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1.
Pediatr Dermatol ; 2024 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-38444084

RESUMO

PIK3CA-related overgrowth spectrum (PROS) encompasses different clinical entities caused by somatic activating mutations in PIK3CA. Among PROS, CLOVES syndrome represents a severe phenotype with poor survival rate. We present the case of a 4-month-old girl with CLOVES syndrome successfully treated with alpelisib, a PIKC3A inhibitor.

2.
J Neuroeng Rehabil ; 21(1): 18, 2024 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-38311729

RESUMO

Practicing clinicians in neurorehabilitation continue to lack a systematic evidence base to personalize rehabilitation therapies to individual patients and thereby maximize outcomes. Computational modeling- collecting, analyzing, and modeling neurorehabilitation data- holds great promise. A key question is how can computational modeling contribute to the evidence base for personalized rehabilitation? As representatives of the clinicians and clinician-scientists who attended the 2023 NSF DARE conference at USC, here we offer our perspectives and discussion on this topic. Our overarching thesis is that clinical insight should inform all steps of modeling, from construction to output, in neurorehabilitation and that this process requires close collaboration between researchers and the clinical community. We start with two clinical case examples focused on motor rehabilitation after stroke which provide context to the heterogeneity of neurologic injury, the complexity of post-acute neurologic care, the neuroscience of recovery, and the current state of outcome assessment in rehabilitation clinical care. Do we provide different therapies to these two different patients to maximize outcomes? Asking this question leads to a corollary: how do we build the evidence base to support the use of different therapies for individual patients? We discuss seven points critical to clinical translation of computational modeling research in neurorehabilitation- (i) clinical endpoints, (ii) hypothesis- versus data-driven models, (iii) biological processes, (iv) contextualizing outcome measures, (v) clinical collaboration for device translation, (vi) modeling in the real world and (vii) clinical touchpoints across all stages of research. We conclude with our views on key avenues for future investment (clinical-research collaboration, new educational pathways, interdisciplinary engagement) to enable maximal translational value of computational modeling research in neurorehabilitation.


Assuntos
Reabilitação Neurológica , Reabilitação do Acidente Vascular Cerebral , Acidente Vascular Cerebral , Humanos , Avaliação de Resultados em Cuidados de Saúde
3.
J Neuroeng Rehabil ; 21(1): 46, 2024 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-38570842

RESUMO

We present an overview of the Conference on Transformative Opportunities for Modeling in Neurorehabilitation held in March 2023. It was supported by the Disability and Rehabilitation Engineering (DARE) program from the National Science Foundation's Engineering Biology and Health Cluster. The conference brought together experts and trainees from around the world to discuss critical questions, challenges, and opportunities at the intersection of computational modeling and neurorehabilitation to understand, optimize, and improve clinical translation of neurorehabilitation. We organized the conference around four key, relevant, and promising Focus Areas for modeling: Adaptation & Plasticity, Personalization, Human-Device Interactions, and Modeling 'In-the-Wild'. We identified four common threads across the Focus Areas that, if addressed, can catalyze progress in the short, medium, and long terms. These were: (i) the need to capture and curate appropriate and useful data necessary to develop, validate, and deploy useful computational models (ii) the need to create multi-scale models that span the personalization spectrum from individuals to populations, and from cellular to behavioral levels (iii) the need for algorithms that extract as much information from available data, while requiring as little data as possible from each client (iv) the insistence on leveraging readily available sensors and data systems to push model-driven treatments from the lab, and into the clinic, home, workplace, and community. The conference archive can be found at (dare2023.usc.edu). These topics are also extended by three perspective papers prepared by trainees and junior faculty, clinician researchers, and federal funding agency representatives who attended the conference.


Assuntos
Pessoas com Deficiência , Reabilitação Neurológica , Humanos , Software , Simulação por Computador , Algoritmos
4.
Entropy (Basel) ; 25(10)2023 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-37895535

RESUMO

Quantifying the dynamical features of discrete tasks is essential to understanding athletic performance for many sports that are not repetitive or cyclical. We compared three dynamical features of the (i) bow hand, (ii) drawing hand, and (iii) center of mass during a single bow-draw movement between professional and neophyte archers: dispersion (convex hull volume of their phase portraits), persistence (tendency to continue a trend as per Hurst exponents), and regularity (sample entropy). Although differences in the two groups are expected due to their differences in skill, our results demonstrate we can quantify these differences. The center of mass of professional athletes exhibits tighter movements compared to neophyte archers (6.3 < 11.2 convex hull volume), which are nevertheless less persistent (0.82 < 0.86 Hurst exponent) and less regular (0.035 > 0.025 sample entropy). In particular, the movements of the bow hand and center of mass differed more between groups in Hurst exponent analysis, and the drawing hand and center of mass were more different in sample entropy analysis. This suggests tighter neuromuscular control over the more fluid dynamics of the movement that exhibits more active corrections that are more individualized. Our work, therefore, provides proof of principle of how well-established dynamical analysis techniques can be used to quantify the nature and features of neuromuscular expertise for discrete movements in elite athletes.

5.
PLoS Comput Biol ; 17(3): e1008707, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33684099

RESUMO

Variability in muscle force is a hallmark of healthy and pathological human behavior. Predominant theories of sensorimotor control assume 'motor noise' leads to force variability and its 'signal dependence' (variability in muscle force whose amplitude increases with intensity of neural drive). Here, we demonstrate that the two proposed mechanisms for motor noise (i.e. the stochastic nature of motor unit discharge and unfused tetanic contraction) cannot account for the majority of force variability nor for its signal dependence. We do so by considering three previously underappreciated but physiologically important features of a population of motor units: 1) fusion of motor unit twitches, 2) coupling among motoneuron discharge rate, cross-bridge dynamics, and muscle mechanics, and 3) a series-elastic element to account for the aponeurosis and tendon. These results argue strongly against the idea that force variability and the resulting kinematic variability are generated primarily by 'motor noise.' Rather, they underscore the importance of variability arising from properties of control strategies embodied through distributed sensorimotor systems. As such, our study provides a critical path toward developing theories and models of sensorimotor control that provide a physiologically valid and clinically useful understanding of healthy and pathologic force variability.


Assuntos
Fenômenos Biomecânicos/fisiologia , Modelos Neurológicos , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Biologia Computacional , Humanos , Neurônios Motores/fisiologia , Recrutamento Neurofisiológico/fisiologia
6.
Ann Fam Med ; 20(3): 227-236, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35606120

RESUMO

PURPOSE: We investigated whether lung ultrasound (US) performed in primary care is useful and feasible for diagnosing community-acquired pneumonia (CAP) compared with chest radiography, as most previous research has been conducted in hospital settings. METHODS: We undertook a prospective observational cohort study of lung US performed in 12 primary care centers. Patients aged 5 years and older with symptoms suggesting CAP were examined with lung US (by 21 family physicians and 7 primary care pediatricians) and chest radiograph on the same day. We compared lung US findings with the radiologist's chest radiograph report as the reference standard, given that the latter is the most common imaging test performed for suspected CAP in primary care. The physicians had varied previous US experience, but all received a 5-hour lung US training program. RESULTS: The study included 82 patients. Compared with chest radiography, positive lung US findings (consolidation measuring >1 cm or a focal/asymmetrical B-lines pattern) showed a sensitivity of 87.8%, a specificity of 58.5%, a positive likelihood-ratio of 2.12, and a negative likelihood-ratio of 0.21. Findings were similar regardless of the physicians' previous US training or experience. We propose a practical algorithm whereby patients having consolidation measuring greater than 1 cm or normal findings on lung US could skip chest radiography, whereas patients with a B-lines pattern without consolidation (given its low specificity) would need chest radiography to ensure appropriate management. Lung US was generally performed in 10 minutes or less. CONCLUSION: Point-of-care lung US in primary care could be useful for investigating suspected CAP (avoiding chest radiography in most cases) and is likely feasible in daily practice, as short training programs appear sufficient and little time is needed to perform the scan.


Assuntos
Infecções Comunitárias Adquiridas , Médicos de Atenção Primária , Pneumonia , Infecções Comunitárias Adquiridas/diagnóstico por imagem , Serviço Hospitalar de Emergência , Humanos , Pulmão/diagnóstico por imagem , Pneumonia/diagnóstico por imagem , Sistemas Automatizados de Assistência Junto ao Leito , Estudos Prospectivos , Radiografia Torácica , Sensibilidade e Especificidade , Ultrassonografia/métodos
7.
Int J Mol Sci ; 23(9)2022 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-35562985

RESUMO

The purinergic system is fundamental in the tumor microenvironment, since it regulates tumor cell interactions with the immune system, as well as growth and differentiation in autocrine-paracrine responses. Here, we investigated the role of the adenosine A2B receptor (A2BR) in ovarian carcinoma-derived cells' (OCDC) properties. From public databases, we documented that high A2BR expression is associated with a better prognostic outcome in ovarian cancer patients. In vitro experiments were performed on SKOV-3 cell line to understand how A2BR regulates the carcinoma cell phenotype associated with cell migration. RT-PCR and Western blotting revealed that the ADORA2B transcript (coding for A2BR) and A2BR were expressed in SKOV-3 cells. Stimulation with BAY-606583, an A2BR agonist, induced ERK1/2 phosphorylation, which was abolished by the antagonist PSB-603. Pharmacological activation of A2BR reduced cell migration and actin stress fibers; in agreement, A2BR knockdown increased migration and enhanced actin stress fiber expression. Furthermore, the expression of E-cadherin, an epithelial marker, increased in BAY-606583-treated cells. Finally, cDNA microarrays revealed the pathways mediating the effects of A2BR activation on SKOV-3 cells. Our results showed that A2BR contributed to maintaining an epithelial-like phenotype in OCDC and highlighted this purinergic receptor as a potential biomarker.


Assuntos
Carcinoma Epitelial do Ovário , Movimento Celular , Receptor A2B de Adenosina , Actinas , Carcinoma Epitelial do Ovário/genética , Carcinoma Epitelial do Ovário/metabolismo , Feminino , Humanos , Neoplasias Ovarianas/genética , Receptor A2B de Adenosina/genética , Receptor A2B de Adenosina/metabolismo , Microambiente Tumoral
8.
J Physiol ; 599(13): 3385-3402, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33963545

RESUMO

KEY POINTS: It is theorized that the nervous system controls groups of muscles together as functional units, or 'synergies', resulting in correlated electromyographic (EMG) signals among muscles. However, such correlation does not necessarily imply group-level neural control. Oscillatory synchronization (coherence) among EMG signals implies neural coupling, but it is not clear how this relates to control of muscle synergies. EMG was recorded from seven arm muscles of 10 adult participants rotating an upper limb ergometer, and EMG-EMG coherence, EMG amplitude correlations and their relationship with each other were characterized. A novel method to derive multi-muscle synergies from EMG-EMG coherence is presented and these are compared with classically defined synergies. Coherent alpha-band (8-16 Hz) drive was strongest among muscles whose gross activity levels are well correlated within a given task. The cross-muscle distribution and temporal modulation of coherent alpha-band drive suggests a possible role in the neural coordination/monitoring of synergies. ABSTRACT: During movement, groups of muscles may be controlled together by the nervous system as an adaptable functional entity, or 'synergy'. The rules governing when (or if) this occurs during voluntary behaviour in humans are not well understood, at least in part because synergies are usually defined by correlated patterns of muscle activity without regard for the underlying structure of their neural control. In this study, we investigated the extent to which comodulation of muscle output (i.e. correlation of electromyographic (EMG) amplitudes) implies that muscles share intermuscular neural input (assessed via EMG-EMG coherence analysis). We first examined this relationship among pairs of upper limb muscles engaged in an arm cycling task. We then applied a novel multidimensional EMG-EMG coherence analysis allowing synergies to be characterized on the basis of shared neural drive. We found that alpha-band coherence (8-16 Hz) is related to the degree to which overall muscle activity levels correlate over time. The extension of this coherence analysis to describe the cross-muscle distribution and temporal modulation of alpha-band drive revealed a close match to the temporal and structural features of traditionally defined muscle synergies. Interestingly, the coherence-derived neural drive was inversely associated with, and preceded, changes in EMG amplitudes by ∼200 ms. Our novel characterization of how alpha-band neural drive is dynamically distributed among muscles is a fundamental step forward in understanding the neural origins and correlates of muscle synergies.


Assuntos
Movimento , Músculo Esquelético , Adulto , Eletromiografia , Humanos , Sistema Nervoso , Extremidade Superior
9.
Mol Reprod Dev ; 88(11): 758-770, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34694051

RESUMO

Ovarian surface epithelium (OSE) is a cell monolayer surrounding the ovary; it is involved in the regulation of the ovulatory process and the genesis of ovarian carcinoma. However, intercellular messengers regulating signaling events, like proliferation in the OSE, have not been completely described. Purines have emerged as novel intercellular messengers in the ovary, in which expression of purinergic receptors has been reported in different cell types. In the present work, we described the functional expression of P2Y2 receptor (P2Y2R), a purinergic receptor widely associated with cell proliferation, in the OSE. The expression of P2Y2R by immunofluorescence and RT-PCR, and its functionality by Ca2+ recording was demonstrated in primary cultured OSE. Functional expression of P2Y2R was also exhibited in situ, by recording of intracellular Ca2+ release and detection of ERK phosphorylation after injection of a selective agonist into the ovarian bursa. Furthermore, P2Y2R activation with UTPγS, in situ, induced cell proliferation at 24 h, whereas continuous stimulation of P2Y2R during a complete estrous cycle significantly modified the size distribution of the follicular population. This is the first evidence of the functional expression of purinergic P2Y2R in the OSE and opens new perspectives on the roles played by purines in ovarian physiology.


Assuntos
Ovário , Animais , Proliferação de Células/fisiologia , Epitélio , Feminino , Camundongos , Fosforilação , Receptores Purinérgicos P2Y2/genética
10.
Appl Opt ; 60(24): 7351-7361, 2021 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-34613024

RESUMO

We present a parametric method to carry out a demodulation process in complex fringe pattern images with either open or closed fringes; this method is based on the parallel demodulation algorithm and introduces a novel way, to the best of our knowledge, to approximate the phase map using the Bezier surface control points. For this study, a recently developed population meta-heuristic called Variable Mesh Optimization is introduced to implement the optimization process. The results of the proposed method improve the phase error and the run time scores in comparison with other global optimization algorithms, which address this type of problem.

11.
Rev Esp Enferm Dig ; 113(2): 150-151, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33207896

RESUMO

Hepatitis C virus (HCV) is estimated to affect 3.26 million children worldwide, with the highest number of cases registered in Pakistan and China. Vertical transmission is the principal route in industrialized countries. However, iatrogenic transmission is relevant in low-income settings. We present the case of a 12-year-old Pakistani child who suffered from beta-thalassemia major and hepatitis C, successfully treated with glecaprevir/pibrentasvir.


Assuntos
Hepatite C Crônica , Hepatite C , Talassemia beta , Ácidos Aminoisobutíricos , Antivirais/uso terapêutico , Benzimidazóis , Criança , China , Ciclopropanos , Genótipo , Hepacivirus , Hepatite C/complicações , Hepatite C/tratamento farmacológico , Hepatite C Crônica/tratamento farmacológico , Humanos , Lactamas Macrocíclicas , Leucina/análogos & derivados , Prolina/análogos & derivados , Pirrolidinas , Quinoxalinas , Sulfonamidas , Talassemia beta/complicações , Talassemia beta/tratamento farmacológico
12.
Int J Mol Sci ; 21(7)2020 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-32225112

RESUMO

Inflammatory and wound healing responses take place during liver damage, primarily in the parenchymal tissue. It is known that cellular injury elicits an activation of the purinergic signaling, mainly by the P2X7 receptor; however, the role of P2Y receptors in the onset of liver pathology such as fibrosis has not been explored. Hence, we used mice treated with the hepatotoxin CCl4 to implement a reversible model of liver fibrosis to evaluate the expression and function of the P2Y2 receptor (P2Y2R). Fibrotic livers showed an enhanced expression of P2Y2R that eliminated its zonal distribution. Hepatocytes from CCl4-treated mice showed an exacerbated ERK-phosphorylated response to the P2Y2R-specific agonist, UTP. Cell proliferation was also enhanced in the fibrotic livers. Hepatic transcriptional analysis by microarrays, upon CCl4 administration, showed that P2Y2 activation regulated diverse pathways, revealing complex action mechanisms. In conclusion, our data indicate that P2Y2R activation is involved in the onset of the fibrotic damage associated with the reversible phase of the hepatic damage promoted by CCl4.


Assuntos
Hepatócitos/metabolismo , Cirrose Hepática/metabolismo , Receptores Purinérgicos P2Y2/metabolismo , Animais , Tetracloreto de Carbono/toxicidade , Células Cultivadas , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Cirrose Hepática/etiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL
13.
Mol Reprod Dev ; 86(3): 308-318, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30624816

RESUMO

Extracellular purines through specific receptors have been recognized as new regulators of ovarian function. It is known that P2Y2 receptor activity induces theca cell proliferation, we hypothesized that purinergic signaling controls the changes related to hyperthecosis in polycystic ovarian syndrome (PCOS). The aim of this study was to analyze the expression of UTP-sensitive P2Y receptors and their role in theca cells (TC) proliferation in experimentally-induced PCOS (EI-PCOS). In primary cultures of TC from intact rats, all the transcripts of P2Y receptors were detected by polymerase chain reaction; in these cells, UTP (10 µM) induced extracellular signal-regulated kinases (ERK) phosphorylation. Rats with EI-PCOS showed a reduced expression of P2Y2R in TC whereas P2Y4R did not change. By analyzing ERK phosphorylation, it was determined that P2Y2R is the most relevant receptor in TC. UTP promoted cell proliferation in TC from control but not from EI-PCOS rats. The in silico analysis of P2yr2 promoter indicated the presence of androgen response elements; the stimulation of TC primary cultures with testosterone promoted a significant reduction in the expression of the P2yr2 transcript. We concluded that P2Y2R participates in controlling the proliferative rate of TCs from healthy ovaries, but this regulation is lost during EI-PCOS.


Assuntos
Síndrome do Ovário Policístico/patologia , Receptores Purinérgicos P2Y2/metabolismo , Células Tecais/patologia , Células Tecais/fisiologia , Uridina Trifosfato/farmacologia , Animais , Proliferação de Células/fisiologia , Células Cultivadas , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Feminino , Fosforilação , Regiões Promotoras Genéticas/genética , Ratos , Ratos Wistar , Receptores Purinérgicos P2/metabolismo , Transdução de Sinais/fisiologia , Testosterona/farmacologia
14.
PLoS Comput Biol ; 14(1): e1005884, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29309405

RESUMO

Involuntary force variability below 15 Hz arises from, and is influenced by, many factors including descending neural drive, proprioceptive feedback, and mechanical properties of muscles and tendons. However, their potential interactions that give rise to the well-structured spectrum of involuntary force variability are not well understood due to a lack of experimental techniques. Here, we investigated the generation, modulation, and interactions among different sources of force variability using a physiologically-grounded closed-loop simulation of an afferented muscle model. The closed-loop simulation included a musculotendon model, muscle spindle, Golgi tendon organ (GTO), and a tracking controller which enabled target-guided force tracking. We demonstrate that closed-loop control of an afferented musculotendon suffices to replicate and explain surprisingly many cardinal features of involuntary force variability. Specifically, we present 1) a potential origin of low-frequency force variability associated with co-modulation of motor unit firing rates (i.e.,'common drive'), 2) an in-depth characterization of how proprioceptive feedback pathways suffice to generate 5-12 Hz physiological tremor, and 3) evidence that modulation of those feedback pathways (i.e., presynaptic inhibition of Ia and Ib afferents, and spindle sensitivity via fusimotor drive) influence the full spectrum of force variability. These results highlight the previously underestimated importance of closed-loop neuromechanical interactions in explaining involuntary force variability during voluntary 'isometric' force control. Furthermore, these results provide the basis for a unifying theory that relates spinal circuitry to various manifestations of altered involuntary force variability in fatigue, aging and neurological disease.


Assuntos
Contração Isométrica/fisiologia , Neurônios Motores/fisiologia , Fusos Musculares/fisiologia , Músculo Esquelético/fisiologia , Células Receptoras Sensoriais/fisiologia , Simulação por Computador , Elasticidade , Humanos , Mecanorreceptores/fisiologia , Modelos Biológicos , Modelos Neurológicos , Tendões/patologia , Tendões/fisiologia , Viscosidade
15.
J Sci Food Agric ; 98(15): 5606-5615, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-29696658

RESUMO

BACKGROUND: The use of a grapevine-shoot extract (VIN) is being studied as an alternative to sulfur dioxide (SO2 ). VIN stabilizes anthocyanins and preserves polyphenolic compounds, and thus improves chromatic wine properties. In this study, selected aroma compounds (esters, C13 -norisoprenoids, oxidation and vine-shoot-related compounds), sensory analysis and the olfactometric profile were determined in the wines treated with VIN at two concentrations. RESULTS: Treatment with VIN hardly modified the content of esters and oxidation-related compounds in the wines. However, the high ß-damascenone and isoeugenol contents and the increase in astringency at tasting in VIN wines were noteworthy, as were some odorant zones. All these were established as VIN markers after the chemometric data analysis. CONCLUSION: These data revealed that only the lowest dose tested may be recommended as a suitable alternative to SO2 . Although some aromatic properties of these wines may change, these changes are not considered to affect the quality of the wines negatively. These results are useful for wineries, which face having to discover the aroma-related processes in the challenge of producing SO2 -free wines without detriment to their sensory properties. © 2018 Society of Chemical Industry.


Assuntos
Aromatizantes/química , Brotos de Planta/química , Vitis/química , Resíduos/análise , Vinho/análise , Humanos , Dióxido de Enxofre/análise , Paladar
16.
J Physiol ; 595(24): 7331-7346, 2017 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-29023731

RESUMO

KEY POINTS: In tonic, isometric, plantarflexion contractions, physiological tremor increases as the ankle joint becomes plantarflexed. Modulation of physiological tremor as a function of muscle stretch differs from that of the stretch reflex amplitude. Amplitude of physiological tremor may be altered as a function of reflex pathway gains. Healthy humans likely increase their γ-static fusimotor drive when muscles shorten. Quantification of physiological tremor by manipulation of joint angle may be a useful experimental probe of afferent gains and/or the integrity of automatic fusimotor control. ABSTRACT: The involuntary force fluctuations associated with physiological (as distinct from pathological) tremor are an unavoidable component of human motor control. While the origins of physiological tremor are known to depend on muscle afferentation, it is possible that the mechanical properties of muscle-tendon systems also affect its generation, amplification and maintenance. In this paper, we investigated the dependence of physiological tremor on muscle length in healthy individuals. We measured physiological tremor during tonic, isometric plantarflexion torque at 30% of maximum at three ankle angles. The amplitude of physiological tremor increased as calf muscles shortened in contrast to the stretch reflex whose amplitude decreases as muscle shortens. We used a published closed-loop simulation model of afferented muscle to explore the mechanisms responsible for this behaviour. We demonstrate that changing muscle lengths does not suffice to explain our experimental findings. Rather, the model consistently required the modulation of  Î³-static fusimotor drive to produce increases in physiological tremor with muscle shortening - while successfully replicating the concomitant reduction in stretch reflex amplitude. This need to control γ-static fusimotor drive explicitly as a function of muscle length has important implications. First, it permits the amplitudes of physiological tremor and stretch reflex to be decoupled. Second, it postulates neuromechanical interactions that require length-dependent γ drive modulation to be independent from α drive to the parent muscle. Lastly, it suggests that physiological tremor can be used as a simple, non-invasive measure of the afferent mechanisms underlying healthy motor function, and their disruption in neurological conditions.


Assuntos
Contração Isotônica , Neurônios Motores gama/fisiologia , Músculo Esquelético/fisiologia , Reflexo de Estiramento , Adulto , Feminino , Humanos , Masculino , Músculo Esquelético/inervação , Neurônios Aferentes/fisiologia , Periodicidade , Tremor/fisiopatologia
17.
J Neurophysiol ; 118(3): 1775-1783, 2017 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-28659460

RESUMO

Coherence analysis has the ability to identify the presence of common descending drive shared by motor unit pools and reveals its spectral properties. However, the link between spectral properties of shared neural drive and functional interactions among muscles remains unclear. We assessed shared neural drive between muscles of the thumb and index finger while participants executed two mechanically distinct precision pinch tasks, each requiring distinct functional coordination among muscles. We found that shared neural drive was systematically reduced or enhanced at specific frequencies of interest (~10 and ~40 Hz). While amplitude correlations between surface EMG signals also exhibited changes across tasks, only their coherence has strong physiological underpinnings indicative of neural binding. Our results support the use of intermuscular coherence as a tool to detect when coactivated muscles are members of a functional group or synergy of neural origin. Furthermore, our results demonstrate the advantages of considering neural binding at 10, ~20, and >30 Hz, as indicators of task-dependent neural coordination strategies.NEW & NOTEWORTHY It is often unclear whether correlated activity among muscles reflects their neural binding or simply reflects the constraints defining the task. Using the fact that high-frequency coherence between EMG signals (>6 Hz) is thought to reflect shared neural drive, we demonstrate that coherence analysis can reveal the neural origin of distinct muscle coordination patterns required by different tasks.


Assuntos
Mãos/inervação , Destreza Motora , Músculo Esquelético/inervação , Adulto , Feminino , Mãos/fisiologia , Humanos , Masculino , Contração Muscular , Músculo Esquelético/fisiologia , Córtex Sensório-Motor/fisiologia , Análise e Desempenho de Tarefas
18.
PLoS Comput Biol ; 12(2): e1004737, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26867014

RESUMO

Much debate has arisen from research on muscle synergies with respect to both limb impedance control and energy consumption. Studies of limb impedance control in the context of reaching movements and postural tasks have produced divergent findings, and this study explores whether the use of synergies by the central nervous system (CNS) can resolve these findings and also provide insights on mechanisms of energy consumption. In this study, we phrase these debates at the conceptual level of interactions between neural degrees of freedom and tasks constraints. This allows us to examine the ability of experimentally-observed synergies--correlated muscle activations--to control both energy consumption and the stiffness component of limb endpoint impedance. In our nominal 6-muscle planar arm model, muscle synergies and the desired size, shape, and orientation of endpoint stiffness ellipses, are expressed as linear constraints that define the set of feasible muscle activation patterns. Quadratic programming allows us to predict whether and how energy consumption can be minimized throughout the workspace of the limb given those linear constraints. We show that the presence of synergies drastically decreases the ability of the CNS to vary the properties of the endpoint stiffness and can even preclude the ability to minimize energy. Furthermore, the capacity to minimize energy consumption--when available--can be greatly affected by arm posture. Our computational approach helps reconcile divergent findings and conclusions about task-specific regulation of endpoint stiffness and energy consumption in the context of synergies. But more generally, these results provide further evidence that the benefits and disadvantages of muscle synergies go hand-in-hand with the structure of feasible muscle activation patterns afforded by the mechanics of the limb and task constraints. These insights will help design experiments to elucidate the interplay between synergies and the mechanisms of learning, plasticity, versatility and pathology in neuromuscular systems.


Assuntos
Braço/inervação , Metabolismo Energético/fisiologia , Mãos/inervação , Modelos Neurológicos , Músculo Esquelético/inervação , Biologia Computacional , Humanos , Fenômenos Fisiológicos Musculoesqueléticos , Análise e Desempenho de Tarefas
19.
J Neuroeng Rehabil ; 14(1): 101, 2017 10 09.
Artigo em Inglês | MEDLINE | ID: mdl-29017508

RESUMO

Biological and robotic grasp and manipulation are undeniably similar at the level of mechanical task performance. However, their underlying fundamental biological vs. engineering mechanisms are, by definition, dramatically different and can even be antithetical. Even our approach to each is diametrically opposite: inductive science for the study of biological systems vs. engineering synthesis for the design and construction of robotic systems. The past 20 years have seen several conceptual advances in both fields and the quest to unify them. Chief among them is the reluctant recognition that their underlying fundamental mechanisms may actually share limited common ground, while exhibiting many fundamental differences. This recognition is particularly liberating because it allows us to resolve and move beyond multiple paradoxes and contradictions that arose from the initial reasonable assumption of a large common ground. Here, we begin by introducing the perspective of neuromechanics, which emphasizes that real-world behavior emerges from the intimate interactions among the physical structure of the system, the mechanical requirements of a task, the feasible neural control actions to produce it, and the ability of the neuromuscular system to adapt through interactions with the environment. This allows us to articulate a succinct overview of a few salient conceptual paradoxes and contradictions regarding under-determined vs. over-determined mechanics, under- vs. over-actuated control, prescribed vs. emergent function, learning vs. implementation vs. adaptation, prescriptive vs. descriptive synergies, and optimal vs. habitual performance. We conclude by presenting open questions and suggesting directions for future research. We hope this frank and open-minded assessment of the state-of-the-art will encourage and guide these communities to continue to interact and make progress in these important areas at the interface of neuromechanics, neuroscience, rehabilitation and robotics.


Assuntos
Força da Mão , Robótica , Fenômenos Biomecânicos , Humanos
20.
J Neuroeng Rehabil ; 13(1): 92, 2016 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-27724916

RESUMO

BACKGROUND: Comparing the efficacy of alternative therapeutic strategies for the rehabilitation of motor function in chronically impaired individuals is often inconclusive. For example, a recent randomized clinical trial (RCT) compared robot-assisted vs. conventional therapy in 77 patients who had had chronic motor impairment after a cerebrovascular accident. While patients assigned to robotic therapy had greater improvements in the primary outcome measure (change in score on the upper extremity section of the Fugl-Meyer assessment), the absolute difference between therapies was small, which left the clinical relevance in question. METHODS: Here we revisit that study to test whether the multidimensional rehabilitative response of these patients can better distinguish between treatment outcomes. We used principal components analysis to find the correlation of changes across seven outcome measures between the start and end of 8 weeks of therapy. Permutation tests verified the robustness of the principal components found. RESULTS: Each therapy in fact produces different rehabilitative trends of recovery across the clinical, functional, and quality of life domains. A rehabilitative trend is a principal component that quantifies the correlations among changes in outcomes with each therapy. CONCLUSIONS: These findings challenge the traditional emphasis of RCTs on using a single primary outcome measure to compare rehabilitative responses that are naturally multidimensional. This alternative approach to, and interpretation of, the results of RCTs may will lead to more effective therapies targeted for the multidimensional mechanisms of recovery. TRIAL REGISTRATION: ClinicalTrials.gov number NCT00719433 . Registered July 17, 2008.


Assuntos
Robótica , Reabilitação do Acidente Vascular Cerebral/métodos , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Análise de Componente Principal , Qualidade de Vida , Ensaios Clínicos Controlados Aleatórios como Assunto , Recuperação de Função Fisiológica , Projetos de Pesquisa , Acidente Vascular Cerebral/psicologia , Sobreviventes , Resultado do Tratamento
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