Biomedical subjects

Roland Csuhaj

Publications and source records attributed to Roland Csuhaj.

4 recordsLinked to original sources

PubMed2006

[Changes in EEG-complexity after subcortical ischemic brain damage].

INTRODUCTION: Complexity analysis of the EEG is a relatively new field in theoretical and clinical electrophysiology. The authors present results of EEG-analysis in a patient with stroke, utilizing the sensitivity of the new procedures with respect to linear and nonlinear synchronization. PARTICIPANTS AND METHODS: The EEG (19 channels) was recorded in a patient with subcortical unilateral ischaemic completed stroke involving the frontoparietal white matter while leaving the cortex intact and in 12 healthy controls in eyes open and in eyes closed conditions. RESULTS: In the patient, increased Omega-complexity was found in slow (delta, theta) and lower alpha frequencies in the side of the stroke and in high frequencies (beta2 in eyes closed, alpha2, beta1 and beta2 in eyes open conditions) in the intact side. Synchronization likelihood was higher in the ischaemic side in the beta2 (eyes closed) and both in the beta1 and beta2 (eyes open) frequencies. Increasing Omega-complexity caused by eyes opening was markedly reduced in the patient in the beta frequencies compared to that seen in the controls. The difference was more conspicuous in the side of the infarct and involved not only the beta but also the alpha frequencies as well. Opening the eyes decreased synchronization likelihood in all frequency bands in the controls and also in the patient except the alpha2, beta1 and beta2 bands in the side of the lesion. CONCLUSIONS: The increased Omega-complexity and decreased synchronization likelihood in the slow frequencies in the infarcted side is probably the result of lesioned interneuronal connections lowering the level of cooperation of neuronal systems involved in this type of activity. The increased Omega-complexity and decreased synchronization likelihood caused by eyes opening could not be observed in the beta and alpha frequencies in the side of the lesion, possibly caused by damaged thalamocortical connections.

Alpha Rhythm↗

PubMed2006

[Spectral EEG-characteristics of subcortical ischemic brain lesion--a case study].

INTRODUCTION: Although the EEG-changes caused by ischemic stroke are well known, data of the literature are rather ambiguous. The EEG-findings recorded in a patient with a unilateral subcortical ischemic lesion are evaluated with special emphasis related to the effect of the dynamics caused by eye opening. PARTICIPANTS AND METHODS: Data recorded from a patient (54 years old male with a completed stroke involving the frontal and parietal subcortical region in the left side) were compared to those of a control group (12 healthy age matched subjects). Absolute and relative frequency spectra, theta/beta quotients, the interaction index characterizing the effect of eyes opening and the symmetry index were calculated from the EEG recorded in eyes closed and eyes open conditions. Data of the patient were compared to those recorded in the control group on the basis of 95% confidence intervals. RESULTS: Irrespective of the recording conditions the predominance of slow activity and the increase of theta/beta quotients were found in the absolute frequency spectra. The increase of beta and beta2 frequency bands following eye opening on the side of the lesion were found to be less obvious than that seen on the intact side and that observed in the control group. With respect to the interaction index related to the side differences caused by eye opening the change of the beta2 frequency band was found to be the most conspicuouS. The symmetry index underscored the predominance of slow (delta, theta, alpha1) frequencies on the lesion side, and that of the fast (beta1, beta2) frequencies on the intact side in both recording conditions. CONCLUSIONS: Localized lesion of the white matter without cortical damage can cause the predominance of slow activity and decrease of the fast frequency bands on the side of the lesion which can be shown by the absolute frequency spectra and is revealed by the symmetry index. The lack of functional reactivity of the fast frequencies in the side of the lesion can clearly be seen in the change of relative spectra following eye opening and on the basis of the calculation of the interaction index reflecting the dynamics of side differences.

Alpha Rhythm↗

PubMed2006

Spectral and complexity features of the EEG changed by visual input in a case of subcortical stroke compared to healthy controls.

OBJECTIVE: To compare spectral and complexity characteristics of the EEG in a unique case of subcortical infarct to those seen in healthy controls. METHODS: Absolute and relative frequency spectra, theta/beta ratio, the brain symmetry index (BSI), Omega-complexity and synchronization likelihood were calculated of the EEG recorded in eyes closed and eyes open conditions. RESULTS: Increased absolute delta, theta, and Omega-complexity in these frequency bands, higher theta/beta ratios, and decreased relative beta activity were found in the side of the infarct. The BSI localized the excess of slow, and decrease of fast frequency activity to the area of ischemia. Following eyes opening the increase of fast and decrease of slow frequencies, the increase of Omega-complexity in the alpha and beta bands, and the decrease of synchronization likelihood for the fast frequency bands were reduced in the side of the infarct. CONCLUSIONS: The subcortical infarct caused ipsilaterally increased slow, and decreased fast frequency activity accompanied by decreased synchronization of slow, increased synchronization of fast frequencies. Reduced reactivity in the ischemic side was particularly apparent for complexity measures. SIGNIFICANCE: Complexity indices of the EEG are sensitive complementary measures of electrophysiological changes caused by local lesions such as subcortical stroke.

Brain Ischemia↗

PubMed2005

[Psychophysiologic and clinical aspects of EEG synchronization related to cognitive processes].

The authors review the various forms of EEG-synchronization with special emphasis on the characteristics of the induced and enhanced rhythms. The suggested role of the various EEG frequency bands in the cognitive processes is demonstrated by examples from the literature. The relationship between linear and nonlinear electrophysiological complexity and EEG synchronization is analyzed, with a touch on the use of Omega-complexity and synchronization likelihood methods. In the present study the EEG recorded during adding and subtracting tasks was analyzed with the above methods. It was found that during the adding task the theta band increased in the frontal area, which may be related to activation of working memory processes. Mapping the scalp-distribution of synchronization likelihood also confirmed increased synchronization in the frontal area in addition to which increased values were found in the left temporo-parietal area. The analysis of linear and nonlinear EEG synchronization associated with cognitive processing is suitable to explore the task-related and region specific features of these events.

Alpha Rhythm↗