Power In Delta Frequency Band Research Articles

Alpha-2a adrenergic receptor activation in genetic absence epilepsy: An absence status model?

The objective of the study was to propose a candidate animal model of absence status epilepticus induced by specific alpha-2a adrenergic receptor (α2AR) activation. We also aim to investigate the responsiveness of this model to classical anti-status or anti-absence medications. An α2AR agonist, dexmedetomidine (DEX), was injected intracerebroventricularly into adult rats with genetic absence epilepsy, and their electroencephalography (EEG) was recorded. The total duration, number, and mean duration of each spike-and-wave discharges (SWDs) were evaluated. The blocks of absence status events were classified as the initial and second sets of absence statuses. Ethosuximide (ETX) was administered as a pretreatment to another group of rats and later injected with 2.5 μg DEX. In addition, ETX, valproic acid (VPA), diazepam (DIAZ), and atipamezole (ATI) were administered after induced status-like events following DEX administration. Power spectral characteristics and coherence analysis were performed on the EEG to assess the absence status events and sleep. The 2.5 μg dose of DEX increased the total SWD duration and induced continuous SWDs up to 26 min. Following the initial absence status event, sleep was induced; then, the second period of absence status-like activities were initiated. ETX pretreatment blocked the occurrence of absence status-like activities. Power spectral density analyses revealed that DEX-induced post-sleep activities had higher power in delta frequency band (1-4 Hz) and attenuated power of 7 Hz harmonics (14 and 21 Hz) than the pre-injection seizure. The mean duration of SWDs were decreased in all the groups, but occasional prolonged activities were seen in ETX or VPA-injected rats but not with DIAZ or ATI. This study presents an absence status epilepticus animal model that is activated by α2AR activation to investigate the pathophysiological role of absence status. Unlike other agents ATI switched off the second set of absence statuses to normal SWDs, without sedation or lethargy, can show it may preferentially block absence status-like activity. This study proposes a rat model for prolonged seizures, resembling absence status epilepticus. Activating the brain's alpha-2a adrenergic receptor with dexmedetomidine induced seizures lasting up to 26 minutes. Ethosuximide pretreatment and post-treatment with valproic acid, diazepam, and atipamezole decreased induced seizures. The findings suggest this model is valuable for studying absence status epilepticus. In addition, atipamezole normalized abnormal seizures without sedation, hinting at its potential for targeted treatment and further research.

EEG spectral changes induced by hemodialysis

ObjectiveTo investigate the EEG spectral changes induced during hemodialysis in patients with chronic kidney disease (CKD), and to identify the risk factors associated with changes in the Central Nervous System (CNS) during hemodialysis. Paradoxical neurological deterioration at the end of hemodialysis sessions, known as dialysis disequilibrium syndrome (DDS) has been described, but previous studies on EEG spectral changes during hemodialysis were controversial. MethodsWe performed quantitative EEG spectral analysis in 56 consecutive patients who underwent hemodialysis. We compared EEG at the start and at the end of the hemodialysis, and we correlated the spectral changes with the biochemical and clinical characteristics of the patients, using multivariate analysis. ResultsAt the end of hemodialysis sessions, we found a significant increase in total EEG power, relative power in delta frequency band and the ratio of delta-theta/alpha–beta power. EEG spectral changes were associated with younger age, recent start of hemodialysis therapy, level of uremia and lower level of glycaemia. ConclusionsQuantitative EEG spectral analysis showed that hemodialysis induced slowing of the EEG background activity. These changes were associated with risk factors of DDS. SignificanceEEG spectral changes are potential biomarkers for monitoring CNS function during hemodialysis.

Brain stimulation method and analysis of eeg seizure time series

The aim of this research work is to develop keeping in mind the sweeping changes in Electro Convulsive Therapy (ECT). It is has been tried to inculcate these improvements to make the research work efficient and feasible. ECT is most effective treatment available to certain severe neurological disorders. Recent studies demonstrate association between certain parameters and methods of ECT seizure induction. There is evidence that the latter and therapeutic potency of ECT related. Seizure was obtained unilateral and bilateral application of electrical stimulus. An adequate seizure during ECT is still defined by its duration. Differing therapeutic potencies of ECT procedures cannot be explained on seizure duration alone; other parameter is spectral power in delta frequency band of EEG. This research work is to examine the clinical application of the findings to elucidate the therapeutic relevance of seizure measures other than seizure duration. The other measuring seizure parameters relevant therapeutic mechanism of ECT are power distribution, synchronization in various phases of EEG time series data collected during ECT and spectral power distribution in frequency bands of EEG. This research work involves several signal processing techniques: four channel EEG time series digital signal calibration, removing baseline drift, filtering processes to eliminate noise and artifacts, an automated selection of seizure phases. From the quantified EEG an empirical criterion for brain stimulus has been obtained.

Normal Electrical Activity of the Brain in Obsessive-Compulsive Patients After Anodal Stimulation of the Left Dorsolateral Prefrontal Cortex.

Introduction:Transcranial Direct Current Stimulation (tDCS) has been used as a non-invasive method to increase the plasticity of brain. Growing evidence has shown several brain disorders such as depression, anxiety disorders, and chronic pain syndrome are improved following tDCS. In patients with Obsessive-Compulsive Disorder (OCD), increased brain rhythm activity particularly in the frontal lobe has been reported in several studies using Eectroencephalogram (EEG). To our knowledge, no research has been done on the effects of electrical stimulation on brain signals of patients with OCD. We measured the electrical activity of the brain using EEG in patients with OCD before and after tDCS and compared it to normal participants.Methods:Eight patients with OCD (3 males) and 8 matched healthy controls were recruited. A 64-channel EEG was used to record a 5-min resting state before and after application of tDCS in both groups. The intervention of tDCS was applied for 15 minutes with 2 mA amplitude where anode was placed on the left Dorsolateral Prefrontal Cortex (DLPFC) and cathode on the right DLPFC.Results:In line with previous studies, the results showed that the power of Delta frequency band in OCD patients are significantly higher than the normal group. Following anodal tDCS, hyperactivity in Delta and Theta bands declined in most channels, particularly in DLPFC (F3, F4) and became similar to normal signals pattern. The reduction in Delta band was significantly more than the other bands.Conclusion:Anodal tDCS over the left DLPFC significantly decreased the power of frequency bands of Delta and Theta in Patients with OCD. The pattern of EEG activity after tDCS became particularly similar to normal, so tDCS may have potential clinical application in these patients.

Spatial Wavelet-Based Coherence and Coupling in EEG Signals With Eye Open and Closed During Resting State

Biological signals represent patterns of change in the rhythms of biological systems providing a complementary way to study the dynamics of these systems. The research reported in this paper is based on methodological approaches used to quantify the dynamical fluctuations of neurophysiological systems. We use time-frequency representation techniques including spatial coupling and spatial wavelet phase coherence to analyze the dynamics of electroencephalographic (EEG) signals in different frequency bands in the form of topographic maps. The distribution of power in different frequency bands is computed. The findings indicated that the power in delta frequency band is mainly distributed in prefrontal and occipital regions, whereas, power in theta band is distributed in fronto-occipital regions. The power in alpha band is distributed in posterior and extended to anterior, power in beta band in posterior and prefrontal regions and gamma band power is dominant in prefrontal and occipital regions. All the frequency bands are involved in different activities in one way or other, however alpha band power revealed dominant anterior-posterior activity where the eye-closed (EC) coherence is higher than eye open (EO) coherence. The phase-phase CFC on multichannel EEG signals with EC and EO during resting state is also computed to investigate which brain regions are affected by phase modulation of low frequency bands. Coupling in different frequency bands is estimated using dynamic Bayesian inference approach. This approach can detect the phase connectivity within a network of time varying coupled oscillator subject to the noise. The self, direct, and common coupling scheme showed strong coupling in delta–alpha to alpha ( $\delta,\alpha \to \alpha$ ) and theta–alpha to alpha ( $\theta,\alpha \to \alpha$ ) bands. However, moderate couplings are found in theta-gamma to gamma ( $\theta,\gamma \to \gamma$ ), alpha–gamma to gamma ( $\alpha,\gamma \to \gamma$ ), and delta–gamma to gamma $\delta,\gamma \to \gamma$ ) bands.