Using the nonlinear control of anaesthesia-induced hypersensitivity of EEG at burst suppression level to test the effects of radiofrequency radiation on brain function

Background  

In this study, investigating the effects of mobile phone radiation on test animals, eleven pigs were anaesthetised to the level where burst-suppression pattern appears in the electroencephalogram (EEG). At this level of anaesthesia both human subjects and animals show high sensitivity to external stimuli which produce EEG bursts during suppression. The burst-suppression phenomenon represents a nonlinear control system, where low-amplitude EEG abruptly switches to very high amplitude bursts. This switching can be triggered by very minor stimuli and the phenomenon has been described as hypersensitivity. To test if also radio frequency (RF) stimulation can trigger this nonlinear control, the animals were exposed to pulse modulated signal of a GSM mobile phone at 890 MHz. In the first phase of the experiment electromagnetic field (EMF) stimulation was randomly switched on and off and the relation between EEG bursts and EMF stimulation onsets and endpoints were studied. In the second phase a continuous RF stimulation at 31 W/kg was applied for 10 minutes. The ECG, the EEG, and the subcutaneous temperature were recorded.     

An improved technique for dental alloy etching with a potentiostatic device

Since a good retention of direct bonded retainers onto abutment teeth is the primary requirement for the fabrication of etched fixed partial dentures, successful formation of a micromechanical retentive architecture on the bonding surface is one of the most important procedures. For creating such a retentive dendritic pattern on nonprecious metal, a 2-electrode electrolytic method has been used. This equipment consists of a low-voltage DC power supply and two electrodes, namely, a working and a counter one. However, the current and voltage should be monitored during the entire processing time and the etching area must be pre-estimated. A potentiostat has been used to automatically stabilize the voltage across the working electrode and reference electrode by adjusting the current, as commonly employed in electro-chemical technology. A 3-electrode corrosion device originally developed for laboratory research was adapted for dental retainer etching in this study. The results revealed that the etching of dental nonprecious metal (Ni-Cr-Be alloy) could successfully be performed by using the system with a potentiostat. Moreover, the working potential was found to be approximately 1.3 volts by taking the midpoint between the breakdown and the critical potentials for passivation on the potentiostatic anode polarization curves. The optimal exposure time has been found to be in a range of 3 to 5 minutes and 4 minutes to be ideal as determined by SEM microphotographic observation which showed a uniform dendritic pattern with regular lattice form of alternating ridges and valleys.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of serotonin on the electrical activity of the cerebral cortex in the rabbit

Application of serotonin on the rabbit cerebral cortex produced prolonged (minutes) periodical oscillations of the activation level and the level of spatial synchronization of neocortical biopotentials. Periodical changes of biopotentials correlation were due above all to a significant reorganization of phasic correlation of the EEG theta-components of remote neocortex points. The changes may be explained by the appearance, due to serotonin, of slow oscillations of the excitation level of the cortical neurones, as a systemic transitional reaction to the change in the balance of excitatory and inhibitory processes. The ability of serotonin to influence phasic relationships of the distantly-synchronous cortical theta-rhythm is of considerable significance for conditioned activity.     

Bioelectrical activity of the brain in rabbit fetuses in relation to the duration of umbilical cord occlusion

Studies have been made on the EEG reactions in 20-, 25- and 28-day rabbit foetuses after complete occlusion of the umbilical cord. It was shown that in 20-day foetuses, EEG after the occlusion of the umbilical cord is presented mainly by low frequency waves. Significant decrease in the EEG amplitude took place to the 120th min, isoelectric stage was observed at the 150th min. In the frequency spectrum, the low frequency activity increased from 22.44 to 30.50%. As revealed by ECG control, the survival time after the occlusion of the umbilical cord is equal to 150 min. In 25-day foetuses, the decrease in the EEG amplitude was observed at the 150th min, isoelectric stage--to the 120th min. All the frequencies in the EEG spectrum were decreased. The survival time of foetuses was equal to 120 min. In 28-day foetuses, after the occlusion of the umbilical cord, a gradual decrease in the amplitude of EEG was observed from the 1st to the 60th min. Isoelectric stage occurred at the 105th min. Foetuses survived for 105 min. It is concluded that after the occlusion of the umbilical cord, re-arrangement in the EEG pattern takes place which includes two critical periods: the first one--immediately after the occlusion--is associated presumably with the reflex reaction of the organism of the foetus, whereas the second period includes the last minutes of survival, when a complete failure in the system of compensatory autoregulation is observed.     

PATTERN OF RNA SYNTHESIS IN RABBIT CORTEX DURING SLEEP

The pattern of RNA biosynthesis in rabbit cerebral cortex was examined during periods of physiological sleep and wakefulness monitored with EEG techniques. The types of newly synthesized RNA were analysed by sedimentation on sucrose gradients. In experiments lasting 60 and 105 minutes the labelling ratio of RNA sedimenting in two regions of the gradient (28 S-50 S50 S) increased with decreasing percentages of EEG synchronization. Analysis of the radioactivity distributions of five homogeneous experiments in terms of moments confirmed the dependence of the RNA synthetic pattern on the electric state of the cortex. The possible nature of the RNA species involved in this effect is discussed.     

Application of Fast Fourier Transform in Electroencephalography

Today the Fourier Transform is also used in the analysis of biological time series with periodical parts. For N = 2^M EEG sampling values the Fast Fourier Transform algorithm of COOLEY and TUKEY is applicable. For this a FORTRAN IV program EEG-FFT has been developed for computation of power spectrum. At the data processing equipment EC 1040 the CPU-time for 2¹⁰ = 1024 EEG sampling values is smaller than 1.5 s. The FORTRAN IV program can be applied both in offline and online data processing.     

Effect of apomorphine on human sleep

The effect of intravenous infusion of apomorphine in non emetic doses (10–15 μg/min) on the sleep of ten subjects was studied. During apomorphine infusion for 180 minutes, a complete suppression of REM sleep and a dramatic reduction of the amount of delta sleep occurred. Thus, the EEG pattern was characterized almost exclusively by the presence of “light” sleep. After discontinuation of apomorphine, a rebound increase in REM sleep occured.     

Mu-delta opioid interactions. I: The delta peptide, DPDPE, increases morphine-induced EEG and EEG spectral power.

The effects of the selective delta peptide, DPDPE ([2-D-penicillamine,5-D-penicillamine]enkephalin), on morphine-induced EEG and EEG power spectra were assessed. Adult female Sprague-Dawley rats were implanted with cortical EEG electrodes and permanent indwelling ICV and IV cannulae. Rats were pretreated with ICV sterile water or ICV DPDPE at 1.25, 2.5, or 5.0 nmol, 10 min before receiving IV morphine at 3 mg/kg. The treatments produced high voltage EEG bursts and associated behavioral stupor. The EEG data were further analyzed on a Pathfinder II computer and statistical analysis of EEG spectral parameters was performed by using a one-way ANOVA followed by Turkey's HSD. ICV DPDPE at 2.5 nmol and 5.0 nmol significantly increased EEG absolute global spectral power. Furthermore, ICV DPDPE at 2.5 and 5.0 nmol significantly increased the duration of morphine-induced high voltage EEG bursts. These data further indicate an in vivo interaction between mu and delta opioid receptors.     

EEG Correlates of Dream Recall in Depressed Outpatients and Healthy Controls

The present study explored EEG correlates of dream recall in 17 symptomatic, unmedicated depressed patients and in 19 healthy adults. EEG segments from the last 30 minutes of sleep, from the five minutes following morning awakening, and the absolute difference between sleep and waking EEG were contrasted between the two groups of participants during successful dream recall and during no recall. Period amplitude analysis was used to quantify EEG frequencies. Increased high-frequency beta incidence in the right hemisphere and amplitude in both hemispheres during sleep were associated with dream recall in both patient and control groups. Depressed patients also showed higher delta amplitude in both hemispheres during sleep associated with recall, but this effect did not reach significance. With regard to the changes between sleep and wakefiilness, a smaller change in right hemisphere beta and delta incidence characterized successful recall in healthy controls. By contrast, those with depression showed recall success when the sleep/wake shifts in right hemisphere beta and delta incidence were larger. Recall failure was characterized by small EEG shifts from sleep to wakefulness in the depressed group. The same effects were observed for beta and delta amplitude measures, except that healthy controls showed a large shift in delta amplitude in the sleep-wake transition during successful recall but not during recall failure. Recall in those with depression was associated with a dramatic shift in left hemisphere delta amplitude. These findings provide support for Koukkou and Lehmann's (1983, 1993) state-shift hypothesis of dream recall in healthy controls (except for left hemisphere delta amplitude) but not in the depressed. It appears that in order to recall a dream, depressed patients must undergo larger shifts in brain activity and perhaps a different pattern of reorganization of EEG frequencies than controls. This finding may account for the low rates of recall reported previously in this clinical group.     

Maintenance and generalization of 40-Hz EEG biofeedback effects

Maintenance of conditioning of 40-Hz EEG activity was investigated in six adults 1 to 3 years after they had experienced biofeedback training to increase 40-Hz EEG. Subjects were first retrained to alternately increase and suppress 40-Hz EEG. All six subjects achieved a preset performance criterion in 16–20 minutes. Five of these subjects also subsequently demonstrated significant control of 40-Hz EEG without feedback. The sixth subject did not demonstrate control after 76 minutes and four sessions of attempted retraining with feedback. Transfer of 40-Hz EEG control to a problem-solving task was tested in all subjects in a final session. Cognitive test items were presented and subjects were instructed to alternately increase and suppress 40-Hz EEG while solving the problems. Rates of 40-Hz EEG in suppression periods during problem solving were significantly greater than during suppression periods without problems. No significant differences in problem-solving performance were found comparing 40-Hz increase and suppression periods. This study supports previous research suggesting an association between 40-Hz EEG and mental activity, and suggests methods for further study of transfer of EEG biofeedback effects.     

Age peculiarities of trace discharges of after-effect and of the activity of epileptogenic zone in the hippocamp of rabbits]

Seizure activity in the hippocamp has been studied on 6-10-, 16-20-day and adult rabbits. The pattern and thresholds of trace discharges of after-effect evoked by the electrical stimulation of the hippocamp were found to be similar in animals of all age groups. However, the amplitude of after-discharges significantly increased during the development of the brain. After the formation of penicillin epileptogenic zone in the hippocamp, EEG of all animals exhibited the identical types of focal interseizure discharges and electrographic correlates of seizures, yet the amplitude of epileptifiorm discharges on the EEG increased with age. Contralateral hippocamp was involved into the pathological process more easily in young rabbits than in adult ones.     

Electroencephalographic (EEG) Measurements of Mindfulness-based Triarchic Body-pathway Relaxation Technique: A Pilot Study

Objective The “Triarchic body-pathway relaxation technique” (TBRT) is a form of ancient Chinese mindfulness-based meditation professed to give rise to positive emotions and a specific state of consciousness in which deep relaxation and internalized attention coexist. The purpose of this study was to examine the EEG pattern generated during the practice of this mindfulness exercise, and compare it to music listening which has been shown to induce positive emotions. Methods Nineteen college students (aged 19–22 years) participated in the study. Each participant listened to both the TBRT and music audiotapes while EEG was recorded. The order of presentation was counterbalanced to avoid order effect. Two EEG indicators were used: (1) alpha asymmetry index, an indicator for left-sided anterior activation, as measure of positive emotions, and (2) frontal midline theta activity, as a measure for internalized attention. Results Increased left-sided activation, a pattern associated with positive emotions, was found during both TBRT exercise and music conditions. However, only TBRT exercise was shown to exhibit greater frontal midline theta power, a pattern associated with internalized attention. Conclusions These results provided evidence to support that the TBRT gives rise to positive emotional experience, accompanied by focused internalized attention.     

Morphine challenges in levo-alpha-acetylmethadol (LAAM) post-addict rats

LAAM dependence was established in female Sprague-Dawley rats over a two week period by a series of twice daily oral intubations. LAAM was then withdrawn. These LAAM post-addict rats along with controls were challenged with 10 mg/kg of i.p. morphine at 15 days, one month, three months, and six months post-withdrawal. In control rats morphine challenges produced, as expected, a biphasic response consisting of 60–90 minutes of EEG slow-wave bursts and behavioral depression followed by 60–90 minutes of EEG and behavioral arousal. In LAAM post-addict rats on day 15 of abstinence morphine challenges produced primarily EEG and behavioral arousal for two to three hours with little or no depression. At one and three months of LAAM abstinence morphine challenges still produced more immediate and sustained EEG and behavioral arousal during the initial two hours than in control rats. At six months in LAAM post-addict rats responses to morphine challenges were biphasic and were similar to those seen in control rats. These results are indicative of protracted abstinence in LAAM post-addict rats, and these results are analogous to those previously reported from our laboratory for morphine post-addict rats.     

Effects of melatonin administration and pinealectomy on the electroencephalogram of the chicken (Gallus domesticus) brain.

Melatonin, injected into chickens, lowers the frequency and increases the amplitude of the electroencephalogram (EEG) within 2 minutes. EEGs of chickens, 10–12 weeks of age, that had been pinealectomized when less than a week old, displayed fewer higher amplitude cycles, suggesting a long-term effect of pinealectomy on brain electrical activity. These results indicate that the pineal gland, perhaps through the action of melatonin, has an influence on brain function in birds.     

EEG power spectrum analysis for monitoring depth of anaesthesia during experimental surgery

The first attempts to introduce computerized power spectrum analysis of the electroencephalogram (EEG) as an intraoperative anaesthesia monitoring device started approximately 30 years ago. Since that time, the effects of various anaesthetic agents, sedative and analgesic drugs on the EEG pattern have been addressed in numerous studies in human patients and different animal species. These studies revealed dose-dependent changes in the EEG power spectrum for many intravenous and volatile anaesthetics. Moreover, EEG responses evoked by surgical stimuli during relative light levels of surgical anaesthesia have been classified as 'arousal' and 'paradoxical arousal' reaction, previously referred to as 'desynchronization' and 'synchronization', respectively. Contrasting reports on the correlation between quantitative EEG (QEEG) variables derived from power spectrum analysis (i.e. spectral edge frequency, median frequency) and simultaneously recorded clinical signs such as movement and haemodynamic responses, however, limited the routine use of intraoperative EEG monitoring. In addition, the appearance of EEG burst suppression pattern and isoelectricity at clinically relevant concentrations/doses of newer general anaesthetics (i.e. isoflurane, sevoflurane, propofol) may have weakened the dose-related EEG changes previously reported. Despite these findings, the EEG power spectrum analysis may still provide valuable information during intraoperative monitoring in the individual subject. The information obtained from EEG power spectrum analysis may be further supplemented by newer EEG indices such as bispectral index and approximate entropy or other neurophysiological monitors including auditory evoked potentials or somatosensory evoked potentials.     

LEDPatNet19: Automated Emotion Recognition Model based on Nonlinear LED Pattern Feature Extraction Function using EEG Signals

Electroencephalography (EEG) signals collected from human brains have generally been used to diagnose diseases. Moreover, EEG signals can be used in several areas such as emotion recognition, driving fatigue detection. This work presents a new emotion recognition model by using EEG signals. The primary aim of this model is to present a highly accurate emotion recognition framework by using both a hand-crafted feature generation and a deep classifier. The presented framework uses a multilevel fused feature generation network. This network has three primary phases, which are tunable Q-factor wavelet transform (TQWT), statistical feature generation, and nonlinear textural feature generation phases. TQWT is applied to the EEG data for decomposing signals into different sub-bands and create a multilevel feature generation network. In the nonlinear feature generation, an S-box of the LED block cipher is utilized to create a pattern, which is named as Led-Pattern. Moreover, statistical feature extraction is processed using the widely used statistical moments. The proposed LED pattern and statistical feature extraction functions are applied to 18 TQWT sub-bands and an original EEG signal. Therefore, the proposed hand-crafted learning model is named LEDPatNet19. To select the most informative features, ReliefF and iterative Chi2 (RFIChi2) feature selector is deployed. The proposed model has been developed on the two EEG emotion datasets, which are GAMEEMO and DREAMER datasets. Our proposed hand-crafted learning network achieved 94.58%, 92.86%, and 94.44% classification accuracies for arousal, dominance, and valance cases of the DREAMER dataset. Furthermore, the best classification accuracy of the proposed model for the GAMEEMO dataset is equal to 99.29%. These results clearly illustrate the success of the proposed LEDPatNet19.     

Comparison of spontaneous activity of mesencephalic reticular neurones in the waking state and during pentobarbital anaesthesia.

In rats immobilized by d-Tubocurarine the spontaneous activity of 100 mesencephalic reticular neurones was recorded extracellularly and statistically evaluated before and after repeated intravenous administration of 15 mg/kg doses of Pentobarbital. Number of spontaneously active neurones decreases quasi-linearly with repeated 15 mg/kg Pentobarbital doses. After a 75 mg/kg cumulative dose practically all neurones ceased firing spontaneously, whereas cortical EEG activity fully disappeared after the 90 mg/kg Pentobarbital dose. The firing rate was characterized by the mean interval with its standard deviation. Mean value for the total sample of spontaneously active neurones was 146.7 +/- 192.3 msec without Pentobarbital and increased to 302.7 +/- 367.5 msec after 15 mg/kg and to 400.6 +/- 452.5 msec after 30 mg/kg cumulative dose of Pentobarbital. The 15 mg/kg dose increased the frequency of firing in 5% of neurones only. The most often encountered type of interval histogram in the mesencephalic reticular formation was the exponential type (59% in unanaesthetized state), which was also most sensitive to Pentobarbital. Synchronized activity in bursts, characterized by periodical peaks and dips frequently occurred in neurones with the exponential-like interspike interval density after Pentobarbital administration. On the contrary, neurones with gamma-like and especially with symmetrical-like types of density were less influenced by Pentobarbital. In many neurones a periodical increase in the firing rate (with intervals of tens of seconds) related to the occurrence of spindles was present in the cortical EEG activity.     

Nanopore unzipping of individual DNA hairpin molecules

We have used the nanometer scale alpha-Hemolysin pore to study the unzipping kinetics of individual DNA hairpins under constant force or constant loading rate. Using a dynamic voltage control method, the entry rate of polynucleotides into the pore and the voltage pattern applied to induce hairpin unzipping are independently set. Thus, hundreds of unzipping events can be tested in a short period of time (few minutes), independently of the unzipping voltage amplitude. Because our method does not entail the physical coupling of the molecules under test to a force transducer, very high throughput can be achieved. We used our method to study DNA unzipping kinetics at small forces, which have not been accessed before. We find that in this regime the static unzipping times decrease exponentially with voltage with a characteristic slope that is independent of the duplex region sequence, and that the intercept depends strongly on the duplex region energy. We also present the first nanopore dynamic force measurements (time varying force). Our results are in agreement with the approximately logV dependence at high V (where V is the loading rate) observed by other methods. The extension of these measurements to lower loading rates reveals a much weaker dependence on V.     

Electroencephalography in the diagnosis of hydrocephalus in golden hamsters (Mesocricetus auratus)

The golden hamster (Mesocricetus auratus) is a popular laboratory animal and is used in a multitude of behavioural studies. However, it has been shown that it suffers from different forms of hereditary hydrocephalus, which may result in behavioural changes. This prospective study was designed to look into the usefulness of electroencephalography (EEG) measurements in the diagnosis of hydrocephalus in hamsters. The EEGs of the hydrocephalic hamsters were evaluated double-blind and showed a high-voltage slow wave activity, with a fast activity superimposed onto it. This pattern has already been well described in other hydrocephalic species and differed significantly from the EEGs that were obtained from the normal hamsters. It was concluded from our study that a background activity with an amplitude over 50 muV in combination with a frequency of < or =5 Hz was highly indicative of hydrocephalus in young hamsters. We believe that the EEG could be a very useful diagnostic tool in the screening for hydrocephalus in hamsters.     

Spectral Analysis of Long Electroencephalographic Records

Spectral analysis of a 10-min electroencephalogram (EEG) record has made it possible to describe the behavior of EEG rhythms as a dynamic spectrum and find a distinct periodic pattern in this behavior. The data on the dynamic spectra of long EEGs offer a new insight into the estimation of the stability of EEG electrical processes in healthy subjects, inter- and intrahemispheric relationships between the electrical activities of different cortical regions, and estimation of phase relations, which were previously performed on the basis of comparison between single EEG spectral patterns.