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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↗
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↗
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

[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↗
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↗
PubMed1977

[Correlation spectral analysis of the spontaneous impulse activity of cerebral cortex neurons].

Spontaneous unit activity in alert unrestrained rabbits was recorded simultaneously with two microelectrodes from the visual and sensorimotor cortex. The correlation analysis revealed that activity of majority of the neurons had no regular rhythm. But spectral analysis of the average correlograms showed existence of oscillations in the delta- and theta-ranges. The synergic type of interaction between cortical neurons was prevalent. Analysis of structure of the distant interaction showed the reduced probability of synergic spikes with periods 150-200 msec and less and the increased one with periods within 200-500 msec.

Animals↗
PubMed1979

Automated detection of EEG artifacts during sleep: preprocessing for all-night spectral analysis.

This paper describes a simple artifact detection algorithm which can be used when large amounts of EEG data are to be automatically processed via spectral analysis techniques in a general purpose digital computer, and visual inspection of each EEG epoch becomes an impossible task. The technique is based on a chi-square (chi(2)) goodness-of-fit test to a Gaussian distribution (CSQ), and it was applied to EEG epochs each 30 sec long. This test proved to be very sensitive to non-stationarities in the EEG amplitude distribution for a particular epoch, and it produced a large value for the chi(2) coefficient when an artifact was present. EEG epochs that gave rise to chi(2) coefficients of value larger than a heuristically determined minimum were discarded from further analysis. The above technique enabled efficient data reduction and reliable automatic off-line processing of 50 nights of sleep EEG via spectral techniques.

Action Potentials↗
PubMedDate not supplied

Imaging the carotid bifurcation using continuous-wave Doppler-shift ultrasound and spectral analysis.

A non-invasive method is described for visualizing the carotid bifurcation using a continuous-wave Doppler-shift technique simultaneously with spectral analysis of the blood velocities from all parts of the vessel lumen. The system is directional so that arteries can be visualized in the presence of signals from adjacent veins. The technique uses a transducer which is attached to a position-sensing arm so that the position of the ultrasound beam on the neck, when sensing arterial blood flow-velocities, can be translated onto a storage oscilloscope. By repeated passes of the transducer across the vessel lumen a 2 dimensional image of the carotid bifurcation is formed. As each image point is marked, the full spectrum of blood-velocities corresponding to that position is continuously displayed on a second oscilloscope beside the image scope. Ultrasound images are compared with arteriograms and both continuous-wave and pulsed Doppler ultrasound imaging systems are discussed.

Adult↗
PubMed1976

A real-time software system on the PDP-11 for two-channel EEG spectral analysis during surgery.

Three functions are performed in real time by a stand-alone PDP-11-assembly language program. First two channels of EEG data are acquired by quantization techniques; second spectral analysis of the EEG data is carried out; third the resulting spectra are displayed as time compressed spectral profiles on an X-Y plotter. The method provides EEG time trends during anesthesia, permitting evaluation of brain functions.

Anesthesia, General↗
PubMed1979

Interaction between intermittent photic stimulation and auditory stimulation on the human EEG. Preliminary investigation through power spectral analysis.

The effects of flicker photic stimulation (6, 8, 9, 10, 11, 12, 14, 16 flashes/sec) and of white noise (80 dB SPL) on the EEG of man were investigated with the aid of power spectral analysis. In order to evaluate both the alpha attenuation response (AAR) and the 'driving' reaction induced by flicker as well as the effect of noise, the analysis was carried out on broad (delta, theta, alpha, beta) and on narrow (bandwidth: 1 Hz) spectral bands. A significant correlation between the amount of AAR induced by noise and a measure of the tendency to exhibit photic driving was found, though there was no clear-cut interaction between the photic stimuli and noise when delivered stimultaneously.

Acoustic Stimulation↗
PubMed1977

EEG and haemodialysis. A structural survey of EEG spectral analysis, Hjorth's EEG descriptors, blood variables and psychological data.

Computerized EEG was performed in 20 patients with renal failure before and after haemodialysis (HD), applying spectral analysis and Hjorth's EEG descriptors in EEG quantification, correlation and factor analysis as statistical procedures to analyse the connections of EEG, blood variables and psychological performance. The main results were: (1) Moderate uraemic encephalopathy -- according to Kiley's (1971) standards -- was present in most of our patients, before and after HD. (2) Before HD, EEG slowing was most strongly connected with the creatinine level and EEG acceleration with hyperkalaemia, which in most cases accompanied a high urea level. (3) Significant EEG changes after HD were: decrease of percentage delta activity, increase of Hjorth's 'mobility', decrease of Hjorth's 'complexity'. (4) The theta/alpha ratio (Matousek 1968) was significantly correlated with the patient's general clinical state after HD. (5) Visual discrimination, memory and maximal tapping speed improved significantly after HD. Only Hjorth's EEG parameters were correlated with test performance in that patients with low voltage and fast EEGs did worse in visual discrimination.

Adult↗