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PubMed1989

Power spectral analysis of spontaneous field potentials in hippocampal slice.

Spontaneous field potential oscillations were recorded from the CA3 distal apical dendritic region of guinea pig hippocampal slices maintained in 'normal' artificial cerebrospinal fluid in vitro. Power spectral analysis revealed a mixture of frequencies mainly under 20 Hz without distinct peaks. High concentrations of extracellular Mg2+ blocked the activity. These findings suggest that the intrinsic spontaneous activity of the hippocampus is produced by partially synchronized synaptic potentials. This in vitro system may provide a suitable model for studying the mechanisms underlying the generation of EEG rhythms.

Action Potentials↗
PubMed1996

Autonomic nervous function in mice and voles (Microtus arvalis): investigation by power spectral analysis of heart rate variability.

We have studied the autonomic nervous function in voles (Microtus arvalis) and mice. For this purpose, ECGs were recorded from conscious and unrestrained voles and mice using radiotelemetry and the autonomic nervous function was investigated by the power spectral analysis of heart rate variability. Heart rate in voles was lower than mice and the coefficient of variance was larger in voles. In the power spectra of voles and mice, there were two major spectral components with the high frequency (HF) peak generally appearing between 2.0 and 4.0 Hz, and the low frequency (LF) peak appearing below 0.6 Hz. On the basis of this data, we set the two frequency bands as LF (0.1-1.0 Hz) and HF (1.0-5.0 Hz) to evaluate autonomic nervous function. The LF and HF powers were larger in voles than mice. The LF/HF ratio was thought to provide a convenient index of autonomic nervous balance and was smaller in voles than mice. The LF powers in both species were reduced by atropine, but propranolol reduced the LF power only in mice. The HF power was reduced by atropine only in voles. The intrinsic heart rate produced by a double blockade with atropine and propranolol in voles was almost the same as control levels, but in mice was lower than controls. The ratio of the LF and HF powers by a double blockade were almost the same as those of the administration of atropine in voles, but nearer to propranolol in mice. These results suggested that the parasympathetic nervous function was predominant in voles, but the sympathetic one was predominant in mice.

Animals↗
PubMed2004

Spectral analysis of colonic intraluminal pressure in patients who received a colonic replacement following radical esophagectomy.

The aim of this study was to evaluate the motor activity of the interposed colonic segment in patients who had received a colonic replacement following radical esophagectomy using spectral analysis and a 24 hr activity graph. The 24-hr ambulatory pressure waves were recorded in the replaced colon after esophagectomy (n=8) using a solid-state manometric catheter (MicroDigitrapper, Synetics). Motility and spectral analyses of the intraluminal pressure waves were performed by Multigram and Gastrosoft (Synetics). It was revealed that after a meal the 3 cpm (cycles per minute) component of the motility index increased but the 12-15 cpm component decreased. The diurnal rhythm showed that colonic motility was high in the daytime and low during sleep. In contrast, duodenal motility was relatively high even during sleep. The motility index increased as the postoperative period increased. The motility of the replaced colon was higher during the daytime and after meals. The higher motility after meals was characterized by an increase in the 3 cpm component. These motor characteristics may help the function of the replaced colon as a substitute for the esophagus.

Aged↗
PubMed1990

Power spectral analysis of heart rate variability in traumatic quadriplegic humans.

This study investigated the spontaneous beat-to-beat variabilities in R-R intervals of six traumatic neurologically complete quadriplegic (QP) males and six age-matched healthy males (control) while they were at rest in the supine position in a climatic chamber (temperature 30 degrees C, relative humidity 60%) by means of autoregressive power spectral analysis. As shown by earlier studies, in the control group there were two major spectral components, a high-frequency (HF) component [center frequency 0.30 +/- 0.02 (SE) Hertz equivalent (Hz eq), power 767.5 +/- 384.6 ms2] and a low-frequency (LF) component (0.11 +/- 0.01 Hz eq, 707.5 +/- 198.8 ms2). On the contrary, in the QP group, only the HF component was observed (0.30 +/- 0.02 Hz eq, 421.8 +/- 134.7 ms2). The results suggest that 1) the disappearance of the LF component in the QP subject is presumably caused by the interruption of the spinal pathways linking supraspinal cardiovascular centers with the peripheral sympathetic outflow, and 2) the cervical spinal sympathetic pathways may be instrumental in the genesis of the LF component in humans.

Adult↗
PubMed1999

Time-variant spectral analysis of LDF signals on the basis of multivariate autoregressive modelling.

Time-variant AR-modelling was used to analyse the non-stationary properties of LDF signals during provocation tests. The procedure for the estimation of time-varying AR parameters based on Kalman filtering is presented. The estimates can be used to calculate instantaneous measures, such as peak frequency, spectral band power and coherence. The resulting course of instantaneous peak frequency of a sinusoidal signal with frequency jump was compared to similar parameters derived from short-time FFT and Hilbert transformation. Univariate time-variant spectral analysis was used to investigate LDF measurements in patients with Raynaud's phenomena. The experimental protocol was splitted into phases of different room temperature. The results demonstrate time-dependent variations of spectral components (amplitude and frequency). By means of time-variant coherence analysis of LDF and diameter measurements of vessels in a hamster skin fold the existence of a main rhythm around 0.1 Hz in the LDF signals which is related to vasomotion is shown.

Algorithms↗
PubMed2000

Differential change in cardiac baroreflex sensitivity estimated by sequence and spectral analysis during etomidate anesthesia.

Spontaneous baroreflex sensitivity, high-frequency gain, (0.15-0.35 Hz), and mid-frequency gain (0.07-0.14 Hz) are noninvasive measures of cardiac baroreflex function derived by spontaneous sequence and cross-spectral analysis. To demonstrate the difference between these baroreflex estimates, 14 patients received etomidate (0.3 mg/kg bolus and 0.9 mg/kg/h infusion), lidocaine (60 mg), and vecuronium (0.1 mg/kg) by intravenous injection. The authors found that spontaneous baroreflex sensitivity and high-frequency gain were decreased (p <0.05) after etomidate anesthesia, whereas mid-frequency gain was maintained. Spontaneous baroreflex sensitivity, high-frequency gain, and mid-frequency gain, although compared simultaneously, did not change in a parallel manner. In another 5 patients, who received normal saline only, measures were unchanged. The authors conclude that spontaneous baroreflex sensitivity, high-frequency gain, and mid-frequency gain are not interchangeable. Experimental results on baroreflex control depend on the parameter selected.

Adult↗
PubMed1986

C(6)-[benzene ring]-indole-3-acetic Acid: a new internal standard for quantitative mass spectral analysis of indole-3-acetic Acid in plants.

Indole-3-acetic acid (IAA) labeled with (13)C in the six carbons of the benzene ring is described for use as an internal standard for quantitative mass spectral analysis of IAA by gas chromatography/selected ion monitoring. [(13)C(6)]IAA was compared to the available deuterium labeled compounds and shown to offer the advantages of nonexchangeability of the isotope label, high isotopic enrichment, and chromatographic properties identical to that of the unlabeled compound. The utility of [(13)C(6)]IAA for measurement of endogenous IAA levels was demonstrated by analysis of IAA in Lemna gibba G-3.

Journal Article↗
PubMed1982

Power spectral analysis of the neonatal primate electroencephalogram during acute hypoxemia.

The effect of acute graded hypoxemia on the electroencephalogram (EEG) of five prematures and five full term Macaca nemestrina in the neonatal period was determined using power spectral analysis--a technique that obviates the limitations of visual inspection. The EEG of selected epochs was analyzed by a Fast Fourier Transform program (POWER) during the 20 min of each trial of hypoxemia and compared with simultaneous arterial oxygen tensions. Levels of hypoxemia were graded as profound (PaO2=15-25 Torr); severe (PaO2=26-35 Torr), moderate (PaO2=36-50 Torr), or mild (PaO2=51-75 Torr). The EEG during normoxemia had a band width of 0.5 to 10 Hz and a peak power at 1-3 Hz. During mild hypoxemia, an increase in power in the delta range (0-3.5 Hz) occurred in the oldest animals. At moderate hypoxemia, the youngest animals showed a depression of absolute power in the delta band. A slowing of the EEG and decrease in power in the theta frequency range (4-8 Hz) followed when severe hypoxemic levels are reached. During profound hypoxemia, all animals at each postnatal age exhibited a significant decrease in EEG power at the delta and theta frequencies (P less than 0.025) except 3-wk-old full term animals in which there was no significant change in the delta band. These results clarify and extend previously reported effects of hypoxemia on the neonatal EEG.

Animals↗
PubMed2001

[Genetic algorithms and its application to spectral analysis].

Genetic algorithm derived from the principle of natural selection and the concepts of genetics is a global search method, which is not only highly effective but also parallel. Its essential theory, operating method, application to spectral analysis and trend of development are reviewed with 66 references.

Algorithms↗
PubMed1989

EEG and spectral analysis in HIV immunocompetent patients free from clinical CNS impairment. A follow-up study in 20 cases.

Twenty HIV immunocompetent subjects without neurological symptoms were studied by EEG and spectral EEG analysis over a period of 6-16 months. 40% of them showed mild diffuse changes in background activity on basal evaluation, but the appearance of neurological symptoms and the evolution of clinical picture seemed unrelated to the presence of aspecific EEG and spectral analysis changes. As most of them were oppiate abusers, these findings could be ascribed to the long-term drug use.

AIDS Dementia Complex↗
PubMed1987

[Compression spectral analysis of the EEG of patients with occlusive diseases of the main vessels of the head].

The authors have examined 37 patients with occlusive lesions of the main vessels of the head using electroencephalogram and compression spectral analysis of the EEG findings. A group of patients with the predominant damage to the carotid and vertebral arteries has been identified on the basis of angiographic data. It has been shown that alterations in the bioelectrical activity of the brain are determined by hemodynamic disturbances in patients with transient disorders of the cerebral circulation and circulatory encephalopathy. In patients with acute impairments of the cerebral circulation, the nature of the EEG and spectrogram depends primarily on localization of the ischemic focus. The quantitative parameters of changes in the bioelectrical activity of the brain in different groups of patients are outlined.

Adult↗
PubMed1993

Decreased heart rate variability in panic disorder patients: a study of power-spectral analysis of heart rate.

We have previously found decreased standard deviations and mean consecutive differences of R-R intervals in panic disorder patients in standing posture, compared with control subjects. In the present study, we used spectral analysis of heart rate variability to examine autonomic function in 21 panic disorder patients and 21 normal control subjects. Patients had a significantly lower standard deviation of heart rate in supine as well as standing postures. Absolute low frequency power (0.01-0.05 Hz) was also significantly lower in panic disorder patients in standing postures. Upon standing, the panic disorder patients had significantly higher relative mid-frequency power (0.07-0.15 Hz). During a standing deep-breathing condition at six breaths per minute, the patients had a significantly decreased absolute and relative mid-frequency (0.07-0.15 Hz) power compared with control subjects. These findings suggest a decrease in cholinergic and a relative increase in adrenergic responsiveness in panic disorder patients compared with control subjects.

Adrenergic Fibers↗
PubMed1997

EEG spectral analysis of the neuroprotective kappa opioids enadoline and PD117302.

The present study characterized the electroencephalographic (EEG) effects of the neuroprotective kappa opioids enadoline and PD117302 in conscious, freely moving rats with the use of computer-assisted spectral analysis (CASA). Enadoline (25-100 microg/kg) or PD117302 (1.25-5.0 mg/kg) was administered intravenously to rats implanted with cortical EEG electrodes. Although both drugs produced an immediate, mild sedation, there were no signs of head-weaving or ataxia, and there was little visual evidence of opioid-like EEG slow-wave bursts or seizures. Both drugs produced only modest increases in total EEG power that were not dose dependent. In contrast, CASA revealed significant dose-dependent frequency shifts in relative power distributions, thereby identifying distinct kappa opioid alterations in awake EEG activity; EEG power decreased in the 0- to 4-Hz frequency band with concomitant increases in power measured in the 4- to 8-Hz frequency range. The kappa opioids produced a dose-dependent consolidation of the EEG waveform centered about a peak frequency of 5.0 Hz (for enadoline) or 4.8 Hz (for PD117302) and a significant shift in the mean EEG frequency from 6.6 Hz (predrug) to 6.2 Hz (postdrug). Further CASA revealed significant postdrug decreases in the edge frequency, mobility and complexity of the EEG. Both drugs produced moderate increases in the latency to slow-wave sleep (SWS). Overall, enadoline (ED50 = 18 microg/kg) was approximately 94 times more potent than PD117302 (ED50 = 1690 microg/kg) in producing the kappa EEG profile. Because the kappa-induced EEG changes were stereospecific for the (-)-enantiomers and inhibited by norbinaltorphimine (nor-BNI), the EEG "fingerprint" described in this study could be attributed to specific activation of brain kappa opioid receptors.

Animals↗
PubMed2003

Spectral analysis of the acoustic emission of laser-produced plasmas.

A Q-switched frequency Nd:YAG laser was focused on copper, aluminum, and lead targets. The acoustic emission accompanying plasma formation was acquired and analyzed in both the time and the frequency domains. Spectral analysis of the shock wave has proved to be a simple and low-cost diagnostic of plasma phenomena. In the time domain, several propagation mechanisms of the shock wave were observed and the velocity profile of the shock wave estimated. Spectral measurements were performed in the acoustic propagation regime of the shock waves. Spectral features related to the plasma formation mechanism were identified and discussed for copper, aluminum, and lead on the basis of the physical properties of these elements, the expansion mechanisms of the plasma, and an empirical parameter representative of the transported energy.

Journal Article↗
PubMed1987

Spectral analysis of R-R interval variability in inspiratory breath holding in man at rest and during emotional strain.

30 young males performed inspiratory breath holdings during expectation of an aversive stimulus and at relative rest. The consecutive R-R intervals of the ECG from breath-hold trial were analysed via spectral analysis of time series. Following parameters were ascertained for each breath holding: mean R-R interval, total R-R interval variability, breath-hold time and relative variability in three spectral bands 3-8 s, 8-12 s and 12-18 s. Neither of these variables was influenced by expectation of an aversive stimulus. The data were subsequently analysed by means of multivariate analysis. Three distinct frequency components were selected according to both histogram data and multivariate analysis. Their modal periods were 5-6 s, 12 s and 16 s respectively. The 8-12 s component of R-R interval variability dominated during breath holdings. The 3-8 s band bore a negative relationship to breath-hold time.

Acoustic Stimulation↗
PubMed1988

Assessment of autonomic regulation in chronic congestive heart failure by heart rate spectral analysis.

Neurohumoral modulation of cardiovascular function is an important component of the hemodynamic alterations in patients with chronic congestive heart failure (CHF). Analysis of heart rate (HR) variability is a noninvasive means of investigating the autonomic control of the heart. The variability of HR and respiratory signals, both derived from ambulatory electrocardiographic recordings, were analyzed with power spectral analysis to evaluate autonomic control in 25 patients with chronic stable CHF (class III or IV) and 21 normal control subjects. In the patients with CHF, HR spectral power was markedly reduced (p less than 0.0001) at all frequencies examined (0.01 to 1.0 Hz, period 1 to 100 seconds) and virtually absent at frequencies greater than 0.04 Hz. Heart rate fluctuations at very low frequencies (0.01 to 0.04 Hz) less effectively differentiated CHF patients from control subjects, due to discrete (about 65 seconds, 0.015 Hz) oscillation in HR, which was associated with a similar pattern in respiratory activity in many of the patients with CHF. These findings demonstrate a marked derangement of HR modulation in patients with severe CHF. The frequency characteristics of HR fluctuations in these patients are consistent with abnormal baroreflex responsiveness to physiologic stimuli, and suggest that there is diminished vagal, but relatively preserved sympathetic, modulation of HR.

Adult↗
PubMed1990

Fundamentals of EEG spectral analysis.

Recent progress in the fields of informatics and engineering has enabled a large diffusion of computers in clinical practice too. Availability of these computing facilities has introduced several quantitative methods to analyze electrophysiological signals. Among these techniques spectral analysis is the most used in quantitative electroencephalography. This article introduces some fundamental concepts of the theory of stochastic processes. The power density function and its descriptors useful in EEG analysis are also presented. The various possibilities of the appropriate application of this methodology are discussed.

Electroencephalography↗