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PubMed1983

Cortical power spectral analysis of acute pathophysiological pain.

In the past decade, advances in quantitative EEG methods, such as the analysis of cortical power spectrum, have proven a useful tool for observing changes in brain activity as a function of physiological and behavioral states. The cortical power spectrum (CPS) is a computer-derived analysis of brain electrical activity using mathematical principles of Fast Fourier Transform function. The total energy output of specific cortical areas can be estimated over time, as a function of EEG spectral frequencies. This report describes the study of CPS in pathophysiological pain patients, using acute dental pain as a model. Seven "walk-in" acute pain patients in an emergency dental clinic were recorded during 10 min of pain, before treatment. Approximately one week later, 10 min recordings during nonpain states were obtained as control. Subjective pain scales and other psychological measures were administered to all subjects before and after recording on each visit. Each 10 min stage of continuous CPS recording consisted of 10 spectra per stage, 6 epochs/spectrum, and 10.24 sec/epoch; each spectrum was stored, averaged, transformed, displayed, printed, and plotted by the Pain Microcomputer System. Results show significant cortical power reduction along all frequency bands (0.5-50 Hz) when pain-states are compared to nonpain states. The magnitude of reduction also appears to correspond to subjective pain report. Analysis for rank order may be inversely related to subjective painfulness, indicating that pain and alpha-desynchronization are closely associated. This study demonstrates that the brain activity of clinical pain patients can be measured. The feasibility of developing a pathophysiological objective pain measuring system is discussed.

Acute Disease↗
PubMed1990

Power spectral analysis of heart rate variability after biofeedback training.

This study investigated the effects of biofeedback/self-management training on heart rate variability (HRV) in six sudden cardiac arrest survivors. The physiological-theoretical basis of the training was cognitively inducing respiratory sinus arrhythmia. Power spectral analyses and nonspectral analyses (Kleiger, Magid, SCANN, BB50 measures) of HRV measured before and after 5 weeks of biofeedback training are described. The posttraining Kleiger measure of mean HRV increased compared to the pretraining mean HRV (159 +/- 37 ms vs 147 +/- 38 ms). After training, the high frequency components (0.27-0.30 Hz) of the power density spectra were markedly increased, suggesting an increase of respiratory-driven parasympathetic activity. After training, the low frequency components (0.05 Hz) were slightly decreased, suggesting a decrease in sympathetic activity. The increases noted in the high frequency components were more striking during 9 hours at night than during the day. These data indicate that subjects who have had sudden cardiac arrest can, through biofeedback/self-management, cognitively increase their HRV over a 5-week period, consequently increasing parasympathetic activity.

Arrhythmia, Sinus↗
PubMed1987

Combined proton NMR imaging and spectral analysis of locust embryonic development.

Images and spectra of desert locust [Schistocerca gregaria (Forskal)] embryos were collected in vivo using a 4.7-tesla proton ((1)H) NMR imaging spectrometer. The 100 x 100 x 500 mum image resolution and 125-nl localized spectral volumes were obtained within minutes of each other. The dynamics of embryonic development were slow enough that the time delay between imaging and spectral measurements is negligible. Thus, image and spectral data correspond closely and approximate real-time observations of embryonic changes. The above procedure was applied every 12 hr during the entire course of development. This analytical approach demonstrates that imaging and localized spectroscopy can be used to visualize and assess changes in embryonic water and lipid content in concert with the development of a living embryo.

Journal Article↗
PubMed2002

Time-variant spectral analysis of heart rate variability during parabolic flight with and without LBNP.

Modifications of autonomic activity during parabolic flight were studied by a time-variant model able to estimate low (LF, 0.04-0.14 Hz) and high (HF, 0.14-0.35 Hz) frequency spectral components on a beat-to-beat basis. Ten subjects were studied with and without lower body negative pressure (LBNP). ECG and Gz load were digitized (500 Hz) and RR interval variability series extracted. Beat-to-beat mean RR, variance, LF and HF power were obtained. One-way ANOVA (p<0.01) was used to compare values obtained during starting 1Gz (I), first 1.8Gz (II), 0Gz (III), second 1.8Gz (IV), ending 1Gz (V). Without LBNP, total and LF power increased during 0Gz to 1.69 +/- 1.41 and 2.87 +/- 4.66 respectively (mean +/- SD, normalized by phase I value). With LBNP, their change during 0Gz (1.38 +/- 1.37 and 1.54 +/- l.04 respectively) reached significance only with phase II and phase V. Phase I HF power was higher than in the other phases, both without and with LBNP.

Journal Article↗
PubMed1992

Spectral analysis of EEG during self-paced movements: differences between untreated schizophrenics and normal controls.

Thirteen untreated schizophrenic patients, among them nine who had never been treated, were compared with a corresponding number of matched normal controls with regard to changes of the spectral composition of the electroencephalogram (EEG) accompanying voluntary movements. Triggered by self-paced movements of the right fingers (fast fist closure), the spectral composition of three epochs was analyzed: (1) rest (2,5-1,5 sec before movement), (2) movement preparation (last sec before movement onset), and (3) movement execution (1st sec following movement onset). For frequencies above 6 Hz, marked differences between schizophrenics and controls were evident, in particular over the parietal electrodes. Whereas patients exhibited a clear decrease of power density during movement as compared to rest, controls showed only a small decrease (left and mid parietal) or virtually none (only right parietal). Consequently there were significant differences over the right parietal area (P4) between patients and controls in the theta, alpha- and beta-bands with regard to the mean power density and center frequencies of these bands. Also at parietal positions, schizophrenics lacked the enhancement of theta-power during the preparatory epoch that was characteristic for normal controls at all parietal positions. The results are discussed with regard to the well-known disturbances of voluntary motor behavior in schizophrenia.

Adolescent↗
PubMed1996

Evaluation of an automated real-time spectral analysis technique.

An adaptive real-time Doppler peak-frequency tracing algorithm was evaluated in vitro and compared to manual peak-frequency traces. A computer-controlled pump was used to generate physiological flow waveforms in a vasculature-mimicking phantom. Spectral waveforms were obtained on an ATL HDI along with real-time estimates of diagnostic parameters, including maximum systolic, minimum diastolic, time-averaged peak frequencies and pulsatility and resistance indices. The effect of the signal-to-noise ratio on the measured parameters was investigated. The imprecision in the measured parameters was found to depend somewhat on the waveform shape; e.g., the imprecision in PI was 4.1% for a normal renal waveform and 8.5% for a waveform having reverse diastolic flow. The peak frequency envelopes of the same waveform data were traced manually by nine operators, and the resulting diagnostic parameters were compared to ones obtained from automated peak-frequency traces of the same waveform data. The agreement between parameters measured by the automated routine and those measured manually was found to depend somewhat on the waveform shape; e.g., the bias in the PI was 1.3% for a renal waveform lacking diastolic flow, and 12% for a waveform with reverse diastolic flow. The between-observer variations in the manual measurements ranged from 0.8% up to 9.4%. The overall variations associated with the automated traces were found to be smaller than or equal to those of the manual traces.

Algorithms↗
PubMed1999

Higher-order spectral analysis of burst patterns in EEG.

Burst suppression patterns in electroencephalograms (EEG's) have been observed in a variety of situations including recovery of a subject from a traumatic brain injury. They are associated with grave prognostic outcomes in neonates. We study power spectral parameters and bispectral parameters of the EEG at baseline, during early recovery from an asphyxic arrest (EEG burst patterns) and during late recovery after EEG evolves into a more continuous activity. The bicoherence indexes, which indicate the degree of phase coupling between two frequency components of a signal, are significantly higher within the delta-theta band of the EEG bursts than in the baseline or late recovery waveforms. The bispectral parameters show a more detectable trend than the power spectral parameters. In the second part of the study, we looked into the possibility of higher (> 2)--order nonlinearities in the EEG bursts using the diagonal slices of the polyspectrum. The diagonal elements of the polyspectrum reveal the presence of self-frequency and self-phase coupling of orders higher than two in majority of the EEG bursts studied. The bicoherence indexes and the diagonal elements of the polyspectrum strongly indicate the presence of nonlinearities of order two and in many cases higher, in the EEG generator during episodes of bursting. This indication of nonlinearity in EEG signals provides a novel quantitative measure of brain's response to injury.

Animals↗
PubMed2002

Folding pattern recognition in proteins using spectral analysis methods.

Divergence in sequence through evolution precludes sequence alignment based homology methodologies for protein folding prediction from detecting structural and folding similarities for distantly related protein. Homolog coverage of actual data bases is also a factor playing a critical role in the performance of those methodologies, the factor being conspicuously apparent in what is called the twilight zone of sequence homology in which proteins of high degree of similarity in both biological function and structure are found but for which the amino acid sequence homology ranges from about 20% to less than 30%. In contrast to these methodologies a strategy is proposed here based on a different concept of sequence homology. This concept is derived from a periodicity analysis of the physicochemical properties of the residues constituting proteins primary structures. The analysis is performed using a front-end processing technique in automatic speech recognition by means of which the cepstrum (measure of the periodic wiggliness of a frequency response) is computed that leads to a spectral envelope that depicts the subtle periodicity in physicochemical characteristics of the sequence. Homology in sequences is then derived by alignment of spectral envelopes. Proteins sharing common folding patterns and biological function but low sequence homology can then be detected by the similarity in spectral dimension. The methodology applied to protein folding recognition underscores in many cases other methodologies in the twilight zone.

Algorithms↗
PubMed2006

A new index of the autonomic nervous balance and its clinical usefulness; a power law 1/f like scale of a spectral analysis of the heart rate variability.

OBJECTIVE: This study was undertaken to develop a new autonomic scoring scale distinct from the conventional sympathetic or parasympathetic parameters cardiac autonomic response. METHODS: The parameters were obtained from a log-log scale of frequency (f ) vs. power spectral (P) amplitude of heart rate variability (HRV). A gradient value in which the graph decreases towards a high frequencies on the X-axis, while showing an absolute value beta itself based on the formula 'P = f (-beta)' was newly named the 'Balance index' by implying a balanced state in the living body. The index was categorized into four bands based on the appearance of the whole frequency ranges (T-Balance Index). Therefore, we compared the responses of the following groups: the patient test group (Group PT), the normal test group (Group NT), and the normal non-test group (group NN). RESULTS: Significant differences in parameters were observed among the three groups. In addition, the difference between the 'High-side Balance Index' and the 'Low-side Balance Index' was 0.75 +/- 0.12 vs. 0.07 +/- 0.04 (p < 0.005) for groups NT vs. PT. This novel analyzing method was useful for evaluating the subtle changes in a living body to regulate the living-power (strength of vitality). Moreover, the difference between the 'T-Balance Index' and 'SV-Balance Index' was 0.18 +/- 0.12 vs. -0.21 +/- 0.15 (p < 0.01) for groups NT vs. PT. CONCLUSIONS: One application of new parameters 'Balance Index' is its ability to evaluate the vital or emotional functions of unconscious patients in a critical condition undergoing a sense challenge test. This method assists in improving our ability to measure the early stage of conscious recovery with greater accuracy by using our novel analysis method for performing senses challenge test, with the aid of media such as music.

Adolescent↗
PubMed2001

Evidence for an analytic perception of multiharmonic sounds in the bat, Megaderma lyra, and its possible role for echo spectral analysis.

For echolocation, the gleaning bat Megaderma lyra relies on short and broadband calls consisting of multiple harmonic components, each of which is downward frequency modulated. The harmonic components in M. lyra's calls have a relatively small frequency excursion and do not overlap spectrally. Broadband calls of other bat species, on the other hand, often consist of only a few harmonics which are modulated over broad and sometimes overlapping frequency ranges. A call consisting of narrow and nonoverlapping harmonic components may provide a less complete representation of target structure than a call which consists of broadly modulated components. However, a multiharmonic call may help the bats to perceive local spectral changes in the echo from shifts in the peak frequencies of single harmonics, and thereby to extract additional information about the target. To assess this hypothesis, the accuracy with which M. lyra can analyze frequency shifts of single partials in multiharmonic complex tones was investigated. A two-alternative, forced-choice behavioral task was used to measure M. lyra's frequency discrimination threshold for the third partial in complex tones whose spectral composition resembled that of the bat's sonar calls. The discrimination threshold for the third partial in a 21.5-kHz harmonic tone amounted to about 2% and was similar to the bat's pure-tone discrimination threshold at 64.5 kHz. Discrimination performance was essentially unaffected by random frequency changes of the other partials and by reducing stimulus duration from 50.5 to 1.5 ms. Both findings are in accordance with predictions made on the basis of the shape of M. Ivra's cochlear filters. The comparison between the observed frequency discrimination performance and a computational estimate of the expected frequency shift in the third harmonic of an echo reflected by a simple, two-front target showed that M. lyra's frequency resolution is sufficient for analyzing the target-specific information conveyed by shifts in the peak frequency of single echo components.

Animals↗
PubMed1985

Spectral analysis of breathing pattern in man.

The periodic oscillations of breathing pattern parameters were studied in 34 healthy subjects. In a three minutes' resting spirometric recording we determined the duration of inspiration, expiration and tidal volume in successive breaths and computed autocorrelation functions and power spectral density. Ten of the subjects were re-examined 2 years later. Pulmonary functions were examined in all of them. Rhythmic changes lasting several respiratory cycles were found in the breathing pattern. Rhythmic changes in the duration of inspiration, expiration and tidal volume differed from one another in the same individual. The spectrograms of the individual breathing pattern parameters in the same individual changed during a 2-year period. Despite individual differences, the power spectral density correlations in the same subject and between different subjects two years later, and the mean curves for power spectral densities, show that in all the subjects the power fell at values of 0 to 0.05 Hz and was then maintained at a roughly constant level. Differences in the spectrograms of the various parameters in the same subject can hardly be attributed to a feedback between peripheral receptors and respiratory centres. Rhythmic changes are probably of central origin.

Biometry↗
PubMed1997

Spectral analysis of a thalamus-to-cortex seizure pathway.

Physiological evidence has shown that the anterior thalamus (AN) and its associated efferents/afferents constitute an important propagation pathway for one animal model of generalized tonic-clonic epileptic seizures. In this study we extend and confirm the support for AN's role by examining neuroelectric signal indicators during seizure episodes. We show that the electroencephalogram (EEG) recorded from AN is highly coherent with the EEG derived from the cortex (CTX). By removing the effects of another thalamic nucleus, posterior thalamus (PT)-unaffiliated with the tract linking AN to cortex-partial coherence analysis leaves the CTX/AN coherence undiminished. The most robust band of strong CTX-AN coherence is centered around the spike-wave pacing frequency of 1-3 Hz. Partial-multiple coherence analysis techniques are used to remove the possible signal contribution from hippocampus in addition to PT. The CTX-AN coherence still remains undiminished in the low-frequency bands. Conclusive evidence from coherence studies and other spectral measures reaffirm the special role of the AN in the propagation of seizure activity from subcortex to cortex.

Analog-Digital Conversion↗
PubMed1978

Spectral analysis of the electromyogram of the temporal muscle in the rhesus monkey (Macaca mulatta).

Spontaneous EMG activity of one mandibular elevator and postural muscle, the anterior temporalis, was recorded from 20 unanesthetized rhesus monkeys subjected to 4 experimental protocols. The EMG activity was analyzed with a spectral analyzer to determine changes in particular frequency bandwidths after (1) administering a dissociative drug, (2) placing weights on the mandible, (3) detaching the muscle, and (4) adaptation of the muscle to oral respiration. The mean distribution of frequency components indicated that ketamine--HCl increased the power of all frequencies below 400 c/sec, particularly those at 20--40 c/sec. A period of hyperactivity and increased recruitment and discharge of motor units occurred within the first 30 min following administration of the drug. Passive and sustained lowering of the jaw with increased weights indicated that increasing the front incisor distance 2--4 cm significantly decreased the frequency components below 400 c/sec accompanying a decrease in active motor units. Comparison of frequency components of the temporalis EMG before and within 40 days after detachment suggested some subtle variations in the mean distributions predominantly around 200 c/sec but without significant changes. Comparison of the mean spectral distribution between 8 nasal-breathing and 8 oral-breathing monkeys indicated a significant loss of power in the normal dominant frequency range of 20--100 c/sec in the oral respiratory group except for enhancement of the 20 c/sec bandwidth. The results suggest that the anterior temporalis alters its EMG activity during both short (i.e., min, h) and long-term (i.e., months, year) adaptations of the muscle.

Animals↗
PubMed1990

Spectral analysis of the EEG (alpha rhythm) and activity in the left hemisphere: the effects of lateral gaze.

This study tests the effect of maintaining right and left lateral gaze during a writing task which preferentially implicates the left hemisphere using an asymmetry parameter calculated from the spectral power of the alpha rhythm (RP-LP/RP + LP) in a right-handed patient undergoing the same experimental regimen nine times. A six derivation EEG was recorded. Maintaining left lateral gaze (toward the active hemisphere) removes the lateralization found during writing while staring straight ahead whereas maintaining right lateral gaze (toward the side opposite the active hemisphere) results in slightly lower values which are however, not significantly different from those obtained during staring straight ahead. This study adds an electrophysiologic aspect to Kinsbournes's paradigm on gaze position and hemispheric activation.

Adult↗
PubMed1983

Spectral analysis of the conformation of polyadenosine diphosphoribose. Evidence indicating secondary structure.

Based on boronic acid chromatography, a rapid method was developed for the purification of polyadenosine diphosphoribose oligomers of various chain lengths. Polyadenosine diphosphoribose oligomers obtained by the new method were distinguished on the basis of spectral criteria. The purity of polyadenosine diphosphoribose was determined by high performance liquid chromatography, which is a highly sensitive method for the detection of contamination by nucleotides derived from other nucleic acids. The A280/A260 ratio, which has been used in the past as one of the criteria of purity of oligomers, was found to be an unsuitable index of purity because it significantly varied as a function of temperature or ionic strength, exhibiting characteristics of temperature- and ionic strength-dependent hypochromicity. Hypochromicity was highly significant at 260 nm but not at 280 nm. The A280/A260 ratio showed a correlation with the oligomer chain length, significantly diminishing below a chain length of 9 adenosine diphosphoribose units, with concomitant loss of hypochromicity. The increase in A280/A260 ratio above a chain length of nine was small and gradual. Circular dichroism of long, medium, and short oligomers was determined at varying temperatures (5-72 degrees C). For long chains, a temperature-dependent change of the major negative theta value and a red shift occurred from 249.5 to 267.5 nm. With medium chain length oligomers, there was no decrease in the theta value at 249.5 nm, only a red shift. In the case of short chain oligomers the major negative theta value was at 267.5 nm and its position was temperature-independent with only a small temperature-related decrease in size. At 72 degrees C, the different patterns of circular dichroism of the three groups of oligomers of differing chain lengths became indistinguishable. These results were interpreted to indicate a significant secondary structure of polyadenosine diphosphoribose of long chain length.

Chromatography, High Pressure Liquid↗
PubMed1989

Comparative spectral analysis of mammalian, fungal, and bacterial catalases. Resonance Raman evidence for iron-tyrosinate coordination.

Resonance Raman spectra are reported for catalases from bovine liver, the ascomycete fungus Aspergillus niger, and the bacterium Micrococcus luteus. The vibrational frequencies of the oxidation-, spin-, and coordination number-sensitive spectral bands are indicative of high spin pentacoordinate hemes in the resting ferric enzymes of each of these organisms. This result is in accord with the crystal structure of bovine catalase (Fita, I., and Rossmann, M.G. (1985) J. Mol. Biol. 185, 21-37). In contrast, the crystallographic study of catalase from the ascomycete Penicillium vitale (Vainshtein, B. K., Melik-Adamyan, W. R., Barynin, V. V., Vagin, A.A., Grebenko, A. I., Borisov, V. V., Bartels, K. S., Fita, I., and Rossmann, M. G. (1986) J. Mol. Biol. 188, 49-61) showed electron density on the distal side of the heme which could imply the presence of a sixth ligand, possibly a water molecule. However, both of these crystallographic studies showed the proximal ligand in catalase to be a tyrosine. The present study confirms tyrosinate coordination in each of the three catalases from the appearance of selected resonance-enhanced tyrosine vibrational modes. The most characteristic band is the tyrosinate ring mode at approximately 1612 cm-1 which is maximally enhanced with 488.0 nm excitation. The appearance of tyrosinate modes at 1607 and 1245 cm-1 in the resonance Raman spectra of M. luteus cyano catalase serves to identify tyrosine as an axial ligand in bacterial as well as eukaryotic catalases. Unlike non-heme iron tyrosinate proteins, whose resonance Raman spectra are dominated by several intense bands diagnostic of tyrosine ligation, the heme-linked tyrosine modes are not easily distinguished from the large number of porphyrin vibrations.

Animals↗
PubMed1987

[Spectral analysis of the EEG of the healthy rat and the rat genetically predisposed to seizure susceptibility].

EEGs of motor and visual cortical zones, hippocampus, caudate nucleus and intralaminal-thalamic nuclei were recorded in two rat strains in "awake-immobility" state and subjected to visual and spectral analyses. KM rats genetically predisposed to audiogenic seizures were shown to differ from unpredisposed Wistar rats in weakening of the relative power of theta rhythm and intensification of the large-amplitude irregular activity in hippocampus and neocortex as well as in reinforcement of the generalized spindle activity. As a result of prolonged application of gradually increasing camphor doses seizure susceptibility reduction in KM rats correlated with EEG spectral density changing to Wistar rats EEG characteristics. The probable role of the brain stem reticular formation mechanisms in the enhanced convulsibility and accompanying EEG pattern are discussed.

Acoustic Stimulation↗
PubMed1993

Twenty-four-hour power spectral analysis by maximum entropy method of blood pressure in primary hyperaldosteronism.

In the present study we estimated the periodic profiles and variance structure of systolic blood pressure, diastolic blood pressure, heart rate and mean arterial pressure by using an autoregressive model of power spectrum, Maximum Entropy Method (MEM) in 8 patients with primary aldosteronism, during long-term therapy with nicardipine slow release. The four blood pressure variables were measured at 30-min intervals, using a noninvasive device (Spacelabs 90202) in 8 hypertensive patients of whom 6 with idiopathic aldosteronism (IHA) and 2 with dexamethasone-suppressible aldosteronism (DSH), before and after 24 weeks of 80 mg nicardipine daily. Blood pressure data were processed by MEM and spectral profiles were obtained. During nicardipine therapy all patients showed a significant decrease of 24-h ambulatory blood pressure values (p < 0.01). Before therapy, spectrum analysis by MEM indicated the presence of high frequency distribution of peaks for SBP, DBP, MAP and HR. The MEM power spectrum showed an increase in amplitude of sharp peaks of systolic, diastolic, MAP and heart rate in all patients after therapy at 24 h corresponding to the circadian rhythm blood pressure. Furthermore, the trend of these variables synchronized themselves in the same period after 24 weeks of nicardipine therapy, with spectral patterns of blood pressure similar to those of normotensive subjects. This chronobiologic approach, by Maximum Entropy Method, may be used as an alternative statistical analysis to search for possible rhythmic behavior of ambulatory blood pressure data before and after pharmacological treatment in secondary hypertensive patients.

Activity Cycles↗