Changes in wrist muscle activity with forearm posture: implications for the study of sensorimotor transformations.

The primate wrist is an ideal model system for studying the reference frames in which movements are coded within the central nervous system, as a simple rotation of the forearm allows dissociation between extrinsic and body-referenced coordinates. Important information regarding coordinate frame transformations has been obtained using this system, particularly from studies involving extracellular cortical and spinal recordings from monkeys. Because preferred directions of muscle use were reported to rotate by less than half of the joint rotation, the system was considered to dissociate three reference frames: extrinsic (direction of movement in space), muscle (activity of muscles), and joint (angle of the wrist joint).

Evaluation of a noninvasive command scheme for upper-limb prostheses in a virtual reality reach and grasp task.

C5/C6 tetraplegic patients and transhumeral amputees may be able to use voluntary shoulder motion as command signals for a functional electrical stimulation system or transhumeral prosthesis. Stereotyped relationships, termed "postural synergies," among the shoulder, forearm, and wrist joints emerge during goal-oriented reaching and transport movements as performed by able-bodied subjects. Thus, the posture of the shoulder can potentially be used to infer the desired posture of the elbow and forearm joints during reaching and transporting movements.

Real-time animation software for customized training to use motor prosthetic systems.

Research on control of human movement and development of tools for restoration and rehabilitation of movement after spinal cord injury and amputation can benefit greatly from software tools for creating precisely timed animation sequences of human movement. Despite their ability to create sophisticated animation and high quality rendering, existing animation software are not adapted for application to neural prostheses and rehabilitation of human movement. We have developed a software tool known as MSMS (MusculoSkeletal Modeling Software) that can be used to develop models of human or prosthetic limbs and the objects with which they interact and to animate their movement using motion data from a variety of offline and online sources.

MSMS software for VR simulations of neural prostheses and patient training and rehabilitation.

In the increasingly complex prosthetic limbs for upper extremity amputees, more mechanical degrees of freedom are combined with various neural commands to produce versatile human-like movements. Development, testing, and fitting of such neural prosthetic systems and training patients to control them effectively are complex processes that cannot be performed efficiently or safely by ad hoc and trial-and-error approaches. We have developed a software tool known as MSMS to enable researchers and engineers to simulate the movement of these neural prostheses and evaluate their performance before they are built and to train the patients in virtual simulation environments to operate their prostheses before receiving them.

Neuromuscular and biomechanical factors codetermine the solution to motor redundancy in rhythmic multijoint arm movement.

How the CNS deals with the issue of motor redundancy remains a central question for motor control research. Here we investigate the means by which neuromuscular and biomechanical factors interact to resolve motor redundancy in rhythmic multijoint arm movements. We used a two-df motorized robot arm to manipulate the dynamics of rhythmic flexion-extension (FE) and supination-pronation (SP) movements at the elbow-joint complex.

Model-based development of neural prostheses for movement.

Neural prostheses for restoration of limb movement in paralyzed and amputee patients tend to be complex systems. Subjective intuition and trial-and-error approaches have been applied to the design and clinical fitting of simple systems with limited functionality. These approaches are time consuming, difficult to apply in larger scale, and not applicable to limbs under development with more anthropomorphic motion and actuation.

The effects of training set on prediction of elbow trajectory from shoulder trajectory during reaching to targets.

Patients with transhumeral amputations and C5/C6 quadriplegia may be able to use voluntary shoulder motion as command signals for powered prostheses and functional electrical stimulation, respectively. Spatio-temporal synergies exist for goal oriented reaching movements between the shoulder and elbow joints in able bodied subjects. We are using a multi-layer perceptron neural network to discover and embody these synergies.

A virtual reality environment for designing and fitting neural prosthetic limbs.

Building and testing novel prosthetic limbs and control algorithms for functional electrical stimulation (FES) is expensive and risky. Here, we describe a virtual reality environment (VRE) to facilitate and accelerate the development of novel systems. In the VRE, subjects/patients can operate a simulated limb to interact with virtual objects.

Fuzzy logic control of FES rowing exercise in paraplegia.

An indoor personal rowing machine (Concept 2 Inc., Morrisville, VT) has been modified for functional electrical stimulation assisted rowing exercise in paraplegia. To successfully perform the rowing maneuver, the voluntarily controlled upper body movements must be coordinated with the movements of the electrically stimulated paralyzed legs.

Development of an indoor rowing machine with manual FES controller for total body exercise in paraplegia.

Concept 2 indoor rowing machine (Concept 2 Inc., USA) was modified for functional electrical stimulation (FES) rowing exercise in paraplegia. A new seating system provides trunk stability and constrains the leg motion to the sagittal plane.

Automatic Finite State Control of FES-Assisted Indoor Rowing Exercise after Spinal Cord Injury.

We modified a commercial indoor rowing machine (Concept 2 Inc., Morrisville, NJ, USA) for a functional electrical stimulation (FES) assisted indoor rowing exercise in which the rowers must repeatedly press the two switches on the handle that stimulate their paralyzed leg muscles. The objective of this study was to automate the delivery of electrical stimulation to prevent potential repetitive strain injuries and to expand the user base to clients with impaired hand function.

The importance of biomechanics.

When neuroscientists gather to discuss "Movement and Sensation", they tend to discuss neurons rather than muscles and bones. Neurons may be more interesting, but their roles in motor control depend on the mechanical properties of the system to be controlled. Understanding of those properties has been surprisingly elusive, despite the well-developed disciplines of biomechanics and muscle physiology.