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At least 325 records · Page 18Linked to original sources
PubMed1999

EMG power spectrum analysis of first dorsal interosseous muscle in pianists.

PURPOSE: Long-term piano training may induce potential biochemical and structural adaptations in hand intrinsic muscles or alter the motor strategy in the nervous systems. METHODS: This study investigated, by electromyography (EMG) and strain gauge, whether this pedagogical training is aerobic or anaerobic by nature. Changes in EMG power spectrum during incremental isometric muscle contractions before and after a sustained, fatiguing muscular performance were studied in the first dorsal interosseous muscle (FDI) of 13 female pianists and 15 sedentary controls. The maximal voluntary contraction (MVC) force of the FDI and the time needed to induce fatigue were also measured. RESULTS: During fatigue, the median frequency (MF) shifted toward the low frequencies in both groups. The MF of 50% and 25%MVC subsequent to fatigue were significantly lower than those before fatigue in the control group (104.0 +/- 45.5 Hz vs 116.7 +/- 41.4 Hz at 50%, P < 0.05; 114.7 +/- 43.4 Hz vs 123.3 +/- 46.7 Hz at 25%, P < 0.05). There were no significant MF changes within the pianists before and after fatigue. The root mean squares (RMS) of 50%, 25%, and 10%MVC of control subjects after fatigue were significantly higher than those before fatigue, but not in pianists. There was no difference in MF and RMS between the two groups at any level of %MVC before or after fatigue, but the pianists tended to show higher MF at each level of %MVC. Although the MVC was similar in both groups, the pianists, however, needed a much longer time to induce fatigue than controls (14.3 +/- 5.8 min vs 5.8 +/- 3.3 min, P < 0.005). CONCLUSIONS: These observations are discussed in terms of the training-induced metabolic adaptations, the changes in the strategy of motor unit recruitment, and the possibility of differences in muscle fiber composition. This study indicates that piano training should not be classified as power training, rather as endurance training. Such findings may also provide information about fine motor training for athletes and other professionals.

Adult↗
PubMedDate not supplied

[Spectrum analysis of ECG of patients with terminal conditions].

Spectral ECG analysis has been performed in 68 patients (126 tests) to assess predictive value of the amplitude-frequency analysis for the prognosis of severity and potential outcome of the disease. ECG was registered in 3 orthogenic leads according to the method of Frank. Spectral analysis was performed using spectrobiograph. Two time periods of the cardiac cycle--the QRS complex and the T wave have been analysed. The results have demonstrated characteristic changes in the amplitude values of high and low-frequency constituents of the ECG spectrum signal in the group of patients under study. The changes observed help elucidate the impaired functional myocardial activity and predict the natural history of the disease.

Adolescent↗
PubMed1995

Effects of neuromuscular blockade on fetal heart rate variability: a power spectrum analysis.

Spectral analysis of fetal heart rate variability allows quantitative determination of the main components that affect this variability. The physiological significance of these components is unclear; however, movements appear to contribute to variability. We studied six fetuses in which immobility required for in utero magnetic resonance or invasive fetal procedures was achieved by fetal intravascular injection of curare between 32 and 36 amenorrhea weeks. For each fetus, we compared spectral density parameters of heart rate variability. After curare administration, mean spectrum power was halved. We did not observe a larger significant decrease in any (very low, low, or high) frequency band. The other parameters of spectral analysis of variability were unaltered. Fetal movements accounted for a significant proportion of human fetal heart rate variability but did not constitute a unique frequency component.

Curare↗
PubMed1984

[Simultaneous use of ultrasound and pulsed Doppler with spectrum analysis of frequency in diseases of the cervical and cerebral vessels. Initial results].

Preliminary results of the use of the ultrasound Duplex Scanner are reported and correlated with angiographic findings. The main interest of this examination resides in its application in cases of atheromatous obstruction of cervical vessels to the brain: definition of type of obstruction: occlusion or stenosis; assessment of hemodynamic alterations: modification of frequency spectrum, of pulsed Doppler signal to 5 degrees as defined by Strandness as a function of extent of narrowing of arterial lumen. Pre-occlusive lesions may be difficult to distinguish from an occlusion. In contrast, minor anomalies: plaque producing little or no stenosis, calcifications, appear to be simpler to detect than by angiography. In intracranial vascular malformations: arteriovenous fistulas and particularly intracranial angiomas of a certain size, this examination provides data on the increase in diameter and acceleration of flow in vessels supplying the malformation. In cases of brain death, the ultrasound Duplex Scanner demonstrates absence or marked reduction in internal carotid artery flow, whereas flow is normal in the external carotid arteries in the absence of collapse. Confirmation of reliability of this non-invasive exploratory procedure requires further evidence of correlations.

Aged↗
PubMed1988

Power spectrum analysis of EEG at diagnosis and follow up of patients with solvent induced chronic toxic encephalopathy.

Electroencephalographic changes have been studied in a group of 32 men aged 30-65 (mean 49) with diagnosed chronic toxic encephalopathy. The group had been carefully scrutinised for other possible causes of brain dysfunction and the diagnosis was based on neuraesthenic symptoms and pathological psychometric performance. The EEGs were recorded from four areas of the brain and the power spectrum analysed. Comparisons have been made with a group of 50 healthy male workers with no occupational exposure to solvents. For 24 of the 32 patients a follow up EEG recording was made after 17-75 months (mean 33). The results showed a doubling of the EEG power in the patients for all four recording channels with a significant reduction at follow up but not to the level of the control group. No exposure effect relation could be established. Acute exposure at the time of the first recording, exposure free, or follow up time did not influence the results. The frequency of the dominant EEG activity and the relative frequency distribution were equal in the two groups and did not change during the follow up period. Five of the 32 subjects took benzodiazepine drugs regularly and they had greater total power in all four recording channels compared with the other 27 patients; the difference was not statistically significant. The relative frequency distribution showed less alpha- and more theta- and beta-power in these five subjects. A reduction in total power during follow up was also found in the subgroup that took benzodiazepines.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Iotrol, a new myelographic agent: 2. Comparative electroencephalographic evaluation by spectrum analysis.

Iotrol, a nonionic dimer isotonic with cerebrospinal fluid at 300 mg l/ml, was evaluated against metrizamide, iopamidol, and iohexol by electroencephalography (EEG) in nonanesthetized cynomolgus monkeys. Each of four monkeys was injected intrathecally with 0.5 ml/kg of 300 mg l/ml of each contrast medium. EEG was obtained before, 45 min, and 3 hr postinjection. EEG spikes, motor disturbances, convulsions, and behavior changes were observed. The EEG from C3 channel was also computer-analyzed. Average percentage differences between control and test energy content of the entire EEG and of the EEG spectrum subdivided into five frequency bands were calculated. With metrizamide, three animals suffered seizures, and all were lethargic and irritable. With iopamidol, two animals convulsed; all animals were lethargic. Transient apathy and motor disturbances were observed in the iohexol animals. No motor or behavior changes were produced by iotrol. Metrizamide and iopamidol increased the spectrum energy in all bands. Neither iohexol nor iotrol affected the EEG significantly. On the basis of these findings, iotrol holds promise as a clinical contrast material for the subarachnoid space.

Animals↗
PubMed1994

[Electromyographic study on the external urethral sphincter of the male--power spectrum analysis with fast Fourier transformation].

In 23 male patients, the electrical activity of external urethral sphincter muscle was sampled before examination of cystometry (Rest), at first desire to void (FDV), maximum desire to void (MDV) and during urination (Void) by means of electromyography (EMG). Sampling time of each event was 2400 msec. The electrical activity was amplified with a lower limiting frequency of 20 Hz and an upper limiting frequency of 10000 Hz, and recorded on magneto-optical desk. Spectra were obtained using a Hamming window. The action potential of the muscle was quantitatively analyzed and power spectrum of the needle EMGs were analyzed from the magneto-optical disk by a spectrum analyzer using fast Fourier transformation (FFT, Sande-Tukey method). From each power spectrum, mean power frequency (MPF) was obtained from a calculator connected to the spectrum analyzer. Twenty three patients were divided into three groups as follows: 8 patients without any neurological abnormality (normal group), 7 patients with neurogenic bladder showing detrusor-sphincter-dyssynergia (DSD+ group) and 8 patients with neurogenic bladder without detrusor-sphincter-dyssynergia (DSD- group). The results obtained were as follows: 1) The motor unit potentials at Rest had the mean amplitude of 210 +/- 59.4 microV, 329.3 +/- 157.1 microV and 177.6 +/- 132.8 microV in normal group, DSD+ group and DSD- group, respectively. The mean duration were 4.3 +/- 0.2 msec, 5.9 +/- 1.9 msec, and 7.3 +/- 4.5 msec., respectively. The mean phases were 2.8 +/- 0.6, 2.8 +/- 0.5 and 2.5 +/- 0.3, respectively. Statistically there was no difference in amplitude, duration and phase among three groups. 2) In normal group, the power over than -20 dB was distributed from 150 to 220 Hz windows at Rest and FDV. The needle EMGs at MDV showed interference pattern and the power increased over -20 dB in all windows. The power of high frequency area relatively increased. The action potential of the muscle disappeared during urination and the power also disappeared. The average MPF was 103 Hz, 102 Hz, 150 Hz and 98 Hz at Rest, FDV, MDV and Void, respectively. 3) In DSD+ group, the needle EMGs showed interference pattern in MDV and Void, and the power increased only in low frequency area. The average MPF was 104 Hz, 105 Hz, 114 Hz and 120 Hz at Rest, FDV, MDV and Void, respectively. 4) Because of damage to nerves, the action potential of the muscle was difficult to obtain from 3 patients of DSD- group, and the power was not demonstrated.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

[Spectrum analysis of heart rate variability in obstructive hypertrophic myocardiopathy. Evidence of altered autonomic function].

Altered sympathetic activity may play an important role in the pathogenesis of hypertrophic obstructive cardiomyopathy (HOCM). Spectral analysis of heart rate variability was employed to assess the sympatho-vagal function and balance in 18 patients with HOCM (11 males, 7 females, mean age 42 years, range 19-59) and in 15 healthy control subjects (9 males, 6 females, mean age 44 years, range 18-65). Electrocardiographic recordings obtained both at rest and during 60 degrees passive tilt, were digitized and analyzed by fast Fourier transform in order to obtain the power spectrum of heart rate variability. The low-frequency band (LF: 0.05-0.17 Hz) and the high-frequency band (HF: 0.18-0.34) of power spectrum were considered as indexes of sympathetic and vagal activities respectively. A semiquantitative two-dimensional echocardiographic score (SES) was used to assess the entity of myocardial hypertrophy whereas the entity of the intraventricular gradient was determined by continuous wave Doppler. Low-frequency band at rest was slightly but significantly reduced in HOCM group with respect to controls (35.2 +/- 2.0 vs 45.0 +/- 2.5 nu, respectively; p < 0.01), whereas the HF band and the LF/HF ratio were not different in the 2 groups. During tilt, control subjects showed a significant reduction of the HF band (-35%, p < 0.001), an increase in the LF band (+36%, p < 0.001) and a sharp increase in the LF/HF ratio (+105%, p < 0.001). On the contrary the baroreflex increase in the LF band and LF/HF ratio during tilt was markedly blunted, or even reverted, in patients with HOCM (-9%, NS and +5%, NS, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2005

Local spectrum analysis of field propagation in an anisotropic medium. Part II. Time-dependent fields.

In Part I of this two-part investigation [J. Opt. Soc. Am. A 22, 1200 (2005)], we presented a theory for phase-space propagation of time-harmonic electromagnetic fields in an anisotropic medium characterized by a generic wave-number profile. In this Part II, these investigations are extended to transient fields, setting a general analytical framework for local analysis and modeling of radiation from time-dependent extended-source distributions. In this formulation the field is expressed as a superposition of pulsed-beam propagators that emanate from all space-time points in the source domain and in all directions. Using time-dependent quadratic-Lorentzian windows, we represent the field by a phase-space spectral distribution in which the propagating elements are pulsed beams, which are formulated by a transient plane-wave spectrum over the extended-source plane. By applying saddle-point asymptotics, we extract the beam phenomenology in the anisotropic environment resulting from short-pulsed processing. Finally, the general results are applied to the special case of uniaxial crystal and compared with a reference solution.

Journal Article↗
PubMed1979

Lipoprotein spectrum analysis of uremic patients maintained on chronic hemodialysis.

It is known that patients maintained on chronic hemodialysis have elevated plasma lipids. In order to establish whether the type of kidney pathology is related to a specific lipoprotein abnormality, we measured plasma lipoprotein in eight patients with glomerulonephritis, two patients with polycystic kidney disease and nine patients that had been surgically nephrectomized. The concentration and composition of plasma very low density lipoproteins (VLDL), low density lipoproteins (LDL) and high density lipoproteins (HDL) in patients were compared to plasma lipoproteins in a control group. In all patient groups, the lipoprotein alterations appeared identical. VLDL were elevated 3 to 4 fold, LDL were decreased 15--35% and HDL were decreased 30--45% when compared to values of our control group. Since no differences in the lipoprotein spectrum were found among the patient groups, it appears that the hypertriglyceridemia of chronic uremia is due to the uremic state per se and is not related to a specific pathology of the kidney.

Adult↗
PubMed1994

In vivo study of online liver tissue classification based on envelope power spectrum analysis.

An ultrasonic imaging and signal analysis system, combining a 3.5 MHz linear array B-scanner and an array processor, has been realized for a clinical liver tissue classification study. Based on the complete unprocessed rf data set of a real time B-image, local envelope power spectra averaged over interactively defined regions are computed. These spectra are partially corrected for several tissue type independent effects that affect comparability. A library containing the in vivo data of 65 patients with known liver tissue states in three groups (normal, cirrhotic, fat) was built up. An algorithm based on numerical optimization of parametrized spectrum characteristics combined with a k-nearest-neighbors classifier, applied to the library, leads to correct classification rates of 85.8 to 87.5 percent in discriminating pathological from normal tissue states. The method can be used for k-weighted color coded tissue type imaging with acceptable spatial resolution.

Algorithms↗
PubMed1994

Doppler spectrum analysis to diagnose rejection during posttransplant acute renal failure.

During posttransplant acute renal failure (ARF), the diagnosis of allograft rejection constitutes a major problem. We evaluated the value of Doppler ultrasonography in identifying grafts at risk of rejection during ARF. In 184 recipients of a renal allograft, Doppler examinations were performed on the first and fifth postoperative day. Doppler spectra were quantitatively analyzed with a user-written computer program. Doppler findings were not used in clinical decision making. ARF was defined as a diuresis < 400 ml/24 hr and/or the necessity for dialysis. Doppler spectra obtained on the first day after transplantation showed a resistance index (RI) of 0.59 +/- 0.09 in recipients with immediately functioning cadaveric grafts (n = 123), while living related donor grafts (n = 20) showed a lower RI (0.55 +/- 0.07; P < 0.05). Grafts with ARF (n = 41) showed a considerably higher RI (0.67 +/- 0.13; P < 0.05). When grafts with a duration of ARF < or = 4 days (n = 17) were compared with ARF > 4 days (n = 24), RI was not significantly different (0.63 +/- 0.07 vs. 0.68 +/- 0.15; NS). However, the acceleration time of the systolic deflection of the spectrum waveform (Tmax) was shorter in grafts with ARF > 4 days (86 +/- 47 msec vs. 128 +/- 39 msec; P < 0.05). On the fifth day after transplantation, Doppler spectra in grafts with ARF > 4 days (n = 24) showed a Tmax < 90 msec in 9 patients, 8 of whom experienced rejection during ARF (positive predictive value, 8/9 = 89%). In the 15 patients with Tmax > or = 90 msec, only 2 rejections occurred (negative predictive value, 13/15 = 87%). For the RI (> 0.85), positive predictive value was 4/5 = 80% and negative predictive value (RI < or = 0.85) was 13/19 = 68%. In conclusion, a short acceleration time of the Doppler waveform on the first day after transplantation is associated with a longer duration of ARF. Quantitative analysis of Doppler spectra can be helpful in the identification of patients at risk for rejection and in the timing of allograft biopsy during ARF. Persistently short Tmax values on the fifth day after transplantation perform better in identifying grafts at risk of rejection than high RI values.

Acute Kidney Injury↗
PubMed1994

Power spectrum analysis of bursting cells in area MT in the behaving monkey.

It is widely held that visual cortical neurons encode information primarily in their mean firing rates. Some proposals, however, emphasize the information potentially available in the temporal structure of spike trains (Optican and Richmond, 1987; Bialek et al., 1991), in particular with respect to stimulus-related synchronized oscillations in the 30-70 Hz range (Eckhorn et al., 1988; Gray et al., 1989; Kreiter and Singer, 1992) as well as via bursting cells (Cattaneo et al., 1981a; Bonds, 1992). We investigate the temporal fine structure of spike trains recorded in extrastriate area MT of the trained macaque monkey, a region that plays a major role in processing motion information. The data were recorded while the monkey performed a near-threshold direction discrimination task so that both physiological and psychophysical data could be obtained on the same set of trials (Britten et al., 1992). We identify bursting cells and quantify their properties, in particular in relation to the behavior of the animal. We compute the power spectrum and the distribution of interspike intervals (ISIs) associated with individual spike trains from 212 cells, averaging these quantities across similar trials. (1) About 33% of the cells have a relatively flat power spectrum with a dip at low temporal frequencies. We analytically derive the power spectrum of a Poisson process with refractory period and show that it matches the observed spectrum of these cells. (2) About 62% of the cells have a peak in the 20-60 Hz frequency band. In about 10% of all cells, this peak is at least twice the height of its base. The presence of such a peak strongly correlates with a tendency of the cell to respond in bursts, that is, two to four spikes within 2-8 msec. For 93% of cells, the shape of the power spectrum did not change dramatically with stimulus conditions. (3) Both the ISI distribution and the power spectrum of the vast majority of bursting cells are compatible with the notion that these cells fire Poisson-distributed bursts, with a burst-related refractory period. Thus, for our stimulus conditions, no explicitly oscillating neuronal process is required to yield a peak in the power spectrum. (4) We found no statistically significant relationship between the peak in the power spectrum and psychophysical measures of the monkeys' performance on the direction discrimination task.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1994

Heart rate power spectrum analysis of autonomic dysfunction in adolescents with anorexia nervosa.

We studied autonomic modulation of heart rate in 8 females with anorexia nervosa (AN) using power spectral analysis (PSA) of heart rate variability in the supine and standing positions at baseline and after 2 weeks of intensive nutritional rehabilitation, and compared findings with healthy female control subjects. The results indicate that there is a decrease in sympathetic modulation of heart rate, evident by a deficit of low frequency (0.01-0.15 Hz) heart rate power in the supine position in AN compared with control subjects. In addition, parasympathetic modulation of heart rate failed to decrease with standing. A trend toward improvement in autonomic control of heart rate in adolescents with AN occurs in the supine position relatively early in weight rehabilitation. PSA is a sensitive, quantitative, and noninvasive means of determining autonomic control of heart rate and could be a useful tool in monitoring the health of patients with AN.

Adolescent↗
PubMed1975

Application of EEG-interval-spectrum-analysis (EISA) to the study of photic driving responses. A preliminary report.

Photic driving responses were analyzed by means of Tönnies' EISA method in 65 normal subjects, 20 patients with brain tumor and 4 cases of severe head injury. The response patterns were classified into 5 types, incidence of which in normals were 1. all band-responsive type (38%), 2. Theta-alpha type (8%), 3. Alpha-beta type (32%), 4. Beta type (8%) and 5. non-responsive type (14%). Each response pattern was compared with the resting EEG activities, however, no significant relationship was found between them. The responses of patients with brain tumor or severe head injury were considerably reduced. The reduction of the photic driving responses in brain tumor cases was not specific to the localization of the tumor. It seems to represent the diminution of the general cerebral reactivity corresponding to the severity of the brain damage. Our results have confirmed that EISA is a simple and practical method for the frequency analysis of long duration and suitable for routine clinical examination.

Adult↗
PubMed1992

Muscle sound and electromyogram spectrum analysis during exhausting contractions in man.

The changes in the soundmyogram (SMG) and electromyogram (EMG) frequency content during exhausting contractions at 20%, 40%, 60% and 80% of the maximal voluntary contraction (MVC) were investigated by the spectral analysis of the SMG and EMG detected from the biceps brachii muscles of 13 healthy men. The root mean squares (rms) of the two signals were also calculated. Throughout contraction the EMG rms always increased while this was true only at 20% MVC for the SMG. A marked decrease was detected at 60% and 80% MVC. With fatigue the EMG spectra presented a compression towards the lower frequencies at all exercise intensities. The SMG showed a more complex behaviour with a transient increase in its frequency content, followed by a continuous compression of the spectra, at 60% and 80% MVC, and a nearly stable frequency content at lower contraction intensities. This study suggested that different aspects of the changes in the motor unit's activation strategy at different levels of exhausting contractions can be monitored by SMG and EMG signals.

Adult↗