FAD-parametric description of EEG time series.

A new method of the EEG time series parametric description was elaborated. The procedure consists of the following steps: calculation of AR model coefficients, the estimation of the transfer function in the form of parallel filters, finding of the impulse response function parameters. The parameters: frequencies, amplitudes and damaging coefficients (FAD) characterise the basic EEG waves. The average properties of the EEG signals are presented in the form of rhythm diagrams. The method overcomes the difficulties in arbitrary partitioning of the EEG power spectrum into the frequency bands and makes possible the reduction of electroencephalographic data to the few parameters characterising basic rhythms.

Pharmaco-EEG analysis by means of FFT and FAD.

The EEG effects of a single oral dose of diazepam, amitriptyline and pernazine were studied in 26 healthy volunteers. The EEG analysis was performed by means of FFT and a new parametric method FAD. The results indicate that the FAD method reveals drug changes significantly more often than does the FFT analysis and that the medication effects are more clearly defined by the FAD. The method can be useful in the assessment of the subtle effects of the psychotropic drugs.

The EEG time series parametrization method in the study of nociception.

A new method of EEG time series parametrization was proposed. The EEG rhythms were described in terms of frequency, amplitude and damping. These parameters were used in multivariate analysis of variance in order to estimate the group differences in terms of Mahalanobis distances. The rhythm diagrams were constructed and their advantages in comparison with averaged power spectra were discussed. The proposed method overcomes the difficulties connected with the arbitrary division of spectrum into the frequency bands. The usefulness of the method in the study of nociception was tested. The effect of nociceptive stimulation in the four brain structures: sensorimotor cortex, ventro-postero-lateral thalamic nuclei, midbrain reticular formation and periaqueductal gray was investigated. The influence of atropine and mecamylamine administered locally was studied.

A new method of presentation of the average spectral properties of the EEG time series.

In framework of the AR model the transfer function and the impulse response function of the EEG time series were found. The parameters of the impulse response function were interpreted in terms of: frequencies, damping factors and amplitudes of the hypothetical brain rhythm generators. The method of the rhythm diagrams was proposed to describe the spectral properties of the EEG time series. It makes possible the accurate estimation of the EEG rhythm's frequencies and their intensities, especially weak components hardly visible in the conventional spectral analysis are well distinguished. Rhythm diagrams can be a useful tool in the clinical applications and offer new possibilities in the direct comparison of the results of modeling with the experimental data.

A study of stability of electrocortical rhythm generators.

By means of the autoregressive model the transfer function and the impulse response function were determined and the parameters characterizing electrocortical oscillators were found for the four brain structures of the experimental animals. Different kinds of the representation of these parameters were compared and their sensitivity to the different factors was tested. The advantages of the proposed method over the conventional spectral analysis were demonstrated. Cluster analysis was applied in order to test the stability of the determined basic rhythms. Proposed method seems to be very useful for the investigation of the processes of rhythmical activity generation and control.

Application of combined median-averaging filters to scintigraphic image processing.

Statistical and deterministic properties of median filters are briefly discussed and their inherent advantages as a prospective tool in scintigraphic data processing are pointed out. The ability of median filters of suppressing impulse noise while the edge-like features of an image are preserved, is demonstrated on phantom data. The residual high-frequency noise remaining after median filtering can be subsequently reduced by standard smoothing procedures. A simple algorithm, made up of the superposition of a median and an averaging filter, is presented and shown to be a promising candidate in the quest for fast and easy-to-implement processing routine.