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PubMed1996

Method for single-trial readiness potential identification, based on singular spectrum analysis.

This paper presents a brief description and the advantages of the singular spectrum analysis (SSA). SSA has recently been recommended for analysis of short, noisy time series. The method was applied to single trials of EEG activity at Cz, Fz, C4, Pz and C3, recorded 3.6 s prior to and 1.2 s after the onset of a voluntary motor act. This specific activity is known in its averaged form as readiness potential (RP) and is considered to reflect the preparation of the voluntary movement. However, some physiological investigations require identification of the parameters of single-trial RPs-their onset and successive phases. SSA is based on analysis of the principal components in vector space of delay coordinates of time series. As a result, SSA algorithm decomposes real data records to components reflecting the trend, alpha and beta frequency bands, respectively, whose oscillations appear or disappear in different time instants. The latter were interpreted to distinguish different dynamical stages of the movement preparatory process.

Adult↗
PubMed1985

Vasculogenic impotence evaluated by high-resolution ultrasonography and pulsed Doppler spectrum analysis.

Vasculogenic impotence was evaluated by high-resolution sonography and quantitative Doppler spectrum analysis in 21 patients and two normal volunteers. Erection was induced by intracorporeal injection of papaverine, and B-scan imaging and Doppler analysis were performed with the penis flaccid and erect. The corpora cavernosa and its deep arteries, median septum, and corpus spongiosum were clearly displayed in every subject, with the dorsal vein and dorsal artery seen ventral to the corpora cavernosa. In the flaccid state, in all subjects, Doppler analysis demonstrated flow in the dorsal arteries but not in the deep arteries. During erection, the B-mode image showed varying degrees of enlargement of the corpora cavernosa, with increased tissue echogenicity, as well as a hypoechoic area in the peri-arterial region. The diameter of the penile arteries and flow within them also increased by varying degrees. Quantification of blood flow through all deep and dorsal arteries is feasible with this technique.

Adult↗
PubMed1979

A comparison of EEG activity in the left and right cerebral hemispheres by power-spectrum analysis during language and non-language tasks.

In 10 female subjects, power-spectrum analysis was performed on the alpha activity elicted during the resting state, 4 right hemispheric tasks, and 3 left hemispheric tasks. The data were treated in 3 ways: approach 1, comparing the right and left hemispheric alpha activity; approach 2, comparing the right and left hemispheric alpha activity adjusted for the resting state; and approach 3, comparing the right and left hemispheric alpha activity adjusted for the previous task. Approaches 1 and 2 revealed few significant differences in the alpha activity of the hemispheres, but approach 3 provided data that better fit the theory of decreased power spectrum of attenuation of activity in the activated hemisphere. Thus, approach 3 may be useful in developing an electroencephalographic test for determining cerebral dominance for language.

Adult↗
PubMed1992

[Modification of the sympatho-vagal interaction in mitral valve prolapse syndrome. Evaluation of heart rate variability by spectrum analysis].

To determine whether clinical manifestations in patients with mitral valve prolapse (MVP) are associated with altered sympatho-vagal tone, 46 patients (mean age 27 +/- 6, range 20-45 years; 18 males and 28 females) were studied by power spectrum analysis of RR variability. Patients were divided in 2 groups, according to echocardiographic criteria: Group A: 11 patients with classical MVP; Group B: 35 patients with non classical MVP. These patients were compared with 30 healthy subjects (Group C) well matched for age, body surface area and heart rate. Our findings indicate that at rest there is a significant difference in the high-frequency component between Group A and Group C. Similarly, during the increase in sympathetic activity induced by 70 degrees head-up tilt all groups showed an increase in the low-frequency component, that was more evident in Group A. The data generated from our laboratory suggest that mitral regurgitation (Group A) is a probable cause of vagal tone increase and that there is an adaptive long-term mechanism towards sympathetic conditions. In addition, probably the normalization, demonstrable by the effect of sympathetic activity in tilt, can mask a dysfunction that may be differently evoked.

Adult↗
PubMed1997

Power spectrum analysis of heart rate variability in Guillain-Barré syndrome. A longitudinal study.

Power spectrum analysis of heart rate variability was repeatedly carried out on 13 patients with Guillain-Barré syndrome for up to 1 year by Fourier analysis of regular beat-to-beat (R-R) intervals which were recorded for 5 min, converted into a continuous function by linear interpolation and resampled at 5 Hz. Low-frequency (LF) power (reflecting a mixture of parasympathetic and sympathetic activity) and high-frequency (HF) power (reflecting parasympathetic tone) were calculated by integrating the spectra from 0.04 to 0.15 Hz and from 0.15 to 0.4 Hz, respectively. At the height of the disease, the HF component was significantly decreased. The LF:HF ratio, which has been suggested to be an indicator for sympathetic activity, was increased compared with the follow-up value after 1 year. Both measures returned to normal gradually over time. Pooled-data analysis suggested that both HF and LF power were significantly related to the responses of standardized parasympathetic function tests, while the LF:HF ratio was inversely correlated with sympathetic vasomotor activity. In patients presenting with tachycardia, LF and HF power were strikingly decreased compared with patients with normal heart rates, while in patients showing vagal over-reactivity, the power of both spectral bands was significantly increased. The results suggest that spectral analysis of heart rate variability is useful for investigating the cardiovascular neural regulation in patients with Guillain-Barré syndrome. In this disorder, the sympathovagal balance is clearly shifted to sympathetic predominance at the height of the disease.

Adult↗
PubMed1978

Spectrum analysis of transient phenomena of the left ventricular pressure.

The application of "real time" spectrum analysis to left ventricular pressure during transient phenomena is described. Transient phenomena generated by the injection of drugs (norepinephrine-isoproterenol), anoxia and occlusion of aorta and carotids show sudden changes in the frequency of heart contraction. Propranolol stabilizes the heart rate in similar circumstances.

Animals↗
PubMed1984

[Doppler frequency spectrum analysis of extracranial carotid artery lesions].

Signals registered from the extracranial carotid artery by direct Doppler-ultrasound with a MHz transducer were subjected to real-time frequency spectrum analysis. A systolic maximal frequency over 3500 Hz was considered abnormal, together with a broadened spectrum. The study was made on 157 subsequently operated carotid arteries, not all of which had previous angiographic studies. Of 47 with a normal angiogram 45 were correctly classified non-invasively (specificity 96%). The non-invasive diagnosis was correct in 16 of 17 occlusions of the internal carotid artery demonstrated angiographically. An abnormal Doppler frequency analysis was present in only 7 of 14 stenoses with a decreased vessel lumen below 25%. An abnormal Doppler frequency analysis was present in 78 of 79 stenoses with more than 25% reduction in lumen diameter, diagnostic sensitivity for all stenoses being 91%.

Adult↗
PubMed1990

A C version of Fourier-derived affinity spectrum analysis (FASA) to resolve binding heterogeneity.

The computer program described in this paper facilitates resolution of binding affinity heterogeneity by transforming binding curve data (bound versus free) into affinity spectra (density versus affinity). The original program, written in FORTRAN, is extended and presented here in the language C. New applications include an ability to transform competition curves into affinity spectra and to evaluate the effects of sampling and experimental error on spectrum analysis. We propose that this program be incorporated in the routine evaluation of binding systems.

Binding, Competitive↗
PubMed1981

Power spectrum analysis of heart rate fluctuation: a quantitative probe of beat-to-beat cardiovascular control.

Power spectrum analysis of heart rate fluctuations provides a quantitative noninvasive means of assessing the functioning of the short-term cardiovascular control systems. We show that sympathetic and parasympathetic nervous activity make frequency-specific contributions to the heart rate power spectrum, and that renin-angiotensin system activity strongly modulates the amplitude of the spectral peak located at 0.04 hertz. Our data therefore provide evidence that the renin-angiotensin system plays a significant role in short-term cardiovascular control in the time scale of seconds to minutes.

Angiotensins↗
PubMed1992

Power spectrum analysis of heart rate fluctuations and respiratory movements associated with cooling the human skin.

A length of respiratory movement and instantaneous heart rate was divided into 32 segments to adopt computerized power spectrum analysis. An array of frequency spectrum across all the segments was then constructed to demonstrate sequential changes in the respiratory rhythm (0.4 Hz), low (less than 0.1 Hz) and high (0.2-0.4 Hz)-frequency components of heart rate fluctuations associated with lowering the skin temperature. A significant increase in the power for the low and high frequency components of heart rate fluctuations accompanying bradycardia occurred by cooling the face to 0 and 10 degrees C, while cooling the foot to 0 degrees C yielded a significant increase and decrease in the power for the former and latter component, respectively, without change in heart rate. The spectral power for respiratory movements was not altered by these stimuli. The maximal change in the power for low- and high-frequency components as well as in the heart rate during cooling the face and foot to 0 degrees C was found to correlate negatively with the relative resting magnitude of the respective parameter in the pre-stimulus period. Similar relationship existed only with the power for low-frequency component of heart rate fluctuations when lowering the temperature of foot to 10 degrees C. The power spectrum array employed in this study thus enabled us to estimate the effectiveness of skin cooling on the three hemodynamic parameters.

Adult↗
PubMedDate not supplied

Electromyography tension and frequency spectrum analysis of some masticatory muscles at rest, isotonic and isometric contractions.

On a population of 52 subjects surface electromyographic recordings of temporals and masseters, simultaneously with mandible dynamic of closure and clenching, were performed, in order to study tension and frequency behaviour in three postural conditions: rest, isotonic and isometric contractions. Frequency was studied using the median resulting from FFT calculation, and a new computing method, which presents the proportion of frequencies making up the whole EMG signal, by steps of 50 Hz. Tension was calculated as well. The results permit us to draw the following conclusions: 1. a period of EMG silence was present in 51 of 52 subjects at mandible closure (SPA--Silent Period Area); 2. SPA onset was before teeth contact (22.5 msec., during the motion of the mandible), while its end was after closure (10.2 msec., during motionless phase of clenching). This allowed to use the SPA as a tool to clearly distinguish isotonic from isometric contraction; 3. the comparison of tension and frequency, expressed as median, showed that at rest a muscle presents low frequency and low tension. In active contraction both increase their values. Nevertheless, in active contraction, while no differences were found in frequency behaviour, tension showed a difference: although higher than at rest, isotonic contraction presented lower values than during isometric contraction; 4. the study performed by the new program showed that the low frequency at rest was due to the high proportion (30-40%) of frequencies of less than 50 Hz, while the increase at function was due to the parallel increase of frequencies comprised between 100 and 250 Hz. Because it is known that muscles are composed of fibers at low frequency and at high frequency of discharge, which play different functional roles, the last finding suggests that the mathematical analysis of the spectrum of frequencies, could provide a functional-histological image of the muscle.

Adolescent↗
PubMed1984

Pulsed Doppler imaging and spectrum analysis for detection of carotid artery disease.

One hundred carotid arteries in 53 patients suffering from transient cerebral ischaemia or amaurosis fugax have been studied prospectively. Internal carotid arteries were assessed by a six-channel pulsed Doppler imaging system combined with Doppler spectrum analysis and the findings compared with those obtained by X-ray contrast arteriography. Stenosis (greater than 25% diameter reduction) was correctly diagnosed by ultrasonography with a sensitivity of 93% and a specificity of 96%. Occlusion was correctly diagnosed with a sensitivity of 92% and a specificity of 97%. The ability to recognize arterial stenosis and occlusion with this noninvasive system suggests that it has a major part to play in screening patients with suspected carotid artery disease.

Adult↗
PubMed1991

Revision of the amino acid sequence of the smallest bc1 complex subunit: use of fast atom bombardment mass spectrometry and mass-analysed ion kinetic energy spectrum analysis.

We have isolated the smallest bc1 complex subunit from an acidic chloroform/methanol extract of bovine cardiac muscle. The identification of the polypeptide was made possible by classical Edman degradation and amino acid analysis. The measurement of its exact molecular weight by fast atom bombardment mass spectrometry (m/z 6519.8), the characterization of a tryptophan cleavage peptide and pepsic peptides by mass measurements and by mass-analysed ion kinetic energy spectrum analysis allow rectification of the amino acid sequence of the smallest bc1 complex subunit. We found a serine residue instead of Gln 22 and tryptophan residues in place of Ser 34 and Ser 38.

Amino Acid Sequence↗
PubMed1973

Spectrum analysis in ultrasonic Doppler blood flow monitoring: experience in its application to deeply situated vessels.

Ultrasonic Doppler monitoring of pulsatile flow patterns in the major systemic arteries has been rendered possible by the development of intravenous and intra-esophageal probes, thereby obviating major surgery or arterial catheterization. The information provided by Doppler flow signals obtained in this way is considerably enhanced by the use of spectrum analysis. The advantages include immunity from interference from noise or extraneous signals, the separation of two or more superimposed flow signals, and superposition of pressure and flow signals for time correlation and comparison.

Abdomen↗
PubMedDate not supplied

Doppler spectrum analysis and vascular imaging in the diagnosis of extracranial carotid artery disease.

Ultrasound methods are well suited for the exploration of the carotid system. High resolution echography can visualize atheromatous defects on the vessels walls with a resolution better than one mm, whereas Doppler examination detects haemodynamic disturbances due to these plaques. Conventional Doppler examination can reveal moderate or severe stenosis (greater than 60%); the recent development of frequency analysis of the Doppler audio signal makes now possible the detection of very light haemodynamic disturbances due to low grade stenosis even as small as 15%. Spectral distribution abnormalities have been classified in four grades according to their amplitude. The combination of the morphological and functional data provided by echography and Doppler spectrum analysis has drastically increased the diagnostic possibilities of the ultrasound methods in the field of the extracranial vascular pathology. With a new duplex system which combines echography and C.W. Doppler examination (duplex probe) it is possible to detect, and quantify carotid stenosis (in percentage of the lumen reduction), and to evaluate blood flow volume in ml/mn.

Carotid Artery Diseases↗
PubMed2001

Mechanisms of female urinary continence under stress: frequency spectrum analysis.

Intravesical and urethral pressure signals during cough and Valsalva maneuvers for 15 continent women were analyzed with frequency spectrum analysis. Clear modulation of the urethral pressure changes by the intravesical pressure rise during stress maneuvers was demonstrated in the frequency bands of 14 and 7 Hz for cough and Valsalva, respectively. The linearity between the urethral and intravesical pressure signals was strong for cough, but relatively weaker for Valsalva. The observed linearity lead to the formulation of a modified continence equation to mathematically quantify stress leak point pressure (sLPP): sLPP=MUCP/(1-alpha1)+RBP. This algebraic equation demonstrated that sLPP depends on pressure transmission, resting bladder pressure, and maximum urethral closure pressure. The equation was validated with excellent theoretical predictions for the 15 continent subjects (R(2)=0.98 and 0.97 for cough and Valsalva leak point pressure, respectively) and good but somewhat weaker predictions for 46 stress incontinent women (R(2)=0.79 and 0.48, respectively). It has been shown that pressure transmission plays the most important role in female continence function, while it may be attributable to passive structural origin as evidenced by the minimal time delay between the two pressure signals, in the order of a few milliseconds. It can be concluded that coughing seems to have a more mechanical, rather than neuromuscular basis for its signal dynamics. This study suggests that a complete assessment of female stress continence function requires comprehensive urodynamic information in terms of pressure transmission, maximum urethral closure pressure, and resting bladder pressure.

Adult↗
PubMed1996

Power spectrum analysis of EMG at different voluntary efforts in normal subjects.

BACKGROUND: In the previous studies, the results from power spectrum frequency changes at different sustained forces have been quite conflicting. This was the result of enormous changing in firing rate and motor units recruited; these were deciding factors of electromyographic power spectrum. The aim of this study was to investigate the characteristics of rate coding and electromyograph (EMG) interference pattern in two EMG-computer sets. METHODS: Thirty-nine healthy subjects were included in our study. Each was in a relaxed sitting position with forearm, wrist, and metacarpophalangeal joints fixed by straps. Two surface electrodes were attached to the muscle belly of extensor digitorum communis. EMG signals were processed at 10%, 25%, 50% and 100% of maximal voluntary contraction (MVC) using visual feedback from a dynamometer. RESULTS: The amplitude in dB remained constant at different isometric forces. The rate-coding parameters showed non-significant decrease as the percentage of MVC increased, ashereas the time-domain parameters revealed significant increase with stepwise increase in force. CONCLUSIONS: EMG power spectrum analysis provides an easy, painless way of assessing global recruitment/rate descriptions of motor units.

Adult↗