Cerebral palsy (CP) is a complex disorder and children frequently have multiple impairments. Dystonia is a particularly frustrating impairment that interferes with rehabilitation and function and is ...difficult to treat. Of the available treatments, deep brain stimulation (DBS) has emerged as an option with the potential for large effect size in a subgroup of children. While brain stimulation has been used in CP for more than 40 years, modern devices and targeting methods are improving both the safety and efficacy of the procedure. Successful use of DBS depends on appropriate selection of patients, identification of effective neuroanatomical targets in each patient, careful neurosurgical procedure, and detailed follow‐up evaluation and programming. The use of functional neurosurgery for neuromodulation in CP remains a technology in its infancy, but improving experience and knowledge are likely to make this one of the safest and most effective interventions for children with moderate‐to‐severe motor disorders. This review summarizes the current procedures for patient and target selection, and surgical implantation of DBS electrodes for CP. The history of DBS and future directions when used in secondary dystonia are also examined.
What this paper adds
Selection of candidates for deep brain stimulation (DBS) requires understanding of dystonia in cerebral palsy .
DBS could become a first‐line treatment option in some children.
Resumen
Estimulación cerebral profunda para la parálisis cerebral: ¿dónde estamos ahora?
La parálisis cerebral (PC) es un trastorno complejo y los niños con frecuencia tienen discapacidades múltiples. La distonía es un deterioro particularmente frustrante que interfiere con la rehabilitación y la función y es difícil de tratar. De los tratamientos disponibles, la estimulación cerebral profunda (DBS, por sus siglas en inglés ‐ deep brain stimulation) ha surgido como una opción con el potencial de un gran tamaño de efecto en un subgrupo de niños. Si bien la estimulación cerebral se ha utilizado en PC durante más de 40 años, los dispositivos modernos y los métodos de detección están mejorando tanto la seguridad como la eficacia del procedimiento. El uso exitoso de la DBS depende de la selección apropiada de los pacientes, la identificación de objetivos neuroanatómicos efectivos en cada paciente, el procedimiento neuroquirúrgico cuidadoso y la evaluación y programación de seguimiento detalladas. El uso de la neurocirugía funcional para la neuromodulación en la PC sigue siendo una tecnología en su infancia, pero es probable que la mejora de la experiencia y los conocimientos hagan de esta una de las intervenciones más seguras y efectivas para los niños con trastornos motores de moderados a graves. Esta revisión resume los procedimientos actuales para la selección de pacientes y objetivos, y la implantación quirúrgica de electrodos DBS para PC. La historia de DBS y las direcciones futuras cuando se utilizan en la distonía secundaria también se examinan.
Resumo
Estimulação cerebral profunda para paralisia cerebral: onde estamos agora?
Paralisia cerebral (PC) é uma desordem complexa e crianças frequentemente apresentam múltiplas deficiências. A distonia é uma deficiência particularmente frustrante que interfere com a reabilitação e função, e é difícil de tratar. Dentre dos tratamentos disponíveis, a estimulação cerebral profunda (ECP) emergiu como uma opção com potencial de grande tamanho de efeito em um subgrupo de crianças. Embora a estimulação cerebral seja usada em PC há mais de 40 anos, dispositivos modernos e métodos de identificação de áreas alvo tem melhorado tanto a segurança quanto a eficácia do procedimento. O uso bem sucedido da ECP depende da seleção apropriada dos pacientes, identificação dos alvos neuroanatômicos efetivos para cada paciente, procedimento neurocirúrgico cuidadoso, e avaliação e programação detalhadas no acompanhamento. O uso de neurocirurgia funcional para neuromodulação em PC ainda é uma tecnologia iniciante, mas a crescente experiência e conhecimento provavelmente farão dela uma das mais seguras e efetivas intervenções para crianças com transtornos motores de moderados a severos. Esta revisão sintetiza os procedimentos atuais para seleção de pacientes e alvos, e a implantação cirúrgica de eletrodos de ECP para PC. A história da ECP e direções futuras, quando usados em distonia secundária, também são examinados.
What this paper adds
Selection of candidates for deep brain stimulation (DBS) requires understanding of dystonia in cerebral palsy .
DBS could become a first‐line treatment option in some children.
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This article is commented on by Meoni and Moro on page 6 of this issue.
Fifty years ago, David Marr and James Albus proposed a computational model of cerebellar cortical function based on the pioneering circuit models described by John Eccles, Masao Ito and Janos ...Szentagothai. The Marr–Albus model remains one of the most enduring and influential models in computational neuroscience, despite apparent falsification of some of the original predictions. We re‐examine the Marr–Albus model in the context of the modern theory of computational neural networks and in the context of expanded interpretations of the connectivity and function of cerebellar cortex within the full motor system. By doing so, we show that the original elements of the codon theory continue to make important predictions for cerebellar mechanism, and we show that evidence appearing to contradict the original model is based on an artificially narrow interpretation of cerebellar structure and motor function.
Overall structure of the cerebro‐cerebellum. We propose that the role of the cerebellar cortex and Purkinje cells is to modulate and select signals from incoming mossy fibres for transmission through the dentate nucleus to a highly compressed representation on the outgoing fibres projecting to frontal cortex. Inferior olive (IO) provides the training signals for plasticity.
Dystonia is a collection of symptoms with involuntary muscle activation causing hypertonia, hyperkinetic movements, and overflow. In children, dystonia can have numerous etiologies with varying ...neuroanatomic distribution. The semiology of dystonia can be explained by gain-of-function failure of a feedback controller that is responsible for stabilizing posture and movement. Because postural control is maintained by a widely distributed network, many different anatomic regions may be responsible for symptoms of dystonia, although all features of dystonia can be explained by uncontrolled activation or hypersensitivity of motor cortical regions that can cause increased reflex gain, inserted postures, or sensitivity to irrelevant sensory variables. Effective treatment of dystonia in children requires an understanding of the relationship between etiology, anatomy, and the specific mechanism of failure of postural stabilization.
The tradeoff between speed and accuracy is a well-known constraint for human movement, but previous work has shown that this tradeoff can be modified by practice, and the quantitative relationship ...between speed and accuracy may be an indicator of skill in some tasks. We have previously shown that children with dystonia are able to adapt their movement strategy in a ballistic throwing game to compensate for increased variability of movement. Here, we test whether children with dystonia can adapt and improve skills learned on a trajectory task. We use a novel task in which children move a spoon with a marble between two targets. Difficulty is modified by changing the depth of the spoon. Our results show that both healthy children and children with acquired dystonia move more slowly with the more difficult spoons, and both groups improve the relationship between speed and spoon difficulty following 1 wk of practice. By tracking the marble position in the spoon, we show that children with dystonia use a larger fraction of the available variability, whereas healthy children adopt a much safer strategy and remain farther from the margins, as well as learning to adapt and have more control over the marble's utilized area by practice. Together, our results show that both healthy children and children with dystonia choose trajectories that compensate for risk and inherent variability, and that the increased variability in dystonia can be modified with continued practice.
This study provides insights into the adaptability of children with dystonia in learning a point-to-point task. We show that these children adjust their strategies to account for increased difficulty in the task. Our findings underscore the potential of task-specific practice in improving motor skills and show higher level of signal-dependent noise can be controlled through repetition and learned strategies, which provides an avenue for the quantitative evaluation of rehabilitation strategies in this challenging group.
Risk-Aware Control Sanger, Terence D
Neural computation,
12/2014, Letnik:
26, Številka:
12
Journal Article
Recenzirano
Human movement differs from robot control because of its flexibility in unknown environments, robustness to perturbation, and tolerance of unknown parameters and unpredictable variability. We propose ...a new theory, risk-aware control, in which movement is governed by estimates of risk based on uncertainty about the current state and knowledge of the cost of errors. We demonstrate the existence of a feedback control law that implements risk-aware control and show that this control law can be directly implemented by populations of spiking neurons. Simulated examples of risk-aware control for time-varying cost functions as well as learning of unknown dynamics in a stochastic risky environment are provided.
In this study, we test the feasibility of the synergy- based approach for application in the realistic and clinically oriented framework of multi-degree of freedom (DOF) robotic control. We developed ...and tested online ten able-bodied subjects in a semi-supervised method to achieve simultaneous, continuous control of two DOFs of a robotic arm, using muscle synergies extracted from upper limb muscles while performing flexion-extension movements of the elbow and shoulder joints in the horizontal plane. To validate the efficacy of the synergy-based approach in extracting reliable control signals, compared to the simple muscle-pair method typically used in commercial applications, we evaluated the repeatability of the algorithm over days, the effect of the arm dynamics on the control performance, and the robustness of the control scheme to the presence of co-contraction between pairs of antagonist muscles. Results showed that, without the need for a daily calibration, all subjects were able to intuitively and easily control the synergy-based myoelectric interface in different scenarios, using both dynamic and isometric muscle contractions. The proposed control scheme was shown to be robust to co-contraction between antagonist muscles, providing better performance compared to the traditional muscle-pair approach. The current study is a first step toward user-friendly application of synergy-based myocontrol of assistive robotic devices.
Summary Movement disorders in children are causally and clinically heterogeneous and present in a challenging developmental context. Treatment options are broad ranging, from pharmacotherapy to ...invasive neuromodulation and experimental gene and stem cell therapies. The clinical effects of these therapies are variable and often poorly sustained, and only a few of the management strategies used in paediatric populations have been tested in randomised controlled studies with age-appropriate cohorts. Identification of the most appropriate treatment is uniquely challenging in children because of the incomplete knowledge about the pathophysiology of movement disorders and their influence on normal motor development; thus, effective therapeutic options for these children remain an unmet need. It is vital to transfer the expanding knowledge of the movement disorders into the development of novel symptomatic or, ideally, disease-modifying treatments, and to assess these therapeutic strategies in appropriately designed and well done trials.
The mechanism by which deep brain stimulation (DBS) improves dystonia is not understood, partly heterogeneity of the underlying disorders leads to differing effects of stimulation in different ...locations. Similarity between the effects of DBS and the effects of lesions has led to biophysical models of blockade or reduced transmission of involuntary activity in individual cells in the pathways responsible for dystonia. Here, we expand these theories by modeling the effect of DBS on populations of neurons. We emphasize the important observation that the DBS signal itself causes surprisingly few side effects and does not normally appear in the electromyographic signal. We hypothesize that, at the population level, massively synchronous rhythmic firing caused by DBS is only poorly transmitted through downstream populations. However, the high frequency of stimulation overwhelms incoming dystonic activity, thereby substituting an ineffectively transmitted exogenous signal for the endogenous abnormal signal. Changes in sensitivity can occur not only at the site of stimulation, but also at downstream sites due to synaptic and homeostatic plasticity mechanisms. The mechanism is predicted to depend strongly on the stimulation frequency. We provide preliminary data from simultaneous multichannel recordings in basal ganglia and thalamus in children with secondary dystonia. We also provide illustrative simulations of the effect of stimulation frequency on the transmission of the DBS pulses through sequential populations of neurons in the dystonia pathway. Our experimental results and model provide a new hypothesis and computational framework consistent with the clinical features of DBS in childhood acquired dystonia.
Surface electromyography is used in research, to estimate the activity of muscle, in prosthetic design, to provide a control signal, and in biofeedback, to provide subjects with a visual or auditory ...indication of muscle contraction. Unfortunately, successful applications are limited by the variability in the signal and the consequent poor quality of estimates. I propose to use a nonlinear recursive filter based on Bayesian estimation. The desired filtered signal is modeled as a combined diffusion and jump process and the measured electromyographic (EMG) signal is modeled as a random process with a density in the exponential family and rate given by the desired signal. The rate is estimated on-line by calculating the full conditional density given all past measurements from a single electrode. The Bayesian estimate gives the filtered signal that best describes the observed EMG signal. This estimate yields results with very low short-time variability but also with the capability of very rapid response to change. The estimate approximates isometric joint torque with lower error and higher signal-to-noise ratio than current linear methods. Use of the nonlinear filter significantly reduces noise compared with current algorithms, and it may therefore permit more effective use of the EMG signal for prosthetic control, biofeedback, and neurophysiology research.
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