Motor modules during adaptation to walking in a powered ankle exoskeleton

Jacobs, Daniel A.; Koller, Jeffrey R.; Steele, Katherine M.; Ferris, Daniel P.

doi:10.1186/s12984-017-0343-x

Cited by 40 publications

(32 citation statements)

References 67 publications

(100 reference statements)

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“…The lack of changes in synergy composition contrasts with research in unimpaired adults, where highly trained individuals have been found to have altered synergies compared to novices [47–49]. Further, interventions such as powered exoskeletons have been shown to alter synergy weights and activations [50–52]. Whether future innovations in treatments such as feedback training [50, 53, 54], forced exploration of new movement patterns [55], or electrical stimulation of the spinal cord [56] can induce similar changes in synergies for individuals with CP remains unknown.…”

Section: Discussionmentioning

confidence: 99%

Muscle synergies demonstrate only minimal changes after treatment in cerebral palsy

Shuman

Goudriaan

Desloovere

et al. 2019

J NeuroEngineering Rehabil

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Background Children with cerebral palsy (CP) have altered synergies compared to typically-developing peers, reflecting different neuromuscular control strategies used to move. While these children receive a variety of treatments to improve gait, whether synergies change after treatment, or are associated with treatment outcomes, remains unknown. Methods We evaluated synergies for 147 children with CP before and after three common treatments: botulinum toxin type-A injection ( n = 52), selective dorsal rhizotomy ( n = 38), and multi-level orthopaedic surgery ( n = 57). Changes in synergy complexity were measured by the number of synergies required to explain > 90% of the total variance in electromyography data and total variance accounted for by one synergy. Synergy weights and activations before and after treatment were compared using the cosine similarity relative to average synergies of 31 typically-developing (TD) peers. Results There were minimal changes in synergies after treatment despite changes in walking patterns. Number of synergies did not change significantly for any treatment group. Total variance accounted for by one synergy increased (i.e., moved further from TD peers) after botulinum toxin type-A injection (1.3%) and selective dorsal rhizotomy (1.9%), but the change was small. Synergy weights did not change for any treatment group (average 0.001 ± 0.10), but synergy activations after selective dorsal rhizotomy did change and were less similar to TD peers (− 0.03 ± 0.07). Only changes in synergy activations were associated with changes in gait kinematics or walking speed after treatment. Children with synergy activations more similar to TD peers after treatment had greater improvements in gait. Conclusions While many of these children received significant surgical procedures and prolonged rehabilitation, the minimal changes in synergies after treatment highlight the challenges in altering neuromuscular control in CP. Development of treatment strategies that directly target impaired control or are optimized to an individual’s unique control may be required to improve walking function.

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Section: Discussionmentioning

confidence: 99%

Muscle synergies demonstrate only minimal changes after treatment in cerebral palsy

Shuman

Goudriaan

Desloovere

et al. 2019

J NeuroEngineering Rehabil

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“…Future research should examine the opportunities of specific therapies that target the neural level and adapt muscle synergies, to improve the walking pattern of children with CP. Previous research in unimpaired individuals showed that both the spatial and temporal structure of muscle synergies can change due to intense training in elite athletes (Sawers et al, 2015 ; Kim M. et al, 2018 ), and with the use of ankle exoskeletons (Steele et al, 2017 ; Jacobs et al, 2018 ). However, current treatments studied in CP were found to have no effect on the spatial structure and merely an effect on the temporal structure of muscle synergies (Shuman et al, 2019 ).…”

Section: Discussionmentioning

confidence: 99%

Muscle Synergies During Walking in Children With Cerebral Palsy: A Systematic Review

et al. 2020

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Background: Walking problems in children with cerebral palsy (CP) can in part be explained by limited selective motor control. Muscle synergy analysis is increasingly used to quantify altered neuromuscular control during walking. The early brain injury in children with CP may lead to a different development of muscle synergies compared to typically developing (TD) children, which might characterize the abnormal walking patterns. Objective: The overarching aim of this review is to give an overview of the existing studies investigating muscle synergies during walking in children with CP compared to TD children. The main focus is on how muscle synergies differ between children with CP and TD children, and we examine the potential of muscle synergies as a measure to quantify and predict treatment outcomes. Methods: Bibliographic databases were searched by two independent reviewers up to 22 April 2019. Studies were included if the focus was on muscle synergies of the lower limbs during walking, obtained by a matrix factorization algorithm, in children with CP. Results: The majority (n = 12) of the 16 included studies found that children with CP recruited fewer muscle synergies during walking compared to TD children, and several studies (n = 8) showed that either the spatial or temporal structure of the muscle synergies differed between children with CP and TD children. Variability within and between subjects was larger in children with CP than in TD children, especially in more involved children. Muscle synergy characteristics before treatments to improve walking function could predict treatment outcomes (n = 3). Only minimal changes in synergies were found after treatment. Conclusions: The findings in this systematic review support the idea that children with CP use a simpler motor control strategy compared to TD children. The use of muscle synergy analysis as a clinical tool to quantify altered neuromuscular control and predict clinical outcomes seems promising. Further investigation on this topic is necessary, and the use of muscle synergies as a target for development of novel therapies in children with CP could be explored.

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“…Second, some synergies were not altered in weights but instead, ceased to be used strongly in patterns. Both of these types of changes are likely significant in motor drive infrastructure, pattern generation, and the pathologies and injury effects where synergies may have impact (27,(33)(34)(35)(36)(37)(38)(39)(40)(44)(45)(46)(47)(48)(49). Synergies normally weakly activated in intact CNS that become active in disease would interfere with normal function and be pathological.…”

Section: Discussionmentioning

confidence: 99%

Motor primitives are determined in early development and are then robustly conserved into adulthood

Yang

Logan

Giszter

2019

Proc. Natl. Acad. Sci. U.S.A.

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Motor patterns in legged vertebrates show modularity in both young and adult animals, comprising motor synergies or primitives. Are such spinal modules observed in young mammals conserved into adulthood or altered? Conceivably, early circuit modules alter radically through experience and descending pathways' activity. We analyze lumbar motor patterns of intact adult rats and the same rats after spinal transection and compare these with adult rats spinal transected 5 days postnatally, before most motor experience, using only rats that never developed hind limb weight bearing. We use independent component analysis (ICA) to extract synergies from electromyography (EMG). ICA information-based methods identify both weakly active and strongly active synergies. We compare all spatial synergies and their activation/drive strengths as proxies of spinal modules and their underlying circuits. Remarkably, we find that spatial primitives/synergies of adult injured and neonatal injured rats differed insignificantly, despite different developmental histories. However, intact rats possess some synergies that differ significantly, although modestly, in spatial structure. Rats injured as adults were more similar in modularity to rats that had neonatal spinal transection than to themselves before injury. We surmise that spinal circuit modules for spatial synergy patterns may be determined early, before postnatal day 5 (P5), and remain largely unaltered by subsequent development or weight-bearing experience. An alternative explanation but equally important is that, after complete spinal transection, both neonatal and mature adult spinal cords rapidly converge to common synergy sets. This fundamental or convergent synergy circuitry, fully determined by P5, is revealed after spinal cord transection.motor primitives | muscle synergies | pattern generation | spinal cord injury | development M otor patterns can show significant modularity in legged vertebrates. Modularity can take several forms (1). Here, we examine modular motor drives in spinal systems. This approach combines both structural and functional neural components. The fundamental idea is that basic movement is largely composed of small numbers of synergies or motor primitives, which act as building blocks (1-5). Synergies for this study are defined as spatial synergies (1), which each represent a premotor drive to motor pools, causing covarying muscle activity in a specific balance. Such drives could arise from a well-defined neural substrate of sets of neurons with specific premotor connectivity. Indeed, some data in frogs and monkeys support this idea (6, 7). Such modularity could arise as follows: first, directly through evolutionarily determined processes in development; second, through plastic online optimizations during development; third, de novo during motor skill learning; or fourth, via some combinations of these (1,2,4,8). The collection of synergies resulting from any of these processes can form a library of compositional elements useful both for new movement con...

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Motor modules during adaptation to walking in a powered ankle exoskeleton

Cited by 40 publications

References 67 publications

Muscle synergies demonstrate only minimal changes after treatment in cerebral palsy

Muscle synergies demonstrate only minimal changes after treatment in cerebral palsy

Muscle Synergies During Walking in Children With Cerebral Palsy: A Systematic Review

Motor primitives are determined in early development and are then robustly conserved into adulthood

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