The cerebellum is a key-piece for information processing and is involved in numerous motor and nonmotor activities, thanks to the anatomical characteristics of the circuitry, the enormous computational capabilities and the high connectivity to other brain areas. Despite its uniform cytoarchitecture, cerebellar circuitry is segregated into functional zones. This functional parcellation is driven by the connectivity and the anatomo-functional heterogeneity of the numerous extra-cerebellar structures linked to the cerebellum, principally brain cortices, precerebellar nuclei and spinal cord. Major insights into cerebellar functions have been gained with a detailed analysis of the cerebellar outputs, with the evidence that fundamental aspects of cerebrocerebellar operations are the closed-loop circuit and the predictions of future states. Cerebellar diseases result in disturbances of accuracy of movements and lack of coordination. The cerebellar syndrome includes combinations of oculomotor disturbances, dysarthria and other speech deficits, ataxia of limbs, ataxia of stance and gait, as well as often more subtle cognitive/behavioral impairments. Our understanding of the corresponding anatomo-functional maps for the human cerebellum is continuously improving. We summarize the topography of the clinical deficits observed in cerebellar patients and the growing evidence of a regional subdivision into motor, sensory, sensorimotor, cognitive and affective domains. The recently described topographic dichotomy motor versus nonmotor cerebellum based upon anatomical, functional and neuropsychological studies is also discussed.

Topography of Cerebellar Deficits in Humans

Neurological tremor is the most common movement disorder, affecting more than 4% of elderly people. Tremor is a non linear and non stationary phenomenon, which is increasingly recognized. The issue of selection of sensors is central in the characterization of tremor. This paper reviews the state-of-the-art instrumentation and methods of signal processing for tremor occurring in humans. We describe the advantages and disadvantages of the most commonly used sensors, as well as the emerging wearable sensors being developed to assess tremor instantaneously. We discuss the current limitations and the future applications such as the integration of tremor sensors in BCIs (brain-computer interfaces) and the need for sensor fusion approaches for wearable solutions.

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Neurological Tremor: Sensors, Signal Processing and Emerging Applications

Robotic gait training is gaining ground in rehabilitation. Room for improvement lies in reducing donning and doffing time, making training more task specific and facilitating active balance control, and by allowing movement in more degrees of freedom. Our goal was to design and evaluate a robot that incorporates these improvements. LOPES II uses an end-effector approach with parallel actuation and a minimum amount of clamps. LOPES II has eight powered degrees of freedom (hip flexion/extension, hip abduction/adduction, knee flexion/extension, pelvis forward/aft and pelvis mediolateral). All other degrees of freedom can be left free and pelvis frontal- and transversal rotation can be constrained. Furthermore arm swing is unhindered. The end-effector approach eliminates the need for exact alignment, which results in a donning time of 10–14 min for first-time training and 5–8 min for recurring training. LOPES II is admittance controlled, which allows for the control over the complete spectrum from low to high impedance. When the powered degrees of freedom are set to minimal impedance, walking in the device resembles free walking, which is an important requisite to allow task-specific training. We demonstrated that LOPES II can provide sufficient support to let severely affected patients walk and that we can provide selective support to impaired aspects of gait of mildly affected patients.

LOPES II—Design and Evaluation of an Admittance Controlled Gait Training Robot With Shadow-Leg Approach

Mechanisms and emerging therapies in tremor disorders / , Mechanisms and emerging therapies in tremor disorders / , کتابخانه دیجیتال جندی شاپور اهواز

Mechanisms and emerging therapies in tremor disorders

Tremor represents one of the most common movement disorders worldwide. It affects both sexes and may occur at any age. In most cases, tremor is disabling and causes social difficulties, resulting in poorer quality of life. Tremor is now recognized as a public health issue given the aging of the population. Tremor is a complex phenomenon that has attracted the attention of scientists from various disciplines. Tremor results from dynamic interactions between multiple synaptically coupled neuronal systems and the biomechanical, physical, and electrical properties of the external effectors. There have been major advances in our understanding of tremor pathogenesis these last three decades, thanks to new imaging techniques and genetic discoveries. Moreover, significant progress in computer technologies, developments of reliable and unobtrusive wearable sensors, improvements in miniaturization, and advances in signal processing have opened new perspectives for the accurate characterization nd daily monitoring of tremor. New therapies are emerging. In this book, we provide an overview of tremor from pathogenesis to therapeutic aspects. We review the definitions, the classification of the varieties of tremor, and the contribution of central versus peripheral mechanisms. Neuroanatomical, neurophysiological, neurochemical, and pharmacological topics related to tremor are pointed out. Our goals are to explain the fundamental basis of tremor generation, to show the recent technological developments, especially in instrumentation, which are reshaping research and clinical practice, and to provide up-to-date information related to emerging therapies. The integrative transdisciplinary approach has been used, combining engineering and physiological principles to diagnose, monitor, and treat tremor. Guidelines for evaluation of tremor are explained. This book has been written for biomedical engineering students, engineers, researchers, medical students, biologists, neurologists, a d biomedical professionals of any discipline looking for an updated and multidisciplinary overview of tremor. It can be used for biomedical courses. Table of Contents: Introduction / Anatomical Overview of the Central and Peripheral Nervous System / Physiology of the Nervous System / Characterization of Tremor / Prinipal Disorders Associated with Tremor / Quantification of Tremor / Mechanisms of Tremor / Treatments

Tremor: From Pathogenesis to Treatment

Wristalyzer is a portable robotic device combining haptic technology with electromyographic assessment. It allows to assess wrist motion in physiological and pathological conditions by applying loads and mechanical oscillations, taking into account the ergonomy and the angular positioning of the joints. The wristalyzer works in a free or loaded mode for assessment of metrics of motion and tremor, analyzes the behavior of the wrist joints and the associated muscle activities during delivery of mechanical oscillations, estimates the maximal voluntary contraction, assesses automatically the impedance of the wrist for assessment of rigidity or spasticity. Position, torques and electromyographic activities are analyzed in real time. The device characterizes the effects of damping on voluntary motion. A personal computer implements control loops and user application. This is the first standardized tool to assess wrist motion with high accuracy and reliability using the haptic technology with concomitant investigation of muscle activity.

A New Myohaptic Device to Assess Wrist Function in the Lab and in the Clinic --- The Wristalyzer

Upper limb postural tremor consists of mechanical-reflex and central-neurogenic oscillations, superimposed upon a background of irregular fluctuations in muscle force. Muscle spindles play key-roles in the information flow to supra-spinal and spinal generators. Oscillations were delivered using a new generation portable myohaptic device, called ldquowristalyzer,rdquo taking into account the ergonomy of upper limbs and allowing a fine adjustment to each configuration of upper limb segments. The nominal torque of the first generation device is 4 Nm, with a maximal rotation velocity of 300 degrees/s and a range of motion of plusmn45 degrees. Reliability was assessed in basal condition and during loading conditions. We assessed the effects of the addition of inertia on postural tremor of the finger in a group of 26 neurological patients and the effects of wrist oscillations upon contralateral postural tremor in 6 control subjects and in 7 neurological patients exhibiting a postural tremor. Patients showed two different behaviors in response to inertia and exhibited an increased variability of postural tremor during fast oscillations (13.3 Hz). One patient with overactivity of the olivocerebellar pathways exhibited a drop in the peak frequency of more than 20%. The relative power of the 8-12 Hz subband was significantly higher in controls both in basal condition and during oscillations (p = 0.028 and p = 0.015, respectively). The second generation wristalyzer allows to investigate the effects of mechanical oscillations up to frequency of 50 Hz. This mechatronic device can assess the responsiveness of tremor generators to stimulation of muscle spindles and biomechanical loading. Potential applications are the monitoring of dysmetria under various inertial or damping conditions, the assessment of rigidity in Parkinson's disease and the characterization of voluntary muscle force.

Effects of Inertia and Wrist Oscillations on Contralateral Neurological Postural Tremor Using the Wristalyzer, a New Myohaptic Device

We investigated fast pointing and fast reversal single-joint movements performed under artificial damping conditions applied with the myohaptic technology. Healthy subjects were able to scale the intensity of the agonist and antagonist electromyographic (EMG) activities when damping was added during both types of movements. Cerebellar patients were able to scale the magnitude of the agonist and antagonist EMG activities during pointing movements. For reversal movements, patients could scale the intensity of the initial agonist EMG activity but were unable to modulate the intensities of the second set of EMG discharges associated with the return to the initial position. Patients were able to adopt the appropriate motor strategy for the first phase of reversal movements, but they were unable to implement the suitable sequential strategy for the superimposition of motor plans during artificial damping. The myohaptic technology is the first to allow the detection of deficits in the implementation of sequential motor coding under the mechanical condition of artificial damping.

Investigation of the Adaptation to Artificial Damping in Cerebellar Ataxia Using the Myohaptic Technology

A gait rehabilitation apparatus (12) uses a mechanical shadow leg (42) positioned behind the biological leg (18) to provide forces and guide the biological leg in use.

Rehabilitation apparatus with a shadow leg

We report a novel form of hypometria in a patient presenting a spinocerebellar ataxia type 2 (SCA2; 32 repeats; Age: 44). We investigated fast pointing (FP) and fast reversal (FR) single-joint movements performed under artificial damping conditions using our myohaptic device called Wristalyzer, which allows an instantaneous regulation of the mechanical characteristics of a wrist manipulandum. The wristalyzer controller has a range of motion from −1 rad to +1 rad. The inertia of the motor/handgrip is 0.004 kg × m2. Movements were studied in free mode and with damping either at 0.1 Nms/rad or 0.2 Nms/rad. Subjects performed sets of FP movements and FR movements over 3 distances (targets: 0.2, 0.3, 0.4 rad). Control subjects (n = 8, mean age: 34.8 +/− 10.2 years; 3 women) were able to scale the intensity of the agonist and antagonist electromyographic (EMG) activities when damping was added during both types of movements. FR movements were accurate in the 3 mechanical conditions: mean movement amplitude was −0.0179 rad, 0.0061 rad and 0.0062 rad in the basal state, following addition of 0.1 Nms/rad and following addition of 0.2 Nms/rad, respectively. The patient scaled the magnitude of the agonist and antagonist EMG activities during FP, but FR movements were dysmetric. The second phase of reversal movements was hypometric. Movement performed in the basal condition was accurate during phase 1 but was hypometric during phase 2. The hypometria worsened with damping: mean movement amplitude (second zero-crossing of the velocity curve) was 0.088 rad in the basal state, 0.1425 rad following addition of 0.1 Nms/rad, and 0.2003 rad with addition of a damping of + 0.2 Nms/rad. This is the first demonstration in human of a deficit in the implementation of the suitable sequential strategy for the superposition of motor plans during artificial damping.

J. Meuleman

Papers

A New Myohaptic Device to Assess Wrist Function in the Lab and in the Clinic --- The Wristalyzer

Effects of Inertia and Wrist Oscillations on Contralateral Neurological Postural Tremor Using the Wristalyzer, a New Myohaptic Device

Investigation of the Adaptation to Artificial Damping in Cerebellar Ataxia Using the Myohaptic Technology

Rehabilitation apparatus with a shadow leg

Unraveling of an original mechanism of hypometria in human using a new myohaptic device — The Wristalyzer