Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spectral Analysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37Linked to original sources
PubMed1994

Power spectral analysis of electroencephalographic desynchronization induced by cocaine in rats: correlation with microdialysis evaluation of dopaminergic neurotransmission at the medial prefrontal cortex.

We evaluated the effect and action mechanisms of cocaine on electroencephalographic (EEG) activity in adult male Sprague-Dawley rats anesthetized with chloral hydrate (400 mg/kg, i.p., with 80 mg/kg/h supplements). On-line and real-time power spectral analysis of the EEG activity continuously quantified its root mean square (RMS) and mean power frequency (MPF) values, and the power of its spectral frequency components (low frequency: 0-4 Hz; high frequency: 4-20 Hz). Administration of cocaine (1.5 or 3.0 mg/kg, i.v.) dose-dependently induced EEG desynchronization, as manifested by a reduction in RMS and an elevation in MPF values, coupled with a differential decrease in both high and low frequency components. Samples collected by in vivo microdialysis at the medial prefrontal cortex (mPFC) and analyzed by HPLC showed that the elevation of cocaine and dopamine (DA) level in the dialysate reached its peak during the time interval when maximal activation of EEG occurred. This EEG activation was antagonized by microinfusion into the mPFC via reverse microdialysis of R(+)-SCH 23390, a selective antagonist for D-1 receptors; sulpiride, a selective antagonist for D-2 receptors; or haloperidol, a nonspecific dopamine antagonist. These results suggest that dopaminergic neurotransmission at the mPFC may be intimately related to the specific spectral pattern of alteration in EEG activity elicited by cocaine in the rat and that both D-1 and D-2 receptors may be involved in the process.

Animals↗
PubMed1993

Spectral analysis of the electroencephalographic response to motion sickness.

Ten subjects participated in a laboratory experiment using cross-coupled angular stimulation to induce motion sickness symptoms. A 14-channel montage using subdermal electrodes was employed to record the electroencephalogram during a pre-Coriolis stimulation baseline through to imminent emesis. Spectral analyses of the EEG were performed upon the recorded data and individual band energies were quantified to attempt to characterize the cortical electrical response to motion sickness. Power spectral analysis was performed upon the temporo-frontal signals through the entire period over the delta, theta, and alpha EEG bands. The power in each of these bands was integrated and the baseline periods compared with that during frank sickness. Mean power spectral energy in the delta band during frank sickness increased by a factor of 13.7 over baseline. Mean theta band energy increased by a factor of 2.2. Mean alpha band energy was not significantly different. EEG power spectral levels in the delta and theta bands increased along with the level of motion sickness symptoms. These changes, particularly those in the delta band, suggest that intense low frequency oscillatory stimulation is being diffusely projected about the central nervous system. These EEG changes, similar to those sometimes seen in partial seizures, and the similarity of the symptom/sign complex in the two disorders, provide evidence that the pathophysiology and electrophysiology of motion sickness may be a variant of seizure activity.

Adult↗
PubMed2000

Power spectral analysis of R-R interval variability before and during the sinusoidal heart rate pattern in fetal lambs.

OBJECTIVE: The appearance of the sinusoidal heart rate pattern found on fetal cardiotocograms has not been fully explained, either physiologically or clinically. In this study we performed power spectral analysis on the sinusoidal heart rate pattern obtained by administration of arginine vasopressin and atropine sulfate to investigate its frequency components in fetal lambs with long-term instrument implantation. STUDY DESIGN: Eleven tests were performed in 4 fetal lambs at 120 to 130 days' gestation. An artificial sinusoidal heart rate pattern was obtained by administration of atropine sulfate and arginine vasopressin in 9 tests. An autoregression model was used to compare the spectral patterns before and during the sinusoidal heart rate pattern. RESULTS: Marked decreases in low-frequency (0.025-0.125 cycles/beat) and high-frequency (0.2-0.5 cycles/beat) areas were observed in the presence of the sinusoidal heart rate pattern. However, there were no significant changes in the very-low-frequency area (0.01-0.025 cycles/beat), which corresponds to the frequency of the sinusoidal heart rate pattern. CONCLUSION: The sinusoidal heart rate pattern may represent a very low-frequency component inherent in fetal heart rate variability that appears when low- and high-frequency components are reduced as a result of strongly suppressed autonomic nervous activity.

Animals↗
PubMed1994

Effects of antihypertensive drugs on flow disturbances: nifedipine, captopril, and metoprolol evaluated by quantitative spectral analysis of Doppler flow patterns in patients with carotid stenosis.

Hemodynamic theories of atherogenesis suggest that flow disturbances (departures from laminar flow including high and low shear) and increases in heart rate may be important in the initiation, progression, and complications of atherosclerosis such as dissection and embolism. It is therefore desirable to evaluate the effects of antihypertensive drugs on the occurrence of such flow disturbances. Effects of metoprolol, nifedipine, and captopril were studied, by quantitative spectral analysis, in 20 patients with carotid stenosis to evaluate 3 indices of disturbed flow: peak velocity, spectral broadening index and window index (WI). Heart rate (HR), and the product of WI by HR, were improved (reduced) significantly by metoprolol (p < 0.05), and worsened by nifedipine (p < 0.05), but most of the effect was due to effects on heart rate. These findings suggest that most of the benefit of antihypertensive drugs on flow disturbances can be identified by counting heart rate. Further developments will require improved methods for quantitation of flow disturbances.

Aged↗
PubMed1997

Spectral analysis of intercycle heart fluctuations in the diethyl-ether-anaesthetized or pithed rat treated with l-hyoscyamine.

1. Within the context of neural regulation of the activity of sinus node pacemaker cells, the study of heart rate variability, as explored in the frequency domain by spectral analysis, was proposed about 15 years ago as a quantitative tool for the evaluation of short-term autonomic cardiovascular control. It has since been postulated that the two main oscillations observed, one at low and the other at high frequency, may respectively be markers of sympathetic vs. vagal efferent cardiac activity, and that the low- and high-frequency signals may reflect a reciprocal or 'push-pull' relationship between sympathetic and parasympathetic control. 2. In our power spectra assessment, ECG R-R intervals were submitted to fast Fourier transformation analysis in order to study the mechanisms underlying the control of heart beats in rats. Data were acquired in conditions of steady arterial blood pressure and cardiac and respiratory activity (spontaneous or artificially stimulated) in diethyl-ether-anaesthetized and pithed rats, as well as in a group of control rats, all in the presence and absence of l-hyoscyamine. 3. With increasing doses of the parasympathetic antagonist, the fractal dimension of the time-series structure remained stable in most cases. The low-frequency spectral component narrowed with increasing drug doses and the high-frequency band underwent either no, or only very slight, changes. 4. In these rodent assays, the low- and high-frequency signals cannot be interpreted as a push-pull relationship between sympathetic and parasympathetic control.

Anesthetics, Inhalation↗
PubMed1998

Effects of clonidine on power spectral analysis of heart rate variability in mild essential hypertension.

Patients with essential hypertension often show alterations of the autonomic nervous system. We evaluated the sympathetic and parasympathetic drive to the heart in 12 mildly hypertensive patients and 9 healthy subjects by power spectral analysis of heart rate variability. All subjects underwent measurements of RR interval, low (LF) and high frequency (HF) components of heart rate variability, LF/HF ratio and blood pressure in the resting and sitting positions, both before and after oral clonidine (300 microg), a central sympatholytic agent. In the supine position before clonidine, hypertensive patients had higher blood pressure and lower HF values than healthy subjects. Clonidine induced increases in RR interval and HF in both groups, while LF and LF/HF ratio decreased in healthy subjects, but not in hypertensive patients. On assuming the sitting position, both groups showed reductions in RR and HF and increments in LF and LF/HF. In healthy subjects, the response to the postural challenge was unaffected by clonidine. In contrast, hypertensive patients showed no changes in LF and LF/HF ratio, and a significantly lower decrease in HF. These differences were probably due to the existence of two subsets of patients, one exhibiting similar responses to clonidine as healthy subjects, and the other showing no appreciable response to the drug. These results suggest that hypertensive patients have an altered sympatho-vagal balance to the heart, which can be unmasked by clonidine. This phenomenon should be taken into account to achieve a better control of the overall cardiovascular risk of hypertensive patients.

Administration, Oral↗
PubMed1981

Spectral analysis of EEG in the late course of primary generalized myoclonic-astatic epilepsy. I. EEG and clinical data.

The EEG of 38 patients suffering from primary generalized myoclonic astatic epilepsy since early childhood is studied in late stages of the disease. Spectral analysis shows that parietal 4-7 cps rhythms (theta rhythms) which are typical of the EEG in the early stages of the disorder can still exist in the EEG of the adult. The rhythms seem to be related to the course of the epilepsy. In the EEG of patients who still have seizures rhythms occur more often than in the EEG of patients who are free of seizures in the two years before the reexamination of their EEG. The functional anomaly producing a 4-7 cps rhythmization of the parietal EEG seems to be one pathogenetic factor in some epileptic disorders of early childhood, especially in primary generalized myoclonic-astatic epilepsy.

Adolescent↗
PubMed1998

Autonomic effects of nicotine patch administration in habitual cigarette smokers: a double-blind, placebo-controlled study using spectral analysis of RR interval and systolic arterial pressure variabilities.

Nicotine patch administration is often used to sustain tobacco abstinence in smoking-cessation programs. There is some concern regarding safety issues, as a consequence of the sympathomimetic action of nicotine. We used spectral analysis of RR interval and (noninvasive) systolic arterial pressure (SAP) beat-by-beat variabilities in a crossover double-blind design to assess the autonomic effects of cigarette smoking, of transdermal nicotine, and of placebo. The study group consisted of 27 heavy smokers (age 43 +/- 2 years). The RR interval and its variability were significantly reduced in the smoking group, as compared with nicotine or placebo groups. The LF component of RR interval variability (in normalized units, nu), and the LF/HF ratio showed greatest values during smoking, as compared with placebo. Values of LF(RR) and LF/HF during nicotine patch treatment were slightly, but not significantly, greater than observed with placebo. No differences were observed in SAP and its variability components. The index alpha (a frequency domain measure of baroreflex gain) was minimal in the smoking period. Habitual cigarette smoking is associated with signs of sympathetic predominance in the autonomic control of the sinoatrial (SA) node. Nicotine patches produce only minor disturbances of autonomic regulation. This corroborates their safe use in smoking-cessation strategies.

Administration, Cutaneous↗
PubMed2003

Temperature-dependent near-infrared spectra of bovine serum albumin in aqueous solutions: spectral analysis by principal component analysis and evolving factor analysis.

Fourier transform near-infrared (FT-NIR) spectra have been measured for bovine serum albumin (BSA) in an aqueous solution (pH 6.8) with a concentration of 5.0 wt% over a temperature range of 45-85 degrees C. Not only conventional spectral analysis methods, such as second-derivative spectra and difference spectra, but also chemometrics, such as principal component analysis (PCA) and evolving factor analysis (EFA), have been employed to analyze the temperature-dependent NIR spectra in the 7500-5500 and 4900-4200 cm-1 regions of the BSA aqueous solution. Intensity changes of bands in the 7200-6600 cm-1 and 4650-4500 cm-1 regions in the difference spectra indicate variations of the hydration and secondary structure of BSA in the aqueous solution, respectively. The plot of a band intensity at 7080 cm-1 in the different spectra shows a clear turning point at 63 degrees C, revealing that a significant change in the hydration occurs at about 63 degrees C. The forward and backward eigenvalues (EVs) from EFA suggest that marked changes in the hydration and secondary structure of BSA take place in the temperature ranges of 61-65 degrees C and 59-63 degrees C, respectively. In addition, the temperature of 71 degrees C marked in the EFA plots may correspond to the onset temperature of increase in the intermolecular beta-sheet structure.

Animals↗
PubMed1997

Impact of liver transplantation on autonomic neuropathy in familial amyloidotic polyneuropathy: an evaluation by spectral analysis of heart rate variability.

OBJECTIVES: To evaluate the impact of liver transplantation on familial amyloidotic polyneuropathy type I (FAP) patients' autonomic neuropathy. DESIGN: An open study. SETTING: A tertiary referral centre. SUBJECTS: Twelve liver-transplanted FAP patients evaluated before and one year or longer after liver transplantation. INTERVENTIONS: Spectral analysis of heart rate variability. The low-frequency band after tilting (sympathetic), and the high-frequency band in supine position (parasympathetic) were analysed, as were the pulse and blood pressure reaction to tilting. Clinical symptoms related to autonomic disturbances were recorded. MAIN OUTCOME MEASURES: Spectral band power for sympathetic and parasympathetic activity. RESULTS: No statistically significant improvements in sympathetic or parasympathetic band power after liver transplantation was found (sympathetic band power: 2.7 (2.2-3.2) before, 2.9 (2.2-3.6) after; parasympathetic 2.0 (1.6-2.4) before and 2.0 (1.7-2.3) after. A significant correlation was noted between orthostatic blood pressure reaction and sympathetic activity before transplantation, but not after the operation. A trend was noted for improved orthostatic blood pressure reaction. Symptomatic improvements in bowel function and orthostatic symptoms were reported by several patients. CONCLUSIONS: Although improvements in autonomic symptoms are reported after liver transplantation, no significant improvement is noted in sympathetic or parasympathetic spectral band power of heart rate variability. However, the follow-up period of 17 months may be too short. Further evaluation after an additional two and four years is needed.

Adult↗
PubMed1985

Hemodynamic regulation: investigation by spectral analysis.

We investigated the hypothesis that beat-to-beat variability in hemodynamic parameters reflects the dynamic interplay between ongoing perturbations to circulatory function and the compensatory response of short-term cardiovascular control systems. Spontaneous fluctuations in heart rate (HR), arterial blood pressure, and respiration were analyzed by spectral analysis in the 0.02- to 1-Hz frequency range. A simple closed-loop model of short-term cardiovascular control was proposed and evaluated in a series of experiments: pharmacological blockades of the parasympathetic, alpha-sympathetic, beta-sympathetic, and renin-angiotensin systems were used to open the principal control loops in order to examine changes in the spectral pattern of the fluctuations. Atrial pacing was used to examine blood pressure variability in the absence of HR variability. We found that respiratory frequency fluctuations in HR are parasympathetically mediated and that blood pressure fluctuations at this frequency result almost entirely from the direct effect of centrally mediated HR fluctuations. The sympathetic nervous system appears to be too sluggish to mediate respiratory frequency variations. Low-frequency (0.02-0.09 Hz) fluctuations in HR are jointly mediated by the parasympathetic and beta-sympathetic systems and appear to compensate for blood pressure fluctuations at this frequency. Low-frequency blood pressure fluctuations are probably due to variability in vasomotor activity which is normally damped by renin-angiotensin system activity. Blockade of the alpha-adrenergic system, however, does not significantly alter low-frequency blood pressure fluctuations.

Animals↗
PubMed2001

Fourier transform infrared and Raman spectral analysis of trans-1,4-polyisoprene.

Polyisoprene is the most widely used polymer in industry and commerce. Fourier transform infrared (FTIR) and Raman spectra of trans-1,4-polyisoprene have been recorded in the range of 4000-400 and 4000-100 cm(-1), respectively. In the present investigation, detailed assignments of the observed fundamental bands of trans-1,4-polyisoprene has been analysed in terms of peak positions and relative intensities. With the hope of providing more and effective information on the fundamental vibrations, a normal co-ordinate analysis has been performed on trans-1,4polyisoprene, by assuming Cs symmetry. The simple general valance force field (SGVFF) method has been employed in normal co-ordinate analysis and to calculate the potential energy distribution (PED) for each fundamental vibration. The PED contribution corresponding to each of the observed frequencies shows the reliability and accuracy of the spectral analysis. The validity of the SGVFF method as a practical tool for complete analysis of vibrational spectra, even for a polymer of this complexity, is confirmed in the present work.

Hemiterpenes↗
PubMed1994

Effects of heart rate on phasic coronary blood flow pattern and flow reserve in patients with normal coronary arteries: a study with an intravascular Doppler catheter and spectral analysis.

To assess the effects of pacing-induced tachycardia on phasic coronary blood flow pattern and flow reserve of left anterior descending artery, we examined 16 patients with chest pain and angiographically normal coronary arteries by using an intravascular Doppler catheter with spectral analysis of the velocity signal. The heart rate was increased from a mean of 68 +/- 11 beats/min during sinus rhythm to 100 beats/min and again to 120 beats/min. Cross-sectional area of the epicardial artery and resting systolic and diastolic coronary blood flows increased progressively, resulting in an elevation of total coronary flow from 142 +/- 54 ml/min during sinus rhythm to 190 +/- 66 ml/min at 100 beats/min (p < 0.05) and to 219 +/- 69 ml/min at 120 beats/min (p < 0.01). During maximal hyperemia with intracoronary injection of 10 to 12 mg of papaverine, there was an increase in the systolic coronary blood flow with a decrease in the diastolic flow, resulting in no significant change in the total flow. These alterations led to progressive reductions in coronary flow reserve from 3.9 +/- 0.7 during sinus rhythm to 2.9 +/- 0.9 at 100 beats/min (p < 0.01) and to 2.3 +/- 0.3 at 120 beats/min (p < 0.001). Thus careful consideration should be given to the effects of heart rate when phasic coronary blood flow pattern and flow reserve are assessed.

Adult↗
PubMed2002

Spectral analysis of prespeech sounds (spontaneous cries) in infants with unilateral cleft lip and palate (UCLP): a pilot study.

OBJECTIVE: The objectives of the present study were: (1) to analyze the cry features of infants with cleft lip and palate (UCLP) by means of spectral analysis, (2) to describe changes of the acoustic parameters from birth until 9 months of age, and (3) to compare these data with existing cry data of infants without cleft (control group). DESIGN: The study was designed on a interdisciplinary, prospective, and longitudinal basis. SETTING: Interdisciplinary study: (1) Institute of Anthropology at the Humboldt-University, Berlin; (2) Heidelberg University Hospital: Interdisciplinary Cleft Palate and Craniofacial Center. PATIENTS AND METHOD: The cry parameters of five patients with complete unilateral cleft lip, alveolar ridge, and hard and soft palate were analyzed from birth to 9 months of age. The patients were treated with the same protocol. At the age of 24 months, sensomotor development was assessed using the KIPHARD test. Perceptual judgment of speech, performed after 36 months of life, included nasal resonance, nasal emission of air, articulation disorders, and speech intelligibility. MAIN OUTCOME MEASURE: The cry parameters of fundamental frequency (F(0)), pitch period perturbation quotient (PPQ), and cry duration (Tsam) were analyzed. RESULTS: Contrary to the expectation that laryngeal parameters are not affected by vocal tract malformations, differences of cry parameters were found between the patients with UCLP and the non-cleft group. Particularly, the F(0) and its short-time variability (PPQ) were affected. CONCLUSIONS: The preliminary results of this study showed that F(0) and PPQ of spontaneous cries are influenced in patients with UCLP, and a cry analysis might become a noninvasive tool for early detection of an at-risk status for neuromuscular development and prediction of an at-risk status for later speech and language acquisition in infants with cleft lip and palate. Future research strategies are outlined.

Articulation Disorders↗
PubMed1999

Metabolic activity patterns in the monkey visual cortex as revealed by spectral analysis.

The metabolic activity pattern of the monkey visual cortex was mapped quantitatively with [14C]-2-deoxyglucose during the performance of a visually guided reaching task. After bandpass filtering of the reconstructed two-dimensional metabolic maps of areas V1 and V2, alternating bands of high and low metabolic activity were apparent in control and experimental hemispheres. The spatial arrangement of active bands was studied with two-dimensional spectral analysis, and bands were found to be more organized in the experimental monkey. In area V1 of the control monkey the spectral amplitude was spread over a wider range of directions and frequencies than in the experimental subject. The finding that layer IV is characterized by more complex spectra than layers I through III suggests the coexistence of more than one active columnar system in the geniculorecipient layer. In area V2, stripes running almost perpendicular to the V1/V2 border were found along with superimposed patches of enhanced metabolic activity. In the experimental hemispheres, the corresponding spectra were extremely sharp yielding a constant periodicity. It is suggested that the well-organized columnar arrangement within areas V1 and V2 of the experimental hemispheres emerges from the diffusely organized background network of activity patterns in the control state.

Algorithms↗
PubMed2004

A simplified procedure for the reduction and alkylation of cysteine residues in proteins prior to proteolytic digestion and mass spectral analysis.

A procedure for reduction and alkylation of cysteine residues in proteins was developed using the volatile reagents triethylphosphine and iodoethanol. These reagents may be used to modify proteins in solution, as well as proteins in gel slices, prior to proteolytic digestion and mass spectral analysis. The procedure eliminates several steps with both types of samples. Samples in solution do not need to be desalted following reduction and alkylation, with excess reagent being removed under vacuum. For gel slices, the procedure combines washing, destaining, reduction and alkylation into a single step. The procedure was applied successfully to samples as complex as serum, and we demonstrated alkylation of cysteines to be quantitative in purified proteins. We also were able to reduce and alkylate proteins with these reagents during the gas phase. Elimination of the need for desalting of samples after reaction raised the possibility of automation of the procedure for liquid samples, which is difficult with conventional reduction and alkylation chemistries.

Alkylating Agents↗
PubMed1982

Carotid artery occlusion following endarterectomy: evaluation by spectral analysis of Doppler ultrasound signals.

The clinical results of carotid endarterectomy are well documented, but there is little objective information on the incidence of postoperative occlusion. We have studied the postoperative patency of the internal and external carotid arteries using continuous wave Doppler ultrasound with spectral analysis (Spectrascribe BOC--Medishield). Seventy-nine patients who had had 89 endarterectomies during the past 5 years entered the study. The mean follow-up was 21 months. Fourteen patients had an occluded internal carotid artery of whom 4 had suffered an immediate postoperative stroke and 1 a delayed stroke: transient ischaemic attacks occurred in another 4 patients. Of the 60 patients with a patent internal carotid artery one suffered an immediate postoperative stroke and 2 a delayed stroke; 6 patients had recurrent transient ischaemic attacks. None of the 5 patients who had an external carotid endarterectomy developed postoperative symptoms, although there was occlusion in 2. The carotid artery was occluded in 4 of 43 completely asymptomatic patients. Thus, 18 per cent of all carotid endarterectomies and 9 per cent of asymptomatic patients in this series had postoperative occlusion of the carotid artery.

Adult↗
PubMed2002

Automatic determination of brain perfusion index for measurement of cerebral blood flow using spectral analysis and 99mTc-HMPAO.

Cerebral blood flow (CBF) can be non-invasively quantified using the brain perfusion index (BPI), determined from radionuclide angiographic data generated by technetium-99m hexamethylpropylene amine oxime ((99m)Tc-HMPAO). We previously reported the use of a spectral analysis (SA) method using (99m)Tc-HMPAO to calculate the BPI. In this report, we demonstrate an automatic method for determining the optimal BPI value and compare the optimal BPI values with the absolute CBF values measured using H(2)(15)O positron emission tomography (PET). Bilateral cerebral hemispheres of 11 patients with various brain diseases were examined using (99m)Tc-HMPAO. In the automatic SA procedure, the radioactivity curve for the aortic arch ( C (a)) was shifted by 0-10 s. The radioactivity curve for the brain ( C (b)) was estimated using the shifted C (a), and the error value between the actually measured and the estimated C (b) (Err) was calculated. When the Err was at a minimum, the BPI value was defined as optimal BPI. The difference in BPI from the optimal BPI was calculated as |BPI - optimal BPI| / optimal BPIx100 (%). In all participants, an H(2)(15)O PET examination was also performed, and the BPI values were compared with the absolute CBF values measured using H(2)(15)O PET (mCBF(PET)). The difference between BPI and the optimal BPI increased significantly from 4.87%+/-1.69% to 18.38%+/-3.93% (mean+/-SD) when the Err value increased. The optimal BPI value ( y) was well correlated with the mCBF(PET) value ( x) ( y=0.21 x-0.0075, r=0.800). Our results suggest that this automatic SA method provides an accurate estimate of BPI that can be used for the quantification of CBF using (99m)Tc-HMPAO SA.

Brain↗