Significant EEG Changes Research Articles

Individual changes in human EEG caused by 450 MHz microwave modulated at 40 and 70 Hz

This study was aimed to investigate the changes in the human electroencephalographic (EEG) signal caused by modulated low-level microwaves. The 450 MHz microwave exposure modulated at 40 Hz and 70 Hz frequencies was applied to a group of 15 volunteers. The field power density at the scalp was 0.16 mW/cm2. Ten cycles of the exposure (1 min on and 1 min off) at both modulation frequencies were applied. Analysis of the EEG signal was performed using three different methods: nonlinear method of scaling analysis for length distribution of low variability periods (LDLVP), relative changes in EEG energy (S-parameter) and beta ratio (H-parameter). The analysis revealed significant changes caused by microwave for the whole group (H-parameter method). The exposure caused increase of the EEG beta power (S-parameter method). Statistically significant changes in EEG were detected for four subjects (26.7%) at 40 Hz modulation frequency (LDLVP method).

Effect of basal forebrain neuropeptide Y administration on sleep and spontaneous behavior in freely moving rats

Neuropeptide Y (NPY) is present both in local neurons as well as in fibers in the basal forebrain (BF), an area that plays an important role in the regulation of cortical activation. In our previous experiments in anaesthetized rats, significant EEG changes were found after NPY injections to BF. EEG delta power increased while power in theta, alpha, and beta range decreased. The aim of the present experiments was to determine whether NPY infusion to BF can modulate sleep and behavior in freely moving rats. In this study, microinjections were made into the BF. Saline was injected to the control side, while either saline or one of two doses of NPY (0.5 μl, 300–500 pmol) to the treated side. EEG as well as behavioral changes were recorded. Behavioral elements after the NPY injections changed in a characteristic fashion in time and three consecutive phases were defined. In phase I (half hour 2), activated behavioral items (moving, rearing, grooming) appeared frequently. In phase II (half hours 3 and 4) activity decreased, while motionless state increased. Reappearance of activity was seen in phase III (half hours 5 and 6). NPY injections caused sleep–wake changes. The three phases described for behavioral changes were also reflected in the sleep data. During phase I, lower NPY dose increased wakefulness and decreased deep sleep. Reduced behavioral activity seen in phase II was partially reflected in the sleep. In this phase, wakefulness tended to increase in the third half hour, while decreased in the 4th half hour. Deep sleep and total slow wave sleep non-significantly decreased in the third and increased in the 4th half hour. In most cases, wakefulness was elevated again during Phase III, while sleep decreased. Length of single sleep–wake epochs did not change after NPY injections. Our results suggest a role for NPY in the integration of sleep and behavioral stages via the BF.

Individual Sensitivity to Low-level Radio-frequency Exposure

P-537 Introduction: The increasing applications of IT and telecommunication devices in everyday life have aroused problem of possible interaction effects of the radio-frequency electromagnetic field (EMF) on human brain physiology. Changes in human electroencephalographic (EEG) signals can be an efficient measure of the EMF effect on brain bioelectrical activity. This study is focused on the individual sensitivity to modulated low-level microwave exposure effects on human EEG rhythms. Methods: The experiments were carried out on four different groups of healthy volunteers exposed to an identical 450 MHz EMF modulated with frequencies 7Hz, 14 Hz, 21 Hz, 40 Hz, 70 Hz, 217 Hz and 1000 Hz. The field power density at the scalp was always 0.16 mW/cm2. Experimental protocol consists of 10 cycles of repetitive EMF exposure (1 min on and 1 min off) and reference (sham) recordings. The EEG signals were continuously recorded during all experimental session. As a measure the relative changes (in pro cents) of the EEG rhythms energy between segments with and without exposure were calculated. 3D ANOVA with post-hoc Bonferroni test was applied for statistical analysis and p values lower than 0.05 were considered as significant. Results: The EMF induced changes in EEG were remarked as an increase in EEG energy. The EMF induced changes were stronger in temporal and parietal channels and for EEG beta rhythms (15–20 Hz and 22–40 Hz). The rate of individuals with statistically significant changes in EEG varied from 12,5% to 30% for different modulation frequencies and groups. Table 1. Rate of subjects with statistically significant changes in EEG Modulation frequency Hz Number of subjects Relative change % Rate of sensitivity Reference 7 23 40 25% Bachmann et al., Med Biol Eng Comput. 2005 14 13 150 30% 21 13 140 23% 40 15 110 20% 70 15 80 12,5% 217 19 60 26% 1000 19 70 21TABLE 1: Rate of Subjects With Statistically Significant Changes in EEGDiscussion and conclusion: Exposure to EMF affected brain bioelectrical activity for part of subjects. Main trend of changes for all modulation frequencies was increase of the EEG energy in beta rhythm. Increased beta absolute power was also observed in alcohol-dependent subjects (Rangaswamy et al. Biol Psychiatr. 2002). The rate of multiple chemical sensitivity (exposures to multiple chemically unrelated compounds at doses far below those established to cause harmful effects occurrence) is estimated to be between 2 and 10% in the general population (Cullen, 1987). Our results suggest that the microwave exposure causes significant changes in human EEG and affects up to 30% of population (more than chemically unrelated compounds) and can have an impact on health.

Transient and permanent magnetic resonance imaging abnormalities after complex partial status epilepticus

Epileptic seizures, especially status epilepticus can produce MRI changes. In contrast to convulsive status epilepticus (CSE), permanent parenchymal loss is not well documented with nonconvulsive status epilepticus (NCSE) and the observed MRI changes are transient. We describe a patient with non-lesional right-sided temporal lobe epilepsy with complex partial seizures and repeated episodes of untreated complex partial status epilepticus (CPSE). Diffusion-weighted MRI exhibited marked and extended signal changes within the right temporal, frontal, insular and cingulate regions. The affected areas are considered propagation pathways of temporal lobe epilepsies. After admission, the patient was treated with i.v. antiepileptic drugs. Behavioral, EEG and MRI signal changes resolved. An atrophy of the right temporal lobe not seen in the pre-status MRI examinations was observed 6 weeks after the resolution of MRI hyperintensities. Prior episodes of CPSE had been correctly treated and remained without permanent brain damage. This case report is in favour of immediate and aggressive treatment of partial NCSE in order to avoid irreversible parenchymal loss.

Protective effect of cerebrocrast on rat brain ischaemia induced by occlusion of both common carotid arteries

Diabetes mellitus is accompanied by several cardiovascular complications including atherosclerosis, cerebral ischaemia and stroke. We examined the neuroprotective effect of a 1,4-dihydropyridine derivative cerebrocrast (C, a new antidiabetic agent, synthesized in the Latvian Institute of Organic Synthesis) on the level of ATP in the brain, and on changes of the EEG and ECG, as well as blood pressure parameters in anaesthetized Wistar male rats before and during 10-min occlusion of both common carotid arteries. Cerebrocrast was administered i.v. at doses of 1.0 and 10 microg/kg in the v. femoralis 20 min prior to ischaemia. After 10-min ischaemia animals were decapitated and the brain was immediately frozen in liquid nitrogen and subsequently used for analysis of changes of ATP contention. Cerebrocrast, administered at doses of 1.0 and 10 microg/kg 20 min prior to occlusion of both common carotid arteries, completely prevented a fall in the ATP content of brain compared with the control rats. In control rats the content of ATP in brain during ischaemia decreased from 2.77 +/- 0.22 (basal level) to 1.74 +/- 0.20 micromol/g as a result of ischaemia. By administration of cerebrocrast 20 min before occlusion of the arteries, the content of ATP in the brain remained at the level of preischaemia (1.0 microg/kg C + ischaemia 2.82 +/- 0.36; 10 microg/kg C + ischaemia 2.42 +/- 0.22 micromol/g). Analysis of EEG parameters both before and during 10 min of occlusion showed that at a C dose of 1.0 microg/kg before occlusion produced a regular alpha rhythm during ischaemia and prevented cerebral bioelectric activity from significant changes. The depression of basal rhythm was observed at a C dose of 10 microg/kg during ischaemia in two rats out of six as well as an increase in the ECG ST segment above the isoelectric line. Blood pressure was decreased by about 10-20 mm Hg. We propose that pretreatment of rats with cerebrocrast at doses of 1.0 or 10 microg/kg 20 min prior to ischaemia can prevent ischaemic damage of rat brain, maintain necessary energy consumption, promote ATP production in brain cells, and prevent significant changes in EEG and ECG parameters. These properties are important in diabetes mellitus and its evoked cardiovascular complications as stroke, ischaemia, etc.

Replicable Functional Magnetic Resonance Imaging Evidence of Correlated Brain Signals Between Physically and Sensory Isolated Subjects

Previous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) experiments have suggested that correlated neural signals may be detected in the brains of individuals who are physically and sensorily isolated from each other. Functional MRI and EEG methods were used in the present study in an attempt to replicate these findings. DESIGN/SETTINGS: Subjects were electrically and magnetically shielded because of the characteristic surroundings of the scanner room. During the experiment, the nonstimulated subject was placed in the scanner with sensory isolating goggles covering the subject's eyes. The stimulated subject was placed 30 feet away and sat in front of a video monitor that presented an alternating schedule of six stimulus-on/stimulus-off conditions. The stimulus- on condition consisted of a flickering checkerboard pattern whereas the stimulus-off condition consisted of a static checkerboard. Stimulus-on/-off conditions were presented in the sequence on/off/on/off/on/off. The duration of these intervals was randomly assigned but consistently provided a total of 150 seconds of flicker and 150 seconds of static. Sessions were repeated twice to assess possible replication of the phenomenon. Changes in fMRI brain activation (relating to blood oxygenation) and EEG signals were measured in the nonstimulated subjects. Changes occurring during stimulus-on conditions were statistically compared to changes occurring during the stimulus-off conditions. Statistically significant changes in fMRI brain activation and EEG signals were observed when comparing the stimulus-on condition to the stimulus-off condition in nonstimulated subjects (p < 0.001, corrected for multiple comparisons). For fMRI, these changes were observed in visual brain areas 18 and 19 (Brodmann areas). One of the subjects replicated the results. These data replicate previous findings suggesting that correlated neural signals may be detected by fMRI and EEG in the brains of subjects who are physically and sensorily isolated from each other.

Investigation of the EEG effects of intravenous lidocaine during halothane anaesthesia in ponies

ObjectiveTo record the electroencephalographic changes during castration in ponies anaesthetized with halothane and given intravenous (IV) lidocaine by infusion. The hypothesis tested was that in ponies, IV lidocaine is antinociceptive and would therefore obtund EEG changes during castration. AnimalsTen Welsh mountain ponies referred to the Department of Clinical Veterinary Medicine, Cambridge for castration under general anaesthesia. Materials and methodsFollowing pre-anaesthetic medication with intramuscular acepromazine (0.02 mg kg−1) anaesthesia was induced with IV guaiphenesin (60 mg kg−1) and thiopental (9 mg kg−1) and maintained with halothane at an end-tidal concentration (Fe′HAL) of 1.2%. A constant rate infusion of IV lidocaine (100 μg kg−1 minute−1) was administered throughout anaesthesia. The electroencephalogram (EEG) was recorded continuously using subcutaneous needle electrodes. All animals were castrated using a closed technique. The raw EEG signal was analysed after completion of each investigation, and the mean values of EEG variables (median frequency, spectral edge frequency, total amplitude) recorded during a baseline period (before surgery began) and the removal of each testicle were compared using anova for repeated measures. ResultsSpectral edge frequency (SEF) 95% decreased during removal of the second testicle compared with baseline recordings. No other significant EEG changes during castration were measured. ConclusionsLidocaine obtunded the EEG changes identified during castration in a previous control study, providing indirect evidence that lidocaine administered peri-operatively was antinociceptive and contributed to anaesthesia during castration. Clinical relevanceThe antinociceptive effect of lidocaine combined with its minimal cardiovascular effects indicate a potential use for systemic lidocaine in clinical anaesthetic techniques.

Bilateral Bispectral Index Monitoring During Suppression of Unilateral Hemispheric Function

Bispectral Index (BIS) has been used to monitor level of "sedation" based on the electroencephalogram (EEG). Patients evaluated for surgery to control a seizure disorder undergo Wada testing, during which one hemisphere is rendered functionally inactive after injecting a short-acting barbiturate. We surmised that the BIS values would reflect these functional changes. Eight epileptic patients were enrolled. A full array of 21 EEG electrodes and 2 BIS XP (Quatro) strips over each frontal region of the scalp were applied. The EEG was continuously recorded. BIS values from each hemisphere were recorded every minute. Angiography was performed by advancing a catheter into each internal carotid artery. Amobarbital or methohexital was injected until the patient developed a hemiparesis. The EEG confirmed a significant lateralized cortical effect of the barbiturate. Repeated measures analysis of variance was used to analyze the differences between the BIS values from monitor electrode strips placed on the left (left BIS) and the right (right BIS) sides of the head as well as the differences in the left and right BIS values before and after each injection of the barbiturate. Injection of barbiturate into either the left or right internal carotid artery produced a significant change on the 21-electrode EEG. However, there was no difference between left BIS to right BIS values (P = 0.84). With repeated injections of barbiturates, some patients became sedated. At these times, both left BIS and right BIS values decreased together before and after injection of barbiturate. The BIS monitor was unable to distinguish significant hemispheric EEG and clinical functional changes except when the patient became sedated.

Adaptive autoregressive identification with spectral power decomposition for studying movement-related activity in scalp EEG signals and basal ganglia local field potentials

We propose a method that combines adaptive autoregressive (AAR) identification and spectral power decomposition for the study of movement-related spectral changes in scalp EEG signals and basal ganglia local field potentials (LFPs). This approach introduces the concept of movement-related poles, allowing one to study not only the classical event-related desynchronizations (ERD) and synchronizations (ERS), which correspond to modulations of power, but also event-related modulations of frequency. We applied the method to analyze movement-related EEG signals and LFPs contemporarily recorded from the sensorimotor cortex, the globus pallidus internus (GPi) and the subthalamic nucleus (STN) in a patient with Parkinson's disease who underwent stereotactic neurosurgery for the implant of deep brain stimulation (DBS) electrodes. In the AAR identification we compared the whale and the exponential forgetting factors, showing that the whale forgetting provides a better disturbance rejection and it is therefore more suitable to investigate movement-related brain activity. Movement-related power modulations were consistent with previous studies. In addition, movement-related frequency modulations were observed from both scalp EEG signals and basal ganglia LFPs. The method therefore represents an effective approach to the study of movement-related brain activity.

Altered central nervous system signal during motor performance in chronic fatigue syndrome

Objective: The purpose of this study was to determine whether brain activity of chronic fatigue syndrome (CFS) patients during voluntary motor actions differs from that of healthy individuals. Methods: Eight CFS patients and 8 age- and gender-matched healthy volunteers performed isometric handgrip contractions at 50% maximal voluntary contraction level. They first performed 50 contractions with a 10 s rest between adjacent trials—‘Non-Fatigue’ (NFT) task. Subsequently, the same number of contractions was performed with only a 5 s rest between trials—‘Fatigue’ (FT) task. Fifty-eight channels of surface EEG were recorded simultaneously from the scalp. Spectrum analysis was performed to estimate power of EEG frequency in different tasks. Motor activity-related cortical potential (MRCP) was derived by triggered averaging of EEG signals associated with the muscle contractions. Results: Major findings include: (i) Motor performance of the CFS patients was poorer than the controls. (ii) Relative power of EEG theta frequency band (4–8 Hz) during performing the NFT and FT tasks was significantly greater in the CFS than control group ( P<0.05). (iii) The amplitude of MRCP negative potential (NP) for the combined NFT and FT tasks was higher in the CFS than control group ( P<0.05). (iv) Within the CFS group, the NP was greater for the FT than NFT task ( P<0.01), whereas no such difference between the two tasks was found in the control group. Conclusions: These results clearly show that CFS involves altered central nervous system signals in controlling voluntary muscle activities, especially when the activities induce fatigue. Significance: Physical activity-induced EEG signal changes may serve as physiological markers for more objective diagnosis of CFS.

Electroencephalographical effects of sarpogrelate hydrochloride versus ticlopidine hydrochloride in elderly patients with peripheral atherosclerosis.

The aim was to determine the efficacy of sarpogrelate (a selective 5-hydroxytryptamine-2-serotonergic receptor antagonist) on cerebrovascular function and mean blood pressure (mBP) in elderly patients (> 60 years old). Patients with peripheral circulatory disorders were studied using electroencephalogram (EEG) and mBP measurements before and after 2 years' treatment with either sarpogrelate (n = 31) or ticlopidine (n = 43). Ticlopidine had no significant effect on the whole brain. Sarpogrelate decreased the percentage of slow waves (%slow), but not significantly, and was associated with a smaller change in the percentage of slow waves (delta slow). In the anterior area, neither drug caused significant EEG changes. In the posterior area, sarpogrelate significantly decreased the %slow and increased the %alpha values, and was associated with a significantly higher delta alpha value than ticlopidine. The results suggest that sarpogrelate hydrochloride can suppress serotonin-induced pathological processes in peripheral circulatory disorders and may be recommended as an anti-platelet agent, even in elderly patients with subclinical arteriosclerosis.

Sound fields in biosphere of the mountain streams and their influence on the human EEG

Low-frequency acoustics fields in the biosphere of the headwater regions in Poland (Bieszczady Mountains and Tatry Mountains) were researched and the the influence of observed low-frequency acoustics field on changes of human EEG signals was analyzed. Several places were found with specific distribution of sound fields where low frequencies dominated. Interesting parameters of distribution of the riverbeds and physical characterization of flows were determined. Standard EEG signal was recorded from subjects until exposure for 20 min. It was ascertained that spectra of sound-pressure levels were with specific shape, very similar for a group of rivers. The influences of SPL on level of power spectrum of EEG signal were analyzed. Changes in the brain waves were observed with increases in delta and decreases in alpha. Tested subjects reported behavior specific for relaxation.

Music Effects on EEG in Intrusive and Withdrawn Mothers with Depressive Symptoms

The EEG patterns of 48 intrusive and withdrawn mothers with depressive symptoms were assessed following a 20-minute music session to determine if the music had mood-altering effects. Half the mothers listened to classical music while half listened to rock music. Intrusive mothers were expected to have more positive responses and more symmetrical EEG following the calming classical music, while withdrawn mothers were expected to have a more positive response and symmetrical EEG following the energizing rock music. Although more positive EEGs were noted for rock music in both groups, only the withdrawn mothers showed a significant change in EEG toward symmetry following rock music, and only the intrusive mothers showed a decrease in cortisol levels following the rock music. Their State Anxiety Inventory (STAI) anxiety levels also decreased, while the Profile of Mood States (POMS) depressed mood levels decreased significantly for all four groups following music.

The effects of subthreshold 1 Hz repetitive TMS on cortico-cortical and interhemispheric coherence.

Repetitive transcranial magnetic stimulation (rTMS) shows promise as a treatment for various movement and psychiatric disorders. Just how rTMS may have persistent effects on cortical function remains unclear. We hypothesised that it may act by modulating cortico-cortical and interhemispheric connectivity. To this end we assessed cortico-cortical and interhemispheric coherence before and after low frequency, subthreshold rTMS of the left motor cortex. Fifteen healthy subjects received one train (1Hz, 90% of active motor threshold, 1500 stimuli) of rTMS to the left motor hand area. Spectral power and coherence estimates were calculated between different electroencephalogram (EEG) signals at rest and while muscles of the distal upper limb were tonically contracted. rTMS over the left motor hand area caused a significant increase in ipsilateral EEG-EEG coherence and in the interhemispheric coherence between motor areas in the alpha band. The effects of rTMS lasted up to 25 min post-stimulation. There was no significant change in EEG-EEG coherence over the hemisphere contralateral to stimulation. Low frequency, subthreshold rTMS of the motor cortex increases ipsilateral cortico-cortical and interhemispheric coherence in the alpha band. This may, in part, mediate the inhibitory effects of low frequency rTMS.

Fuzzy systems to process ECG and EEG signals for quantification of the mental workload

In this paper, we analyze the ECG and EEG signals by using a set of fuzzy systems developed for signal processing and try to see if one can quantify the mental workload based on the trend of EEG signal changes and the variation of pulse width from ECG signal. The signal data were taken from nuclear power plant operators while they perform the turbine operations. First, we apply a fuzzy system to extract the heart beat intervals from the ECG and a smoothing algorithm for the variation of the resulting heart beat intervals to obtain a trend variable. Next, we apply the same smoothing algorithm to the α-band frequencies and to the θ -band frequencies to get their trend curves. Finally, the three trend variables; the variation of the heart beat intervals, the α -band power, and the θ -band power are combined by a pair of fuzzy systems to estimate the mental workload during nuclear power plant operations. The results of applying our algorithm to three different data sets are included, along with a comparison between these results and the results obtained by applying a linear combination of the three variables. Compared results show that the `mental workload' computed by fuzzy systems with nonlinear rules reflects the changes more clearly than the ones computed by linear functions .

Phase and amplitude analysis in time–frequency space—application to voluntary finger movement

Two methods operating in time–frequency space were applied to analysis of EEG activity accompanying voluntary finger movements. The first one, based on matching pursuit approach provided high-resolution distributions of power in time–frequency space. The phenomena of event related desynchronization (ERD) and synchronization (ERS) were investigated without the need of band-pass filtering. Time evolution of μ- and β-components was observed in a detailed way. The second method was based on a multichannel autoregressive model (MVAR) adapted for investigation of short-time changes in EEG signal. The direction and spectral content of the EEG activity propagation was estimated by means of short-time directed transfer function (SDTF). The evidence of ‘cross-talk’ between different areas of motor and sensory cortex was found. The earlier known phenomena, connected with voluntary movements, were confirmed and a new evidence concerning focal ERD/surround ERS and β activity post-movement synchronization was found.

Quantitative EEG changes associated with loss and return of consciousness in healthy adult volunteers anaesthetized with propofol or sevoflurane

Significant changes in topographic quantitative EEG (QEEG) features were documented during induction and emergence from anaesthesia induced by the systematic administration of sevoflurane and propofol in combination with remifentanil. The goal was to identify those changes that were sensitive to alterations in the state of consciousness but independent of anaesthetic protocol. Healthy paid volunteers were anaesthetized and reawakened using propofol/remifentanil and sevoflurane/remifentanil, administered in graded steps while the level of arousal was measured. Alterations in the level of arousal were accompanied by significant QEEG changes, many of which were consistent across anaesthetic protocols. Light sedation was accompanied by decreased posterior alpha and increased frontal/central beta power. Frontal power predominance increased with deeper sedation, involving alpha and, to a lesser extent, delta and theta power. With loss of consciousness, delta and theta power increased further in anterior regions and also spread to posterior regions. These changes reversed with return to consciousness.

EEG changes with vagus nerve stimulation.

Vagus nerve stimulation (VNS) has been shown to induce EEG changes in animals, but human studies have not shown any significant acute EEG changes. This study is to determine the long-term effect of VNS on EEG. Twenty-one patients aged 4 to 31 years (mean: 14.1 +/- 7.0 years) were studied for a mean duration of 16.8 months with serial EEGs performed at baseline and at 3 months, 6 months, and 12 months after receiving a VNS implant. Five patients who showed active spikes/spike and wave activity on baseline EEGs were found to have synchronization of epileptiform activity, progressive increase in duration of spike-free intervals (P < 0.05), and progressive decrease in duration and frequency of spikes/spike and wave activity (P < 0.01) with time. The remaining 16 patients with less active baseline EEGs did not show obvious synchronization or clustering of spikes but also showed a statistically significant progressive decrease in the number of spikes on EEG with time (P < 0.004 at 3 months, P < 0.008 at 6 months, and P < 0.004 at 1 year). Vagus nerve stimulation induces progressive EEG changes in the form of clustering of epileptiform activity followed by progressively increased periods of spike-free intervals. This may reflect the mechanism of action of VNS in achieving seizure control: alternating synchronization and desynchronization of EEG, with the latter being progressively the dominant feature.

Anticipation of epileptic seizures from standard EEG recordings

New methods derived from non-linear analysis of intracranial recordings permit the anticipation of an epileptic seizure several minutes before the seizure. Nevertheless, anticipation of seizures based on standard scalp electroencephalographical (EEG) signals has not been reported yet. The accessibility to preictal changes from standard EEGs is essential for expanding the clinical applicability of these methods. We analysed 26 scalp-EEG/video recordings, from 60 min before a seizure, in 23 patients with temporal-lobe epilepsy. For five patients, simultaneous scalp and intracranial EEG recordings were assessed. Long-term changes before seizure onset were identified by a measure of non-linear similarity, which is very robust in spite of large artifacts and runs in real-time. In 25 of 26 recordings, measurement of non-linear changes in EEG signals allowed the anticipation of a seizure several minutes before it occurred (mean 7 min). These preictal changes in the scalp EEG correspond well with concurrent changes in depth recordings. Scalp-EEG recordings retain sufficient dynamical information which can be used for the analysis of preictal changes leading to seizures. Seizure anticipation strategies in real-time can now be envisaged for diverse clinical applications, such as devices for patient warning, for efficacy of ictal-single photon emission computed tomography procedures, and eventual treatment interventions for preventing seizures.

Nonlinear Dynamics Estimation of EEG Signals Accompanying Self-Paced Goal-Directed Movements

The study was aimed at comparison of several nonlinear characteristics (NC) computed in time for one and the same EEG record accompanying voluntary goal-directed movements. This allowed us to reveal different aspects of the nonlinear behavior of the process underlying the self-paced movement organization. Parallel alterations of these characteristics during the task performance supported the hypothesis that cognitive task performance is reflected by the changes in the nonlinear dynamics of the EEG activity. Four NCs of scalar EEG time series were estimated: Point-wise Correlation Dimension (PD2), Kolmogorov Entropy (K2), and Largest Lyapunov Exponent (LLE) as a function of time, and Nonlinear Prediction (NP) for successive EEG segments. The time evolution of these characteristics exhibited several transients between chaos-like states to almost periodic states during the task performance: the gradual increase to higher values indicating chaos are probably related to the onset of the successive phases of brain organization of the movement. The results suggest that even in short periods an EEG signal changes its dynamic structure and these periods could be determined precisely enough using different methods of nonlinear dynamics.