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Rehabilitation Engineering, IEEE Transactions on

Issue 4 • Date Dec. 1999

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Displaying Results 1 - 13 of 13
  • Author index

    Page(s): 1 - 3
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    Freely Available from IEEE
  • Subject index

    Page(s): 3 - 8
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    Freely Available from IEEE
  • Adaptive one-switch row-column scanning

    Page(s): 464 - 473
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    Row-column scanning is a very slow method of communication. Options for increasing text entry rate include 1) dynamically changing the configuration of the row-column matrix or 2) using rate-enhancement techniques like word prediction, but evidence suggests that increased cognitive load imposed by these methods on the user can result in little or no improvement in test generation rate. An alternative we are investigating is adapting a system's scan delay during run-time. Our goal is to allow a scanning system to adjust its parameters “on the fly” (as opposed to the current practice of setting parameters during clinical assessments). This paper describes the evolution of a one-switch row-column scanning system that adapts its scan rate based on measurements of user performance. Two experiments have been performed to explore the effects of automatically adapting scan delay on users' test entry rate. Our results indicate that automatic adaptation has the potential to enhance test-entry rate without increasing task complexity View full abstract»

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  • Endoneural selective stimulating using wire-microelectrode arrays

    Page(s): 399 - 412
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    In acute experiments eight 5- to 24-wire-microelectrode arrays were inserted into the common peroneal nerve of the rat, to investigate whether the electrodes could selectively stimulate motor units of the extensor digitorum longus (EDL) muscle. Twitch-force-recruitment curves were measured from the EDL for each array electrode. The curves were plotted on a double-logarithmic scale and parameterized by the low-force slope (which represents the power p in the power-law relationship of force F versus stimulus current I, or F~Ip) and the threshold current. The slopes and threshold currents measured with array electrodes did not differ significantly from those obtained with randomly inserted single wire-microelectrodes. This indicates that, although involving a more invasive insertion procedure, electrode arrays provide neural contacts with low-force recruitment properties similar to those of single wires. Array results revealed partial blocking of neural conduction, similar to that reported with microneurographic insertion with single needles. The efficiency of the array was defined as the fraction of array electrodes selectively contacting a motor unit and evoking the corresponding threshold force. Efficiency thus expresses the practical value of the used electrode array in terms of the total number of distinct threshold forces that can be stimulated by selecting the appropriate electrodes. The eight arrays were capable of evoking threshold forces selectively with an average efficiency of 0.81 (or 81%) View full abstract»

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  • Implanted functional electrical stimulation system for mobility in paraplegia: a follow-up case report

    Page(s): 390 - 398
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    A 16-channel functional electrical stimulation (FES) system has been implanted in a person with T10 paraplegia for over a year. The system consists of two eight-channel radio frequency controlled receiver-stimulators delivering stimuli through a network of 14 epimysial and two intramuscular electrodes. Using this system and a walker for support, the subject was able to stand up for 8 min and walk regularly for 20 m. The standing duration was limited by arm fatigue since upper extremities supported an average of 25% of body weight. This was due to suboptimal hip extension and some undesired recruitment of rectus femoris and sartorius with stimulation of quadriceps electrodes. The left quadriceps exhibited rapid fatigue that limited walking distance and duration. The metabolic energy requirements were well within the aerobic limits of the sedentary paraplegic population. At one-year follow-up evaluation all electrodes are functional except one intramuscular electrode. The implant caused no adverse physiological effects and the individual reported health benefits such as increased energy and overall fitness as a result of the FES system use. With further improvements in muscle response through innovative surgical techniques, the 16-channel implanted FES system can be a viable addition to exercise and mobility function in persons with paraplegia View full abstract»

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  • Frequency component selection for an EEG-based brain to computer interface

    Page(s): 413 - 419
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    A new communication channel for severely handicapped people could be opened with a direct brain to computer interface (BCI). Such a system classifies electrical brain signals online. In a series of training sessions, where electroencephalograph (EEG) signals are recorded on the intact scalp, a classifier is trained to discriminate a limited number of different brain states. In a subsequent series of feedback sessions, where the subject is confronted with the classification results, the subject tries to reduce the number of misclassifications. In this study the relevance of different spectral components is analyzed: (1) on the training sessions to select optimal frequency bands for the feedback sessions and (2) on the feedback sessions to monitor changes View full abstract»

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  • The new design of an infrared-controlled human-computer interface for the disabled

    Page(s): 474 - 481
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    This paper reports on the development of an eyeglass-type infrared (IR)-controlled computer interface for the disabled. This system may serve to assist those who suffer from spinal cord injuries or other handicaps to operate a computer. This system is comprised of three major components: 1) an infrared transmitting module, 2) an infrared receiving/signal-processing module, and 3) a main controller, the Intel-8951 microprocessor. The infrared transmitting module utilizes tongue-touch circuitry which is converted to an infrared beam and a low power laser (<0.1 mW) beam. The infrared receiving/signal-processing module, receives the infrared beam and fine tunes the unstable infrared beam into standard pulses which are used as control signals. The main controller is responsible for detecting the input signals from the infrared receiving/signal-processing module and verifying these signals with the mapping table in its memory. After the signal is verified, it is released to control the keys of the computer keyboard and mouse interface. This design concept was mainly based on the idea that the use of an infrared remote module fastened to the eyeglasses could allow the convenient control of the input motion on the keys of a computer keyboard and mouse which are all modified with infrared receiving/signal-processing modules. The system is designed for individuals with spinal cord injuries and disabled in which the subjects' movement are severely restricted. The infrared transmitting module can be easily mounted on eyeglasses or artificial limbs View full abstract»

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  • Characteristics of visual feedback in postural control during standing

    Page(s): 427 - 434
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    In the present study, the visual feedback system in postural control was investigated. To suppress the vestibular and proprioceptive feedback paths, a subject stood on a force-measuring plate with a fixed back support. Because the subject's body was immovable under these conditions, the subject controlled a computer model which simulated body dynamics. Information on the sway angle of the model was fed visually. Under this condition, frequency response functions for the ankle movement in response to the sway angle were calculated. The experimental results suggest that the visual feedback system contains a large time delay and, consequently, the visual system does not by itself allow a subject to maintain an upright posture View full abstract»

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  • Automatic adaptation in the NavChair Assistive Wheelchair Navigation System

    Page(s): 452 - 463
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    The NavChair Assistive Wheelchair Navigation System is an adaptive shared control system being developed to provide mobility to those individuals who would otherwise find it difficult or impossible to use a power wheelchair due to cognitive, perceptual, or motor impairments. The NavChair provides task-specific navigation assistance to the wheelchair operator in the form of several distinct operating modes, each of which distributes control differently between the wheelchair and the operator. This paper describes the NavChair's mechanism for automatically selecting the most appropriate operating mode based on a combination of the wheelchair's immediate situation and its global location. Results from two experimental evaluations of the adaptation method are presented View full abstract»

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  • Kinetics of stiff-legged gait: induced acceleration analysis

    Page(s): 420 - 426
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    Treating spastic paretic stiff-legged gait, defined as reduced knee flexion in swing, holds a high priority in the rehabilitation of patients with upper motor neuron lesions. We propose a method to determine the relative contributions of hip, knee, and ankle inpairments to this disability. We analyzed the gait of ten patients with stiff-legged gait (SLG) due to a single stroke and ten healthy, able-bodied controls. Using subject specific models, we analyzed the induced accelerations (IAs) at the knee. Knee IAs throughout the gait cycle were calculated and the sum of the IAs was compared to the knee joint angular acceleration estimated from kinematic data. The preswing and early swing IAs were the focus of our examination as these largely determine knee kinematics in swing. Knee angular accelerations estimated from IAs and kinematic data agreed for both controls and patients. Gait cycle IA analysis of individual patients identified highly variable causes of SLG including ankle and hip joint impairments. Induced acceleration analysis (IAA) suggested that multiple impairments, not just about the knee, but also about the hip and ankle, lead to this disability. Individual subjects are likely to have individual reasons for their stiff-legged gait. Defining the link between the patients specific impairments and their gait disability should be a goal of clinical gait analysis. IAA is a useful tool for this purpose with a strong potential for clinical application View full abstract»

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  • The NavChair Assistive Wheelchair Navigation System

    Page(s): 443 - 451
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    The NavChair Assistive Wheelchair Navigation System is being developed to reduce the cognitive and physical requirements of operating a power wheelchair for people with wide ranging impairments that limit their access to powered mobility. The NavChair is based on a commercial wheelchair system with the addition of a DOS-based computer system, ultrasonic sensors, and an interface module interposed between the joystick and power module of the wheelchair. The obstacle avoidance routines used by the NavChair in conjunction with the ultrasonic sensors are modifications of methods originally used in mobile robotics research. The NavChair currently employs three operating modes: general obstacle avoidance, door passage, and automatic wall following. Results from performance testing of these three operating modes demonstrate their functionality. In additional to advancing the technology of smart wheelchairs, the NavChair has application to the development and testing of “shared control” systems where a human and machine share control of a system and the machine can automatically adapt to human behaviors View full abstract»

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  • A new rehabilitation training system for postural balance control using virtual reality technology

    Page(s): 482 - 485
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    A new rehabilitation training system, designated as a virtual cycling system, was developed to improve postural balance control by combining virtual reality (VR) technology with a bicycle. Several parameters including path deviation, path deviation velocity, cycling time, and head movement were extracted and evaluated to quantify the extent of control. The system was effective as a training device and, in addition, the technology might have a wider applicability to the rehabilitation field View full abstract»

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  • A low-cost, portable system for the assessment of the postural response of wheelchair users to perturbations

    Page(s): 435 - 442
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    Maintaining seated postural stability presents a serious challenge to wheelchair users in vehicles, even during normal driving conditions. The purpose of this research was to develop a system for the study of seated postural control in response to perturbations similar to those that might be experienced during vehicle turning and braking. A servo-controlled tilt platform was constructed to provide a low-cost, small, and easily transportable device for generating precise and repeatable perturbations. Tilt platform operation was examined for accuracy and reproducibility of a desired perturbation. Repeatability was high with a mean signal-to-noise ratio (SNR) of 45.4 for a given perturbation measured across 11 subjects. An initial comparison of stability results obtained on the tilt platform and in a vehicle showed a correspondence, although differences were apparent. The tilt platform has been used successfully to assess balance in spinal cord-injured subjects and to test wheelchair securement systems View full abstract»

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Aims & Scope

This Transaction ceased publication in 2000. The current retitled publication is IEEE Transactions on Neural Systems and Rehabiliation Engineering.

Full Aims & Scope