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Biomedical subjects

D Graupe

Publications and source records attributed to D Graupe.

At least 19 recordsLinked to original sources

A novel large-memory neural network as an aid in medical diagnosis applications.

This paper describes the application of a large memory storage and retrieval (LAMSTAR) neural network to medical diagnosis and medical information retrieval problems. The network is based on Minsky's knowledge-lines (k-lines) theory of memory storage and retrieval in the central nervous system. It employs arrays of self-organized map modules, such that the k-lines are implemented via link weights (address correlation) that are being updated by learning. The network also employs features of forgetting and of interpolation and extrapolation, thus being able to handle incomplete data sets. It can deal equally well with exact and fuzzy information, thus being specifically applicable to medical diagnosis where the diagnosis is based on exact data, fuzzy patient interview information, patient history, observed images, and test records. Furthermore, the network can be operated in closed loop with Internet search engines to intelligently use data from the Internet in a higher hierarchy of learning. All of the above features are shown to make the LAMSTAR network suitable for medical diagnosis problems that concern large data sets of many categories that are often incomplete and fuzzy. Applications of the network to three specific medical diagnosis problems are described: two from nephrology and one related to an emergency-room drug identification problem. It is shown that the LAMSTAR network is hundreds and thousands times faster in its training than back-propagation-based networks when used for the same problem and with exactly the same information.

Computational Biology↗

Control of neuromuscular stimulation for ambulation by complete paraplegics via artificial neural networks.

The paper describes the application of a neural network (ANN) for controlling a functional neuromuscular stimulation (FNS) system to facilitate patient-responsive ambulation by paralyzed patients with traumatic, thoracic-level spinal cord injuries. The particular ANN that is employed is a modified Adaptive-Resonance-Theory (ART-1) network. It serves as a controller in an FNS system (the Parastep system) that is presently in use by approximately 500 patients worldwide (but still without ANN control) and which was the first and only FNS system approved by FDA. The proposed neural network discriminates above-lesion upper-trunk electromyographic (EMG) time series to activate standing and walking functions under FNS and controls FNS stimuli levels using response-EMG signals. For this particular application, several modifications are introduced into the standard ART-1 ANN. First, a modified on-line learning rule is proposed. The new rule assures bi-directional modification of the stored patterns and prevents noise interference. Second, a new reset rule is proposed, which prevents 'exact matching' when the input is a subset of the chosen pattern. A single ART-1-based structure is being applied to solving two problems, namely (1) signal pattern recognition and limb function determination, and (2) control of stimulation levels. This also facilitates ambulation of paraplegics under FNS, with adequate patient interaction in initial system training, retraining the network when needed, and in allowing patient's manual over-ride in the case of error, where any manual over-ride serves as a re-training input to the neural network. The ANN control facilitates continuous update of control settings during normal use, without formal retraining.

Electromyography↗

On the inter-relations between artificial and physiological neural networks.

This paper discusses the inter-relations between findings on the physiological neural network (PNN) and artificial neural networks (ANN). It discusses the interaction of progress in both PNN and ANN for the purpose of borrowing from ANN's mathematical understandings to establish pointers for further explorations to better understand the PNN, and also for the reciprocal transferring of knowledge from PNN findings to improve ANN schemes. Such improvements in ANN are essential for better handling the needs of the information technology (IT) explosion in dealing with huge data bases and where data often defy analysis and are incomplete and fuzzy. On the other hand, principles and elements of ANN designs that appear to be important and successful can serve as guides for identifying them in the PNN, to be subsequently confirmed by bioanalytical tests. Hence progress in PNN is obviously essential for progress in ANN, as is progress in ANN helpful in PNN modeling, though its laboratory confirmation is still a far lengthier process. We discuss certain specific ANN schemes with respect to the above inter-relations with PNN. We feel that the progress in both PNN and ANN research provides a major link between the thrust in information technology developments and the thrust in biological science research, which are most probably the two major focus areas of research at the dawn of the 21st century.

Animals↗

Stochastically-modulated stimulation to slow down muscle fatigue at stimulated sites in paraplegics using functional electrical stimulation for leg extension.

This short communication is a preliminary report on a study concerning slowing down the rate of muscle fatigue when FES (Functional Electrical Stimulation) is applied for standing and walking by complete (traumatic) thoracic-level paraplegics. It is shown that randomly modulating the inter-pulse interval between FES pulses (which serve to trigger action potentials in the peripheral nerves concerned) results in a significantly lower rate of muscle fatigue, as tested in a series of leg extensions, when FES was applied at the quadriceps. Specifically, we report that the best results (longest durations of leg extension prior to onset of muscle-fatigue) were achieved with a +/- 5 msec uniformly-distributed (pseudo-) white-noise modulation at a 42 msec inter-pulse interval (24 pulses per sec). These resulted in an average increase in duration of leg extension of approximately 37% in this pilot study, as compared with unmodulated (fixed-rate) trains of FES pulses. This significant increase, even in a very preliminary study appears to merit careful further examination, since it may allow a possibly significant increase in standing duration and in walking range of paraplegics using FES for ambulation.

Electric Stimulation Therapy↗

Ambulation by traumatic T4-12 paraplegics using functional neuromuscular stimulation

The review describes and discusses the status of the major approaches to functional neuromuscular stimulation (FNS) for the purpose of ambulation by traumatic complete thoracic-level paraplegics, namely, hybrid body bracing with FNS, percutaneous FNS, fully implanted FNS, and transcutaneous FNS. For each approach, the review discusses the system for which the most published user data are available and, where relevant, where the largest user population exists. The review covers methodologies and system descriptions. The Analysis sections of the review discuss ambulation performance, patient-training aspects, and, when available, multi-user medical, physiological, and psychological evaluation data. A comparative tabulation is given in the Synthesis section of the review.

Journal Article↗

Functional neuromuscular stimulator for short-distance ambulation by certain thoracic-level spinal-cord-injured paraplegics.

BACKGROUND: Functional Neuromuscular Stimulation (FNS) for unbraced short-distance ambulation by traumatic complete/near-complete T4 to T12 paraplegics is based on work by Graupe et al (1982), Kralj et al (1980), Liberson et al (1961), and others. This paper discusses methodology, performance, training, admissibility criteria, and medical observations for FNS-ambulation using the Parastep-I system, which is the first and only such system to have received FDA approval (1994) and which emanated from these previous works. METHOD: The Parastep system is a transcutaneous non-invasive and microcomputerized electrical stimulation system built into a Walkman-size unit powered by eight AA batteries that is controlled by finger-touch buttons located on a walker's handbars for manual selection of stimulation menus. The microcomputer shapes, controls, and distributes trains of stimulation signals that trigger action potentials in selected peripheral nerves. Walker support is used for balance. The patient can don the system in under 10 minutes. At least 32 training sessions are required. RESULTS: Approximately 400 patients have used the Parastep system, essentially all achieving standing and at least 30 feet of ambulation, with a few reaching as much as 1 mile at a time. Recent literature presents data on the medical benefits of using the Parastep system-beyond the exercise benefits of short distance ambulation at will-such as increased blood flow to the lower extremities, lower HR at subpeak work intensities, increased peak work capability, reduced spasticity, and psychological benefits. CONCLUSIONS: We believe that the Parastep FNS system, which is presently commercially available by prescription, is easily usable for independent short-distance ambulation. We believe that its exercise benefits and its other medical and psychological benefits, as discussed, make it an important option for thoracic-level traumatic paraplegics.

Blood Pressure↗

Motor unit number estimation by spatial-temporal summation of single motor unit potentials.

Current techniques for motor unit number estimation (MUNE) rely on the amplitude of the compound muscle action potential (CMAP) evoked by supramaximal stimulation and mean amplitude of single motor unit potentials (SMUPs). The phase cancellation during summation is not considered. We developed a technique to address this issue. Slow and fast types of motor unit potentials were collected from 5 normal subjects from their abductor pollicis brevis muscles by low-level voluntary contractions, and near-threshold nerve stimulation, respectively. Two of each type of SMUPs were used as templates for reconstructing the best fitted CMAP using a feed-forward neural network. The total number of SMUPs simulated from the four templates during the reconstruction served as MUNE. The mean MUNE was 222 +/- 98. The technique is simple and noninvasive, and may be applied in the future for MUNE in patients.

Action Potentials↗

Transcutaneous functional neuromuscular stimulation of certain traumatic complete thoracic paraplegics for independent short-distance ambulation.

The paper describes a system for transcutaneous functional neuromuscular stimulation (FNS) of certain traumatic thoracic-level complete paraplegics for independent unbraced short distance ambulation. The system described has been approved by the FDA in 1994 for that purpose. Its design, control, operation principles and parameters are described. Patient acceptance criteria and contraindications are outlined as is patient's training. Ambulation results are discussed and clinical and medical observations are reviewed. Finally general comments are made on the system's shortcomings and on possible improvements.

Adolescent↗

Artificial neural network control of FES in paraplegics for patient responsive ambulation.

This paper describes an ART-1-based artificial neural network (ANN) adapted for controlling functional electrical stimulation (FES) to facilitate patient-responsive ambulation by paralyzed patients with spinal cord injuries. This network is to serve as a controller in an FES system developed by the first author which is presently in use by 300 patients worldwide (still without ANN control) and which was the first and the only FES system approved by the FDA. The proposed neural network discriminates above-lesion upper-trunk electromyographic (EMG) time series to activate standing and walking functions under FES and controls FES stimuli levels using response-EMG signals. For this particular application, we introduce several modifications of the binary adaptive resonance theory (ART-1) for pattern recognition and classification. First, a modified on-line learning rule is proposed. The new rule assures bidirectional modification of the stored patterns and prevents noise interference. Second, a new reset rule is proposed which prevents "exact matching" when the input is a subset of the chosen pattern. We show the applicability of a single ART-1-based structure to solving two problems, namely, 1) signal pattern recognition and classification, and 2) control. This also facilitates ambulation of paraplegics under FES, with adequate patient interaction in initial system training, retraining the network when needed, and in allowing patient's manual override in the case of error, where any manual override serves as a retraining input to the neural network. Thus, the practical control problems (arising in actual independent patient ambulation via FES) were all satisfied by a relatively simple ANN design.

Electric Stimulation Therapy↗

Topographic component (parallel factor) analysis of multichannel evoked potentials: practical issues in trilinear spatiotemporal decomposition.

We describe a substantive application of the trilinear topographic components/parallel factors model (TC/PARAFAC, due to Möcks/Harshman) to the decomposition of multichannel evoked potentials (MEP's). We provide practical guidelines and procedures for applying PARAFAC methodology to MEP decomposition. Specifically, we apply techniques of data preprocessing, orthogonality constraints, and validation of solutions in a complete TC analysis, for the first time using actual MEP data. The TC model is shown to be superior to the traditional bilinear principal components model in terms of data reduction, confirming the advantage of the TC model's added assumptions. The model is then shown to provide a unique spatiotemporal decomposition that is reproducible in different subject groups. The components are shown to be consistent with spatial/temporal features evident in the data, except for an artificial component resulting from latency jitter. Subject scores on this component are shown to reflect peak latencies in the data, suggesting a new aspect to statistical analyses based on subject scores. In general, the results support the conclusion that the TC model is a promising alternative to principal components for data reduction and analysis of MEP's.

Brain Mapping↗

Topographic components analysis of evoked potentials: estimation of model parameters and evaluation of parameter uniqueness.

The purpose of this paper is to evaluate the practicability of the 'topographic components model' proposed by Möcks for the spatio-temporal characterization of multi-channel evoked potentials (EP), and to present a complete and detailed algorithm for this method of analysis. Details of the algorithm are discussed along with various computational issues, especially with regard to contrasts with traditional principal components analysis. The algorithm is applied to multi-channel pattern-shift visual EP data obtained from normal subjects, and the model is demonstrated to provide data reduction of 71% with a relative mean-squared error (MSE) of 2%. Obvious features of the data are seen to be reflected in the estimated model parameters, lending support to the appropriateness of the model. The results also demonstrate that although the model parameters are uniquely identifiable in theory, care must be taken when fitting the model to insure that the MSE is not so insensitive to perturbations in the model parameters that they are rendered 'non-unique' for all practical purposes. The proper selection of model order is shown to play a critical role in avoiding this problem. Finally, a theoretical analysis is presented which evaluates the relationship between parameter 'uniqueness', model order, and the non-orthogonality of the model components.

Algorithms↗

EMG pattern analysis for patient-responsive control of FES in paraplegics for walker-supported walking.

This paper describes and discusses the employment of EMG pattern analysis to provide upper-motor-neuron paraplegics with patient-responsive control of FES (functional electrical stimulation) for the purpose of walker-supported walking. The system described employs above-lesion surface EMG signals to activate standing and walking functions in a patient-responsive manner. This system has been experimentally applied to paraplegics at Michael Reese Hospital and Medical Center in Chicago since early 1982. Below-lesion response-EMG control from the stimulated sites has been added in 1987 to regulate stimuli levels in the face of fatigue. Although transcutaneous FES alone is being employed, the system is applicable in principle also to implantable FES systems.

Electric Stimulation Therapy↗

Above- and below-lesion EMG pattern mapping for controlling electrical stimulation of paraplegics to facilitate unbraced walker-assisted walking.

We describe and evaluate above- and below-lesion EMG control of functional electrical stimulation (FES) in upper motor neuron paraplegics, in order to provide them with a patient-responsive system for walking with a walker support. Control is considered in terms of a combination of above-lesion EMG control and below-lesion response-EMG control. The above-lesion EMG is used to control the activation of limb functions involved in standing up and walking with FES, control being accomplished by analysing raw surface-EMG time-series patterns to discriminate between upper-trunk muscle contraction patterns, which in turn, are correlated with intended lower-limb functions involved in walking, so that natural and instinctive balance changes in paraplegics are controlled by the patient from above the lesion. The below-lesion response-EMG is the EMG produced in response to the FES pulses at the stimulation sites, for adjusting stimulation levels as needed when contractions weaken due to muscle fatigue. Above-lesion EMG is a stochastic (random-like) signal, being a response to unsynchronized motor neuron firings, whereas the below-lesion EMG is a deterministic signal responding to synchronized firings that result solely from the FES pulses. We also discuss the merits and difficulties of EMG control, and evaluate patient performance under such control, noting that FES-activated walking without adequate and patient-responsive control is of very limited use to paraplegics.

Electric Stimulation Therapy↗

A critical review of EMG-controlled electrical stimulation in paraplegics.

This review presents a description and provides a comparative performance evaluation of EMG control vs. other approaches to controlling functional electrical stimulation (FES) in upper-motor-neuron paraplegics to provide them with a certain degree of walking ability with walker support. EMG control is considered in terms of a combination of above-lesion EMG control and below-lesion response-EMG control. The above-lesion EMG is to control the activation of different limb functions involved in standing up and walking via FES. This control is accomplished by analyzing raw surface EMG time-series patterns to discriminate between upper-trunk muscle contraction patterns which, in turn, are correlated with intended lower-limb functions involved in walking, so that natural and instinctive balance changes of paraplegics are reflected and controlled by the patient only above the lesion. The below-lesion response-EMG is the EMG produced in response to the FES pulses at the stimulation sites, for adjusting stimulation levels as needed when contractions weaken due to muscle fatigue. Above-lesion EMG is a stochastic (random-like) signal, being a response to unsynchronized motor-neuron firings, whereas the below-lesion EMG is a deterministic signal responding to synchronized firings that result solely from the FES pulses. The present review discusses the merits and difficulties of EMG control and attempts to give a critical evaluation of patient performance under such control, contrasted to other methods of control, noting that FES-activated walking without adequate and patient-responsive control is of very limited attraction and use to paraplegics. Of the various control methods, only foot- or hand-switch control comes close in overall performance to above-lesion EMG control. Although one cannot categorically prefer EMG control to foot- or hand-switch control performance-wise, psychologically, EMG control has the advantage in that concentration is not diverted to the patient's fingers, whereas foot switches are inadequate for patients lacking reasonable natural (non-FES) pelvic thrust control. However, for stimulation-level control, below-lesion response-EMG appears to be the clear answer. It is shown that below-lesion EMG control of stimulation levels can be used independent of above-lesion EMG control. Below-lesion EMG control can thus be combined also with hand-switch control or, in case of low level upper-motor-neuron lesions, with pelvis control. Hence, and since FES-activated walking is as good as its control, we conclude that EMG control should be given serious consideration in any FES walking.(ABSTRACT TRUNCATED AT 400 WORDS)

Electric Stimulation Therapy↗

A single-microphone-based self-adaptive filter of noise from speech and its performance evaluation.

This paper discusses a single-microphone-based self-adaptive filter of environmental noise from speech. This filter, based on the work of Graupe (3) and of Graupe and Causey (4), has been incorporated in standard in-the-ear (ITE) and in behind-the-ear (BTE) hearing aids by several hearing aid manufacturers. Intelligibility tests by the authors and by independent researchers are presented in this paper to illustrate the filter's performance. Significant monosyllabic-word-list intelligibility improvements are shown in hearing-impaired and in normal-hearing subjects for virtually any environmental noise, including white noise, babble (interfering background conversations), cafeteria noise, high-frequency noise, and low-frequency noise at signal-to-noise ratios to below -20 dB.

Acoustics↗

Stochastic analysis of myoelectric temporal signatures for multifunctional single-site activation of prostheses and orthoses.

This paper is concerned with a stochastic time-series analysis of the temporal signatures of myoelectric (ME) signals including the determination of model order and sampling rate. The paper considers the use of time-series parameters for the activation of artificial limbs for high-level amputees, of stimulation electrodes or of powered braces for paralysed persons, in several degrees of freedom, from a single or two surface-electrode pairs at locations where considerable ME cross-talk exists. The multifunctional capability from a single site is based on the differences between the time-series (TS) parameters for different muscle activation patterns at the same ME site, these differences being thus used for limb function discrimination via easily trainable muscle activation patterns at the vicinity of the electrode site. Specifically, the analysis is in terms of identifying the AR parameters of a time-domain autoregressive (AR) signature model both for the complete ME spectrum and for parts thereof, and in terms of the autocorrelation of the signal and of the models residual. Determination of sampling rate and of model orders is discussed in detail. It is shown that, using online real-time analysis, differences in the AR time-series parameters can be observed for different trainable patterns of muscle activation, at the same electrode location, even at the same ME power levels, as long as considerable cross-talk exists at the electrode site. These parameter differences can be accentuated if one considers the AR parameters for lower-frequency spectral windows. A case is made in this paper for employing TS analysis to squeeze out information in a distinct but low-level ripple of the low frequency spectrum of the signal. This information tends to be ignored in frequency domain, but is all that the AR parameters care for in TS analysis, since they are not concerned, with a flat-average low-frequency spectrum, i.e., its white-noise-like part, which is the residual term of the AR Model and not an AR parameter. Discrimination between different functions from a single electrode-site, at even the same power level, is thus shown to require considerable cross-talk at the given site, and to require the consideration of only the low-frequency part of the spectrum.

Artificial Limbs↗

Energy cost and physiological reactions to effort during activation of paraplegics by functional electrical stimulation.

In this study, the aim was to evaluate the influence on the cardiopulmonary system of muscular contractions of the paralyzed limbs in paraplegia, activated by FES during treatment, and the energy cost of standing and walking while using FES as an orthotic aid. Three traumatic spastic paraplegics were selected for the measurements. At the end of a 6 month training program heart rate and oxygen consumption of the patients were evaluated as follows: at rest; following 30 minutes of FES in the sitting position; following 15 minutes of standing; and during ambulation. Lactic acid level during maximal effort was evaluated as well. The results indicated a low energy cost of FES in the sitting position and during usage of FES as an orthotic device for standing, confirming the beneficial effect of FES for spastic paraplegics. However, effort invested during ambulation by means of FES was found exhaustive and FES is therefore advisable for young subjects mainly.

Adult↗