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M Palus

Publications and source records attributed to M Palus.

8 recordsLinked to original sources
PubMed1998

Coarse-grained entropy rates quantify fast Ca2+ dynamics modulated by pharmacological stimulation.

Calcium (Ca2+) is an ubiquitous intracellular messenger which regulates cellular processes, such as secretion, contraction, and cell proliferation. A variety of cell types respond to hormonal stimuli with periodic oscillations of the intracellular free Ca2+ concentration ([Ca2+]i) which can be modulated in their frequency in a dose-dependent manner. The period of these well-studied oscillations varies normally between 30 sec and a couple of minutes. Here we study [Ca2+]i oscillations in clonal beta cells (hamster insulin secreting cells, HIT) under pharmacological stimulation. Besides the well-known high-amplitude low frequency oscillations we try to analyze for the first time low-amplitude high frequency oscillations of [Ca2+]i under pharmacological stimulation which have not been explored in experimental approaches to date. Using coarse-grained entropy rates computed from information-theoretic functionals we demonstrate differences in temporal complexity of the fast low-amplitude [Ca2+]i dynamics corresponding to different phases of pharmacological stimulation which are additional to the well-known dose-dependent pattern of low-frequency high amplitude [Ca2+]i dynamics.

Algorithms↗
PubMed1996

Nonlinearity in normal human EEG: cycles, temporal asymmetry, nonstationarity and randomness, not chaos.

Two-hour vigilance and sleep electroencephalogram (EEG) recordings from five healthy volunteers were analyzed using a method for identifying nonlinearity and chaos which combines the redundancy-linear redundancy approach with the surrogate data technique. A nonlinear component in the EEG was detected, however, inconsistent with the hypothesis of low-dimensional chaos. A possibility that a temporally asymmetric process may underlie or influence the EEG dynamics was indicated. A process that merges nonstationary nonlinear deterministic oscillations with randomness is proposed for an explanation of observed properties of the analyzed EEG signals. Taking these results into consideration, the use of dimensional and related chaos-based algorithms in quantitative EEG analysis is critically discussed.

Algorithms↗
PubMed1995

Global dimensional complexity of the EEG in healthy volunteers.

In contrast to the single-channel dimensional complexity, the global dimensional complexity is calculated from a multichannel EEG. The intention with the method is to measure the spatial distribution of information processing in the brain. The method seems to be of interest in psychopharmacological research, but the interpretation of the results in physiological terms is rather difficult. To get a more detailed information on the physiological significance of the EEG complexity measures, the influence of well-known physiological factors was studied in a group of 14 healthy subjects aged from 1.5 to 61 years. It was found that the correlation dimension was somewhat higher in older individuals, but the correlation with age was not statistically significant. However, the global correlation dimension was significantly lower during full alertness than during drowsiness. These results might reflect the changes in spatial structure of information processing, a high complexity suggesting a 'disorganisation' during drowsiness. As regards the age-dependent changes of the correlation dimension, the spatial 'flexibility' of information processing was also studied, using the differences between the 'alert' and 'drowsy' parts of the same EEG as indicator. It was found that the differences 'drowsy minus alert' were significantly related to age. A plausible interpretation seems to be that the spatial distribution of information processing is more changeable, or more flexible, in adults than in children.

Adolescent↗
PubMed1993

Dynamics of the effects of levoprotiline and maprotiline on EEG in patients with major depressive episodes (DSM-III-R).

The presented study compares the effect of the well-tested antidepressant maprotiline and a new antidepressant with an atypical pharmacological profile, levoprotiline, on EEG during repeated assessment after single dose administration. From the original number of 34 patients fulfilling the criteria of a major depressive episode (DSM-III-R) on account of a low-voltage record or pathological findings 11 were eliminated. To 12 of the remaining patients levoprotiline was administered and to 11 maprotiline, after a one-week placebo period, in doses of 150 mg. The EEG was recorded after an accommodation session immediately before, 1.5, 3, 4.5, 6 and 24 hours after a single dose administration. The record was taken on a 16-channel average reference montage at rest with closed eyes. Two-minute intervals were divided into 30 four-second periods at a sampling frequency of 128 Hz. From the signal by means of FFT the spectra were estimated and the mean spectrum for the entire recording was calculated. This was then divided into 10 frequency bands. The new method of frequency analysis of alpha-entropy was also used which is a global measure of the difference between two spectra. Three hours after administration of a single dose levoprotiline had an EEG profile corresponding to the profile of tricyclic antidepressants, i.e. it increased the values of the power spectra density in the region of 5-8.5 Hz and in the entire beta band; the decline of power in the alpha band was, however, absent. As regards maprotiline, 3 hours after administration a profile typical for antidepressants was not found; obviously because of the great variance of values of power spectra density as a result of great interindividual differences in the ingestion phase. Changes of the EEG spectrum expressed as values of alpha-entropy during different periods of apparently assessment are not incidental. After the initial rise of values a decline occurs.

Adult↗
PubMed1991

The spectral dynamics and its applications in EEG.

The method of spectral dynamics is introduced to process slow changes in EEG. This method is based on evaluation of distance between EEG spectra. The typical application field is pharmaco-EEG after single dose drug administration, where distances between pre and post drug EEG spectra are computed. The distance between two spectra may be, however, defined in several different ways. The paper deals with the well known Lp metrics and with the metrics alpha that plays an important role in discriminating stationary processes with different spectra. The Lp and alpha metrics are non-equivalent and their properties, consistency and robustness, are studied in a simple statistical model.

Animals↗