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Spectral analysis of photic stimulation in migraine.

In seeking an electrophysiologic discriminator of migraine, we applied computer technology to power spectral analysis of the EEG with photic stimulation. In 11 normal volunteers and 11 migraineurs (both classic and common) we were able to classify all migraineurs and misclassified only one normal based on the spectral analysis. The discriminator contained 5 elements: the increased driving power of migraineurs with photic stimulation at 24 flashes/sec, 34 flashes/sec, and 38 flashes/sec; and the increased power in the alpha band in both parietal and occipital leads at 20 flashes/sec. Power spectral analysis in conjunction with photic stimulation may provide the necessary data for effective discrimination of migraine from non-migraine states.

Adult↗

Artefacts in standard and time-dependent spectral analysis of arterial blood pressure signals obtained by Finapres: importance and correction.

The non-invasive Finapres (finger arterial pressure) device is widely used for the measurement of arterial blood pressure (BP) in BP variability studies, in particular in experimental studies. In our work, we have noticed that the calibration pauses of the Finapres, occurring approximately every 80 heart beats, introduce artefacts in standard and time-dependent spectral analysis of the arterial BP signal. This report describes these artefacts and indicates their dependence on the heart rate (HR) of the subject. In standard spectral analysis, they appear principally for low HR subjects, whereas in time-dependent spectral analysis, they distort the time-dependent spectrum both for low and high HR subjects. A possible correction procedure is presented which eliminates these pauses, causing minimal distortion from the original arterial BP time series. This correction keeps the total time-duration of the corrected signal equal to that of the original signal, thus allowing reliable spectral analysis of arterial BP fluctuations to be performed.

Adult↗

Amplitude spectral analysis of theta/alpha/beta waves in preterm infants.

The aim of this study is to clarify the usefulness of amplitude spectral analysis for the evaluation of maturational changes of theta, alpha, and beta activities in preterm infants. We chose 10 healthy infants, who were born without complications other than prematurity, who were 29-30 weeks, 31-32 weeks, and 33-34 weeks of postconceptional age, respectively, at time of electroencephalogram recordings. Fast Fourier transform algorithm was applied for amplitude spectral analysis. The analyzed data were divided into five frequency bands: theta 1 4-6 Hz, theta 2 6-8 Hz, alpha 8-13 Hz, beta 1 13-20 Hz, and beta 2 20-30 Hz. The average amplitude of six segments with continuous patterns with high-voltage slow waves of preterm infants was calculated in each frequency band. A significant reduction of the amplitude along with postconceptional age was present in all leads in theta 1 and theta 2 bands. On the other hand, a significant correlation with postconceptional age was not observed in alpha, beta 1, or beta 2 bands. In conclusion, maturational electroencephalographic changes assessed by amplitude spectral analysis were prominent in theta activities and were not remarkable in alpha or beta activities.

Brain↗

Spectral analysis of electroencephalography in premature newborn infants: normal ranges.

Continuous EEG monitoring has not been used widely in neonatal intensive care, especially in the care of extremely premature infants, probably in part because of a lack of a reliable quantitative method. The purpose of this study was to quantify the EEG of the very premature infants just after birth by using spectral analysis and to describe the characteristics of the spectral signal when infants were clinically stable. Digital EEG recordings were performed on 53 infants who were < or =30 wk gestation for 75 min each day during the first 4 d after birth. Artefact was rejected manually after visual inspection of trace. The EEG was analyzed by manual measurement of interburst interval and automatically by spectral analysis using Fast Fourier Transformation. Spectral analysis generated the normal ranges of the relative power of the delta (0.5-3.5 Hz), theta (4-7.5 Hz), alpha (8-12.5 Hz), and beta (13-30 Hz) frequency bands, spectral edge frequency, and symmetry. The median (range) relative power of the delta band increased significantly from 68% (62-76%) on day 1 to 81% (72-89%) on day 4 (p=0.001). The interburst intervals became progressively shorter between days 1 [14s (10-25)] and 3 [8s (6-12)]; there were no significant differences between days 3 and 4. The relative power of the delta band seemed to be the most useful and repeatable spectral measurement for continuous long-term monitoring. However, automatic artefact rejection software needs to be developed before continuous quantitative EEG monitoring can be used in the neonatal intensive care environment.

Age Factors↗

Spectral analysis of fetal heart rate variability as a predictor of intrapartum fetal distress.

OBJECTIVE: To evaluate the usefulness of power spectral analysis on fetal heart rate variability as a new diagnostic method of fetal distress. STUDY DESIGN: Among 76 pregnant women who underwent computerized electronic fetal monitoring and cord blood gas analysis, we divided them into three groups: normal fetus group (36); presumed distress group (26); and acidemic distress group (14). In order to perform linear analysis on the raw data of the fetal heart rate, after resampling, we performed Fourier transformation and investigated power distributions among very low frequency (VLF), low frequency (LF), high frequency (HF) bands, and autonomic balance (LF/HF). RESULTS: The results of the spectral analysis showed that in normal fetus group, the difference in the distribution of power spectrums of VLF, LF and HF was significantly higher than in presumed distress group and acidemic distress group. In fetal distress, the LF and VLF value (< or = 0.0023, > or = 0.0437) were good predictors (sensitivity 97.5%, 75.0% and specificity 86.1%, 94.4%). The LF value (< or = 0.0013) was a good predictor in fetal acidemia (sensitivity 97.5% and specificity 86.1%). CONCLUSIONS: A computerized spectral analysis of fetal heart rate variation is a good predictor of fetal distress, which is made automatically and objectively.

Adult↗

Impact of changes in respiratory frequency and posture on power spectral analysis of heart rate and systolic blood pressure variability in normal subjects and patients with heart failure.

1. Autonomic dysfunction is a major feature of congestive cardiac failure and may have an important role in determining progression and prognosis. The low-frequency/high-frequency ratio derived from power spectral analysis of heart rate variability has been proposed as a non-invasive method to assess sympatho-vagal balance. However, the effects of different respiratory rates or posture are rarely accounted for, but may be relevant in patients with heart failure in whom clinical improvement is accompanied by a fall in respiratory rate and an increased proportion of the day in the upright position. 2. We have assessed the effect of controlled respiration at different rates (10, 15, 20 breaths/min or 0.17, 0.25 and 0.33 Hz), while supine and standing, on power spectral analysis of heart rate and blood pressure variability in 11 patients with heart failure and 10 normal subjects. 3. Heart rate variance and low-frequency power (normalized units) were reduced in patients with heart failure (absent in six). During controlled breathing while supine, the power of the high-frequency component was significantly greater at 10 breaths/min than at 20 breaths/min in patients with heart failure, whether expressed in absolute units (P = 0.005) or percentage of total power (P = 0.03). 4. On standing, controlled breathing in patients with heart failure produced less change in high-frequency power (P = 0.054), but the low-frequency/high-frequency ratio at lower respiratory rates was reduced (P = 0.05). In normal subjects, as expected, respiratory rate had a highly significant effect on high-frequency power. Also, in normal subjects there was the expected increase in heart rate low-frequency power (P = 0.04) moving from supine to standing with an increase in the low-frequency/high-frequency ratio (P = 0.003), while in the patients with heart failure this was absent, reflecting blunted cardiovascular reflexes. 5. Systolic blood pressure low- and high-frequency components and their ratio were significantly affected by respiration (P < 0.03) and change in posture (P < 0.03) in both patients with heart failure and normal subjects, with a significant increase in the low-frequency/high-frequency ratio (P = 0.03) on standing in patients with heart failure, indicating that autonomic modulation of blood pressure is still operating in heart failure. 6. Thus, respiratory rate and changes in posture have a significant effect on measurements derived from spectral analysis of heart rate and blood pressure variability. Studies that use power spectral analysis as a measure of sympatho-vagal balance should control for these variables.

Adult↗

A comparison of period amplitude and power spectral analysis of sleep EEG in normal adults and depressed outpatients.

Three experiments were carried out to evaluate the relationship between two techniques for quantifying electroencephalographic (EEG) data during sleep: period amplitude analysis (PAA) and power spectral analysis (PSA). In Experiment 1, canonical correlations and regression analyses were computed on PSA and PAA data from 40 undergraduate volunteers. The results yielded an average canonical correlation of 0.98. Further, multiple regression analyses demonstrated that the PSA variables accounted for approximately 66% of the variance in the PAA data, whereas PAA variables captured 88% of the variance in the PSA data. Epoch-to-epoch correlations were higher for PAA measures than for PSA data, perhaps indicating greater stability of PSA measures across epochs of sleep. In Experiment 2, PSA and PAA data were compared in 17 unmedicated outpatients with unipolar depression. Canonical correlations and regression analyses indicated that the overlap in variance between PSA and PAA did not exceed 50%, regardless of whether PSA or PAA variables were used as predictors. Epoch-to-epoch correlations between PAA measures were significantly higher than correlations among PSA variables, again suggesting greater stability of PAA data across epochs of sleep. The range of correlations for either data set was, however, substantially lower in the depressed than in the normal group. Experiment 3 evaluated the possibility that filter settings and artifact-rejection procedures had contributed to reduced overlap in PSA-PAA variance and reduced stability in depressed patients. An additional group of eight healthy volunteers served as subjects. Findings in Experiment 3 indicated that methodological differences between Experiments 1 and 2 did not account for the reduced correlations in the depressed group. It was concluded that PSA and PAA data should be comparable in normal subjects but are relatively independent in depressed patients. Epoch-to-epoch correlations were higher for PAA data than those found between PSA measures in both normal subjects and depressed patients, suggesting that PAA may be more stable across sleep epochs. Reduced stability may be a reflection of nonstationarity in the EEG of depressed patients.

Adolescent↗

Noninvasive detection of iliac artery disease and prediction of its severity from Doppler spectral analysis in common femoral artery.

The direct interrogation of iliac artery disease (IAD) with color-coded duplex scanning is limited by the presence of intestinal gas or obesity. The purposes of this study were to examine the diagnostic accuracy of duplex ultrasound (DUS) analysis of spectral waves in common femoral artery (CFA) for detection of IAD and to predict its severity. DUS and arteriography were performed in 107 lower extremities in this study. The following were calculated from the CFA spectral waves obtained by DUS: peak systolic velocity (PSV), acceleration (PSV/pulse rise time), and deceleration (PSV/pulse decay time). In patients with isolated IAD, the treadmill exercise test was also performed to evaluate the ischemic severity expressed as recovery rate of ankle pressure index five minutes after exercise (RR-API). Forty-six lower extremities with IAD and 61 without IAD were diagnosed by arteriography. PSV was significantly reduced in lower extremities with IAD (109.5 +/- 32.7 vs 59.8 +/- 32.9 cm/s, P < 0.05). The deceleration detected IAD with a greater specificity and sensitivity vs acceleration (100.0 vs 82.0% and 97.8 vs 82.6%, respectively). Moreover, the acceleration and deceleration significantly correlated with the RR-API (r = 0.589, P < 0.05 and r = 0.779, P < 0.01, n = 14, respectively). The present evaluation is a simple and accurate technique to augment other examinations for detection of IAD and to assess its ischemic severity.

Angiography, Digital Subtraction↗

[The method of time series modeling and its application in the spectral analysis of lubricating oil].

In this paper, we discuss the applications of time series modeling method in the analysis of lubricating oil of mechanical equipment. We obtained satisfactory results by applying AR model to perform time series modeling and forecasting analysis to the collected spectral analysis data of the air engine. So we have built a practical method for state monitoring and trouble forecasting of mechanical equipment.

English Abstract↗

Spectral analysis of the systolic blood pressure signal in secondary hypertension: a method for the identification of phaeochromocytoma.

OBJECTIVE: To seek in hypertensive patients rhythmic variations of the systolic blood pressure signal obtained by ambulatory blood pressure monitoring of any inherent cycle of intermediate value between 1 and 24 h. DESIGN: Subjects (62 hypertensive, 39 normotensive) were evaluated by 24-h ambulatory blood pressure monitoring. The hypertensive group consisted of 48 patients with essential hypertension, nine with renovascular hypertension and five with phaeochromocytoma. The groups were matched for age and weight. METHODS: The ambulatory systolic blood pressure recording served as the input for a filtering procedure that rejected unacceptable values according to predetermined criteria. The whole-day systolic blood pressure series thus obtained were subjected to Fourier analysis to obtain a spectral analysis of daily systolic blood pressure fluctuations. Daily (first 12 h), nightly (second 12 h) and whole-day average systolic blood pressure values were calculated and compared for the various groups. RESULTS: The average nocturnal systolic blood pressure was found to be lower than its daily counterpart in the normal subjects and in the patients with essential hypertension, whereas in the patients with renovascular hypertension or phaeochromocytoma no such nocturnal decrease was found. The power spectrum of patients with phaeochromocytoma was statistically different from that of other aetiologies of hypertension. This was achieved due mainly to a statistically significant difference in the power spectrum integral over the low-frequency band (0-0.2 cycles/h) of the power spectrum of the 24-h systolic blood pressure signal. Resection of the phaeochromocytoma normalized the power spectrum as found by analysis of the postoperative ambulatory blood pressure monitoring data in two patients who underwent a repeat recording. CONCLUSIONS: The technique described enables the discrimination of patients with phaeochromocytoma as a cause of hypertension from other aetiologies of hypertension. Patients with renovascular hypertension could not be distinguished from those with essential hypertension on the basis of their power spectrum. However, this technique may prove to be a valuable modality for characterizing hypertensive patients of different aetiologies.

Activity Cycles↗

[Application of digital filtering and phase spectral analysis to middle latency response and 40Hz event related potential in central nerve system disorders].

40Hz event related potential, or 40Hz-ERP, described by Galambos in 1981 has been considered as the useful potential in predicting hearing threshold across the audiometric frequencies. Although 40Hz-ERP was reported by Galambos as the summation of middle latency responses (MLR), its origin has not been clarified. Moreover reports of the clinical use of 40Hz-ERP in patients with the neurological disorders were rare. Therefore, we recorded ABR, MLR and 40Hz-ERP in 35 patients with central nerve system disorders, or CNS disorders, and analysed the relation between central lesions and modality of MLR- or 40Hz-ERP from the view point of phase spectral analysis comparing with the digital filtered waveform analysis. For the phase spectral analysis, synchrony measure method described by Fridman in 1984 was applied to MLR and 40Hz-ERP. Following results were obtained. 1) By the digital filtered waveform analysis, the latencies of Po, Na, Pa and the amplitudes of Po, Na, Pa, Nb were recorded clearly in normal cases. In cases with the central lesions, many of them were revealed reduction of the amplitude of Po, but other parameters were not useful for the detection of CNS disorders because of their wide normal ranges. 2) The parameters of the phase spectral analysis were obtained from 17 records of the normal subjects. The SM (30 + 40 + 50Hz), which is the average of CSM 30Hz, CSM 40Hz and CSM 50Hz, was applied to MLR, and the SM (40 + 80 + 120Hz) was applied to 40Hz-ERP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Spectral analysis of the DNA targeting bisalkylaminoanthraquinone DRAQ5 in intact living cells.

BACKGROUND: We report on the potential DNA binding modes and spectral characteristics of the cell-permeant far red fluorescent DNA dye, DRAQ5, in solution and bound within intact cells. Our aim was to determine the constraints for its use in flow cytometry and bioimaging. METHODS: Solution characteristics and quantum yields were determined by spectroscopy. DRAQ5 binding to nuclear DNA was analyzed using fluorescence quenching of Hoechst 33342 dye, emission profiling by flow cytometry, and spectral confocal laser scanning microscopy of the complex DRAQ5 emission spectrum. Cell cycle profiling utilized an EGFP-cyclin B1 reporter as an independent marker of cell age. Molecular modeling was used to explore the modes of DNA binding. RESULTS: DRAQ5 showed a low quantum yield in solution and a spectral shift upon DNA binding, but no significant fluorescence enhancement. DRAQ5 caused a reduction in the fluorescence intensity of Hoechst 33342 in live cells prelabeled with the UV excitable dye, consistent with molecular modeling that suggests AT preference and an engagement of the minor groove. In vivo spectral analysis of DRAQ5 demonstrated shifts to longer wavelengths upon binding with DNA. Analysis of spectral windows of the dual emission peaks at 681 and 707 nm in cells showed that cell cycle compartment recognition was independent of the far red-near IR emission wavelengths monitored. CONCLUSIONS: The study provides new clues to modes of DNA binding of the modified anthraquinone molecule in vivo, and its AT base-pair selectivity. The combination of low quantum yield but high DNA affinity explains the favorable signal-to-noise profile of DRAQ5-nuclear fluorescence. The robust nature of cell cycle reporting using DRAQ5, even when restricted spectral windows are selected, facilitates the analysis of encroaching spectral emissions from other fluorescent reporters, including GFP-tagged proteins.

Anthraquinones↗

[Studies on the effects of constant exercise around the ventilatory threshold using spectral analysis of EMG and ECG-RR interval variability].

The effects constant exercise at three levels around the ventilatory threshold (VT) were investigated by spectral analysis of EMG and RR interval variability of ECG. The subjects were 11 healthy male students (ranging from 20 to 25 years old). Surface EMG from the knee extensor muscular (m. vastus medialis) and the RR interval of the ECG were recorded by bicycle ergometer during the three levels of exercise which were 20% less than the VT level (-20% VT), the VT level and 20% more than the VT level (+20 VT). Power spectral analysis of EMG was performed to obtain the power spectral density (PSD) of 4 bands (20-50Hz, 50-100Hz, 100-150Hz, 150-200Hz) every 2 seconds by the maximum entropy method (MEM). Power spectral analysis of RR interval variability of ECG was performed every 1 minute by MEM to obtain the low-frequency band (LFB, 0.04 to 0.15 Hz), the high-frequency band (HFB, 0.15 to 0.4 Hz) and the ratio of LFB to HFB (L/H ratio). Changes in Total PSD from 20 Hz to 200 Hz on EMG showed a higher value at the +20 VT level than at the VT level or -20 VT level. The %PSD of EMG at the band of 100-150 Hz and 150-200 Hz increased in the work load at the +20 VT level more than at the VT level or -20 VT level. Comparisons of the EMG parameters suggested a progressive recruitment of fast twitch fibers (type II b) with time. HF component of the RR interval variability showed a rapid decrease in proportion to load, whereas there was no such trend in the L/H ratio during the 3 levels of constant exercise levels. In each case, HF components of RR interval variability could be used as an indicator of parasympathetic nervous activities, but the L/H ratio did not clearly show sympathetic nervous activities during the constant exercise.

Adult↗

Spectral analysis of EEG during carotid endarterectomy.

Spectral analysis of the electroencephalogram (EEG) was monitored during 105 carotid endarterectomies. Seventy-eight percent of the patients showed no significant change in EEG spectral power as a result of clamping of the internal carotid artery. Two patterns of change were observed in the remaining 22% of patients: partial reduction (significant decrease of power in one or two of three frequency bands) and global reduction (significant decrease of power in all three frequency bands). High frequencies (over 10.5 Hz) changed more frequently with clamping than did low frequencies (less than 6 Hz), but reduction of high frequencies alone was tolerated with no postoperative deficits. The only non-shunted patient demonstrating global EEG reduction for the duration of carotid clamping suffered a transient hemiparesis.

Aged↗

Ictal video-polysomnography and EEG spectral analysis in a child with severe Panayiotopoulos syndrome.

OBJECTIVE: To describe the ictal polysomnographic features of a patient with Panayiotopoulos syndrome, a peculiar epileptic syndrome characterized by infrequent, often single, prolonged, nocturnal, focal seizures comprising an unusual constellation of autonomic symptoms (malaise, nausea, pallor, tachycardia, vomiting) and unilateral deviation of the eyes at the onset of seizures. These clinical, ictal manifestations are rarely followed by post-ictal headache. In the literature, there is little information on the ictal EEG characteristics of Panayiotopoulos syndrome and, in particular, on certain autonomic manifestations, such as tachycardia, as the sole ictal phenomena at the onset of seizures. METHODS AND RESULTS: One, all-night videopolysomnography, during which one seizure was recorded. Video-EEG data were evaluated visually and by means of quantitative spectral analysis. The spectral analysis of the recorded seizure showed a complex ictal pattern of cortical involvement with focal onset in the right occipital area followed by the recruitment of widespread extra-occipital cortical regions. CONCLUSIONS: This is the first such analysis of this peculiar epileptic condition. Most of the symptoms were consistent with a diagnosis of severe Panayiotopoulos syndrome, although the patient also presented "atypical findings": a relatively high frequency of seizures, post-ictal headache, no spontaneous remission of seizures with age, and late onset of visual hallucinations; this last finding is more frequent in "Gastaut-type childhood occipital epilepsy", in which onset typically occurs later than in Panayiotopoulos syndrome. [Published with video sequences].

Anticonvulsants↗

Digital filtering and spectral analysis of the low intensity ABR.

Spectral analysis along with zero and standard-phase shift digital filtering were performed on evoked potentials recorded from 12 normal hearing subjects. The results indicated a progressive shifting of the mean spectral content of the ABR toward the low frequencies as the stimulus intensity was lowered. Despite this, the effects of zero-phase shift high-pass digital filtering at 100 Hz (36 dB/oct) did not significantly differ between waveforms elicited by a 75 dB nHL, 55 dB nHL, and 35 dB nHL stimulus. The major response frequency of the ABR is related to the distance between the peak (IV/V) and the following major trough (approximates one-half the response period). In waveforms where the major trough occurred before 10 msec, the use of 100 Hz, 36 dB/oct, zero-phase shift high-pass filters produced only a small reduction in response amplitude, even at low stimulus intensity levels. Waveforms which had a major trough (Na1) between 10 to 15 msec were reduced in amplitude by 100 Hz, 36 dB/oct, zero-phase shift high-pass filters (the longer period of the response energy in these waveforms corresponds to a lower energy frequency). However, this trough has a latency that prevents it from being recorded on a 10 msec time base or defined as an ABR. Based on these results, the use of zero-phase shift high-pass filters with a high-pass cutoff frequency that is equal to or less than the resolution of the time base (1/time base) appears to be a desirable method of reducing muscle artifact and other electrical contamination of the ABR.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Amplitude spectral analysis of maturational changes of delta waves in preterm infants.

The aim of this study is to clarify the usefulness of amplitude spectral analysis for an evaluation of maturational changes of delta activities in preterm infants. We chose each ten healthy infants without complications who were 29-30, 31-32, and 33-34 weeks of post-conceptional age (PCA) at electroencephalogram (EEG) recordings. Fast Fourier transform algorithm was applied for amplitude spectral analysis. The analyzed data were divided into four frequency bands; D1 0.53-1, D2 1-2, D3 2-3, and D4 3-4Hz. The average amplitude of six segments with high voltage slow waves was calculated in each frequency band. A significant reduction of the amplitude along with PCA was present in all leads in D1 band. On the other hand, a significant negative correlation with PCA was observed only in the occipital leads in D2, D3 or D4 bands. In conclusion, maturational EEG changes assessed by amplitude spectral analysis were prominent in the occipital areas, and in the frequency less than 1Hz.

Algorithms↗

Which linear compartmental systems can be analyzed by spectral analysis of PET output data summed over all compartments?

General linear time-invariant compartmental systems were examined to determine which systems meet the conditions necessary for application of the spectral analysis technique to the sum of the concentrations in all compartments. Spectral analysis can be used to characterize the reversible and irreversible components of the system and to estimate the minimum number of compartments, but it applies only to systems in which the measured data can be expressed as a positively weighted sum of convolution integrals of the input function with an exponential function that has real-valued nonpositive decay constants. The conditions are met by compartmental systems that are strongly connected, have exchange of material with the environment confined to a single compartment, and do not contain cycles, i.e., there is no possibility for material to pass from one compartment through two or more compartments back to the initial compartment. Certain noncyclic systems with traps, systems with cycles that obey a specified loop condition, and noninterconnected collections of such systems also meet the conditions. Dynamic positron emission tomographic data obtained after injection of a radiotracer, the kinetics of which can be described by any model in the class of models identified here, can be appropriately analyzed with the spectral analysis technique.

Algorithms↗