Comparative effect of bisoprolol and losartan in the treatment of essential hypertension.

OBJECTIVE: We investigated the effects of bisoprolol and losartan on subjects with essential hypertension, by conducting heart rate variability (HRV) analysis of ECG signals. Our intention was to establish the set of linear and nonlinear heart rate variability parameters, which could be used as a noninvasive markers in the treatment of hypertension. MATERIALS AND METHODS: Sixty subjects with essential hypertension included in this study were divided in two groups. During the four weeks medical treatment, the first group was administered with daily oral dose of 5 mg of bisoprolol and the second with daily oral dose of 50 mg of losartan. We recorded ECG signals, and performed HRV analysis of consecutive RR time intervals, before and after a month of pharmacological therapy. RESULTS: IN THE CASE OF BISOPROLOL, STATISTICALLY THE MOST SIGNIFICANT CHANGES OF HRV PARAMETERS WERE: TP (1814.1 ± 1731.3 ms(2) vs. 761.3 ± 725.0 ms(2), P < 0.0001), RR (870.2 ± 105.7 ms vs. 1027.2 ± 150.0 ms, P < 0.0001), HR (70.81 ± 8.42 bp/min vs. 60.10 ± 9.52 bp/min, P < 0.0001). In the case of losartan, the most significant changes were: SDNN (43.16 ± 17.27 ms vs. 237.98 ± 118.54 ms, P = 0.002), rmSDD (27.09 ± 18.27 ms vs. 46.82 ± 37.71 ms, P = 0.003), SD2 (55.18 ± 20.6 vs. 70.67 ± 26.12, P < 0.019) and DF2 (0.69 ± 0.21 vs. 0.86 ± 0.25, P < 0.014). CONCLUSION: Effects of bisoprolol and losartan were especially manifested among the set of linear HRV parameters. As a consequence of effect of losartan, we singled out the nonlinear parameters SD2 and DF2.

Wavelet and fractal analysis of rat brain activity in seizures evoked by camphor essential oil and 1,8-cineole.

We investigated the rat brain activity in acute seizures evoked by camphor essential oil or its main constituent 1,8-cineole by wavelet (primarily) and fractal analysis. Experiments were performed on anesthetized animals before and after intraperitoneal camphor oil or cineole administration. The properties of frequency bands in pre-ictal, ictal and inter-ictal stages have been determined by wavelet analysis. The domination of delta frequency band was confirmed in obtained brain activities, which participate with approximately 45% of mean relative wavelet energy (MRWE) in control signals and arise up to approximately 76% MRWE in energy spectrum during the ictal stage (after drug administration). Other frequency bands decreased during ictal stage and arised in inter-ictal stage. There was a dosedependent response of cineole effect: increase in cineole concentration leaded to the higher values of relative wavelet energy (RWE) of delta frequency band while there were slight changes of the mean fractal dimension (FD) values as a measure of system complexity.

Estimation of parameter kmax in fractal analysis of rat brain activity.

We recorded electrocortical activity in anesthetized rats and constructed k(max) new self-similar time series, applying Higuchi's algorithm. The aim of this study was to estimate value of the parameter k(max) in order to obtain fractal dimension values as an optimum measure of biosignal change. After our analysis, electrocortical activity recordings resulted in a family of curves f(k(max)). Three regions could be distinguished 2 < or = k(max) < 8, with a U-shape; 8 < or = k(max) < or = 30, with a steeper quasilinear increase; and k(max) > or = 30, with a smaller slope quasilinear increase. We suggest the optimum region for k(max): 8 < k(max) < 18, specifically k(max) = 8.

Spectral analysis of cerebellar activity after acute brain injury in anesthetized rats.

We investigated cerebellar electrocortical activity before and after unilateral brain injury in anesthetized rats. Spectral analysis of cerebellar activity was obtained by Fast Fourier Transformation. There was a dominance of delta frequency range, while the wide gamma range presented no more than 5% of the total mean power spectra of cerebellar activity before brain injury. A few minutes after brain injury and within the first 90 minutes, there was a decrease of total mean power spectra and a relative decrease of delta range power to about 30%, some increase of beta range, and an increase of gamma range to 20-25%. Relative increase of gamma range in the cerebellar mean power spectra was still present 120 min after the brain injury, while other changes started to diminish. We suggest that spectral changes within slow and fast (gamma) frequency ranges of cerebellar activity may be indicators of the brain state after acute injury.

The functional neuroimaging evidence of cerebellar involvement in the simple cognitive task.

Cerebellar involvement in cognitive functions has been revealed in numerous anatomical, clinical and neuroimaging studies and several hypotheses about potential the role of the cerebellum in higher level brain function have been established. The aim of this study was to show involvement of the cerebellum in simple cognitive tasks. For this matter, we contrasted two tasks from the same semantic domain with specific cognitive content and level of practice: counting forward and counting backward. Twelve volunteers participated in this fMRI study and they were asked to perform both tasks within the same number range (1 to 30 and vice versa). Results showed greater activation in the right cerebellum for the task of counting forward than for counting backward, while for counting backward greater activation was found in prefrontal cortex, supplementary motor area, and anterior cingulate of both hemispheres. Our results correlate with already established hypotheses about cerebellar role in precise and smooth control, not only in well-trained motor but in well trained cognitive tasks as well.

Spectral and fractal measures of cerebellar and cerebral activity in various types of anesthesia.

The features of rat cerebral and cerebellar electrocortical activity (ECoG) under different types of anaesthesia (nembutal, ketamine or zoletil) were examined by the distribution of spectral entropy across frequency bands of ECoG and by calculation of fractal dimension determined on the basis of Higuchi's algorithm. Spectral entropy, as a measure of activity, in the case of cerebrum had greater values than the spectral entropy of cerebellum in low frequency ranges, regardless of the type of applied anesthetic. Various anesthetics evoked different effects on spectral entropy of electrocortical activity: spectral entropy of delta range greatly dominated under nembutal anesthesia, while ketamine or zoletil appeared to affect the spectral entropy of higher frequency ranges. The pronounced effect of ketamine or zoletil anesthesia on spectral entropy of higher frequency was confirmed by the higher values of Higucihi's fractal dimension (FD) of ECoGs, with a tendency of higher FD values in cerebellar activity than cerebral activity.

Gender differences in brain areas involved in silent counting by means of fMRI.

BACKGROUND: Pattern of brain asymmetries varies with handedness, gender, age, and with variety of genetic and social factors. Large-scale neuroimaging analyses can optimize the detection of asymmetric features and confirm the factors that might modulate pattern of brain asymmetries. We attempted to evaluate eventual differences between genders in hemodynamic responses to a simple language task. METHODS: 12 healthy right-handed volunteers (age 24-46), 6 men and 6 women underwent fMRI scanning while performing the simple cognitive - language processing task - silent number counting in Serbian. RESULTS: Group analysis of hemodynamic responses shows activation in expected brain language areas of inferior frontal gyrus (IFG) and superior temporal gyrus (STG) in both hemispheres. In the male group, aside from dedicated language areas in IFG and STG, activation was noted in right frontal region and interhemispheric supplementary motor area. On the other hand, in the female group, besides activation in dedicated language areas, activation was noted, in right hippocampus, limbic brain and cerebellum bilaterally. CONCLUSIONS: Our results on differences in silent counting by means of fMRI suggest that those differences may be based on different brain pattern activation in men and women. The relation between performance, strategies and regional brain activation should be the topic of further studies when considering not only gender differences in language processing but also differences that may be attributed to the variations in the task details, stimuli, and the stimulus presentation methods.

Fractal dimension values of cerebral and cerebellar activity in rats loaded with aluminium.

Aluminium interferes with a variety of cellular metabolic processes in the mammalian nervous system and its intake might increase a risk of developing Alzheimer's disease (AD). While cerebral involvement even at the early stages of intoxication is well known, the role of cerebellum is underestimated. Our aim was to investigate cerebral and cerebellar electrocortical activity in adult male rats exposed to chronic aluminium treatment by nonlinear analytic tools. The adult rats in an aluminium-treated group were injected by AlCl(3), intraperitoneally (2 mg Al/kg, daily for 4 weeks). Fractal analysis of brain activity was performed off-line using Higuchi's algorithm. The average fractal dimension of electrocortical activity in aluminium-treated animals was lower than the average fractal dimension of electrocortical activity in the control rats, at cerebral but not at cerebellar level. The changes in the stationary and nonlinear properties of time series were more expressed in cerebral electrocortical activity than in cerebellar activity. This can be useful for developing effective diagnostic and therapeutic strategies in neurodegenerative diseases.

Signatures of depression in non-stationary biometric time series.

This paper is based on a discussion that was held during a special session on models of mental disorders, at the NeuroMath meeting in Stockholm, Sweden, in September 2008. At this occasion, scientists from different countries and different fields of research presented their research and discussed open questions with regard to analyses and models of mental disorders, in particular depression. The content of this paper emerged from these discussions and in the presentation we briefly link biomarkers (hormones), bio-signals (EEG) and biomaps (brain-maps via EEG) to depression and its treatments, via linear statistical models as well as nonlinear dynamic models. Some examples involving EEG-data are presented.

Spectral and fractal analysis of cerebellar activity after single and repeated brain injury.

The cerebellum, even when not directly damaged, is potentially interesting for understanding the adaptive responses to brain injury. Cerebellar electrocortical activity (ECoG) in rats was studied using spectral and fractal analysis after single and repeated unilateral injury of the parietal cortex. Local field potentials of cerebellar paravermal cortex were recorded before brain injury, in the acute phase (up to 2.5 hours) after a first injury of anesthetized rats, and then before and after second, third, and, in some cases, fourth injury. Relative gamma power (32.1-128.0 Hz) and fractal dimension of ECoGs were temporarily increased after the first injury. However, there was a permanent mild increase in gamma activity and a mild increase in the fractal dimension of cerebellar activity as a chronic change after repeated remote brain injury. There was a negative linear correlation between the normalized difference in fractal dimensions and normalized difference in gamma powers of cerebellar activity only in the case of repeated brain injury. This is the first study showing that correlation between the parameters of spectral and fractal analyses of cerebellar activity can discriminate between single and repeated brain injuries, and is, therefore, a promising approach for identifying specific pathophysiological states.