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PubMed1982

EEG spectral analysis in vital depression: ultradian cycles.

Ten=hour sleep monitoring was carried out in 34 patients suffering from a vital depressive illness as well as in a group of 16 healthy volunteers; 18 of the depressed patients were deprived of treatment. The EEG was evaluated visually for data concerning the REM cycle and the REM latency. Spectral analysis of the all-night recordings yielded interval histograms for a group comparison of background activity. Fourier spectrograms and digital filtering were used to analyze ultradian patterns within the long-term frequency distribution. The result showed a trend in depression toward prolongation of the REM cycle and shortening of REM latencies. More significant, however, was the activation of 16- to 8-Hz waves together with a decreased occurrence of delta activity in depressed subjects without treatment. Depressed patients had significantly slower ultradian periodicities with 102-min cycles compared to 86-min cycles in healthy subjects. This disturbance could be temporally located in the early morning hours.

Adult↗
PubMed1985

Spectral analysis for base composition of DNA undergoing melting.

A microcomputer-controlled spectrophotometer is described for obtaining the base composition of melting domains in DNA from derivative melting curves. Values have been determined for the differential molar extinction coefficients for the A-T and G-C base pair at the three wavelengths most useful for spectral analysis of base composition, 260, 270 and 282 nm. The average RMS error for these values was 29 l(mol X cm)-1 for the melting of 14 DNA specimens ranging in base composition from 0-0.72 F(G + C). A precision of approximately 1% in base composition of domains is possible. Such analysis is useful for confirming or establishing assignments of domains to particular subtransitional features in high resolution melting curves.

Base Composition↗
PubMed1993

Power spectral analysis of the electroencephalographic and hemodynamic correlates of propofol anesthesia in the rat: intravenous infusion.

Based on the tail-flick response to noxious thermal stimuli, we determined in the present study that effective antinociception could be achieved in adult male Sprague-Dawley rats 15 min after intravenous infusion of propofol at 60 mg/kg/h. Simultaneous power spectral analysis of the electroencephalographic (EEG) and systemic arterial pressure signals further revealed a concomitant depression of the activity of all EEG frequency bands (delta, theta, alpha, beta), alongside hypotension, negative inotropic and chronotropic actions, and attenuated baroreceptor reflex and vasomotor activity. These effects were congruent with a plasma concentration of propofol in the arterial blood of 1.70 +/- 0.13 micrograms/ml, as determined by high-performance liquid chromatography.

Anesthesia↗
PubMed2000

Autonomic cardiovascular regulation in patients with obstructive sleep apnoea: a study based on spectral analysis of heart rate variability.

The aim of this study was to assess the function of the autonomic nervous system in patients with obstructive sleep apnoea syndrome (OSAS). The study was designed as a cross-sectional case-control study. Fifty-one patients were included, and the findings were compared with those in 66 controls. Spectral analysis of heart rate variability (HRV) during supine rest, during controlled breathing and after tilting was performed in each patient and control case. The patients performed overnight sleep recordings the night before the HRV recordings. Individuals with an apnoea-hypopnoea index (AHI) above 20 were regarded as OSAS patients and those with AHI lower than 20 as snorers. Differences in HRV and blood pressure between patients and controls were analysed by multiple linear regression with age, body mass index and sex as independent variables. During free and controlled breathing there was a significant decrease in indices reflecting vagal modulation, indicating parasympathetic dysfunction in OSAS patients compared with controls. The mid-frequency component was also significantly reduced in OSAS patients after tilting but not in the lying position. This may be related to the parasympathetic dysfunction, but could also indicate a decreased sympathetic reserve capacity. We found no significant relation between AHI and indices of vagal modulation in the patient group. Our findings show an autonomic dysfunction in patients with OSAS. The dysfunction involves the parasympathetic system, and may be related to the increased cardiovascular mortality and malignant arrhythmia described in OSAS.

Adult↗
PubMedDate not supplied

Power spectral analysis of heart rate variability in Type As and Type Bs during mental workload.

Recently several studies have suggested that there are differences in autonomic balance between Type As and Type Bs. This study evaluates a sympathovagal interaction in Type A (n = 8) and Type B (n = 11) male students during a mental arithmetic task by power spectral analysis of heart rate variability. The low-frequency component to high-frequency component ratio was significantly greater in Type As than in Type Bs during a resting period. No significant differences were found in heart rate changes and blood pressure between the two kinds of subject groups. The present findings indicate that there was a significant difference in sympathovagal balance between Type As and Bs. Type As showed dominant sympathetic activity.

Adult↗
PubMed1998

Spectral analysis of oscillatory neural circuits.

Oscillatory dynamics are found at all levels of the nervous system. The goal of our current research on the control of rhythmic motor output by the lamprey spinal cord is to determine the features of neuronal coupling that lead to stable oscillatory activity and precisely-controlled intersegmental phase. Since our experimental manipulations can greatly increase the variability of the ventral root bursting pattern, it is important for us to employ a data analysis method which remains valid independent of this variability. Traditional analysis approaches which rely on identification of burst event times do not generally satisfy this requirement. In this paper, we illustrate the application of a straightforward statistically-based method for determining important parameters of oscillatory motor circuits using Fourier spectral analysis of spike trains. The frequency, phase, and their variabilities can be quantified; and the relative strength of coupling between different parts of the circuit can be tested for statistical significance. The approach we adopt is highly convenient for neuroscientists who study oscillatory systems as it operates directly on trains of action potentials stored as lists of event times (point-processes). Basic concepts and practical issues concerning use of Fourier analysis are discussed.

Animals↗
PubMed1993

Spectral analysis of antepartum fetal heart rate variability from fetal magnetocardiogram recordings.

Fetal heart rate variability was derived from fetal magnetocardiogram recordings in ten subjects at gestation ages 32-38 weeks. Maternal interference was negligible and R-wave detection was highly reliable. Oscillations suggestive of respiratory sinus arrhythmia (RSA) were prominent in many of the heart rate tracings. Spectral analysis was used to quantify heart rate variability and to examine the influence of the RSA-like oscillations on heart rate variability. The oscillations were associated with increased power in the frequency range 0.4-1.0 Hz (P < or = 0.05). Magnetic recording appears to offer significant advantages for investigation of beat-to-beat fetal heart rate throughout the latter stages of pregnancy.

Adult↗
PubMed2002

Parsimonious basis selection in exponential spectral analysis.

Sums of decaying real exponentials (SDREs) are frequently used in models of time-varying processes. First-order compartmental models are widely employed to describe mass transit in chemical and biological systems. In these models the evolution of compartment concentration versus time is represented as the convolution of an input function with an SDRE. In exponential spectral analysis (ESA) the nonlinear problem of estimating the SDRE rate constants is replaced by the linear estimation of the coefficients of a preselected set of exponential basis functions (EBFs). This work addresses the problem of selecting the number of EBFs and the rate constant of each basis element. Basis dimension is established via model selection, in which approximation error and parameter redundancy are the criteria. The latter is estimated via simulation of the fitted model over multiple noise realizations. A constrained Cramér-Rao lower bound is derived for ESA parameters. The resulting parsimonious ESA algorithm (PESA) ameliorates the inherent problem of non-uniqueness in ESA parameters. Consequently, sets of time series may be compared in a statistically meaningfully way in terms of physically or physiologically significant parameters. PESA is applied to compare the retention of two radiotracers in the artificially perfused rabbit heart.

Algorithms↗
PubMed2006

[Preparation and spectral analysis of a new type of blue light-emitting material delta-Alq3].

In the present article, delta-Alq3, a new type of blue light-emitting material, was synthesized and investigated by IR spectra, XRD spectra, UV-Vis absorption spectra, photoluminescence (PL) spectra, and electroluminescence (EL) spectra. The relationship between molecular spatial structure and spectral characteristics was studied by the spectral analysis of delta-Alq3 and alpha-Alq3. Results show that a new phase of Alq3 (delta-Alq3) can be obtained by vacuum heating alpha-Alq3, and the molecular spatial structure of alpha-Alq3 changes during the vacuum heating. The molecular spatial structure of delta-Alq3 lacks symmetry compared to alpha-Alq3. This transformation can reduce the electron cloud density on phenoxide of Alq3 and weaken the intermolecular conjugated interaction between adjacent Alq3 molecules. Hence, the pi--pi* electron transition absorption peak of delta-Alq3 shifts toward short wavelength in UV-Vis absorption spectra, and the maximum emission peak of delta-Alq3 (lamda max = 480 nm) blue-shifts by 35 nm compared with that of alpha-Alq3 (lamda max = 515 nm) in PL spectra. The maximum emission peaks of delta-Alq3 and alpha-Alq3 are all at 520 nm in EL spectra.

English Abstract↗
PubMed1992

Assessment of cardiovascular autonomic function: age-related normal ranges and reproducibility of spectral analysis, vector analysis, and standard tests of heart rate variation and blood pressure responses.

To establish normal ranges for assessment of autonomic dysfunction, a battery of cardiovascular reflex tests was performed in 120 healthy subjects aged 15-67 years using a computer-based technique. Tests of heart rate variation (HRV) included 8 measures at rest: coefficient of variation (CV), root mean squared successive difference (RMSSD), spectral analysis of HRV in the low frequency, mid frequency, and high frequency bands in the supine and standing postures; 5 measures during deep breathing: CVb, RMSSDb, Expiration-Inspiration (E-I) difference, E/I ratio, and mean circular resultant of vector analysis; Valsalva ratio, and max/min 30:15 ratio. In addition, the change in systolic and diastolic blood pressure in response to standing and the diastolic blood pressure response to sustained handgrip were determined. The results of all measures, the blood pressure tests excepted, declined significantly with increasing age (r = -0.16 to -0.59; p less than 0.05). Moreover, RMSSD, RMSSDb, and E-I difference decreased considerably with increasing heart rate (r = -0.37 to -0.52; p less than 0.001). The longest and shortest R-R intervals in response to standing were distributed within beats 21-39 and 6-24, respectively. All tests were independent of sex. Log transformation was used to define the age-related lower limits of normal at the 2.3 centile for all tests of HRV, except for the E/I, Valsalva, and max/min 30:15 ratios. The results of these tests had to be analysed using a log(y-1) transformation. The intra-individual reproducibility determined on two consecutive days in 20 healthy subjects and 21 diabetic patients indicated that there were no major differences between the two groups regarding the day-to-day variation of test results, which was highest for the Valsalva ratio. We conclude that: (1) all indices of spectral and vector analyses of HRV are age-dependent and have the advantage of being independent of heart rate; (2) RMSSD, E-I difference, and the 30:15 ratio as it was used previously are not suitable for evaluation of autonomic dysfunction in diabetes; (3) log(y-1) transformation is required to determine age-dependent normal ranges and reproducibility for the three ratios.

Adolescent↗
PubMed1990

Spectral analysis of blood pressure and heart rate in conscious rats: effects of autonomic blockers.

We investigated the fluctuations which underly the spontaneous variability of blood pressure and heart rate in conscious rats. Intrafemoral blood pressure was computed to generate evenly spaced signals (systolic, diastolic, mean blood pressure, heart rate) at 200 ms intervals. This equidistant sampling allowed a direct spectral analysis using a Fast Fourier Transform algorithm. Systolic blood pressure and heart rate exhibited low-frequency oscillations (Mayer waves, 20-605 mHz) and a high- frequency oscillation related to respiration (1855 mHz). The respiratory fluctuations in heart rate were almost abolished by vagal blockade (atropine). Heart rate fluctuations in the low-frequency regime were diminished by vagal blockade or cardiac sympathetic blockade (atenolol). The respiratory frequency fluctuations in systolic blood pressure were markedly increased by alpha-sympathetic blockade (prazosin). In contrast, the low-frequency oscillations in systolic blood pressure were reduced by alpha-sympathetic blockade. These data indicate that in conscious rats: (1) the heart rate oscillation with respiration is vagally mediated; (2) the heart rate fluctuation in the low-frequency range is jointly mediated by beta-sympathetic and parasympathetic activities; (3) the respiratory oscillation in systolic blood pressure depends on fluctuations in cardiac output and is normally counteracted by the sympathetic tone; (4) the low-frequency oscillations in systolic blood pressure reflect the sympathetic activity to the resistance vessels.

Animals↗
PubMed1993

Power spectral analysis of the electroencephalographic and hemodynamic correlates of propofol anesthesia in the rat: intravenous bolus administration.

Based on the tail-flick response to noxious thermal stimuli, we determined in the present study that the minimal effective antinociceptive dose of propofol in adult, male Sprague-Dawley rats, given in an intravenous bolus manner, was 10 mg/kg. Simultaneous power spectral analysis of the electroencephalographic (EEG) and systemic arterial pressure signals further revealed a concomitant transient suppression of the EEG activity, primarily in the theta and sigma bands, alongside minor hypotensive and negative inotropic and chronotropic actions, but with maintained vasomotor tone. These alterations followed a time course that paralleled the plasma concentration of propofol in the arterial blood, as detected by high-performance liquid chromatography.

Anesthesia, Intravenous↗
PubMed2002

[Comparison of spectral analysis and non-linear analysis of EEG in patients with cognitive decline].

Twenty-five elder subjects were classified in two groups according to the MMS score and the cognitive evoked potentials. Normal subjects (n = 15) had mean MMS = 27.6 and mean P3 amplitude = 7.1 uV), while patients with cognitive decline (n = 10) had respective values of 18 (MMS) and 3.3 uV (P3). Spectral analysis and non-linear analysis of EEG (recurrence plots of dynamical systems) were performed and both showed statistically significant differences between groups for all the parameters analysed. Subjects' classification with discriminant analysis was slightly better using the non-linear parameters. The recurrence plot method applied to EEGs, gave similar results as the dimension of correlation (D2) calculation, and was in favour of a more constraint and less complex dynamics of brain activity associated with cognitive decline.

Aged↗
PubMed1996

Surface EMG reliability using spectral analysis.

Several papers have recently appeared in the literature questioning the usefulness of surface EMG in the management of temporomandibular dysfunction (TMD) patients. One of the concerns is the stability of EMG over time in any one patient. This study was undertaken on normal subjects to determine the level of surface EMG stability over time using a variety of spectral analysis parameters. Four male and seven female subjects, ranging from 24 to 38 years of age, were selected for the study. All subjects had class I occlusions, intact dentition and no history of TMD. Oral and perioral hard and soft tissues were within normal limits. EMG data from the bilateral masseter muscles were obtained during four states of jaw activity: rest, right-sided chewing, left-sided chewing, and 50% maximal clench. Three sets of recordings were obtained in each study session. Three 10-min study sessions were obtained for each subject. Six measures, which included SP-50, central frequency, band width, effective band width, zero crossings and power spectrum, were analysed to assess their reliability and sensitivity over time during the several states of jaw activity. The conclusion of the study was that bilateral masseter EMG band width, effective band width, and power spectrum in normal humans are all reliable enough to be stable over a 6 week period, and sensitive enough to differentiate among jaw rest, right chewing, left chewing and 50% clench; power spectra being the most sensitive.

Adult↗
PubMed1991

Spectral analysis of the electroencephalogram in neonatal rats chronically treated with the NMDA antagonist MK-801.

In order to study the involvement of NMDA-receptor activation in brain development, rat pups were chronically treated with the non-competitive NMDA antagonist MK-801 during the neonatal period. We recorded the cortical EEG at various vigilance states throughout the treatment period. Spectral analysis of the EEG showed reduced power in the delta (delta) frequency range (1.5-4 Hz) during quiet sleep and less power in the theta (theta) range (4-7 Hz) during REM-sleep in MK-801 animals than in controls. No significant differences were found for the total time spent in each of the different vigilance states. We conclude that chronic MK-801 treatment probably causes a developmental retardation in state-related brain activities.

Animals↗
PubMed1999

Autonomic function in the early stage of panic disorder: power spectral analysis of heart rate variability.

Previous studies of autonomic nervous system (ANS) function in panic disorder (PD) patients have yielded conflicting results. We speculate that these differences might result from the variety of clinical stages of PD. In order to investigate this, we compared ANS activity in untreated patients in the early stage of PD with control subjects using power spectral analysis of electrocardiogram R-R intervals (PSR-R) in supine rest and during head-up tilt, which was performed according to the maximum entropy method (MEM). It recognizes two main components: high-frequency power (HF), which mainly reflects cardiac parasympathetic activity, and low-frequency power (LF), which reflects both cardiac sympathetic and parasympathetic activity. The patients with PD had significantly higher values for all components of PSR-R only in tilt position total power (TP), LF, and HF than did the control subjects (P<0.01, <0.01, <0.02, respectively). However, the LF/HF ratio which indicated sympathovagal balance did not differ significantly between the two groups in tilt position. Our findings suggest that patients with PD in the early stage of illness have co-activation of sympathetic and parasympathetic nervous systems, which might act to maintain a balance between the two autonomic systems.

Adult↗
PubMed1975

Pulmonary mechanics by spectral analysis of forced random noise.

The magnitude (Zrs) and phase angle (thetars) of the total respiratory impedance (Zrs), from 3 to 45 Hz, were rapidly obtained by a modification of the forced oscillation method, in which a random noise pressure wave is imposed on the respiratory system at the mouth and compared to the induced random flow using Fourier and spectral analysis. No significant amplitude or phase errors were introduced by the instrumentation. 10 normals, 5 smokers, and 5 patients with chronic obstructive lung disease (COPD) were studied. Measurements of Zrs were corrected for the parallel shunt impedance of the mouth, which was independently measured during a Valsalva maneuver, and from which the mechanical properties of the mouth were derived. There were small differences in Zrs between normals and smokers but both behaved approximately like a second-order system with thetars = 0 degree in the range of 5--9 Hz, and thetars in the range of +40 degrees at 20 Hz and +60 degrees at 40 Hz. In COPD, thetars remained more negative (compared to normals and smokers) at all frequencies and crossed 0 between 15 and 29 Hz. Changes in Zrs, similar in those in COPD, were also observed at low lung volumes in normals. These changes, the effects of a bronchodilator in COPD, and deviations of Zrs from second-order behavior in normals, can best be explained by a two-compartment parallel model, in which time-constant discrepancies between the lung parenchyma and compliant airway keep compliant greater than inertial reactance, resulting in a more negative phase angle as frequency is increased.

Adult↗
PubMed1996

A functional model for G protein activation of the muscarinic K+ channel in guinea pig atrial myocytes. Spectral analysis of the effect of GTP on single-channel kinetics.

To elucidate the functional interaction between the active G protein subunit (GK*) and the cardiac muscarinic K+ (KACh) channel, the effect of intracellular GTP on the channel current fluctuation in the presence of 0.5 microM extracellular acetylcholine was examined in inside-out patches from guinea pig atrial myocytes using spectral analysis technique. The power density spectra of current fluctuations induced at various concentrations of GTP ([GTP]) were well fitted by the sum of two Lorentzian functions. Because the channel has one open state, the open-close transitions of the channel gate represented by the spectra could be described as C2<-->C1<-->O. As [GTP] was raised, the channel activity increased in a positive cooperative manner. The powers of the two Lorentzian components concomitantly increased, while the corner frequencies and the ratio of the powers at 0 Hz remained almost constant. This indicates that G protein activation did not affect the gating of each channel but mainly increased the number of functionally active channels in the patch to enhance the channel activity. Regulation of the number of functionally active channels could be described by a slow transition of the channel states, U (unavailable)<-->A (available), which is independent of the gating. The equilibrium of this slow transition was shifted by GTP from U to A. Monod-Wyman-Changeux's allosteric model for the channel state transition(U<-->A) could well describe the positive cooperative increase in the channel availability by GTP, assuming that, in the presence of saturating concentrations of ACh, [GK*] linearly increased as [GTP] was raised in our experimental range. The model indicates that the cardiac KACh channel could be described as a multimer composed of four or more functionally identical subunits, to each of which one GK* binds.

Animals↗