Abstract
The parameter analysis of EEG is based upon a model that describes its spectral properties in parametric form. The spectrum is divided into several components of two general types, I and II. A component of Type I has its greatest spectral density at zero frequency and is described by one frequency parameter, the bandwidth, and one power parameter, the power content. A component of Type II is described by two frequency parameters, the centre frequency and the bandwidth, and by two power parameters, the power content and a parameter describing spectral asymmetry around the centre frequency. A computer program is available for estimating the EEG parameters and for calculating the statistical uncertainty in these parameters. This study is a first attempt to apply the analysis in practice. In twenty-five healthy young men, EEGs classified as normal on visual evaluation were selected for analysis. Continuous records of 20–120 sec duration were selected for analysis and checked to be free from artefacts. The analysis was carried out with a model of fifth order which, in most cases, resulted in a spectrum with one component of Type I and two components of Type II, called delta, alpha and beta components. The physiological interpretation of these parameters is discussed. The estimated parameters for the whole group are summarized in terms of mean values and standard deviations. The analysis permits an exact determination of the parameters and their relationships. The hypothesis that beta activity is a harmonic of alpha activity is discussed. The relation between the bandwidths for delta and alpha components is investigated. Detailed studies are made on the alpha activity: a comparison of the power content in different regions of the brain, the relation between bandwidth and power content and a comparison of the centre frequency and power content for recordings taken symmetrically on the skull. Variations with time in the centre frequency of the alpha activity have been studied.
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