in leg kinematics. Here, we took a close look at the time course of these adjustments as stick insects compensate for various kinds of disturbances to load distribution. In particular, we tested whether the transition from one steady state to another involves distinct transition steps or follows a graded process. To resolve this, we combined simultaneous recordings of whole-body kinematics and hindleg muscle activity to elucidate how freely walking Carausius morosus negotiated a step-change in substrate slope. Step-by-step adjustments revealed that muscle activity changed in a graded manner as a function of body pitch relative to gravity. We further show analogous transient adjustment of muscle activity in response to destabilizing lift-off events of neighboring legs and the disappearance of antagonist co-activation during crawling episodes. Given these three examples of load-dependent regulation of antagonist muscle co-contraction, we conclude that stick insects respond to both transient and sustained changes in load distribution by regulating joint stiffness rather than through distinct transition steps.

Muscle co-contraction and pre-activation in knee and ankle joint during a typical Tai Chi brush-knee twist-step

ABSTRACT This study aimed to investigate the co-contraction and pre-activation of agonistic and antagonistic muscles in experienced Tai Chi (TC) practitioners during normal walking (NW) and brush-knee twist-step (BKTS). The electromyographic activities of rectus femoris, biceps femoris, and tibialis anterior and lateral gastrocnemius muscles were collected during BKTS and NW in 28 TC practitioners. The pre-activation of knee and ankle joints before initial landing of left foot, and the co-contraction of knee and ankle joint in double-stance phase I (DSI), single-stance phase (SS), double-stance phase II (DSII), and swing phase (SW) were calculated during BKTS and NW. Ankle co-contraction significantly increased during DSI and SS in BKTS movements than compared with that in NW. For DSI and SW, SS and DSII, and DSII and SW, a significant difference was found in BKTS. The pre-activation of knee joint significantly decreased in BKTS and NW. This study indicated greater ankle joint muscle co-contraction in DSI and SS of stance phase and lower knee joint muscle co-contraction and pre-activation than in NW in BKTS movement. In addition, greater ankle joint muscle co-contraction was observed in the DSI, SS, and DSII of stance phase than those of swing phase in BKTS movement.

Proximal and distal spinal neurons innervating multiple synergist and antagonist motor pools.

Motoneurons (MNs) control muscle contractions, and their recruitment by premotor circuits is tuned to produce accurate motor behaviours. To understand how these circuits coordinate movement across and between joints, it is necessary to understand whether spinal neurons pre-synaptic to motor pools have divergent projections to more than one MN population. Here, we used modified rabies virus tracing in mice to investigate premotor interneurons projecting to synergist flexor or extensor MNs, as well as those projecting to antagonist pairs of muscles controlling the ankle joint. We show that similar proportions of premotor neurons diverge to synergist and antagonist motor pools. Divergent premotor neurons were seen throughout the spinal cord, with decreasing numbers but increasing proportion with distance from the hindlimb enlargement. In the cervical cord, divergent long descending propriospinal neurons were found in contralateral lamina VIII, had large somata, were neither glycinergic, nor cholinergic, and projected to both lumbar and cervical MNs. We conclude that distributed spinal premotor neurons coordinate activity across multiple motor pools and that there are spinal neurons mediating co-contraction of antagonist muscles.

SY2.4. Sensori-motor organisation in focal hand dystonia

Focal Hand Dystonia is a task specific dystonia with co-contraction of agonists and antagonistic muscles. This disorder is attributed to a plausible dysfunction of the basal ganglia, but the exact role and sites are not yet well characterized. At our institution, we did experiments’ to explore the ontogeny of muscle contraction, sensory abnormalities and precision grip studies to explore dysfunction. The first study looked at the utility of 16 Channel surface EMG using customized software to objectively assess FHD during different phases of a writing task used to study timing, activation patterns and spread of muscle contractions in FHD when compared to normal controls. SEMG of FHD subjects showed ‘early onset’ during motor imagery, rapid proximal recruitment, co-contraction of agonist-antagonist proximal muscle groups, delayed offset after stopping to write, mirror activity in contralateral limb when compared to controls. The second experiment aimed to look at the degree of sensory dysfunction in subjects with Writer’s cramp using tasks for spatial discrimination and Aristotle illusory phenomenon and to look for Neural correlates using f MRI. There were abnormalities of sensory processing in patients with FHD in both spatial and illusory phenomenon. Spatial discriminatory abnormality was see in both hands indicating abnormalities in bilateral somatosensory cortex leading to abnormal sensory motor integration and resultant maladaptive plasticity and f MRI showed lack of good separation of activity for index and little finger stimulation with JVP dome. The third experiment looked at precision grip (both qualitative and quantitative measures) to discriminate FHD and PD from normal subjects. Healthy controls and patients (PD/FHD) gripped and lifted objects of 2 different weights;1.3 N &1.7 N with Dry Skin Condition and Very Wet Skin Condition. After practice trials, subjects were asked to reach, lift and hold stationary an object for 5 seconds and release the object on command. The force, rate and time parameters are measured and a ROC curve was measured and this study could qualitatively differentiate FHD and PD. These studies highlight that in FHD there is motor and sensory processing abnormalities demonstrating abnormal plasticity.

Enhancing KCC2 activity decreases hyperreflexia and spasticity after chronic spinal cord injury

After spinal cord injury (SCI), the majority of individuals develop spasticity, a debilitating condition involving involuntary movements, co-contraction of antagonistic muscles, and hyperreflexia. By acting on GABAergic and Ca2+-dependent signaling, current anti-spastic medications lead to serious side effects, including a drastic decrease in motoneuronal excitability which impairs motor function and rehabilitation efforts. Exercise, in contrast, decreases spastic symptoms without decreasing motoneuron excitability. These functional improvements coincide with an increase in expression of the chloride co-transporter KCC2 in lumbar motoneurons. Thus, we hypothesized that spastic symptoms can be alleviated directly through restoration of chloride homeostasis and endogenous inhibition by increasing KCC2 activity. Here, we used the recently developed KCC2 enhancer, CLP257, to evaluate the effects of acutely increasing KCC2 extrusion capability on spastic symptoms after chronic SCI. Sprague Dawley rats received a spinal cord transection at T12 and were either bike-trained or remained sedentary for 5 weeks. Increasing KCC2 activity in the lumbar enlargement improved the rate-dependent depression of the H-reflex and reduced both phasic and tonic EMG responses to muscle stretch in sedentary animals after chronic SCI. Furthermore, the improvements due to this pharmacological treatment mirror those of exercise. Together, our results suggest that pharmacologically increasing KCC2 activity is a promising approach to decrease spastic symptoms in individuals with SCI. By acting to directly restore endogenous inhibition, this strategy has potential to avoid severe side effects and improve the quality of life of affected individuals.

Impedance Control of Human Ankle Joint With Electrically Stimulated Antagonistic Muscle Co-Contraction.

Functional electrical stimulation (FES) is often used, typically in an open-loop manner, to restore paralyzed motor function for daily living activities. Several feedback control strategies have been developed to improve the performance and usability of FES-evoked movement. However, most of them have been position controllers, while the control strategy for human movement has been known as impedance modulation. Moreover, few studies have attempted to use antagonistic co-contraction for FES feedback control despite its expected benefits, such as enhanced stability and performance and better rehabilitation outcome. In this paper, we propose a robust impedance controller for FES that can adjust the intrinsic joint stiffness using co-contraction. It consists of an impedance control law based on time-delay estimation to compensate for the nonlinear uncertain joint dynamics and an antagonistic muscle co-contraction allocator to address the intrinsic joint stiffness caused by the co-contraction. The proposed controller was implemented on the ankle joints of five healthy subjects to simulate a standing balance situation. The results verified that the proposed controller can achieve desired impedance accurately by adjusting the intrinsic stiffness that stems from the change in the amount of co-contraction (up to 48.4% better impedance achievement with high desired stiffness).

Muscle co-contraction in an upper limb musculoskeletal model: EMG-assisted vs. standard load-sharing

Estimation of muscle forces in over-actuated musculoskeletal models involves optimal distributions of net joint moments among muscles by a standard load-sharing scheme (SLS). Given that co-contractions of antagonistic muscles are counterproductive in the net joints moments, SLS might underestimate the co-contractions. Muscle co-contractions play crucial roles in stability of the glenohumeral (GH) joint. The aim of this study was to improve estimations of muscle co-contractions by incorporating electromyography (EMG) data into an upper limb musculoskeletal model. To this end, the model SLS was modified to develop an EMG-assisted load-sharing scheme (EALS). EMG of fifteen muscles were measured during arm flexion and abduction on a healthy subject and fed into the model. EALS was compared to SLS in terms of muscle forces, GH joint reaction force, and a stability ratio defined to quantify the GH joint stability. The results confirmed that EALS estimated higher muscle co-contractions compared to the SLS (e.g., above 50 N higher forces for both triceps long and biceps long during arm flexion).

Internet-based cognitive behavioural therapy programme as an intervention for people diagnosed with adult-onset, focal, isolated, idiopathic cervical dystonia: a feasibility study protocol

BackgroundDystonia is one of the most common forms of movement disorder, caused by the co-contraction of antagonistic muscles, leading to abnormal postures and considerable disability. Non-motor symptoms, notably psychiatric disorders, are well recognised comorbid features of the disorder. However, there is no standardised model for the management of these symptoms in dystonia, with them frequently going undiagnosed and untreated. An internet-based cognitive behavioural therapy programme may provide a future model of care that also maximises available resources.MethodsThis study represents a two-armed randomised feasibility trail, aiming to recruit a total of 20 participants with a diagnosis of adult-onset primary focal cervical dystonia. Participants will be recruited from the Global Myoclonus Dystonia Registry and Dystonia Non-Motor Symptom Study (conducted at Cardiff University) based on presence of moderate symptoms of anxiety/depression as indicated by standardised questionnaires. All participants will undergo assessment at baseline, 3 and 6 months, with this including questionnaires for assessment of non-motor symptoms and clinical assessment of motor symptom severity. Participants will be randomised to either the control (n = 10) or treatment (n = 10) groups. The treatment group will be asked to complete one session of the online CBT program a week, for 8 weeks. The primary outcome measure will be the engagement of participants with the programme, with secondary outcomes of non-motor and motor symptom scores.DiscussionPromising results have been shown using face-to-face cognitive behavioural therapy to reduce levels of anxiety and depression in individuals with a diagnosis of dystonia. However, no studies to date have sought to determine the feasibility of an internet-delivered cognitive behavioural therapy programme. A number of effective internet-based programmes have been developed that combat anxiety and depression in the general population, suggesting the potential for its effectiveness in cervical dystonia patients. Success with this study would significantly impact the clinical care delivery for patients with cervical dystonia, as well as widening potential access to effective treatment.Trial registrationThis feasibility trial has been registered with Health and Care Research Wales Research Directory. Trial registration number 44245. Date of registration: 21 November 2019. https://www.healthandcareresearch.gov.wales/research-studies-in-wales/

Computational evidence for nonlinear feedforward modulation of fusimotor drive to antagonistic co-contracting muscles

The sensorimotor integration during unconstrained reaching movements in the presence of variable environmental forces remains poorly understood. The objective of this study was to quantify how much the primary afferent activity of muscle spindles can contribute to shaping muscle coactivation patterns during reaching movements with complex dynamics. To achieve this objective, we designed a virtual reality task that guided healthy human participants through a set of planar reaching movements with controlled kinematic and dynamic conditions that were accompanied by variable muscle co-contraction. Next, we approximated the Ia afferent activity using a phenomenological model of the muscle spindle and muscle lengths derived from a musculoskeletal model. The parameters of the spindle model were altered systematically to evaluate the effect of fusimotor drive on the shape of the temporal profile of afferent activity during movement. The experimental and simulated data were analyzed with hierarchical clustering. We found that the pattern of co-activation of agonistic and antagonistic muscles changed based on whether passive forces in each movement played assistive or resistive roles in limb dynamics. The reaching task with assistive limb dynamics was associated with the most muscle co-contraction. In contrast, the simulated Ia afferent profiles were not changing between tasks and they were largely reciprocal with homonymous muscle activity. Simulated physiological changes to the fusimotor drive were not sufficient to reproduce muscle co-contraction. These results largely rule out the static set and α-γ coactivation as the main types of fusimotor drive that transform the monosynaptic Ia afferent feedback into task-dependent co-contraction of antagonistic muscles. We speculate that another type of nonlinear transformation of Ia afferent signals that is independent of signals modulating the activity of α motoneurons is required for Ia afferent-based co-contraction. This transformation could either be applied through a complex nonlinear profile of fusimotor drive that is not yet experimentally observed or through presynaptic inhibition.

Non-invasive brain stimulation and kinesiotherapy for treatment of focal dystonia: Instrumental analysis of three cases

Dystonia is a disabling movement disorder characterized by co-contraction of antagonist and agonist muscles, leading to abnormal sustained postures and impaired motor control. Cervical Dystonia (CD) and Hand Focal Dystonia (HFD) have been the most common forms of focal dystonia (FD). Do Non-Invasive Brain Neuromodulation (NIBS) such as Transcranial Direct Current Stimulation (tDCS) and repetitive Transcranial Magnetic Stimulation (rTMS) modulate the excitability of the connections between the motor cortical areas and may represent a therapeutic alternative for focal dystonia? Herein, we reported three cases of focal dystonia, two of them with cervical dystonia (CD) and one with hand focal dystonia (HFD), treated with NIBS combined to kinesiotherapy. The patients were daily submitted to 15 sessions of NIBS combined simultaneously with kinesiotherapy. CD patients were treated with tDCS (2 mA, 20 min, over the primary motor cortex), and HFD patient with rTMS (1 Hz, 1200 pulses, 80% of resting motor threshold, over the premotor cortex). For the CD patient’s assessment, the Modified Toronto Scale for Cervical Dystonia Assessment (MTS), quiet balance test, and visual postural assessment were applied to observe the therapeutic effects. Quality handwriting analysis, tremor acceleration amplitudes, and the Wrinter’s Cramp Rating Scale (WCRS) were used to assess the NIBS effect on HFD symptoms. Patients were evaluated before (pretest), immediately after (posttest), and three months after treatment (retention). NIBS associated with kinesiotherapy produced a long-term improvement of dystonia symptoms in all three patients. rTMS and tDCS associated with kinesiotherapy showed to be useful and safe to relief the dystonia symptoms in individuals with different types of focal dystonia with distinct functional disorders. SignificanceThe combined use of these intervention strategies seems to optimize and anticipate satisfactory clinical results in these neurological conditions, characterized by its difficult clinical management.