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PubMedDate not supplied

Power spectral analysis of auditory evoked response.

Five normal hearing adults were examined for power spectral analysis of AER to 1000-Hz pure tone. Major frequency components of responses to stimuli at 50 dB hearing level exist at 1 to 14 c/s. The power spectra of responses to stimuli at 10 dB hearing level are greater than those of the SBA in the frequency components between 3 and 9 c/s; furthermore, the total power of 3 to 9 c/s indicates a clear difference between the 2. Incidentally, at 512-msec analysis time, the total power of 3 to 9 c/s of the AER are significantly greater than that at 1024-msec analysis time, whereas those of the SBA show little discrepancy at the 2; thus at 512-msec analysis time, the total power of 4 to 9 c/s yields a clear difference between the AER and the SBA responses averaged over 50 stimuli even at 10 dB hearing level.

Adult↗
PubMed1993

Power spectral analysis of heart rate variability: a noninvasive signature of cardiac autonomic function.

Power spectral analysis of short segments of beat-to-beat heart rate variability (PS/HRV) reveals three distinct peaks. In human PS/HRV, the high frequency (HF) band (0.15 to 0.4 Hz) is correlated with respiratory driven vagal efferent input to the sinus node. The low frequency band (LF) 0.06 to 0.15 Hz is believed to be due to baroreceptor mediated blood pressure control. Therefore, PS/HRV represents a noninvasive signature of the balance between sympathetic and parasympathetic components of the autonomic nervous system. This paper reviews the literature on the methodological issues relevant to signal processing, computational, and clinical applications of PS/HRV. Factors affecting the power in the LF and HF bands are examined in healthy controls. Recent work from several laboratories suggests that PS/HRV is a potentially powerful tool for exploring neurocardiac dysfunction in patients with a variety of cardiac and autonomic disorders. Mathematical models which simulate neurocardiac control are examined. Concerns regarding the lack of standardization between different laboratories are expressed. As the PS/HRV attains the status of a clinical diagnostic test, we hope that this review serves as a source of integrated information for researchers in this field.

Adult↗
PubMed1979

Spectral analysis of EEG during mental activity (author's transl).

With the use of power spectral analysis, the occipital and frontal EEGs in normal young subjects were examined during mental activity under closed-eye and open-eye conditions. Under the closed-eye condition, the peak of power spectral density in the alpha band was suppressed during mental activity, as compared with the finding obtained without mental loading. Moreover, the peak frequency of the alpha band shifted to higher frequencies under the mental loading condition in all of the subjects. Under the open-eye condition, alpha waves were prominently suppressed and no peak of power spectral density in the alpha band could be detected. However, during mental activity the peak of power spectral density could be detected in the delta wave band of both occipital and frontal EEGs.

Adolescent↗
PubMed2000

Application of autoregressive methods to multigate spectral analysis.

Multigate analysis is known to be capable of detecting accurate blood velocity profiles from human vessels. Experimental systems so far presented in the literature use time-domain frequency estimations and, more recently, the fast Fourier transform (FFT) for real-time analysis of Doppler signals from multiple range cells. This experimental study is aimed at evaluating the application of an autoregressive (AR) method (Burg algorithm) to multigate Doppler analysis. Both in vitro and in vivo results were collected with a commercial Duplex scanner coupled with a prototype multigate unit developed in our laboratory. The same multigate signals are, thus, processed according to both the FFT and the Burg algorithms. The related spectral and maximum frequency profiles are reported and statistically compared. AR, implemented with the Burg algorithm, is demonstrated to be a way to perform multigate spectral analysis with reduced spectral variance, suitable for maximum velocity profile extraction through a simple threshold.

Artifacts↗
PubMedDate not supplied

Spectral analysis of fetal heart rate variability in fetuses with supraventricular extrasystoles.

OBJECTIVE: Fetal heart rate (FHR) variability is an important indicator of fetal well-being. In fetal tachyarrhythmias, however, visual analysis of FHR variability is limited. We therefore applied power spectral analysis of FHR to evaluate the fetal state. METHODS: Fetal R-R intervals were detected by means of an external ECG in 3 fetuses with supraventricular extrasystoles after cardiac malformations had been excluded by fetal echocardiography. Using an autoregressive model, power spectral densities were calculated from 20 consecutive 256-beat segments for the following frequency bands: <0.03 Hz (very low frequency), 0.03-0.069 Hz (low frequency; LF), 0.07-0.129 Hz (mid-frequency) and 0.13-1.0 Hz (high frequency; HF). RESULTS: The FHR variability in fetal supraventricular extrasystoles mainly resulted from the HF component (63.91 +/- 6.97%). The sympatho-vagal balance (LF/HF) was decreased in the tracings with extrasystoles (0.13). CONCLUSION: The analysis of FHR variability in fetal supraventricular extrasystoles revealed an imbalance between sympathetic and parasympathetic regulation.

Adult↗
PubMed1999

Spectral analysis of laser-Doppler perfusion signal measured during thermal test.

The method of spectral analysis of laser-Doppler perfusion signal measured during thermal test is proposed. During three 20 min phases with 40, 5, and 40 degrees C of thermal test laser-Doppler perfusion signal was recorded. For each signal phase frequency spectra were calculated using the FFT method. Quantitative parameter Spectral Factor for results evaluation was proposed. In total 94 patients were measured: 69 with Raynaud's phenomenon and 25 normal subjects. Additionally in 18 Raynaud's patients the influence of Nifedipine was studied. Results suggest that proposed parameter is able to differentiate between Raynaud's patients and normal subjects and that is useful for evaluation of Nifedipine effectiveness. However, further studies are needed to improve the method to differentiate between primary and secondary Raynaud's patients.

Adult↗
PubMed1985

Non-invasive detection of carotid bifurcation disease by continuous-wave Doppler with spectral analysis.

The diagnostic accuracy of 5 MHz continuous-wave (C-W) Doppler with spectral analysis for detecting carotid bifurcation disease was evaluated. In a first phase of the study, normal confidence intervals for peak frequency data and spectrum width were established and Doppler spectrum abnormalities were separated into three types (spectral broadening with preserved window, spectral broadening without window, sequence of abnormalities including inverted Doppler spectrum). In a second phase the diagnostic accuracy of these variables was tested on 86 carotid arteries as independently compared with angiography. Whereas both peak frequency data and spectrum distribution findings were invariably abnormal in stenoses greater than or equal to 60%, spectrum distribution findings were more accurate in 30-59% stenosis. Using spectrum distribution criteria, sensitivity and specificity for stenosis greater than or equal to 30% were 94.6% and 90.7% respectively. All variables were insensitive for stenoses less than 30% lumen diameter reduction.

Adult↗
PubMed1997

Spectral analysis of heart rate fluctuations and optimum thermal management for low birth weight infants.

Spectral analysis of heart rate variability is studied in 10 healthy growing premature infants to investigate the changes in autonomic balance achieved as a function of changes in skin temperature. Heart rate is obtained from ECG recordings and the power spectrum of beat-to-beat heart rate fluctuations is computed. The infants maintain mean rectal temperature within 36.3-37.2 degrees C, while skin temperature changes. The respiratory rate does not change at the different servocontrol set points. Heart rate is found to increase slightly, but consistently. The low-frequency band (0.02-0.2 Hz), reflecting the interplay of the sympathetic and parasympathetic tone and known to be maximum at the thermoneutral zone, is maximum at 35.5 and 36 degrees C and decreases gradually to a lower level at a servocontrol temperature of 36.5-37 degrees C. The high-frequency band (0.2-2.0 Hz), coinciding with the respiratory peak and reflecting parasympathetic activity, is significantly elevated at 36 degrees C (p < 0.01). The minimum low: high ratio, indicating the minimum sympathetic-parasympathetic balance and possibly reflecting the most comfortable conditions, occurs at 36 degrees C, although the differences are not statistically significant. Servocontrol skin temperature may thus be adapted, and possibly selected at 36 degrees C for growing premature infants in an attempt to achieve thermal comfort and more balanced autonomic activity.

Electrocardiography↗
PubMed1985

The ontogeny of fetal lamb electrocortical activity: a power spectral analysis.

With the use of a relatively inexpensive microcomputer-based system for power spectral analysis, we have been able to provide quantitative information on maturational changes in electrocorticogram waveforms in the third-trimester fetal lamb. Twenty-six electrocorticogram recordings were obtained from nine fetal lambs, with gestational ages ranging from 114 to 139 days' gestation. The transition from disorganized to cyclic electrocorticogram activity (high-voltage slow activity and low-voltage fast activity) occurred at approximately 115 to 120 days' gestation. However, quantitative changes in waveform characteristics of the electrocorticogram continued throughout the rest of gestation. These maturational changes occurred primarily in the low-voltage fast activity periods, with a decrease in power density in the delta (0.3 to 3 Hz) band and an increase in the maximum frequencies detected in the beta (15 to 30 Hz) band. There were no significant changes in the power spectrum of the high-voltage slow activity periods as a function of gestational age.

Analog-Digital Conversion↗
PubMed1983

[Spectral analysis of fast EEG rates in normal 6-to-16-year-old children].

Spectral analysis of EEGs from 208 school children aged from 6 to 16 shows two types of beta activity: anterior beta which is low in amplitude but increases in energy in response to eye opening and posterior beta which, like alpha, decreases in response to eye opening. After reviewing the role of the FFT in frequency analysis we conclude that anterior beta activity corresponds to the classic beta rhythm of visual analysis, while posterior beta activity probably represents harmonics of alpha or even theta activity. In any case, beta activity in the normal child is very low in amplitude and energy.

Adolescent↗
PubMed1993

Spectral analysis of erector spinae EMG during intermittent isometric fatiguing exercise.

The applicability of EMG spectral analysis in the study of muscular fatigue of the erector spinae muscle was investigated. At three locations (L1, L2, L5) of the erector spinae muscle, representing different functional parts, EMG was sampled during fatiguing intermittent isometric extension of the trunk. The multifidus muscle (L5) appeared to show the most consistent changes of the EMG power spectrum as a consequence of fatigue. Whether the effects of the increase in muscle temperature on the power spectrum could be eliminated by low-pass filtering the data (60 Hz and 40 Hz) was also investigated. It was expected that this would make it possible to detect better the effects of fatigue on the firing characteristics of the motorunits by the inherent changes in the power spectrum. Low-pass filtering did not cause a more significant trend of the median frequency of the power spectrum. Future research will have to explore which parts of the power spectrum are affected by an increase of the muscle temperature.

Adult↗
PubMed1996

Estimation of arterial blood pressure variability by spectral analysis: comparison between Finapres and invasive measurements.

In order to assess the accuracy of spectral analysis of beat-by-beat arterial blood pressure fluctuations recorded by the finger technique we analysed simultaneous ipsilateral resting sequences (180 s) of systolic blood pressure (SP) and diastolic blood pressure (DP) obtained by brachial artery cannulation and by the Finapres device in 26 post-myocardial infarction (post-MI) and 24 chronic heart failure (CHF) patients. We estimated: (i) the total variability and the power in the bands 0.01-0.04 Hz (band 1), 0.04-0.07 Hz (band I), 0.07-0.15 Hz (band III) and 0.15-0.45 Hz (band IV); and (ii) the group-average transfer function between the invasive and non-invasive channel. The total variability of intra-arterial SP was greatly enhanced by the Finapres device in both populations (p < 0.01) mainly due to the increase of power in bands I and II (mean percentage errors 157 and 111% in post-MI and 368 and 245% in CHF patients respectively). The power in band IV was significantly reduced in post-MI (p < 0.001) but not in CHF patients. The total DP variability increased in post-MI patients (p < 0.001) due to the increase in bands I and II (mean percentage errors 62 and 43% respectively). No significant difference was found in bands III and IV of the same group and in the overall variability of CHF. Linear system analysis showed that intra-arterial SP oscillations in both groups are amplified by the Finapres device in bands I and II, with a higher gain in CHF patients, whereas they are attenuated in band IV. Band III acts as a transition band. DP oscillations recorded non-invasively are slightly amplified in bands I and II of post-MI patients only and are attenuated in band IV of both groups. A substantial fraction (approximately 30%) of the non-invasive SP variability in band I cannot be explained as a pure linear transformation (amplification) of the invasive signal. A phase delay in the range 7 degrees-10 degrees relates the non-invasive signal to the invasive one in the region 0.025-0.17 Hz and approaches zero elsewhere. Several mechanisms were examined as potential causes of the invasive-non-invasive differences. We argue that these differences are mainly due to the complex rhythmic behaviour of peripheral resistance vessels.

Adult↗
PubMed2002

Spectral analysis of distributions: finding periodic components in eukaryotic enzyme length data.

We introduce the spectral analysis of distributions (SAD), a method for detecting and evaluating possible periodicity in experimental data distributions (histograms) of arbitrary shape. SAD determines whether a given empirical distribution contains a periodic component. We also propose a system of probabilistic mixture distributions to model a histogram consisting of a smooth background together with peaks at periodic intervals, with each peak corresponding to a fixed number of subunits added together. This mixture distribution model allows us to estimate the parameters of the data and to test the statistical significance of the estimated peaks. The analysis is applied to the length distribution of eukaryotic enzymes.

Algorithms↗
PubMed1989

Enzymatic extraction and spectral analysis of the chromophore from cell walls of nutritionally deficient streptococci.

We demonstrated by spectral analysis a method to enzymatically cleave the chromophore precursor from nutritionally deficient streptococcal cell walls by treatment with lysozyme. The peak absorbances without and with lysozyme pretreatment were 511.4 +/- 2.02 nm and 513.1 +/- 0.69 nm, respectively. Extraction yields varied among strains and were found to be growth phase dependent. A secondary peak of absorbance (mean of 477 nm) was found in only five of eight strains. The chromophore at a neutral pH undergoes a reaction with phenol consistent with that of a furan, indicating its carbohydrate composition.

Cell Wall↗
PubMed1987

Assessment of baroreceptor reflex sensitivity by means of spectral analysis.

A method of determining baroreceptor reflex sensitivity is proposed that is based on spectral analysis of systolic pressure values and RR interval times, namely, the modulus (or gain) in the mid frequency band (0.07-0.14 Hz) between these two signals. Results using this method were highly correlated (0.94; n = 8) with results of the phenylephrine method. In addition, compared with the values for the preceding rest period, the modulus decreased during mental challenge, as might be expected from the literature.

Adult↗
PubMed1992

Power spectral analysis of heart-rate variations improves assessment of diabetic cardiac autonomic neuropathy.

Power spectral analysis (PSA) of heart-rate variations has recently proved a useful tool in evaluating cardiovascular autonomic activity. It offers the possibility of examining both the functioning of parasympathetic and sympathetic pathways through breakdown into two frequency bands, and of their effects on heart-rate cyclic variability. We applied an autoregressive model for PSA to study overall autonomic tone in 20 male age-matched control subjects and 53 insulin-dependent (type I) diabetic subjects, subdivided into three groups of 20, 15, and 18, each group presenting different degrees of autonomic involvement. We found that: 1) power spectrum density (PSD) values at high-frequency bands (parasympathetic dependent) were similar in diabetic subjects without cardiac autonomic neuropathy (CAN) and in control subjects, but differed significantly from diabetic subjects with mild CAN and severe CAN, both standing and lying; 2) PSD values at low frequency (mainly sympathetic dependent) were similar, or slightly different, in diabetic subjects without CAN and in control subjects, but differed significantly from diabetic subjects with mild and severe CAN, both standing and lying; 3) as an expression of parasympathetic versus sympathetic coherence, correlations, both standing and lying, existed between PSD values at low- and high-frequency bands in control and diabetic subjects without CAN, but not in diabetic subjects with CAN; and 4) different degrees of correlation characterized the PSD values of high and low frequencies versus traditional cardiovascular test values in the diabetic subjects. The best correlation was between PSD low-frequency values and the lying-to-standing maneuver.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[A power spectral analysis of the EEG in the newborns. I. Developmental changes of normal babies].

Power spectral analysis of the EEG at the neonatal period was performed in 50 premature babies and 36 mature babies. The gestational age ranged from 26 to 40 weeks, and birth weight from 762 g to 3,232 g. All EEGs were recorded when the babies reached to 37-41 weeks of conceptional age, and analyzed using fast Fourier transformation. The relative power in active sleep was evaluated in this study. The percent power of the delta 1 band ranging from 0.5 to 2.0 Hz decreased immediately with increasing conceptional age, while that of the delta 2 (2.2-3.8 Hz), theta 1 (4.0-5.4 Hz) and theta 2 (5.6-7.8) increased with conceptional age. However, no significant change was recognized in the alpha (8.0-12.8 Hz) and beta 13.0-29.8 Hz). These results suggest that the development of the EEG depends on the post conceptional age. The percent power of delta 1 to beta bands was compared among the frontal, central, parietal and occipital regions. The development of EEG in the central region was prominent among other 3 regions in EEG development. The EEGs of premature babies were compared to those of mature babies at the same conceptional age. The percent power of premature babies was higher at the delta 1 band, whereas lower at the delta 2, theta 1 and theta 2 bands than that of mature babies. The data showed that premature babies were more immature than age-matched mature babies in the development of EEGs.

Brain↗
PubMed1983

Spectral analysis of neocortical and hippocampal EEG in the protein malnourished rat.

In these studies, power spectral analysis techniques were utilized to quantify changes in the cortical and hippocampal EEG obtained from rats reared on either an 8% or 25% casein diet as they mature from 14 to 22 days of age. Analyses of the power spectral data obtained from the frontal cortex of rats reared on the 25% casein diet during this preweaning period (14-22 days) indicated increases in the power in the 0.5-3.5 c/sec frequency band primarily during slow-wave sleep. Prenatal protein malnutrition (8% casein diet) significantly reduced the low frequency power content in the cortical EEG obtained during slow-wave sleep at 18 and 22 days of age. Analyses of power spectral data obtained from the hippocampal EEG during REM sleep also revealed developmental and diet-related differences. The frequency at which the peak power occurs in the theta band (4-11 c/sec) was found to increase normally in a linear fashion from 14 to 22 days of age (from 4.4 to 5.5 c/sec) in rats reared on the 25% casein diet. In addition, power in the 4-7 c/sec band significantly increased during this preweaning period. Prenatal protein malnutrition significantly slowed the development of theta frequency and produced higher values of power in the component of theta rhythm. Finally, vigilance profiles showed that rats normally progress from 14 days of age when REM sleep dominates their vigilance profile, to 22 days of age when they spend significantly more time in slow-wave sleep. Prenatal protein malnutrition retards this normal developmental sequence by significantly reducing the REM sleep time at 14 and 18 days of age and increasing the time spend in aroused waking at both these ages. However, at the time of weaning, i.e., at 22 days of age, these differences in sleep-waking behavior were no longer observed to be significant.

Animals↗