scholarly journals Evidence that alpha blocking is due to increases in system-level oscillatory damping not neuronal population desynchronisation

2019 ◽  
Author(s):  
David T. J. Liley ◽  
Suresh D. Muthukumarswamy
Keyword(s):  
Moving Average ◽  
Nmda Antagonist ◽  
Neuronal Population ◽  
System Level ◽  
Oscillatory Activity ◽  
Alpha Band ◽  
Eyes Closed ◽  
Alpha Blocking ◽  
Time Series Modelling ◽  
Eyes Open

AbstractThe attenuation of the alpha rhythm following eyes-opening (alpha blocking) is among the most robust features of the human electroencephalogram with the prevailing view being that it is caused by changes in neuronal population synchrony. To further study the basis for this phenomenon we use theoretically motivated fixed-order Auto-Regressive Moving-Average (ARMA) time series modelling to study the oscillatory dynamics of spontaneous alpha-band electroencephalographic activity in eyes-open and eyes-closed conditions and its modulation by the NMDA antagonist ketamine. We find that the reduction in alpha-band power between eyes-closed and eyes-open states is explicable in terms of an increase in the damping of stochastically perturbed alpha-band relaxation oscillatory activity. These changes in damping are putatively modified by the antagonism of NMDA-mediated glutamatergic neurotransmission but are not directly driven by changes in input to cortex nor by reductions in the phase synchronisation of populations of near identical oscillators. These results not only provide a direct challenge to the dominant view of the role that thalamus and neuronal population de-/synchronisation have in the genesis and modulation of alpha electro-/magnetoencephalographic activity but also suggest potentially important physiological determinants underlying its dynamical control and regulation.

scholarly journals Shifts in broadband power and alpha peak frequency observed during long-term isolation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jan Weber ◽  
Timo Klein ◽  
Vera Abeln
Keyword(s):  
Sensory Deprivation ◽  
Peak Frequency ◽  
Neuronal Population ◽  
Confined Space ◽  
Eyes Closed ◽  
Eyes Open ◽  
Eeg Recordings ◽  
Induced Changes ◽  
Alpha Peak

Abstract Prolonged periods of social isolation and spatial confinement do not only represent an issue that needs to be faced by a few astronauts during space missions, but can affect all of us as recently shown during pandemic situations. The fundamental question, how the brain adapts to periods of sensory deprivation and re-adapts to normality, has only received little attention. Here, we use eyes closed and eyes open resting-state electroencephalographic (EEG) recordings to investigate how neural activity is altered during 120 days of isolation in a spatially confined, space-analogue environment. After disentangling oscillatory patterns from 1/f activity, we show that isolation leads to a reduction in broadband power and a flattening of the 1/f spectral slope. Beyond that, we observed a reduction in alpha peak frequency during isolation, but did not find strong evidence for isolation-induced changes that are of oscillatory nature. Critically, all effects reversed upon release from isolation. These findings suggest that isolation and concomitant sensory deprivation lead to an enhanced cortical deactivation which might be explained by a reduction in the mean neuronal population firing rate.

scholarly journals Radiofrequency signal affects alpha band in resting electroencephalogram

2015 ◽  
Vol 113 (7) ◽  
pp. 2753-2759 ◽  
Author(s):  
Rania Ghosn ◽  
Lydia Yahia-Cherif ◽  
Laurent Hugueville ◽  
Antoine Ducorps ◽  
Jean-Didier Lemaréchal ◽  
...  
Keyword(s):  
Salivary Cortisol ◽  
Spectral Power ◽  
Electrode Impedance ◽  
Alpha Band ◽  
Double Blind ◽  
Eyes Closed ◽  
Before And After ◽  
Sham Exposure ◽  
Eyes Open ◽  
Young Subjects

The aim of the present work was to investigate the effects of the radiofrequency (RF) electromagnetic fields (EMFs) on human resting EEG with a control of some parameters that are known to affect alpha band, such as electrode impedance, salivary cortisol, and caffeine. Eyes-open and eyes-closed resting EEG data were recorded in 26 healthy young subjects under two conditions: sham exposure and real exposure in double-blind, counterbalanced, crossover design. Spectral power of EEG rhythms was calculated for the alpha band (8–12 Hz). Saliva samples were collected before and after the study. Salivary cortisol and caffeine were assessed by ELISA and HPLC, respectively. The electrode impedance was recorded at the beginning of each run. Compared with the sham session, the exposure session showed a statistically significant ( P < 0.0001) decrease of the alpha band spectral power during closed-eyes condition. This effect persisted in the postexposure session ( P < 0.0001). No significant changes were detected in electrode impedance, salivary cortisol, and caffeine in the sham session compared with the exposure one. These results suggest that GSM-EMFs of a mobile phone affect the alpha band within spectral power of resting human EEG.

scholarly journals Inferring a simple mechanism for alpha-blocking by fitting a neural population model to EEG spectra

2020 ◽  
Author(s):  
Agus Hartoyo ◽  
Peter J. Cadusch ◽  
David T. J. Liley ◽  
Damien G. Hicks
Keyword(s):  
Population Model ◽  
Alpha Rhythm ◽  
Neural Population ◽  
Parameter Estimates ◽  
Inhibitory Input ◽  
Alpha Oscillations ◽  
Eeg Spectra ◽  
Eyes Closed ◽  
Alpha Blocking ◽  
Eyes Open

AbstractAlpha blocking, a phenomenon where the alpha rhythm is reduced by attention to a visual, auditory, tactile or cognitive stimulus, is one of the most prominent features of human electroencephalography (EEG) signals. Here we identify a simple physiological mechanism by which opening of the eyes causes attenuation of the alpha rhythm. We fit a neural population model to EEG spectra from 82 subjects, each showing different degrees of alpha blocking upon opening of their eyes. Although it is notoriously difficult to estimate parameters from fitting such models, we show that, by regularizing the differences in parameter estimates between eyes-closed and eyes-open states, we can reduce the uncertainties in these differences without significantly compromising fit quality. From this emerges a parsimonious explanation for the spectral changes between states: Just a single parameter, pei, corresponding to the strength of a tonic, excitatory input to the inhibitory population, is sufficient to explain the reduction in alpha rhythm upon opening of the eyes. When comparing parameter estimates across different subjects we find that the inferred differential change in pei for each subject increases monotonically with the degree of alpha blocking observed. In contrast, other parameters show weak or negligible differential changes that do not scale with the degree of alpha attenuation in each subject. Thus most of the variation in alpha blocking across subjects can be attributed to the strength of a tonic afferent signal to the inhibitory cortical population.Author summaryOne of the most striking features of the human electroencephalogram (EEG) is the presence of neural oscillations in the range of 8-13 Hz. It is well known that attenuation of these alpha oscillations, a process known as alpha blocking, arises from opening of the eyes, though the cause has remained obscure. In this study we infer the mechanism underlying alpha blocking by fitting a neural population model to EEG spectra from 82 different individuals. Although such models have long held the promise of being able to relate macroscopic recordings of brain activity to microscopic neural parameters, their utility has been limited by the difficulty of inferring these parameters from fits to data. Our approach is to fit both eyes-open and eyes-closed EEG spectra together, minimizing the number of parameter changes required to transition from one spectrum to the other. Surprisingly, we find that there is just one parameter, the external input to the inhibitory neurons in cortex, that is responsible for attenuating the alpha oscillations. We demonstrate how the strength of this inhibitory input scales monotonically with the degree of alpha blocking observed over all 82 subjects.

Note on the EEG Orienting Response in Children

1982 ◽  
Vol 54 (2) ◽  
pp. 675-677
Author(s):  
Janice Westlund Bryan
Keyword(s):  
Visual Stimulation ◽  
Orienting Response ◽  
Older Children ◽  
Eyes Closed ◽  
Alpha Blocking ◽  
Eyes Open

Time durations of “alpha bursts” and of “alpha blocking” (no-alpha) intervals, which was the index of the orienting response, were measured by the EEG for 61 children, ages 5–6 and 9–10 yr. Three conditions were examined: (1) eyes closed in the dark (EC), (2) eyes open in the dark (EO), and (3) feedback visual stimulation (VS). Alpha durations were progressively briefer, while no-alpha durations were progressively longer, from EC to EO to VS. Older children had longer no-alpha durations. The differences among the three conditions were greater for older than for younger children with regard to no-alpha durations. The results suggest that the alpha-blocking response is changing between the ages of 5 and 10 yr.

scholarly journals The Difference of Brain Functional Connectivity between Eyes-Closed and Eyes-Open Using Graph Theoretical Analysis

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Bo Tan ◽  
Xianxian Kong ◽  
Ping Yang ◽  
Zhenlan Jin ◽  
Ling Li
Keyword(s):  
Functional Connectivity ◽  
Alpha Band ◽  
Topological Parameters ◽  
Eyes Closed ◽  
Synchronization Likelihood ◽  
Functional Brain Networks ◽  
Eyes Open ◽  
The Difference ◽  
Path Lengths ◽  
Brain Functional Connectivity

To study the differences in functional brain networks between eyes-closed (EC) and eyes-open (EO) at resting state, electroencephalographic (EEG) activity was recorded in 21 normal adults during EC and EO states. The synchronization likelihood (SL) was applied to measure correlations between all pairwise EEG channels, and then the SL matrices were converted to graphs by thresholding. Graphs were measured by topological parameters in theta (4–7 Hz), alpha (8–13 Hz), and beta (14–30 Hz) bands. By changing from EC to EO states, mean cluster coefficients decreased in both theta and alpha bands, but mean shortest path lengths became shorter only in the alpha band. In addition, local efficiencies decreased in both theta and alpha bands, while global efficiencies in the alpha band increased inversely. Opening the eyes decreased both nodes and connections in frontal area in the theta band, and also decreased those in bilateral posterior areas in the alpha band. These results suggested that a combination of the SL and graph theory methods may be a useful tool for distinguishing states of EC and EO. The differences in functional connectivity between EC and EO states may reflect the difference of information communication in human brain.

scholarly journals Topography and asymmetry of visual EEG reactivity in healthy school-age children

2002 ◽  
Vol 130 (1-2) ◽  
pp. 13-18
Author(s):  
Dusan Ristanovic ◽  
Zarko Martinovic ◽  
Vesna Jovanovic-Cupic
Keyword(s):  
Power Spectra ◽  
Asymmetry Index ◽  
School Age Children ◽  
Total Power ◽  
School Age ◽  
Alpha Band ◽  
Theta Band ◽  
Eeg Power Spectra ◽  
Eyes Closed ◽  
Eyes Open

In order to quantify the visual reactivity of EEC to opening the eyes, the topography of EEG power spectra in a sample of 72 healthy subjects aged from 7-15 years, was studied. The EEGs were recorder at 14 scalp sites under eyes closed (ECL) and eyes open (EOP). It has been established that the absolute powers in total and in alpha band were significant- ly higher in all derivations under ECL as compared with EOP condition. Except for the frontal derivations, absolute power in theta band under ECL condition was significantly higher than that under EOP condition. Changes in delta and beta powers were seldom significant. In beta 2 band no EEG blocking was noticed in anterior area. Opening the eyes significantly influenced the values of asymmetry index in alpha band and total power. In all frequency bands and under both conditions, the differences of powers between the hemi spheres were found mainly in the prefrontal and laterofrontal areas. The results showed that the visual blocking of EEG was mostly due to a higher degree of EEG desynchronization after opening the eyes.

scholarly journals Hemispheric differences in altered reactivity of brain oscillations at rest after posterior lesions

2021 ◽  
Author(s):  
Jessica Gallina ◽  
Mattia Pietrelli ◽  
Marco Zanon ◽  
Caterina Bertini
Keyword(s):  
Visual System ◽  
Resting State ◽  
Visual Processing ◽  
Right Hemisphere ◽  
Oscillatory Activity ◽  
Alpha Oscillations ◽  
Eyes Closed ◽  
Eyes Open ◽  
The Right ◽  
Theta Range

AbstractA variety of evidence supports the dominance of the right hemisphere in perceptual and visuo-spatial processing. Although growing evidence shows a strong link between alpha oscillations and the functionality of the visual system, asymmetries in alpha oscillatory patterns still need to be investigated. Converging findings indicate that the typical alpha desynchronization occurring in the transition from the eyes-closed to the eyes-open resting state might represent an index of reactivity of the visual system. Thus, investigating hemispheric asymmetries in EEG reactivity at the opening of the eyes in brain-lesioned patients may shed light on the contribution of specific cortical sites and each hemisphere in regulating the oscillatory patterns reflecting the functionality of the visual system. To this aim, EEG signal was recorded during eyes-closed and eyes-open resting state in hemianopic patients with posterior left or right lesions, patients without hemianopia with anterior lesions and healthy controls. Hemianopics with both left and right posterior lesions showed a reduced alpha reactivity at the opening of the eyes, suggesting that posterior cortices have a pivotal role in the functionality of alpha oscillations. However, right-lesioned hemianopics showed a greater dysfunction, demonstrated by a reactivity reduction more distributed over the scalp, compared to left-lesioned hemianopics. Moreover, they also revealed impaired reactivity in the theta range. This favors the hypothesis of a specialized role of the right hemisphere in orchestrating oscillatory patterns, both coordinating widespread alpha oscillatory activity and organizing focal processing in the theta range, to support visual processing at the opening of the eyes.

scholarly journals Probabilistic, entropy-maximizing control of large-scale neural synchronization

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0249317
Author(s):  
Melisa Menceloglu ◽  
Marcia Grabowecky ◽  
Satoru Suzuki
Keyword(s):  
Maximum Entropy ◽  
Large Scale ◽  
Stochastic Dynamics ◽  
Spectral Power ◽  
Oscillatory Activity ◽  
Power Dynamics ◽  
Precise Control ◽  
Oscillatory Dynamics ◽  
Eyes Closed ◽  
Eyes Open

Oscillatory neural activity is dynamically controlled to coordinate perceptual, attentional and cognitive processes. On the macroscopic scale, this control is reflected in the U-shaped deviations of EEG spectral-power dynamics from stochastic dynamics, characterized by disproportionately elevated occurrences of the lowest and highest ranges of power. To understand the mechanisms that generate these low- and high-power states, we fit a simple mathematical model of synchronization of oscillatory activity to human EEG data. The results consistently indicated that the majority (~95%) of synchronization dynamics is controlled by slowly adjusting the probability of synchronization while maintaining maximum entropy within the timescale of a few seconds. This strategy appears to be universal as the results generalized across oscillation frequencies, EEG current sources, and participants (N = 52) whether they rested with their eyes closed, rested with their eyes open in a darkened room, or viewed a silent nature video. Given that precisely coordinated behavior requires tightly controlled oscillatory dynamics, the current results suggest that the large-scale spatial synchronization of oscillatory activity is controlled by the relatively slow, entropy-maximizing adjustments of synchronization probability (demonstrated here) in combination with temporally precise phase adjustments (e.g., phase resetting generated by sensorimotor interactions). Interestingly, we observed a modest but consistent spatial pattern of deviations from the maximum-entropy rule, potentially suggesting that the mid-central-posterior region serves as an “entropy dump” to facilitate the temporally precise control of spectral-power dynamics in the surrounding regions.

scholarly journals Probabilistic, entropy-maximizing control of large-scale neural synchronization

2020 ◽  
Author(s):  
Melisa Menceloglu ◽  
Marcia Grabowecky ◽  
Satoru Suzuki
Keyword(s):  
Maximum Entropy ◽  
Large Scale ◽  
Stochastic Dynamics ◽  
Spectral Power ◽  
Oscillatory Activity ◽  
Power Dynamics ◽  
Precise Control ◽  
Oscillatory Dynamics ◽  
Eyes Closed ◽  
Eyes Open

AbstractOscillatory neural activity is dynamically controlled to coordinate perceptual, attentional and cognitive processes. On the macroscopic scale, this control is reflected in the U-shaped deviations of EEG spectral-power dynamics from stochastic dynamics, characterized by disproportionately elevated occurrences of the lowest and highest ranges of power. To understand the mechanisms that generate these low- and high-power states, we fit a simple mathematical model of synchronization of oscillatory activity to human EEG data. The results consistently indicated that the majority (∼95%) of synchronization dynamics is controlled by slowly adjusting the probability of synchronization while maintaining maximum entropy within the timescale of a few seconds. This strategy appears to be universal as the results generalized across oscillation frequencies, EEG current sources, and participants (N = 52) whether they rested with their eyes closed, rested with their eyes open in a darkened room, or viewed a silent nature video. Given that precisely coordinated behavior requires tightly controlled oscillatory dynamics, the current results suggest that the large-scale spatial synchronization of oscillatory activity is controlled by the relatively slow, entropy-maximizing adjustments of synchronization probability (demonstrated here) in combination with temporally precise phase adjustments (e.g., phase resetting generated by sensorimotor interactions). Interestingly, we observed a modest but consistent spatial pattern of deviations from the maximum-entropy rule, potentially suggesting that the mid-central-posterior region serves as an “entropy dump” to facilitate the temporally precise control of spectral-power dynamics in the surrounding regions.

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