EGG Signals Research Articles

Wavelet analysis in a canine model of gastric electrical uncoupling

Abnormal gastric motility function could be related to gastric electrical uncoupling, the lack of electrical, and respectively mechanical, synchronization in different regions of the stomach. Therefore, non-invasive detection of the onset of gastric electrical uncoupling can be important for diagnosing associated gastric motility disorders. The aim of this study is to provide a wavelet-based analysis of electrogastrograms (EGG, the cutaneous recordings of gastric electric activity), to detect gastric electric uncoupling. Eight-channel EGG recordings were acquired from 16 dogs in basal state and after each of two circular gastric myotomies. These myotomies simulated mild and severe gastric electrical uncoupling, while keeping the separated gastric sections electrophysiologically active by preserving their blood supply. After visual inspection, manually selected 10 min EGG segments were submitted to wavelet analysis. Quantitative methodology to choose an optimal wavelet was derived. This ‘matching’ wavelet was determined using the Pollen parametrization for 6-tap wavelet filters and error minimization criteria. After a wavelet-based compression, the distortion of the approximated EGG signals was computed. Statistical analysis on the distortion values allowed us to significantly (p < 0.05) distinguish basal state from mild and severe gastric electrical uncoupling groups in particular EGG channels.

Wavelet analysis of turbulence in the glottal jet flow

Airflow from the lungs drives the vocal folds into oscillation and exits the glottis as a turbulent jet, even though laminar flow is documented entering the glottis. Incomplete glottal closure may result in air leakage that becomes turbulent. This turbulence is thought to be the main source of breathiness in the voice. Few studies have measured degree of turbulent noise in the glottis. This turbulent noise adds significant amounts of energy to the voice signal and cannot be extracted easily without changing the voice. In this study, the turbulent jet was investigated in an excised canine larynx model with simultaneous recordings of air particle velocity, subglottal pressure, airflow rate, and EGG signal for various conditions of phonation. The velocity was measured with a constant-temperature hot-wire anemometer system. To separate the turbulence from the periodic component of the velocity signal, the technique of wavelet denoising was employed. In this method, unlike the Fourier transform which decomposes the signal into periodic components, wavelet denoising uses template matching transform to approximate the signal with different resolution or scale. Results indicate that the high resolution part contains the turbulent noise. [Work supported by NIDCD Grant No. R01 DC03566.]

Time normalization of voice signals using functional data analysis.

The harmonics-to-noise ratio (HNR) has been used to quantify the waveform irregularity of voice signals [Yumoto et al., J. Acoust. Soc. Am. 71, 1544-1550 (1982)]. This measure assumes that the signal consists of two components: a harmonic component, which is the common pattern that repeats from cycle-to-cycle, and an additive noise component, which produces the cycle-to-cycle irregularity. It has been shown [J. Qi, J. Acoust. Soc. Am. 92, 2569-2576 (1992)] that a valid computation of the HNR requires a nonlinear time normalization of the cycle wavelets to remove phase differences between them. This paper shows the application of functional data analysis to perform an optimal nonlinear normalization and compute the HNR of voice signals. Results obtained for the same signals using zero-padding, linear normalization, and dynamic programming algorithms are presented for comparison. Functional data analysis offers certain advantages over other approaches: it preserves meaningful features of signal shape, produces differentiable results, and allows flexibility in selecting the optimization criteria for the wavelet alignment. An extension of the technique for the time normalization of simultaneous voice signals (such as acoustic, EGG, and airflow signals) is also shown. The general purpose of this article is to illustrate the potential of functional data analysis as a powerful analytical tool for studying aspects of the voice production process.

Autocorrelation function analysis of ECG signals in 20 rabbits.

In this experiment, we measured ECG signals of lead I, respectively, during normal and arrhythmia after 20 rabbits were anaesthetized. These signals were recorded, then the information was put into a computer and it analyzed Autocorrelation (AC) Function, and Power Spectrum. The results make us know: (1) periodicity corresponding relationship of ECG in normal rabbits can derive reflects from changes of ECG AC function changes of ECG signals in arrhythmia rabbits can derive relatively sensitive reflection from changes of ECG function (attenuating area S and the value of k) in normal rabbits. (2) The Autocorrelation Function of Electrocardio change but ECG in the normal. All these provide another useful method for the diagnosis of arrhythmia.

Molecules on the sperm's route to fertilization.

In eutherian mammals billions of sperm are deposited at ejaculation in the female reproductive tract, but only a few thousand enter the oviduct. A few reach the ampulla at the time of fertilization and only one sperm fertilizes the egg. In most mammalian species the lower isthmus of the fallopian tubes has taken over the function of a reservoir in which sperm are stored under conditions that save sperm energy by suppressing motility and increase viability. Close to the time when the egg is ovulated into the ampulla, the sperm undergo a complex sequence of processes, named capacitation. Capacitation is a prerequisite for fertilization, enabling the sperm to recognize the egg and to respond to the egg signals in the appropriate manner. Sperm bind to the egg extracellular matrix, the zona pellucida, and upon binding undergo the acrosome reaction, followed by the passage of the zona pellucida and binding to and fusion with the egg oolemma, thus triggering the embryonic developmental program. The oviduct and the egg itself appear to coordinate sperm function to ensure that two functional competent gametes will meet, leading to fertilization. For the communication between sperm and somatic cells as well as between both gametes the information potential of carbohydrates is utilized, and this event probably prepares the next level of interactions, e.g., capacitation, acrosome reaction, egg binding, and fusion. The current perspective focuses on the role of molecules possibly implicated in sperm-oviduct and sperm-egg interactions. J. Exp. Zool. (Mol. Dev. Evol.) 285:259-266, 1999.

Turbulent glottal flow during phonation

Human phonation is the flow-induced oscillation of the vocal folds, producing pulsatile jet through the glottis, which may become turbulent. This turbulent jet was investigated in an excised canine larynx model with simultaneous recordings of air particle velocity, subglottal pressure, airflow rate, and EGG signal for various conditions of phonation. Canine larynges were mounted on a plastic air tube and sustained oscillations were established and maintained by mechanically manipulating the cartilages to mimic the function of laryngeal muscles. The major control parameters were the airflow rate and the glottal adduction. The velocity was measured with a constant-temperature hot-wire anemometer system. To separate the turbulence from the periodic component of the velocity signal, the technique of phase shift averaging was employed. Results suggest that subglottal inlet flow to the larynx is pulsatile but mostly laminar, while the exiting jet is nonuniform and turbulent. The Reynolds number based on the mean glottal velocity and glottal hydraulic diameter varied between 1600 and 7000, the Strouhal number varied between 0.002 and 0.032, and the Womersley number ranged from 2.6 to 15.9. These results help define the conditions required for computational models of laryngeal flow. [This work was supported by NIDCD Grant No. DC03566-01.]

Comparison between DyWT- and EGG-based estimation of glottal closure instant for speech signal

Recently, wavelet transform has found many applications. Mallat has shown that, with a proper choice of wavelet function, the local maxima of wavelet transformed signal indicate the position of the signal sharp variation points. Since the glottal closure causes sharp changes in the derivative of air flow in the glottis and transient in the speech signal, wavelet analysis can be used for detection of glottal closure instant (GCI) from the speech signal. It is known that the point of maximum negative value in a differentiated EGG signal agrees well with the closing time of the vocal folds. Due to the limited practical utility of the EGG signal, however, a speech-only-based GCI detection method is still needed. In this paper, GCI detection algorithm based on the dyadic wavelet transform (DyWT) is proposed and experimental results are shown. Using the EGG signal as a reference, experimental results are analyzed and discussed for evaluation of its performance. Preliminary experimental results show that DyWT-based GCI detection method has some speaker dependency and wavelet transformed speech signal at scale 4 gives more reliable GCI information than that of others. [This work has been partially supported by a grant from Korea Science and Engineering Foundation (KOSEF 971-0917- 103-2).]

Computer simulation of the impact of different dimensions of the stomach on the validity of electrogastrograms.

The impact of the dimensions of the stomach on cutaneous recordings of gastric electrical activity (GEA) has not been adequately studied. The stomach was represented as a truncated conoid in a spherical coordinate system. The gastric electric field was modelled using a previously described methodology. Electrical potentials were calculated from sets of points simulating standard cutaneous recordings. The frequency of the signals was maintained at 3 cycles min-1 (period of repetition: 20 s), while the velocity of propagation of the depolarisation waves was reduced relative to the reduction in gastric dimensions. The signals were digitally contaminated with a random artificial artefact with a constant amplitude range of 0.2 mV, while the dimensions of the conoid (the circumferential radii and the length of the central axis) were decreased by factors of 1.5, two, four, six and eight. Simulated EGG signals were evaluated quantitatively. Simulated EGG records contaminated with random signals recorded from stomachs with decreasing dimensions exhibited non-linearly increasing standard deviations (p < 0.001). Randomly contaminated EGGs calculated from stomachs with dimensions reduced four, six and eight times were abnormal according to previously established quantitative criteria. Computer modelling indicated that gastric dimensions can significantly influence the validity of EGGs. These findings could be particularly important in a paediatric electrogastrography.

Neural network based noise cancellation of EGG signals

Neural network based noise cancellation of EGG signals

Neural network based adaptive time frequency analysis of EGG signals

Neural network based adaptive time frequency analysis of EGG signals

Time-frequancy analysis of EGG signals by using GED and BUD

Time-frequancy analysis of EGG signals by using GED and BUD

Precise glottal closure instant detector for voiced speech

An algorithm which can extract precise GCI information directly from speech is described. By utilising the average pitch and the area informations, accurate GCI positions are obtained. The result compared with the manually classified GCI information using EGG signals only shows 0.2 ms average error.

Non-invasive electrogastrography. Part 2. Human electrogastrogram.

The electrical activity of human stomach muscle wall-electrogastrogram (EGG), was led off by surface (cutaneous) electrodes placed on the abdominal wall and recorded on an electrogastrograph. A method for complete elimination of the cardiac artefact was elaborated and successfully implemented. It consists of a preliminary elimination of the QRS complex, based on its higher amplitude and slope. The eliminated intervals were replaced by linear segments. A subsequent low-pass filtering allowed to obtain a high quality EGG signal. The electrical activity of the stomach of healthy volunteers was characterized by waves with a frequency of 3.35 +/- 0.09 cpm during the quiescent periods and 2.99 +/- 0.14 cpm during the activity periods of the migrating myoelectrical complex (MMC). Bearing in mind the correlation between the bursts of spike potentials with the slow waves in the dog EGMG and the high-amplitude waves, characterizing the periods of activity in the dog EGG, we can better differentiate the periods of quiescence and activity by the amplitude of the waves. The wave amplitude during periods of quiescence was 81.13 +/- 20.61 microV, significantly different from the wave amplitude during periods of activity being 164.74 +/- 43.34 microV (n = 7). Thus with this method in visual inspection it is possible to identify MMC of the human stomach by the changes in the amplitude of the waves in the EGG.

Possible usages of LPC error for the estimation of voice characteristics

Using the autocorrelation method, LPC error signals were computed as differences between the original waves and the predicted waves at each time instant. Analyses of synthesized and human vowel sounds show that the shapes and spectral contents of the instantaneous error signals are almost identical with those of the voice source for synthesized vowel sounds, and that the instants of glottal closure are well defined as maximally negative peaks in the error signals for both kinds of vowel sounds. Time integration of error signals was also performed. For male voices the shapes of integrated and instantaneous error signals are found to be very similar with those of EGG and differentiated EGG signals, respectively. This result supports the possibility that open and closed phases of the vocal folds within each glottal cycle can be determined from such LPC error signals. It was also found that automatic detection of valleys (or peaks) in the integrated error signal may be a robust pitch estimation method for voiced speech segments including synthetic diplophonic sounds. These and other results suggest that these simple LPC error analyses may provide significant information about the voice source.

A Putative ATP-Activated Na + Channel Involved in Sperm-Induced Fertilization

Extracellular application of adenosine triphosphate (ATP) to defolliculated Xenopus laevis oocytes activated a saturating inward current with a maximal amplitude E(max) of 2.4 +/- 0.2 microamperes and an apparent Michaelis constant of 197.6 micromolar. The current was carried predominantly by sodium ions and potently inhibited by amiloride, guanosine triphosphate (GTP), and its nonhydrolyzable analogs guanosine 5'-[beta,gamma-imido]triphosphate (GppNHp) and guanosine 5'-O-(3-thiotriphosphate). Likewise, in vitro fertilization using mature eggs and Xenopus sperm was inhibited by amiloride, GTP, and GppNHp. Hence, an ATP receptor on the egg membrane may be the recipient target for ATP originating in sperm, suggesting that an ATP-induced increase in sodium permeability mediates the initial sperm to egg signal in the fertilization process.

Bewertung der laryngealen Klanggeneration mit der FFT-Analyse der glottischen Impedanz bei Patienten mit Rekurrensparese

The electroglottogram (EEG) is known to be related to the motion of vocal folds. The major hypothesis is that the EGG is related to the area of contact of the vocal folds. EGG is thought to be incapable of measuring or monitoring non-contact type vibratory events in the larynx. Recently it was demonstrated by fast Fourier transformation (FFT) analysis of EGG curves that the resulting EGG can be interpreted as a sum of a 'laryngeal fundamental with overtones'. This necessitates a new interpretation of normal EGG waveshape. This study was undertaken to prove the hypothesis that (pathological) EGG curves contain information even about non-contact type vibratory events in the larynx during phonation when analyzed by FFT. Patients with vocal fold paralysis were asked to phonate sustained vowels (/a/, /e/, /i/, /o/, /u/). Voice sounds and EGG signals were recorded simultaneously, routed to a frequency analyzer and subjected to real-time FFT analysis. In all cases original EGG signals would have been classified as pathological. However, in all recordings the laryngeal fundamental frequency and--in some patients--overtones with their intensities could be extracted and compared to harmonics extracted from voice sound. This is the first report of FFT analysis of EGG signals in patients with vocal fold paralysis. It is proposed that vocal folds vibratory events may be of non-contact type and that they can be monitored by analysis of glottic impedance.

Frequency Response of the Fourcin Electroglottograph and Measurement of Temporal Aspects of Laryngeal Movement During Swallowing

The purpose of this investigation was to study the frequency response of a modified Fourcin EGG at frequencies associated with the slow varying laryngeal movement of swallowing and to compare those findings with the response characteristics of the EGG at frequencies associated with phonation. Frequency-dependent differences were found. At very low frequencies the EGG output was found to be the derivative of the changes in neck impedance; at higher frequencies the EGG output directly represented the changes in neck impedance. Three of the four phases of the pharyngeal stage of the swallow are represented by the EGG signal.

A Study of Egg and Simultaneous Subglottal Pressure Signals

A Study of Egg and Simultaneous Subglottal Pressure Signals

Comparison of four high‐precision pitch extraction methods

The accuracies of four pitch extraction methods are introduced and compared for high‐precision perturbation measurement. They include combinations of peak‐picking, zero‐crossing, and waveform‐matching strategies. The effects of sampling frequency, signal‐to‐noise ratio, pitch frequency, and signal modulation on the accuracies are explored. It is shown that methods with the waveform‐matching technique give the best results for most cases. For near‐sinusoidal stimuli (e.g., EGG signals), the zero‐crossing technique gives higher accuracy than the peak‐picking technique. At a low signal‐to‐noise ratio, a higher sampling frequency does give better results for the waveform‐matching technique, but the accuracy of the peak‐picking method may reduce as sampling frequency increases. As the signal‐to‐noise ratio increases, the effect of sampling frequency on accuracy diminishes when interpolation is used. A variety of waveforms are currently being tested to check the suitability of these methods for different applications. [Work supported by NIH.]

Acoustic and physiological study of traditional Japanese singing

Acoustic and physiological characteristics of four genres of traditional Japanese singing were extracted. Subjects were professional singers of each genre: Sohkyoku, Yohkyoku, Minyoh, and Kyogen. Audio and video-fiberseopic recordings were made, while the singers were producing the singing voice of some typical phrases of their singing modes and the speaking voice as well. EGG recording was also made for a singer of Kyogen. Spectral analyses revealed prominent peaks at 4–4.5 kHz in the subject's singing voice, implying an evidence for the “singing formant” of traditional Japanese singing. Acoustic characteristics of the peculiar tone ornament suggest that the singers controlled F0 and intensity independently. Fiberscopic observation of the vocal tract and EGG signals provided some physiological bases to understand the singers' fine control of the phonatory system for such specific voice production.