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Neural Systems and Rehabilitation Engineering, IEEE Transactions on

Issue 3 • Date Sept. 2003

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Displaying Results 1 - 16 of 16
  • Effects of muscle immobilization at different lengths on tetrodotoxin-induced disuse atrophy

    Page(s): 209 - 217
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB) |  | HTML iconHTML  

    Previous studies have shown that immobilization causes muscle atrophy and that the rate of atrophy depends on the length at which the muscle is immobilized. However, most studies have been carried out in neurologically intact animals that were capable of generating at least some voluntary muscle activation. In this study, terrodotoxin was applied chronically to the rat sciatic nerve to produce complete paralysis of distal muscles for seven days, and the ankle was immobilized to hold the muscles at long or short lengths. Paralysis without immobilization resulted in relative weight losses of 36% for soleus, 19% for tibialis anterior (TA), and 17% for lateral gastrocnemius (LG) muscles. Casting the ankle in plantarflexion stretched TA and reduced its weight loss to 10%. Soleus and LG were shortened by this intervention and had increased losses of 43% and 28%, respectively. Fixing the limb in dorsiflexion resulted in a posture similar to that adopted by the unrestrained rats and had no significant effect on the amount of muscle atrophy compared to that in unrestrained paralyzed animals. View full abstract»

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  • Prevention of muscle disuse atrophy by low-frequency electrical stimulation in rats

    Page(s): 218 - 226
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (918 KB) |  | HTML iconHTML  

    When muscles lose neural drive, they atrophy rapidly. Neuromuscular electrical stimulation (NMS) has been used in attempts to prevent or reverse the atrophy, but optimal stimulation programs and parameters are not well defined. In this study, we investigated the effects of four different stimulation patterns on disuse atrophy produced in the tibialis anterior, lateral gastrocnemius, and soleus muscles of rats paralyzed with tetrodotoxin for seven days. Stimulation paradigms differed from one another by their stimulation frequency (2 or 10 pulses/s) and by their stimulation period (2 or 10 h a day). Results showed that stimulation with 2 pulses/s, paradigms were more effective at preventing disuse muscle atrophy than higher-frequency stimulation. The most marked difference was in the slow soleus muscle, which had only 10% mean atrophy when stimulated at 2 pulses/s for 10 h, compared to 26% atrophy when stimulated at 10 pulses/s for either 2 or 10 h and 32% atrophy in unstimulated, paralyzed controls. The level of atrophic change was not correlated with the levels of serum creatine kinase, used as an index of muscle damage. Results suggest that remediation of disuse atrophy may be accomplished using unphysiologically low rates of motor-unit activation despite the relatively low force produced by such unfused contractions. This may have significant implications for the design of therapies for muscle paralysis consequent to upper-motoneuron lesions. View full abstract»

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  • Comparison of joint torque evoked with monopolar and tripolar-cuff electrodes

    Page(s): 227 - 235
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (453 KB) |  | HTML iconHTML  

    Using a self-sizing spiral-cuff electrode placed on the sciatic nerve of the cat, the joint torque evoked with stimulation applied to contacts in a monopolar configuration was judged to be the same as the torque evoked by stimulation applied to contacts in a tripolar configuration. Experiments were carried out in six acute cat preparations. In each experiment, a 12-contact electrode was placed on the sciatic nerve and used to effect both the monopolar and tripolar electrode configurations. The ankle torque produced by electrically evoked isometric muscle contraction was measured in three dimensions: plantar flexion, internal rotation, and inversion. Based on the recorded ankle torque, qualitative and quantitative comparisons were performed to determine if any significant difference existed in the pattern or order in which motor nerve fibers were recruited. No significant difference was found at a 98% confidence interval in either the recruitment properties or the repeatability of the monopolar and tripolar configurations. Further, isolated activation of single fascicles within the sciatic nerve was observed. Once nerve fibers in a fascicle were activated, recruitment of that fascicle was modulated over the full range before "spill-over" excitation occurred in neighboring fascicles. These results indicate that a four contact, monopolar nerve-cuff electrode is a viable substitute for a 12 contact, tripolar nerve-cuff electrode. The results of this study are also consistent with the hypothesis that multicontact self-sizing spiral-cuff electrodes can be used in motor prostheses to provide selective control of many muscles. These findings should also apply to other neuroprostheses employing-cuff electrodes on nerve trunks. View full abstract»

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  • Influence of different stimulation frequencies on power output and fatigue during FES-cycling in recently injured SCI people

    Page(s): 236 - 240
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (315 KB) |  | HTML iconHTML  

    This study investigated whether power output during 30 min sessions of functional electrical stimulation (FES)-cycling can be increased by using stimulation frequencies higher than 30 Hz. The stimulation frequencies of FES-cycling training sessions of 19 recently injured para- and tetraplegics were randomly set at 30, 50, or 60 Hz and power output (PO) was measured continually. The mean PO of the 30 min, the PO of the last minute of each session, and the minimum PO were significantly greater at 60 and 50 Hz than at 30 Hz (ANOVA without cross-product). A 19% and 25% higher mean PO was reached at 50 and 60 Hz, respectively, compared to 30 Hz. The PO of the last minute of each session was almost always higher than the mean PO of the whole session and also higher at higher frequencies, which indicates that no muscle fatigue could be detected in 30 min FES-cycling at any of the tested frequencies. View full abstract»

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  • Preliminary evaluation of a controlled-brake orthosis for FES-aided gait

    Page(s): 241 - 248
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (447 KB) |  | HTML iconHTML  

    A hybrid functional-electrical stimulation (FES) gait system that incorporates a computer-controlled orthosis system has been developed to address the problems of rapid muscle fatigue and poor movement control that are characteristic of FES-aided gait. The orthosis is a long-leg brace that contains controllable friction brakes at both hip and knee joints. The system achieves desirable limb trajectories by utilizing the stimulated muscles as a source of unregulated power and regulating the power at each joint by computer control of the friction brakes. Muscle fatigue is reduced by locking the controllable brakes to provide the isometric joint torques necessary during stance. The hybrid gait system was evaluated and compared to conventional four channel FES-aided gait using four subjects with paraplegia. The results demonstrated significant reduction in muscle fatigue and improvement in trajectory control when using the orthosis combined with FES compared to using FES alone. Results for distance and speed improvements varied across subjects. Considerable work remains in the design of the hardware before the system is feasible for use outside the laboratory. View full abstract»

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  • The development of a potential optimized stimulation intensity envelope for drop foot applications

    Page(s): 249 - 256
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (625 KB) |  | HTML iconHTML  

    An optimized stimulation intensity envelope for use in hemiplegic drop foot applications has been developed. The traditional trapezoidal stimulation intensity approach has been examined and found to be inconsistent with the muscle activity patterns observed in healthy gait and therefore unsuitable. Experimental functional electrical stimulation (FES)-elicited tibialis anterior (TA) electromyography (EMG) data was taken over the ankle range of interest (occurring during active dorsiflexion and loading response) while also taking into account the type of TA muscle contraction occurring (concentric, eccentric, and isometric) and the speed of hemiplegic ankle joint rotation. Using the processed data, a model of normalized EMG versus pulsewidth was developed. Implementation of this model showed the unsuitability of the trapezoidal approach in the reproducing of a natural EMG profile. An optimized stimulation intensity profile is proposed which is expected to accurately reproduce the natural TA EMG profile during gait. View full abstract»

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  • An investigation into formatting and layout errors produced by blind word-processor users and an evaluation of prototype error prevention and correction techniques

    Page(s): 257 - 268
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (603 KB) |  | HTML iconHTML  

    This paper presents the results of an investigation into tools to support blind authors in the creation and checking of word processed documents. Eighty-nine documents produced by 14 blind authors are analyzed to determine and classify common types of layout and formatting errors. Based on the survey result, two prototype tools were developed to assist blind authors in the creation of documents: a letter creation wizard, which is used before the document is produced; and a format/layout checker that detects errors and presents them to the author after the document has been created. The results of a limited evaluation of the tools by 11 blind computer users are presented. A survey of word processor usage by these users is also presented and indicates that: authors have concerns about the appearance of the documents that they produce; many blind authors fail to use word processor tools such as spell checkers, grammar checkers and templates; and a significant number of blind people rely on sighted help for document creation or checking. The paper concludes that document formatting and layout is a problem for blind authors and that tools should be able to assist. View full abstract»

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  • Pattern identification as a function of stimulation on a fingertip-scanned electrotactile display

    Page(s): 269 - 275
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (365 KB) |  | HTML iconHTML  

    Two studies were conducted to determine the effect of stimulation current on pattern perception on a 49-point fingertip-scanned electrotactile (electrocutaneous) display. Performance increased monotonically from near chance levels at the lowest subthreshold current levels tested to approximately 90% at the highest comfortable current levels. This suggests the existence of a tradeoff between spatial performance and usable "gray scale" range in electrotactile presentation of graphical information. View full abstract»

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  • Detection of movement-related patterns in ongoing single-channel electrocorticogram

    Page(s): 276 - 281
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (389 KB) |  | HTML iconHTML  

    Adaptive autoregressive parameters and a linear classifier were used to detect movement related desynchronization and synchronization patterns in single-channel electrocorticogram (ECoG) obtained from implanted electrode grids. The best classification accuracies found had more than 90% hits and less than 10% false positives. The findings show that the detection of event-related desynchronization and synchronization in ECoG data can be used to reliably provide switch control directly by the brain and is therefore very suitable as the basis of a direct brain interface. View full abstract»

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  • A phone-assistive device based on Bluetooth technology for cochlear implant users

    Page(s): 282 - 287
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (442 KB) |  | HTML iconHTML  

    Hearing-impaired people, and particularly hearing-aid and cochlear-implant users, often have difficulty communicating over the telephone. The intelligibility of telephone speech is considerably lower than the intelligibility of face-to-face speech. This is partly because of lack of visual cues, limited telephone bandwidth, and background noise. In addition, cellphones may cause interference with the hearing aid or cochlear implant. To address these problems that hearing-impaired people experience with telephones, this paper proposes a wireless phone adapter that can be used to route the audio signal directly to the hearing aid or cochlear implant processor. This adapter is based on Bluetooth technology. The favorable features of this new wireless technology make the adapter superior to traditional assistive listening devices. A hardware prototype was built and software programs were written to implement the headset profile in the Bluetooth specification. Three cochlear implant users were tested with the proposed phone-adapter and reported good speech quality. View full abstract»

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  • Design, development, and characteristics of an in-shoe triaxial pressure measurement transducer utilizing a single element of piezoelectric copolymer film

    Page(s): 288 - 293
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB) |  | HTML iconHTML  

    In gait analysis, there is growing awareness of the need to simultaneously measure shear and vertical forces for the diagnosis and treatment assessment of pathological foot disorders. This is especially the case in the measurement of the forces between the plantar surface of the foot and the shoe. Although clinical awareness of the need to simultaneously measure shear and vertical forces under the foot has increased little has been done to provide the technology. This is mainly due to the difficulty in constructing devices capable of carrying out this task in the in-shoe environment. The aim of this paper is to describe the development and characteristics of a miniature triaxial transducer measuring 10 × 10 × 2.7 mm and a weight of only 2 g. This transducer is capable of simultaneously measuring three orthogonal forces under any location of the plantar surface of the foot utilizing a single element piezoelectric copolymer P(VDF-TrFE). Transducer sensitivity, linearity, hysteresis, crosstalk and temperature dependence is presented. As well as in-shoe force measurement, this triaxial transducer could have other biomedical and general engineering applications, e.g., prosthetic interface forces, handgrip forces, sport, robotics, etc. View full abstract»

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  • Multidimensional EMG-based assessment of walking dynamics

    Page(s): 294 - 300
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (571 KB) |  | HTML iconHTML  

    The electromyogram (EMG) provides a measure of a muscle's involvement in the execution of a motor task. Successful completion of an activity, such as walking, depends on the efficient motor control of a group of muscles. In this paper, we present a method to quantify the intricate phasing and activation levels of a group of muscles during gait. At the core of our method is a multidimensional representation of the EMG activity observed during a single stride. This representation is referred to as a "trajectory." A hierarchical clustering procedure is used to identify representative classes of muscle activity patterns. The relative frequencies with which these motor patterns occur during a session (i.e., a series of consecutive strides) are expressed as histograms. Changes in walking strategy will be reflected as changes in the relative frequency with which specific gait patterns occur. This method was evaluated using EMG data obtained during walking on a level and a moderately-inclined treadmill. It was found that the histogram changes due to artificially altered gait are significantly larger than the changes due to normal day-to-day variability. View full abstract»

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  • Multidimensional signal exploration using correspondence analysis. An example of a load lifting study

    Page(s): 301 - 310
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (597 KB) |  | HTML iconHTML  

    Most empirical studies concerning rehabilitation yield numerous multidimensional signals (dozens of time variables are obtained for dozens of empirical situations). The purpose of this paper is to suggest a statistical analysis procedure based on: 1) space-time fuzzy windowing; 2) signal behavior characterization within the windows using membership value averages (MVA); and 3) MVA analysis using the multiple correspondence analysis (MCA). A load lifting study provided an example of 78 multidimensional signals including 89 time variables (forces, energy indicators, linear and angular positions, speeds, and accelerations). The main goal of MCA was to compare and contrast biomechanical signals from two lifting modes: "free" and "isokinetic." In the first mode, three loads were tested - light, medium, and heavy. In the second, three speeds were tested - slow, medium, and fast. Thirteen male individuals without disabilities participated in this study. The MCA showed that most of the free load-lifting strategies cannot be used in isokinetic lifting because the constraints of the subject and the environment are different. In addition, as the level of difficulty increases, free lifting became more economical while isokinetic lifting became less economical. These results would appear to indicate that movement strategies used for free lifting cannot be learned using an isokinetic machine during rehabilitation sessions for chronic low back pain. MCA was also suggested as a tool for comparing patients with control individuals. To achieve this aim, the notion of "supplementary data" was introduced. View full abstract»

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  • Whole-body vibration during manual wheelchair propulsion with selected seat cushions and back supports

    Page(s): 311 - 322
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB) |  | HTML iconHTML  

    Although the exposure to whole-body vibrations (WBV) has been shown to be detrimental to seated humans, the effects of wheelchairs and seating systems on the transmission of vibration to an individual have not been thoroughly examined. The purpose of this study was to determine if the selected wheelchair seat cushions and back supports minimize the transmission of vibrations. Thirty-two wheelchair users traversed an activities of daily living course three times using 16 randomly selected seating systems as well as their own. Vibrations were measured using triaxial accelerometers at the seat and participant's head. The weighted fore-to-aft (Tx), vertical (Tz), and resultant (Tr) transmissibility based on the vibrational-dose-value (VDV) were used to determine if differences existed among the four seat cushions and back supports. The obstacles that seem to have the largest effect on the transmission of WBV are the single event shocks and the repeated event shocks. Comparisons between the individuals own seating system and the tested seating systems suggest that the individuals are not using the most appropriate seating system in terms of the reduction of vibration transmission. View full abstract»

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  • Modeling of a stair-climbing wheelchair mechanism with high single-step capability

    Page(s): 323 - 332
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (996 KB) |  | HTML iconHTML  

    In the field of providing mobility for the elderly and disabled, the aspect of dealing with stairs continues largely unresolved. This paper focuses on presenting the development of a stair-climbing wheelchair mechanism with high single-step capability. The mechanism is based on front and rear wheel clusters connected to the base (chair) via powered linkages so as to permit both autonomous stair ascent and descent in the forward direction, and high single-step functionality for such as direct entry to and from a van. Primary considerations were inherent stability, provision of a mechanism that is physically no larger than a standard powered wheelchair, aesthetics, and being based on readily available low-cost components. View full abstract»

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  • Adaptive tracking for pneumatic muscle actuators in bicep and tricep configurations

    Page(s): 333 - 339
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB) |  | HTML iconHTML  

    Adaptive tracking techniques are applied to pneumatic muscle actuators arranged in bicep and tricep configurations. The control objective is to force the joint angle to track a specified reference path. Mathematical models are derived for the bicep and tricep configurations. The models are nonlinear and in general time-varying, making adaptive control desirable. Stability results are derived, and the results of simulation studies are presented, contrasting the nonlinear adaptive control to a nonadaptive PID control approach. View full abstract»

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IEEE Transactions on Neural Systems and Rehabilitation Engineering focuses on the rehabilitative and neural aspects of biomedical engineering.

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Editor-in-Chief
Paul Sajda
Columbia University