[An epidemiologic survey of occupational exposure to car and industrial lacquers].
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Adult↗
Biomedical subjects
A Isaksson
Publications and source records attributed to A Isaksson.
Long-term exposure to jet fuel. II. A cross-sectional epidemiologic investigation on occupationally exposed industrial workers with special reference to the nervous system.
Thirty jet fuel exposed workers selected according to exposure criteria and thirty nonexposed controls from a jet motor factory were examined, with special reference to the nervous system, by occupational hygiene physicians, psychiatrists, psychologists, and neurophysiologists. The controls and the exposed subjects were matched with respect to age, employment duration, and education. Among the exposed subjects the mean exposure duration was 17 years, and 300 mg/m3 was calculated as a rough time-weighted average exposure level. The investigation revealed significant differences between the exposed and nonexposed groups for (a) incidence and prevalence of psychiatric symptoms, (b) psychological tests with the load on attention and sensorimotor speed and (c) electroencephalograms. When the control group was selected, it was ensured that the two groups were essentially equivalent except for exposure to jet fuel. It is concluded, therefore, that the differences found between the groups are probably related to exposure to jet fuel.
Adult↗
Visible and non-visible EEG changes demonstrated by spectral parameter analysis.
A change of the heart rate in patients with complete AV-block and externally controllable cardiac pace-makers was earlier shown to influence cerebral function, as measured by psychological tests. To determine whether this influence manifests itself in the EEG, 9 patients aged 43-83 years were examined, all having complete AV-block and externally controllable pace-makers. Their EEGs were recorded at different heart rates between 40 and 100/min at rest and during a mental arithmatic test. The EEG record was evaluated visually and analysed by means of Spectral Parameter Analysis (SPA), introduced by Zetterberg (1969). The changes in the spectral parameters in relation to the heart rates were analysed statistically, In several cases significant changes appeared but the interindividual variations were large. Certain typical patterns could, however, be observed and their importance as a measure of cerebral function due to changes in the cerebral blood flow are discussed. These EEG changes revealed through SPA did not correspond to any visually observable changes in the EEG records. Differences in the spectral parameters between rest and test situations were analysed. Some of the differences found could easily be observed by visual inspection of the EEG. The advantage with SPA was that the changes could be described both qualitatively and quantitavely because SPA separates the spectral properties of the signals into components corresponding to well-known components of the EEG signal.
Adult↗
An EEG simulator-a means of objective clinical interpretation of EEG.
In 1969 Zetterberg presented a method for describing the spectral properties of an EEG signal, starting from the assumption that the signal is essentially stationary during the analysis epoch. The method involves determination of the parameters for a model consisting of a lenear filter with the ability to produce a signal with the same spectral properties as the EEG signal. Zetterberg and Ahlin described in 1975 an analogue simulator based on this model theory. With this simulator it is possible to reproduce practically all types of stationary, as well as a number of non-stationary, EEG signals. We have used this simulator to demonstrate in an illustrative manner the relation between the properties of a signal in the spectral domain and in the time domain. We have also endeavoured to anser the question: if one starts from the frequency spectrum, what does the EEG signal corresponding to this spectrum look like? We also draw attention to the usefulness of the simulator in connection with training and as an instrument for testing computer and other systems of EEG analysis.
Computers↗
Visual evaluation and computer analysis of the EEG--a comparison.
Spectral parameter analysis (SPA) of the EEG provides a description of the distribution of spectral power in the EEG signal in the form of a rational spectrum with not more than 8 parameters. The spectrum is divided into 1-3 components described by frequency and power parameters: bandwidth (delta), peak frequency (f) and power (G). These spectral parameters are determined with the aid of a computer. The character of the EEG signal decides whether 1, 2 or 3 components (delta, alpha, beta) are needed to describe the spectrum. To test its practical value, the result of SPA was compared with that of ordinary visual evaluation of the EEG of 65 healthy men between the ages of 18 and 22 years. 20 sec sections from different leads were analysed and evaluated visually. Each EEG section was graded according to the amount of visually evaluated slow activity (VESA). To investigate the relation between the degree of VESA and the SPA result, statistical calculations (variance and regression analyses) were carried out, both for single SPA parameters and for the general type of spectrum, i.e., the number of components composing the spectrum. The SPA results from sections with artefacts were treated separately and compared statistically with results from artefact-free sections. In records with a high degree of VESA, all the leads analysed showed a tendency to have a power spectrum of low order, i.e., with few components. In most leads there was a linear regression between the degree of VESA and the bandwidth and power of the delta and alpha components. In several cases this relation was an expression of a significant linear change of the SPA parameter as a function of the degree of VESA. On the other hand the parameters of the beta component showed no relation to the degree of VESA. It was found that muscle activity could influence any spectral component thereby providing it with a strongly increased bandwidth. This is probably due to the fact that muscle activity resembles white noise in this particular frequency range. Low frequency artefacts affected only the delta component the bandwidth of which was significantly smaller than in the artefact-free sections.
Adolescent↗