Dominant Alpha Frequency Research Articles

In silico Effects of Synaptic Connections in the Visual Thalamocortical Pathway.

We have studied brain connectivity using a biologically inspired in silico model of the visual pathway consisting of the lateral geniculate nucleus (LGN) of the thalamus, and layers 4 and 6 of the primary visual cortex. The connectivity parameters in the model are informed by the existing anatomical parameters from mammals and rodents. In the base state, the LGN and layer 6 populations in the model oscillate with dominant alpha frequency, while the layer 4 oscillates in the theta band. By changing intra-cortical hyperparameters, specifically inhibition from layer 6 to layer 4, we demonstrate a transition to alpha mode for all the populations. Furthermore, by increasing the feedforward connectivities in the thalamo-cortico-thalamic loop, we could transition into the beta band for all the populations. On looking closely, we observed that the origin of this beta band is in the layer 6 (infragranular layers); lesioning the thalamic feedback from layer 6 removed the beta from the LGN and the layer 4. This agrees with existing physiological studies where it is shown that beta rhythm is generated in the infragranular layers. Lastly, we present a case study to demonstrate a neurological condition in the model. By changing connectivities in the network, we could simulate the condition of significant (P < 0.001) decrease in beta band power and a simultaneous increase in the theta band power, similar to that observed in Schizophrenia patients. Overall, we have shown that the connectivity changes in a simple visual thalamocortical in silico model can simulate state changes in the brain corresponding to both health and disease conditions.

Altered Spatiotemporal Dynamics of the Resting Brain in Mild Cognitive Impairment with Lewy Bodies.

Electrophysiological markers of prodromal dementia with Lewy bodies were described in the spectral domain. The sub-second temporal resolution may provide additional information. To evaluate electroencephalography (EEG) microstates in patients with mild cognitive impairment with Lewy bodies and to assess the association between their temporal dynamics and the spectral marker. Temporal parameters of microstates were compared between 21 patients with mild cognitive impairment with Lewy bodies and 21 healthy controls. The dominant alpha frequency was correlated with microstate parameters. Microstates A-D showed higher occurrence in the patient group. Microstate B additionally revealed shorter mean duration and increased time coverage; its occurrence correlated with the dominant alpha frequency in the patient group. Temporal dynamics of all EEG microstates were altered in medication-naïve subjects with prodromal dementia with Lewy bodies. Longitudinal follow-up may reveal how EEG microstates reflect progression of brain function deficits and effects of treatment manipulations. © 2021 International Parkinson and Movement Disorder Society.

Electroencephalographic Predictors of Neuropathic Pain in Subacute Spinal Cord Injury

It is widely believed that cortical changes are a consequence of longstanding neuropathic pain (NP). In this article, we demonstrate that NP in individuals with subacute spinal cord injury (SCI) has characteristic electroencephalography markers (EEG) that precede the onset of pain. EEG was recorded in a relaxed state and during motor imagination tasks in 10 able-bodied participants and 31 patients with subacute SCI (11 with NP, 10 without NP, and 10 who had pain develop within 6 months of EEG recording). All 20 patients with SCI initially without NP were tested for mechanically induced allodynia, but only 1 patient, who later had pain develop, reported an unpleasant sensation. The EEG reactivity to eye opening was reduced in the alpha band and absent in the theta and beta bands in the patients who later developed pain and was reduced in those who already had pain. Alpha band power was reduced at BA7 in both the relaxed state and during motor imagination in patients who either had or later developed pain compared with those without pain. All SCI groups had reduced dominant alpha frequency and beta band power at BA7. EEG reactivity to eye opening and reduced spontaneous and induced alpha activity over the parietal cortex were predictors of future NP, as well as markers of existing NP.Clinical Trial Registration Number: NCT02178917 PerspectiveWe demonstrate that brain activity in patients with subacute SCI reveals both early markers and predictors of NP, which may manifest before sensory discomfort. These markers and predictors may complement known sensory phenotypes of NP. They may exist in other patient groups suffering from NP of central origin.

P1.028 EEG dominant alpha frequency variability forecasts the appearance of fluctuating cognition in PDD patients

P1.028 EEG dominant alpha frequency variability forecasts the appearance of fluctuating cognition in PDD patients

Double-blind, placebo-controlled pharmacodynamic studies with a nutraceutical and a pharmaceutical dose of ademetionine (SAMe) in elderly subjects, utilizing EEG mapping and psychometry

In a double-blind, placebo-controlled crossover study, the effects of S-adenosyl- l-methionine (SAMe) on brain function measures of 12 normal elderly volunteers (6 m/6 f, aged 57–73 years, mean: 61 years) were investigated by means of EEG mapping and psychometry. In random order, the subjects were orally administered a pharmaceutical dose of 1600 mg SAMe, a nutraceutical dose of 400 mg SAMe and placebo, each over a period of 15 days, with wash-out periods of 2 weeks in between. EEG recordings, psychometric tests and evaluations of tolerability and side effects were carried out 0, 1, 3 and 6 h after drug administration on days 1 and 15. Multivariate analysis based on MANOVA/Hotelling T 2 tests of quantitative EEG data demonstrated significant central effects of SAMe as compared with placebo after acute, subacute and superimposed drug administration of both the nutraceutical and the pharmaceutical dose. EEG changes induced by SAMe were characterized by an increase in total power, a decrease in absolute and relative power in the delta/theta and slow alpha frequencies, an increase in absolute and relative power in the alpha-2 and beta frequencies as well as an acceleration of the alpha centroid and the centroid of the total power spectrum. The delta/theta and the beta centroid showed variable changes over time. The dominant alpha frequency was accelerated, the absolute and relative power in the dominant alpha frequency attenuated after SAMe as compared with placebo. These acute and subacute pharmaco-EEG findings in elderly subjects are typical of activating antidepressants. Time-efficacy calculations showed that acute oral administration of SAMe in both the nutraceutical and the pharmaceutical dose induced the pharmacodynamic peak effect in the first hour with a subsequent decline. The 3rd and 6th hours still showed a significant encephalotropic effect after the 1600 mg dose. The maximum EEG effect was noted after 2 weeks of oral administration of both 1600 mg/die and 400 mg/die. The superimposed dose induced significant encephalotropic effects in the 3rd hour after 400 mg and in the 3rd and 6th hours after 1600 mg as compared with pre-treatment. Dose-efficacy calculations showed that the pharmaceutical dose of 1600 mg had a more pronounced effect on the CNS than the nutraceutical dose of 400 mg, with both doses being superior to placebo. Psychometric tests concerning noopsychic and thymopsychic measures as well as critical flicker fusion frequency generally demonstrated a lack of differences between SAMe and placebo, which reflects a good tolerability of the drug in elderly subjects. This was corroborated by the findings on side effects, pulse and blood pressure.

EEG Coherence Effects of Audio-Visual Stimulation (AVS) at Dominant and Twice Dominant Alpha Frequency

The effects of a single session of audio-visual stimulation (AVS) at the dominant alpha rhythm and twice-dominant alpha frequency on EEG coherence were studied in 23 subjects. An eyes-closed baseline EEG determined each subject’s dominant alpha frequency. Subjects were stimulated at their dominant alpha frequency or at their twice dominant alpha frequency for 20 minutes, while EEG was recorded in five-minute intervals. A post-session baseline was recorded 30 minutes after each session. AVS decreased coherence in the intrahemispheric projections from the occipital region and the parietal midline, and generally increased coherence, with few exceptions, among all other longitudinal pairs. Interhemispheric coherence increased posteriorly and at high frequencies, and tended to decrease frontally and at low frequencies. Alpha AVS was more effective than twice-alpha AVS at increasing interhemispheric coherence, and tended to produce more effects overall. Although main effects of frequency and time were observed, when individual coherence pairs changed, they almost always changed in only one direction. Overall coherence was greater during the first 10 minutes than the last 10 minutes, and greatest in the beta 1 and delta 2 bands, and lowest in the alpha and delta 1 bands. Few, if any, significant effects persisted into the post-stimulation baseline. A new method of assessing the effects of multiple comparisons on experimentwise error, based on randomization theory, is proposed and implemented.

EEG mapping in patients with social phobia

Recent studies have suggested an information-processing bias in social phobia (SP). Little is known about the electrophysiological correlates of anxiety in SP. The aim of the present study was to investigate the quantitative electroencephalogram (EEG) in 25 drug-free patients with SP as compared with age- and sex-matched normal controls and to correlate anxiety and depressive symptoms with EEG data. EEG was recorded under vigilance-controlled and resting conditions. The Spielberger State and Trait Anxiety Scale (STAI) and the Beck Depression Inventory (BDI) were administered to assess anxiety and depression levels. Multivariate analysis of variance revealed significant differences between patients and controls, specifically frontopolarly and right centrally. Statistical analysis demonstrated a decrease in absolute and relative delta, theta power, alpha-adjacent slow-beta and fast beta power and an increase in absolute and relative intermediate beta power, as well as an acceleration of the total centroid and a slowing in beta centroid and its variability. Trait anxiety and depression scores correlated positively with the dominant alpha frequency and the alpha centroid, and negatively with absolute theta and slow alpha power as well as with the centroid of the delta/theta frequency band. In conclusion, EEG mapping in patients with SP revealed significant differences from normal controls suggesting a hyperarousal as a pathogenetic factor of anxiety.

Temporallappenepilepsie: EEG-Alphafrequenz, Gedächtnisleistungen und Lokalisation von Läsionen

Background: lt has been established that lesions in the temporal lobe of the dominant hemisphere lead to specific deficits in memory performance. Furthermore, there is a relationship between memory performance and alpha frequency. We compared the individually determined dominant alpha frequency of patients with a lesion in the temporal lobe of the dominant hemisphere with those with a lesion in the subdominant hemisphere. Purpose: To investigate the memory performance and alpha peak frequency in patients with temporal lobe epilepsy and to correlate this with side of the lesion. Methods: Nine patients (mean age 29.1, SD 12.6) with unilateral temporal lobe epilepsy (TLE) were examin-ed. The Wechsler Memory Scale (WMS) was used for all patients to test the memory performance. The EEG-alpha peak was determined individually for each patient using a power-spectrum calculated within a 15-minute artifact-free EEG-epoch during a resting condition with eyes closed. Results: The results indicate that patients with a lesion in the dominant hemisphere shows significantly poorer memory performance as compared to patients with a lesion in the subdominant hemisphere. In addition, the group of patients with poorer memory performance show a tendency towards a lower alpha peak. Furthermore, statistical analysis gives evidence of a lower alpha peak in the EEG of patients with a lesion in the dominant hemisphere. Conclusion: We conclude that the localization of the lesion is a predominant factor for memory performance and alpha frequency in patients with unilateral temporal lobe epilepsy.

Lithium-Induced EEG Changes in Patients with Affective Disorders

In 12 patients with affective disorders (ICD-10: F31, F32, F33), EEGs were recorded before and after 4.4 months of lithium treatment. Effects of lithium on the EEG were analyzed by power spectral analysis controlled for vigilance. We found (1) an increase in relative power in both delta and theta band which was related to the lithium plasma level, (2) a decrease in relative alpha power especially at occipital leads and (3) a reduction of the dominant alpha frequency. The changes in relative power were more pronounced in the right hemisphere, which is in contrast to the hypothesis of a site-specific localization of lithium effects only in left anterior regions.

Effects of 20-min audio-visual stimulation (AVS) at dominant alpha frequency and twice dominant alpha frequency on the cortical EEG

The effects of audio-visual stimulation at the dominant alpha frequency and twice dominant alpha frequency on the EEG were investigated. An eyes-closed baseline EEG determined each subject's dominant alpha frequency. Subjects were stimulated at their dominant alpha frequency and at twice dominant alpha frequency for 20 min on two occasions. A 30-min post-session eyes-closed EEG was recorded after each session. Power data were analyzed for 19 locations in six bandpasses using repeated-measures ANOVAs and appropriate post-hoc tests. Alpha stimulation significantly increased power over baseline levels in the delta 1, delta 2, theta, beta 1 and beta 2, with significant effects remaining 30 min later in beta 1. Twice alpha stimulation significantly increased theta, beta 1 and beta 2 power over baseline levels, with significant effects remaining 30 min later in theta, alpha, beta 1 and beta 2.

Acute effects of 1,1,1-trichloroethane inhalation on the human central nervous system

The object of this study was to examine the immediate nervous effects of variable 1,1,1-trichloroethane (TCE) exposure combined with physical exercise. The effects on the quantitative electroencephalography (EEG), visual evoked potentials (VEP) and body sway were analyzed. Nine male volunteers were exposed to either a stable or a fluctuating exposure pattern with the same time-weighted average concentration of 200 ppm (8.1 mumol/l). In both cases, the subjects engaged in physical exercise during the exposures. Exercise alone induced an increase in the dominant alpha frequency in the EEG and, after an initial drop, an increase in the alpha percentage with a concomitant decrease in theta, whereas delta and beta bands remained unaffected. By contrast, exposure to TCI and exercise did not affect the alpha, theta or delta activities but induced changes in beta during the morning recordings at peak exposure to TCE. The body sway tended to decrease slightly during the fluctuating TCE exposure, and the later peaks in VEPs showed slight prolongations. Overall, no deleterious effects of exposure were noted.

Comparison of the effects of nicotine on a fixed rate and a subject-paced version of the rapid information processing task.

In a modified "subject-paced" rather than fixed rate version of a rapid information processing (RIP) task, the presentation rate of the stimuli is continuously adapted to the individual performance level. Thus, this modified task version probably assesses a continuous "speed function" rather than mere "vigilance". In order to compare the two task versions more directly, we carried out a study which assessed the effects of a regular nicotine cigarette and the nearly nicotine-free cigarette NEXT on both task versions under the same experimental conditions. The dominant alpha frequency pointed to a greater arousal evoked by the subject-paced RIP version compared with the fixed rate version. With the fixed rate version, smoking nicotine cigarettes reduced reaction times, whereas with the subject-paced version, processing rate was improved. Additionally, smoking NEXT decreased craving less than smoking the regular cigarettes. It was concluded that the two task versions are sensitive to different cognitive functions. Whereas the subject-paced version was more sensitive to effects on the speed of processing, the fixed rate version was more sensitive to effects on reaction time.

Effect of subcutaneous nicotine injections on EEG alpha frequency in non-smokers: a placebo-controlled pilot study

The effect of two subcutaneous injections of 0.6 mg nicotine, administered 40 min apart, was compared with placebo in four non-smoking subjects in a counter-balanced double-blind crossover design. The nicotine injections produced mean peak plasma nicotine concentrations of 5.3 ng/ml 10 min after the first injection and 8.5 ng/ml 10 min after the second injection. The nicotine injections produced an increase in mean dominant alpha frequency on the electroencephalogram (EEG) which was 2 Hz greater than the effect of placebo (P = 0.049) and also produced a heart-rate boost which was 8 beats per minute greater than that produced by placebo (P = 0.022). These effects on dominant alpha frequency and heart rate were most apparent in the 10 min following each nicotine injection. The increase in dominant alpha frequency found in non-smokers in this study was similar to that following nicotine inhalation in abstinent smokers in previous studies, and suggests that this is a primary effect of nicotine, rather than simply a reversal of withdrawal-induced EEG slowing.

Relationship of electroencephalographic and cardiovascular changes to plasma nicotine levels in tobacco smokers

The effects of smoking one tobacco or placebo cigarette on the mean change in voltage of the electroencephalogram (EEG), arterial blood pressure, heart, and eye blink rates were correlated with the increase in plasma nicotine, exhaled carbon monoxide, and carboxyhemoglobin levels. Twenty nonsmokers (age range, 19 to 42 years; mean age +/- SE, 27.0 +/- 1.9 years) and 65 regular tobacco smokers (age range, 20 to 48 years; mean age +/- SE, 27.7 +/- 0.8 years) were studied about 10 to 12 hours after overnight tobacco deprivation and immediately after inhaling air through a straw or after smoking one of their own brands of cigarettes, respectively. An increase of at least 10 ng/ml plasma nicotine was needed to obtain a statistically significant decrease in alpha 1 and an increase in beta EEG activity. An increase of at least 15 ng/ml plasma nicotine was needed to obtain a statistically significant decrease in delta EEG activity. The mean dominant alpha frequency, heart rate, systolic and diastolic blood pressure, exhaled carbon monoxide, and carboxyhemoglobin levels increased significantly with increasing plasma nicotine concentrations. Measurement of plasma nicotine levels is especially important to quantify the relationship between tobacco smoking, mean EEG activity, and cardiovascular changes. Nicotine plasma concentrations greater than 10 micrograms/ml produce consistent and statistically significant changes in brain wave activity. Smaller increments in plasma nicotine produce less consistent EEG changes.

Photic Driving of EEG Alpha Activity in Recovering Cocaine-Dependent and Alcohol-Dependent Patients

Electroencephalographic (EEG) activity was evaluated in nine cocaine-dependent and five alcohol-dependent patients after 1, 3, and 12 weeks of verified abstinence. A group of 15 non-drug-dependent control subjects were evaluated after comparable intervals. The EEG was recorded from posteriorleadsites during an eyes-open resting condition and during square-wave photic stimulation delivered at two different intensities. The stimulation rate was set relative to each subject's dominant alpha frequency at rest. Analyses revealed no significant group differences in resting EEG activity in the standard frequency bands. However analyses of power at the dominant alpha frequency revealed a reliable increase as stimulus intensity was increased, but only in the control group. The cocaine-dependent and alcohol-dependent groups exhibited no evidence of a photic driving response at any of the three time points.

Topographic mapping of EEG during sleep.

Topographic aspects of all night sleep EEG were investigated in 10 healthy volunteers (age 20-35 years). EEG brain maps showed an increase of delta power from stage 1 to 4, a decrease of alpha power most pronounced parieto-occipitally and a slowing of the dominant alpha frequency. Differences of EEG power in different sleep stages (as compared to wakefulness) are displayed topographically. Analysis of the course of stage 2 showed an increase of delta power and a decrease of theta power in the first sections of the night, and an increase of beta power later in the night.

Effects of cigarette smoking upon frequencies of EEG alpha rhythm and finger tapping

Under the influence of nicotine, an increase in EEG alpha frequency as well as finger tapping speed has been reported from separate experiments, and it has also been shown that tapping and alpha frequencies may correlate in defined experimental settings. The present study aimed at the analysis of smoking effects using parallel recordings of both EEG and finger tapping. Twelve healthy subjects were tested in two sessions (smoking deprivation versus smoking). After smoking, both dominant alpha frequency (P less than 0.05) and tapping performance (P less than 0.001) were higher than during deprivation. In most subjects, the increase of both parameters developed in parallel, and during phases of very stable tapping the ratio of alpha and tapping frequencies was close to 2:1. Both frequencies correlated during the deprived (r = 0.6108, P = 0.035) as well as the smoking (r = 0.7009, P = 0.011) conditions. Results confirm earlier findings regarding the effect of smoking upon EEG and tapping, and the parallel changes of both parameters may be attributed to the pharmacological properties of nicotine. Besides possible peripheral and spinal effects of nicotine, the increase of tapping performance parallels the increased frequency of central nervous pacemakers.

Electroencephalographic Findings during Experimental Human Exposure to m-Xylene

Aromatic hydrocarbon solvents, used widely in industry, cause central nervous system symptoms in exposed workers. Acute effects of m-xylene were studied in nine voluntary subjects exposed experimentally to stable or varying concentrations of m-xylene at rest or while exercising. Each subject participated in four exposure and two control sessions in a single-blind fashion. The time-weighted average (TWA) m-xylene concentration was always 200 parts per million (ppm) (8.2 mumol/l) during the 4-h exposure period, complying to a TWA of 4.1 mumol/l.8 h, which is equivalent to the hygienic limit allowed in work situations. The short-term peak concentrations were 400 ppm or less. Electroencephalography was recorded at the beginning of exposure, during exposure, and after exposure was stopped. Eighteen 60-s EEG samples for each subject on each experimental day were analyzed automatically. Exercise increased theta percentage and delta power and percentage; these changes were more prominent in the control session without exposure. Exposure increased the dominant alpha frequency and alpha percentage during the early phase of exposure and also counteracted the effects of exercise. The effects of short-term m-xylene exposure on EEG were minor, and no deleterious effects were noted. Perhaps alpha activation is indicative of stimulating and excitatory effects induced by m-xylene exposure, which has been noted heretofore in the absorption phase of alcohol intake.

Development of central and peripheral smoking effects over time

The present study compared for the first morning cigarettes CO and nicotine absorption as well as the effects on EEG and peripheral functions across a period of 90 min. Eighteen smokers participated in two sessions, one in which they smoked two cigarettes in succession and another in which they smoked three cigarettes at 30-min intervals. Smoking two cigarettes in succession produced a particularly wide range in nicotine absorption so that the subjects could be grouped into high (HN) and low (LN) nicotine absorbers, differing significantly in their CO and nicotine absorption. The smoking-induced cardioacceleration was greater and lasted longer in the HN than in the LN group. While the dominant alpha frequency increased to a significant extent in the HN group only, beta power increased in both groups, alpha power remained unaffected, theta power decreased in the HN group only and the effects on heart rate, dominant alpha frequency and beta power were significantly correlated with nicotine absorption across both groups. Smoking three cigarettes at 30-min intervals produced qualitatively similar but generally smaller effects. However, neither nicotine uptake nor any of the physiological parameters showed differential developments between the two groups, except the dominant alpha frequency, which increased in the HN group only. The development of acute tolerance to smoking across three cigarettes was observed only for finger vasoconstriction, craving to smoke and sickness after smoking, but not for cardioacceleration or any EEG parameters.

Electroencephalographic and evoked potential monitoring in the hyperbaric environment

The purpose of this study was to investigate brain bioelectrical activity during hyperbaric oxygenation by continuous and simultaneous monitoring of electroencephalographic and bimodal (auditory, somatosensory) evoked potentials. Multivariable recordings (electroencephalogram, brainstem auditory evoked potentials, early somatosensory evoked potentials, heart rate, heart rate variability, and transcutaneous partial pressure of oxygen) were measured with a new technique in 12 healthy male volunteers 26 to 52 years old (mean +/- SD, 35.9 +/- 9.5 years). Recordings were obtained while the subjects breathed (1) air at normal atmospheric pressure, (2) 100% oxygen at normal atmospheric pressure, (3) air at 2 atm (10 meters sea water [msw]), and (4) 100% oxygen at 2 atm (10 msw). Spontaneous brain electrical activity, somatosensory evoked potentials, and heart rate variability were not significantly affected during hyperbaric oxygenation, whereas the heart rate showed a significant decrease (paired t test, P less than 0.05). Alterations in brainstem auditory evoked potentials were seen under hyperbaric conditions and did not reach statistical significance (increase of the I-V interpeak latency by paired t test; P less than 0.2). All subjects showed insignificant increases in dominant alpha frequency and decreases in delta frequency under hyperbaric situations.