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Neural Systems and Rehabilitation Engineering, IEEE Transactions on

Issue 4 • Date Dec. 2003

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Displaying Results 1 - 19 of 19
  • Time-frequency analysis of SEMG with special consideration to the interelectrode spacing

    Publication Year: 2003 , Page(s): 341 - 345
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (367 KB)  

    The surface electromyogram (SEMG) is a complex, nonstationary signal. The spectrum of the SEMG is dependent on the force of contraction being generated and other factors like muscle fatigue and interelectrode distance (IED). The spectrum of the signal is time variant. This paper reports the experimental research conducted to study the influence of force of muscle contraction and IED on the SEMG signal using time-frequency (T-F) analysis. Two T-F techniques have been used: Wigner-Ville distribution (WVD) and Choi-Williams distribution (CWD). The experiment was conducted with the help of ten healthy volunteers (five males and five females) who performed isometric elbow flexions of the active right arm at 20%, 50%, and 80% of their maximal voluntary contraction. The SEMG signal was recorded using surface electrodes placed at a distance of 18 and 36 mm over biceps brachii muscle. The results indicate that the two distributions were spread out across the frequency range at smaller IED. Further, regardless of the spacing, both distributions displayed increased spectral compression with time at higher contraction level. View full abstract»

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  • A sensorized thumb for force closed-loop control of hand neuroprostheses

    Publication Year: 2003 , Page(s): 346 - 353
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (489 KB)  

    In this paper, we presented a sensorized thumb based on a matrix of piezoresistive force sensors, with an acquisition unit and a special wearing support. The sensor was calibrated and then the device was tested during different tasks simulating activities of daily living performed by seven able-bodied subjects. By means of these experiments, we verified that the device proposed can be used to extract force information during grasp. In fact, the device was able to provide useful force information in the 98% of the trials with a good repeatability during all the different conditions. Moreover, we evaluated the patterns obtained during the different grasping tasks. The palmar grasps were performed in a similar manner, whereas the lateral pinch and the spherical volar grip were more different. This device can provide force information with good performance and acceptability and it can be used for force closed-loop control of hand neuroprostheses. View full abstract»

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  • Enabling computer decisions based on EEG input

    Publication Year: 2003 , Page(s): 354 - 360
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (395 KB) |  | HTML iconHTML  

    Multilayer neural networks were successfully trained to classify segments of 12-channel electroencephalogram (EEG) data into one of five classes corresponding to five cognitive tasks performed by a subject. Independent component analysis (ICA) was used to segregate obvious artifact EEG components from other sources, and a frequency-band representation was used to represent the sources computed by ICA. Examples of results include an 85% accuracy rate on differentiation between two tasks, using a segment of EEG only 0.05 s long and a 95% accuracy rate using a 0.5-s-long segment. View full abstract»

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  • Analyzing EEG signals using the probability estimating guarded neural classifier

    Publication Year: 2003 , Page(s): 361 - 371
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (433 KB)  

    This paper introduces a neural network architecture for classifying feature vectors symbolizing portions (or segments) of an electroencephalogram (EEG) trace of a human subject. This classification task is the one that is typically required when developing a so-called brain-computer interface (BCI), which analyzes the EEG signals of a subject in order to "understand" the subject's thoughts. However, instead of merely saying which "category of thoughts" (i.e., which class) the respective input feature vector belongs to, the network described here estimates the probabilities of an EEG segment being associated with each individual class. The network, which is called PeGNC (for probability estimating guarded neural classifier), is tested with two kinds of experiments. In the first experiment, the α-rhythm associated with a human subject closing the eyes is detected online with the help of a frequency-based representation. Since the EEG signal is, in general, always a mixture of numerous action potentials generated simultaneously and it is, thus, very likely that mental activities result in overlapping classes, it is reasonable to believe that the PeGNC network - which does not select any one single class, but determines probability values for each mental category - is particularly suitable for this kind of EEG analysis. The second experiment deals with this issue on the basis of an offline analysis of simulated data. View full abstract»

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  • Wavelength and intensity dependence of retinal evoked responses using in vivo optic nerve recording

    Publication Year: 2003 , Page(s): 372 - 376
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (270 KB) |  | HTML iconHTML  

    We use a whole-animal model and wavelength-selective optical stimulation to investigate relationships between optical stimulus characteristics and neural signaling. Light-emitting diodes are used to selectively stimulate rod and cone pathways in Rana pipiens. A suction electrode is used to make in vivo measurements of the compound action potential from the optic nerve as the wavelength and intensity of the stimulus is varied. Our results demonstrate that the cone and rod pathways can be separately stimulated and analyzed with our method and, thus, provide a means to model the response of such pathways to more complex stimuli. View full abstract»

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  • Foot placement alters the mechanisms of postural control while standing and reaching

    Publication Year: 2003 , Page(s): 377 - 385
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (558 KB) |  | HTML iconHTML  

    This study investigated the effects of altering foot placement on the strategies used by able-bodied subjects to perform reaching tasks while standing. The motivation for this study was to consider the results in the context of a person with a spinal cord injury using a functional neuromuscular stimulation (FNS) system to stand while reaching. Three foot placement conditions were compared as subjects reached to the left, right, and center. Centers of pressure (COP), joint angles, and joint moments were calculated as postural parameters using force platform and video marker data. Side-by-side and wide foot placements resulted in similar postural parameters. In contrast, the modified tandem stance (feet spaced at pelvic width with one foot shifted forward) resulted in anterior/posterior COP excursions that were larger in magnitude and more consistent across reach directions when compared to the other foot placement conditions. Furthermore, the movement patterns used during the tandem stance were more consistent and may be more readily achievable with FNS than the movement patterns utilized with the side-by-side and wide stances. These results suggest that the modified tandem stance may enhance the functionality of FNS standing systems and may also be useful in other standing rehabilitation programs. View full abstract»

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  • A rapid speech synthesizing software on a PDA for Japanese with speech impairments

    Publication Year: 2003 , Page(s): 386 - 391
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB) |  | HTML iconHTML  

    We developed a Japanese-language, rapid synthesizing software application for use on a personal digital assistant. It has an unrestricted vocabulary and can synthesize words and sentences within 3 s. Eight hundred common sentences and words are preregistered. By touching the first character at the head of a preregistered sentence or word from an on-screen Kana (Japanese alphabet) chart, the user can select the sentence or word to be spoken. Characters on the Kana chart can also be input sequentially. Two Japanese subjects with speech impairments rated the device highly for its portability and quick response. Whereas communication previously had to be done by writing or sign language, it was easy for listeners with or without specialized training in communication with persons with speech impairments to understand the output from this device, making conversation easier which, in turn, improved the quality of life and social activity of these persons with speech impairments. View full abstract»

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  • Vibrotactile display coding for a balance prosthesis

    Publication Year: 2003 , Page(s): 392 - 399
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (303 KB) |  | HTML iconHTML  

    Preliminary experiments have demonstrated the potential usefulness of a precursor balance prosthesis that displays the tilt of the subject using tactile vibrators (tactors) which arc in contact with the subject's skin. The device consists of a motion sensing system mounted on the head or body whose signals are converted into estimates of head or body tilt. Tilt is displayed to the subject by coding the tilt estimate into signals that are sent to the tactors using one of several schemes. Because full blown, end-to-end balance experiments are relatively time consuming and expensive, and because there are many possible display schemes, we have developed a quantitative means to evaluate the display step separately. We used a modified version of the manual control critical tracking task (CTT) to help us make an initial selection of the more promising vibrotactile display schemes for further evaluation. The classic CTT is a compensatory form of tracking in which the operator attempts to control an increasingly unstable system using a joystick to regulate a tracking error signal (system minus joystick) that is visually displayed as a dot on a cathode ray tube. Our modification added vibrotactile display of the error signal. For a given subject and vibrotactile display scheme, the level of difficulty at which the subjects lost control, called the critical lambda (λc), was highly repeatable. Four different coding schemes were evaluated using an array of 16 vibrators that were attached to the lower backs of 11 healthy subjects. The first scheme, called interval-based coding, modulated the interval between pulses that were sent to single tactors mounted on the subject's right and left side. A greater tracking error magnitude was displayed as a faster pulse rate. A positive error was displayed on the right side while a negative one was displayed on the left. The remaining three schemes, called position-based coding, used a horizontal row of 14 tactors. Tracking error magnitude was mapped to position of the activated vibrator so that an error near zero corresponded to a vibrator near the center of the back. The three position-based schemes tested used three, four, or seven tactors per side. Averaged over all subjects, the value of λc for the - interval-based scheme was significantly less than it was for each of the three position-based schemes. There was no significant change in λc as the number of position-based tactors was increased from three to seven per side. The prediction of better actual balance performance using position-based relative to interval-based vibrotactile display was validated by a preliminary study of six normal subjects that compared the body sway produced during quiet standing while providing head tilt estimates using both display modes. Our study provides basic characterization using λc for several vibrotactile display schemes in human subjects. The quantitative CTT measure of performance can logically be extended to other applications of vibrotactile displays and to other kinds of display schemes used for rehabilitation. View full abstract»

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  • Wavelet analysis of surface electromyography

    Publication Year: 2003 , Page(s): 400 - 406
    Cited by:  Papers (36)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (595 KB) |  | HTML iconHTML  

    Muscle fatigue is often a result of unhealthy work practice. It has been known for some time that there is a significant change in the spectrum of the electromyography (EMG) of the muscle when it is fatigued. Due to the very complex nature of this signal however, it has been difficult to use this information to reliably automate the process of fatigue onset determination. If such a process implementation were feasible, it could be used as an indicator to reduce the chances of work-place injury. This research report on the effectiveness of the wavelet transform applied to the EMG signal as a means of identifying muscle fatigue. We report that with the appropriate choice of wavelet functions and scaling factors, it is possible to achieve reliable discrimination of the fatigue phenomenon, appropriate to an automated fatigue identification system. View full abstract»

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  • Stimulation artifact in surface EMG signal: effect of the stimulation waveform, detection system, and current amplitude using hybrid stimulation technique

    Publication Year: 2003 , Page(s): 407 - 415
    Cited by:  Papers (12)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1082 KB) |  | HTML iconHTML  

    The purpose of this study was to investigate the amplitude properties of the artifact generated on the recorded surface electromyography (EMG) signals during transcutaneous electrical muscle stimulation. The factors which were investigated are the shape of the stimulation waveform, the distance of the stimulating electrode from the recording system, the interelectrode distance of the detection system, the spatial filter used for signal detection, and the stimulation current amplitude. Surface EMG signals were recorded during electrical stimulation of the biceps brachii motor point with a linear adhesive array of eight electrodes. Electrical stimulation was applied with seven stimulation waveforms (mono- and biphasic triangular, sinusoidal, and rectangular), generated by a specifically designed neuromuscular stimulator with hybrid output stage. The stimulation peak current was linearly increased from 0 mA to the maximum tolerated by the subject. The detection systems investigated were single and double differential with interelectrode distances multiple of 5 mm. Two trials for each contraction were performed on three different days. The average rectified artifact values (both absolute and normalized with respect to the corresponding M-wave values) were computed to investigate the artifact amplitude properties. Results indicated that, while the artifact average rectified value, normalized with respect to the M-wave amplitude, depended on the distance of the detecting electrodes from the stimulation point, it did not depend on the stimulation waveform, on the current intensity, on the interelectrode distance, and on the spatial filter. It was concluded that, using hybrid stimulation techniques, the selection of particular stimulation waveforms, interelectrode distances, or spatial filters has a minor effect on the reduction of the artifact when recording M-waves. View full abstract»

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  • Sonification of range information for 3-D space perception

    Publication Year: 2003 , Page(s): 416 - 421
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    We present a device that allows three-dimensional (3-D) space perception by sonification of range information obtained via a point laser range sensor. The laser range sensor is worn by a blindfolded user, who scans space by pointing the laser beam in different directions. The resulting stream of range measurements is then converted to an auditory signal whose frequency or amplitude varies with the range. Our device differs from existing navigation aids for the visually impaired. Such devices use sonar ranging whose primary purpose is to detect obstacles for navigation, a task to which sonar is well suited due to its wide beam width. In contrast, the purpose of our device is to allow users to perceive the details of 3-D space that surrounds them, a task to which sonar is ill suited, due to artifacts generated by multiple reflections and due to its limited range. Preliminary trials demonstrate that the user is able to easily and accurately detect corners and depth discontinuities and to perceive the size of the surrounding space. View full abstract»

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  • "Virtual keyboard" controlled by spontaneous EEG activity

    Publication Year: 2003 , Page(s): 422 - 426
    Cited by:  Papers (47)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB) |  | HTML iconHTML  

    A "virtual keyboard" (VK) is a letter spelling device operated for example by spontaneous electroencephalogram (EEG), whereby the EEC is modulated by mental hand and leg motor imagery. We report on three able-bodied subjects, operating the VK. The ability in the use of the VK varies between 0.85 and 0.5 letters/min in error-free writing. View full abstract»

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  • Noninvasive measurement of torque development in the rat foot: measurement setup and results from stimulation of the sciatic nerve with polyimide-based cuff electrodes

    Publication Year: 2003 , Page(s): 427 - 437
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (821 KB) |  | HTML iconHTML  

    In neural rehabilitation, selective activation of muscles after electrical stimulation is mandatory for control of paralyzed limbs. For an evaluation of electrode selectivity, a setup to noninvasively measure the force development after electrical stimulation in the rat foot was developed. The setup was designed in accordance to the anatomical features of the rat model to test the isometric torque development at given ankle positions in an intact leg. In this paper, the setup design and development is presented and discussed. In a first study, the selectivity of small nerve cuffs with 12 electrodes implanted around the rat sciatic nerve was investigated. Special attention was drawn to the performance of the torque measurement setup in comparison to electrophysiological data obtained from compound muscle action potential recordings. Using one cuff around the nerve, electrical stimulation on different electrode tripoles led to plantarflexion and dorsiflexion of the foot without an a priori alignment of the cuff. View full abstract»

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  • A PC-based system for evaluating the efficacy of the NESS Handmaster orthosis

    Publication Year: 2003 , Page(s): 438 - 442
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (587 KB) |  | HTML iconHTML  

    Functional electrical stimulation (FES) is a viable alternative to conventional treatments aimed at restoring function and mobility following central nervous system (CNS) damage. Muscle contractions are converted into functional activity, thus, its wide range of clinical applications. Research efforts are currently focused on the development of programmable stimulators that enable the patient to perform tasks related to activities of daily living. Herein, we present a PC-based surface stimulator that enables the user to vary the stimulus waveform and the activation sequence of different muscle groups within a wide range of options. This instrumentation is not only a development platform for other, more sophisticated neuroprostheses, but an essential tool for evaluating the rehabilitative efficacy of the NESS Handmaster (NESS Ltd., Israel). Our PC-based stimulator reproduces Handmaster motor tasks by selectively activating the five muscle groups that control the hand, palmar, and lateral grasps. The stimulator is entirely controlled by the plegic patient with the push of a button. The ancillary software permits acquisition of up to sixteen analog channels, so that feedback signals for closed-loop control of the grasp function can be measured. View full abstract»

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  • A model-based approach to stabilizing crutch supported paraplegic standing by artificial hip joint stiffness

    Publication Year: 2003 , Page(s): 443 - 451
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (642 KB) |  | HTML iconHTML  

    The prerequisites for stable crutch supported standing were analyzed in this paper. For this purpose, a biomechanical model of crutch supported paraplegic stance was developed assuming the patient was standing with extended knees. When using crutches during stance, the crutches will put a position constraint on the shoulder, thus reducing the number of degrees of freedom. Additional hip-joint stiffness was applied to stabilize the hip joint and, therefore, to stabilize stance. The required hip-joint stiffness for changing crutch placement and hip-joint offset angle was studied under static and dynamic conditions. Modeling results indicate that, by using additional hip-joint stiffness, stable crutch supported paraplegic standing can be achieved, both under static as well as dynamic situations. The static equilibrium postures and the stability under perturbations were calculated to be dependent on crutch placement and stiffness applied. However, postures in which the hip joint was in extension (C postures) appeared to the most stable postures. Applying at least 60 N · m/rad hip-joint stiffness gave stable equilibrium postures in all cases. Choosing appropriate hip-joint offset angles, the static equilibrium postures changed to more erect postures, without causing instability or excessive arm forces to occur. View full abstract»

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  • Static and dynamic evaluation of the influence of supplementary hip-joint stiffness on crutch-supported paraplegic stance

    Publication Year: 2003 , Page(s): 452 - 462
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (603 KB) |  | HTML iconHTML  

    Paraplegic persons can stand with hip-knee-ankle-foot orthoses (HKAFO) and crutches. However, current HKAFOs restrict body movement extensively, which may impede functional upper-body movements. A more compliant body support using a more compliant orthosis or well-controlled functional electrical stimulation system may increase freedom of movement to the user, but should not impede stability and required arm support. In the current study, we investigated the consequences of varying stiffness applied at the hip to postural stability and required crutch force during paraplegic stance. Experiments were performed on five paraplegic persons with spinal cord lesions varying from Tl to T12. Static postures and dynamic responses to perturbations were tested for varying hip stiffness and crutch placements. The minimal hip-joint stiffness for stable stance appeared to depend on lesion level. In contrast to the predictions of a previous modeling study, no statistically significant influences of hip-joint stiffness or crutch-to-foot distance on posture and applied crutch forces were found. It is hypothesized that the main reasons of this discrepancy are the active upper-body efforts the paraplegic HKAFO users are still able to exert and the remaining flexibility of the upper trunk and shoulder region, which is present despite the restrictions of the orthosis. View full abstract»

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  • Morse code application for wireless environmental control systems for severely disabled individuals

    Publication Year: 2003 , Page(s): 463 - 469
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (607 KB) |  | HTML iconHTML  

    Some physically-disabled people with neuromuscular diseases such as amyotrophic lateral sclerosis, multiple sclerosis, muscular dystrophy, or other conditions that hinder their ability to write, type, and speak, require an assistive tool for purposes of augmentative and alternative communication in their daily lives. In this paper, we designed and implemented a wireless environmental control system using Morse code as an adapted access communication tool. The proposed system includes four parts: input-control module; recognition module; wireless-control module; and electronic-equipment-control module. The signals are transmitted using adopted radio frequencies, which permits long distance transmission without space limitation. Experimental results revealed that three participants with physical handicaps were able to gain access to electronic facilities after two months' practice with the new system. View full abstract»

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  • Author index

    Publication Year: 2003 , Page(s): 470 - 473
    Save to Project icon | Request Permissions | PDF file iconPDF (181 KB)  
    Freely Available from IEEE
  • Subject index

    Publication Year: 2003 , Page(s): 473 - 479
    Save to Project icon | Request Permissions | PDF file iconPDF (206 KB)  
    Freely Available from IEEE

Aims & Scope

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