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Results for “spectral analysis”

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At least 19 recordsLinked to original sources

PubMed1976

Quantification of chorea in Huntington's disease by power spectral analysis.

A spectral analysis technique for quantifying dyskinesia in patients with diagnosis of Hungtington's Disease (chorea) (H.D.) is described. Spectral analysis involves computation of the magnitude of abnormal involuntary movements (AIMS) and of their distribution in frequency. It has the advantage of providing an objective measure of such movements. Three H.D. patients under different drug regimens and three age-matched controls have been evaluated and representative time records and power spectra are presented. Analysis established marked differences in the amplitude and shape of the normal and patient spectra. In addition, spectral analysis proved sensitive to differences in drug treatments among patients suggesting its additional use in evaluating the efficacy of therapeutic agents in the treatment of movement disorders.

Adult↗

PubMedDate not supplied

Myocardial wall motion evaluation using amplitude frequency spectral analysis.

Frequency spectral analysis of cardiac wall motion as calculated from the recorded video kymogram are demonstrated. Characteristic harmonics following the fundamental frequency of the cardiac rate have been demonstrated to have an alternating sequential energy distribution as measured from the free margin of the left ventricle of humans. The characteristic patterns occur in approximately 80% of the 50 patients evaluated. The correlation of these harmonics with physiologic events is not yet complete. Amplitude frequency spectral analysis offers an objective method for analysis of cardiac kymography not otherwise possible.

Adult↗

PubMed1977

EEG operant conditioning in a monkey model: II. EEG spectral analysis.

EEG power spectral analysis was studied from 14 (alumina-gel) chronically epileptic, undrugged monkeys during an EEG operant conditioning experiment. The composite profile of the average epileptic monkey shows the majority of power to be below 10 Hz. Because of the large variance in the data, no significant changes in the EEG power spectra could be detected as a function of conditioning. The possible reasons for this large variance are discussed. Hypothesis from previous human "biofeedback" studies would allow the prediction that those frequencies corresponding to the mu and sensory-motor-rhythm should negatively covary with seizure frequency. Data from this study did not support such assertions. The method of using spectral analysis for quantifying changes in the EEG which covary with operant conditioning is evaluated.

Animals↗

PubMed1976

Applications of spectral analysis in medical ultrasonography.

Spectral analysis of ultrasonic reflections from biological tissues can be used to determine basic tissue parameters for use in differential diagnosis. This paper describes the use of the technique under circumstances encountered in several types of clinical examinations. The applications are illustrated with results obtained from laboratory measurements with a system now being employed in a clinical evaluation programme. The test objects studied simulate tissues with planar boundaries, tissues with heterogeneous interior structure, and tissues causing acoustic 'shadowing' of posterior regions.

Animals↗

PubMed1977

Spectral analysis of Doppler ultrasonic decompression data.

Several aspects of spectral analysis of bubble transients in Doppler ultrasonic decompression data are discussed. The computation of energy density spectra, using fast Fourier transform techniques for analyzing bubble transients, is described. Spectral analysis of data from probes implanted within animals, using a conventional Fourier analyzer, provided good visual indications of bubble events and interesting changes in spectral structure. A new transient spectral analysis technique that is suitable for quantitative real-time monitoring of small decompression bubbles is described. In a feasibility study using data from an implanted probe, an increase of 900% in bubble signal/noise ratio was observed.

Animals↗

PubMed1976

[EEG spectral analysis of caffeine effects].

Spectral EEG analysis is shown to quantify the centrally stimulating effects of caffeine. Comparing the effects of coffee, decaffeinated coffee, caffeine solution and placebo results in two groups of substances: coffee and caffeine solution on one side, decaffeinated coffee and placebo on the other. The within-group differences are negligible, whereas the between-group differences are highly significant. It may be concluded that caffeine is the effective factor. This study gives no valid evidence confirming possible effects of other coffee ingredients.

Adult↗

PubMed1976

[Multichannel EEG spectral analysis of the caffeine effect].

By means of multichannel Eeg spectral analysis the central effects of caffeine have been investigated during a controlled factorial study with 9 male volunteers. The effects of coffee and caffeine solution with equal concentration, decaffeinated coffee and hot water have been compared on the basis of analysis of variance. The factorial experimental design implemented a randomization concerning the sequence of substances as well as days of week. The principal findings are following: coffee and caffeine solution of equal concentration on the one hand cannot be readily distinguished concerning their Eeg effects, on the other hand the decaffeinated coffee and hot water exhibit very similar Eeg effects. Very marked differences, however, have been found between the two groups of substances. Coffee and caffeine solution both produce a remarkable, highly significant reduction of theta-amplitude, dominant theta-frequency and theta-frequency-variation. The alterations within the alpha range are mainly increase of dominant frequency and decrease of amplitude. These findings may be interpreted as signs of remarkable activation and elevation of vigilance. It should be pointed out that the Eeg effects of caffeine, as well as those of other compounds with central effects, are characterized by topographically different effects. These are not only quantitative, but partially qualitative differences.

Alpha Rhythm↗

PubMedDate not supplied

[The use of spectral analysis in studying the E.E.G. under enflurane (author's transl)].

Spectral study of E.E.G. activity under enflurane anaesthesia shows a mild and early increase in global power distributed over the whole spectrum up to 20 c/sec, initially without dominant activity. Slow activity at 4-6 c/sec occurs later and gradually becomes slower, although without providing what could be called a specific pattern. These results have been compared with the same spectral analysis approach in anoxia in the normal subject and in epileptic subjects. Our experience so far does not allow the identification of the discharges observed the enflurane as epileptic discharge.

Adolescent↗

PubMed1978

[Alpha activity in a group of schizophrenics: spectral analysis and comparison with a control group (author's transl)].

Spectral analysis of tracings from four leads; C3-P3, P3-O1, C4-P4, and P4-O2, were used to compare the results of fiftyseven electroencephalograms from 10 schizophrenics, and 14 normal subjects used as controls. The results show that the mean frequencies of the alpha waves are identical in schizophrenics and controls. Patients with hebephrenia show the lowest variations in alpha wave frequency but with the highest voltage, whereas paranoid schizophrenics have tracings with the lowest amplitude and the greatest variation in frequency. There is also better left intrahemispheric correlation of relative alpha intensities in those patients with the lowest variation in right alpha intensity in relation to controls. The preliminary results suggest that there is a reduction in functional asymmetry of the hemispheres in the electroencephalograms from schizophrenics, when looking at the alpha activity.

Adult↗

PubMed1979

Spectral analysis of the normal electrocardiogram in children and adults.

We performed spectral analysis of the X-lead Frank VCG from six normal adults (Group A) and eight normal children (Group B) using a Fast Fourier Transform. The Group A magnitudes were consistently and significantly lower than Group B in the 20--90 Hz region. Similarly, the -40 dB point was 75 Hz for Group A and 107 Hz for Group B. The P waves of the two groups had similar spectra, as did their T waves. When the entire cardiac cycle was analyzed, there was again a consistent and significant difference in the frequencies from 25--80 Hz. Despite the significant differences in the Group A and B spectra, the vast majority of the information contained in the ECG signal was confined to frequencies below 100 Hz. Therefore, a bandwidth of 100 Hz is probably adequate for accurate recording of the ECG signal from children, as well as from adults.

Adult↗

PubMed1975

Spectral analysis of the EEG recorded during stimulation of the human fovea.

Computer spectral analysis was performed on the EEGs of 6 subjects recorded during monocular foveal stimulation. Stimulus wavelength and subjective brightness were varied independently to determine their importance to changes in the ongoing EEG. The contribution of oculomotor control to these effects and the retinal area of their origin were also investigated. The major results were as follows. (1) Stimulation of the fovea reduced the amplitude of the EEG and the coherence between hemispheres at all frequencies, but most dramatically in the alpha band. (2) It increased the variance of EEG amplitudes and widths of spectral peaks in the alpha band and shifted these peaks to lower frequencies. (3) Auto-spectral intensities in the alpha band were enhanced slightly at brightness levels near photopic threshold, but were unaffected by changes in stimulus wavelength. (4) The fovea appeared to be the most effective retinal area in which irradiation attenuated ongoing alpha activity.

Accommodation, Ocular↗

PubMed1975

Spectral analysis as a diagnostic aid in the management of high-risk pregnancy.

Spectral analysis of the fetal heart rate and intrauterine pressure was done with data obtained during labor for 24 patients delivered of their infants in an obstetric intensive care unit. The patients were grouped according to clinical assessment of labor and neonatal outcome as normal (11), abnormal/premature (4), and prolonged labor/cesarean section (9). A comparison among groups of spectral density functions and of coherence functions and phase angles failed to reveal consistent features that could be used to distinguish between groups. However, an analysis of the variance (integrated spectrum) and the mean of the base-line component of the fetal heart rate showed that the values for the normal and abnormal/premature groups could be distinguished from the background population. It is suggested that a study of the joint statistics of the variance and the mean may lead to the development of a diagnostic aid to the early detection of incipient fetal distress.

Analysis of Variance↗

PubMed1976

A study of anaesthesia depth by power spectral analysis of the electroencephalogram (EEG).

The feasibility of using computer-based EEG spectral analysis to monitor the level of anaesthesia during nitrous oxide-alphaprodine anaesthesia has been established by this study. At present, this system is capable of estimating the level of anaesthesia correctly from 55 per cent to 80 per cent of the time. There are several possible clinical applications of such a monitoring system during anaesthesia. It provides a continuous estimation of the depth of anaesthesia, without requiring any special EEG training on the part of the anaesthetist. This system can also be of particular benefit during anaesthesia for critically ill patients, or in specific cases, as in neurosurgery and caesarian section when there may be periods of time when the gross clinical evaluation of depth of anaesthesia may not be precise or reliable and yet it is imperative not to deepen the anaesthesia unnecessarily. In such instances it appears that a monitoring system such as we have developed could provide valuable indication of the depth of anaesthesia. Other potential applications might be in the training of students in the clinical assessment of patients during anaesthesia and in the study of new anaesthetic agents.

Adult↗

PubMedDate not supplied

Power spectral analysis of auditory evoked response.

Five normal hearing adults were examined for power spectral analysis of AER to 1000-Hz pure tone. Major frequency components of responses to stimuli at 50 dB hearing level exist at 1 to 14 c/s. The power spectra of responses to stimuli at 10 dB hearing level are greater than those of the SBA in the frequency components between 3 and 9 c/s; furthermore, the total power of 3 to 9 c/s indicates a clear difference between the 2. Incidentally, at 512-msec analysis time, the total power of 3 to 9 c/s of the AER are significantly greater than that at 1024-msec analysis time, whereas those of the SBA show little discrepancy at the 2; thus at 512-msec analysis time, the total power of 4 to 9 c/s yields a clear difference between the AER and the SBA responses averaged over 50 stimuli even at 10 dB hearing level.

Adult↗

PubMed1979

Spectral analysis of EEG during mental activity (author's transl).

With the use of power spectral analysis, the occipital and frontal EEGs in normal young subjects were examined during mental activity under closed-eye and open-eye conditions. Under the closed-eye condition, the peak of power spectral density in the alpha band was suppressed during mental activity, as compared with the finding obtained without mental loading. Moreover, the peak frequency of the alpha band shifted to higher frequencies under the mental loading condition in all of the subjects. Under the open-eye condition, alpha waves were prominently suppressed and no peak of power spectral density in the alpha band could be detected. However, during mental activity the peak of power spectral density could be detected in the delta wave band of both occipital and frontal EEGs.

Adolescent↗

PubMed1979

Spectral analysis of urinary reactions: a preliminary study based on a novel concept.

The concept of spectral analysis of urinary reactions (a range of simple chemical tests combined with pattern analysis) is described. A preliminary study in which we used 10 nonspecific tested on untimed urine specimens from 20 controls and 20 diabetics, matched for age and sex, suggested that a combination of these tests could be used to separate diabetics from healthy subjects. This combination, however, did not prove satisfactory for a further group of 13 diabetics. Closer examination revealed that factors such as therapy and glycosuria affected the results of these tests. This approach, which should extend the usefulness of urinalysis, may prove viable when larger groups, and possibly a different set of tests, are used to establish a more robust combination of tests.

Adult↗

PubMed1977

Local spectral analysis in the visual cortex.

On the basis of experimental evidence presented earlier a model of local spectral analysis of the image performed by the complex receptive fields of the visual cortex has been proposed. An essential feature of the model is that the generalized piece-wise Fourier transform is performed not over the image luminance function but over the logarithm contrast function resulted from analysis of the image by the round receptive fields of the preceding levels. Such an assumption removes a number of experimental objections offered against the hypothesis of two-dimensional Fourier transform in the visual system. The consequences from the piece-wise expansion in a series of basic functions have been considered and among them: the channel frequency characteristics which can have more than one maximum; the possibility of describing the image by a limited number of channels with overlapping frequency characteristics; the existence of mechanisms for estimation of phase shift between frequencies.

Models, Neurological↗

PubMed1976

EEG spectral analysis in children with febrile convulsions.

The abnormal theta-rhythm of the EEG can be identified by use of spectral analysis. The rhythms appear as peaks in the power spectrum and can be considered as given, if the intensity of this peak is significantly higher than the average intensity and if a left-right coherence is present. Abnormal theta-rhythms in the parietal region are significantly more frequent in children with a histroy of febrile convulsions than in controls. This difference becomes especially obvious in the records with open eyes. According to previous investigations, the abnormal theta-rhythm is correlated with a genetically determined susceptibility to convulsions.

Child, Preschool↗