scholarly journals No changes in parieto-occipital alpha during neural phase locking to visual quasi-periodic theta-, alpha-, and beta-band stimulation

2017 ◽  
Author(s):  
Christian Keitel ◽  
Christopher SY Benwell ◽  
Gregor Thut ◽  
Joachim Gross
Keyword(s):  
Alpha Rhythm ◽  
Visual Stimulation ◽  
Phase Locking ◽  
Stimulation Frequency ◽  
Alpha Band ◽  
Human Visual Perception ◽  
Beta Band ◽  
Frequency Bands ◽  
Low Intensity ◽  
Increased Sensitivity

ABSTRACTRecent studies have probed the role of the parieto-occipital alpha rhythm (8 – 12 Hz) in human visual perception through attempts to drive its neural generators. To that end, paradigms have used high-intensity strictly-periodic visual stimulation that created strong predictions about future stimulus occurrences and repeatedly demonstrated perceptual consequences in line with an entrainment of parieto-occipital alpha. Our study, in turn, examined the case of alpha entrainment by non-predictive low-intensity quasi-periodic visual stimulation within theta-(4 – 7 Hz), alpha-(8 – 13 Hz) and beta (14 – 20 Hz) frequency bands, i.e. a class of stimuli that resemble the temporal characteristics of naturally occurring visual input more closely. We have previously reported substantial neural phase-locking in EEG recording during all three stimulation conditions. Here, we studied to what extent this phase-locking reflected an entrainment of intrinsic alpha rhythms in the same dataset. Specifically, we tested whether quasi-periodic visual stimulation affected several properties of parieto-occipital alpha generators. Speaking against an entrainment of intrinsic alpha rhythms by non-predictive low-intensity quasi-periodic visual stimulation, we found none of these properties to show differences between stimulation frequency bands. In particular, alpha band generators did not show increased sensitivity to alpha band stimulation and Bayesian inference corroborated evidence against an influence of stimulation frequency. Our results set boundary conditions for when and how to expect effects of entrainment of alpha generators and suggest that the parieto-occipital alpha rhythm may be more inert to external influences than previously thought.

scholarly journals Resistance-induced brain activity changes during cycle ergometer exercises

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Ming-An Lin ◽  
Ling-Fu Meng ◽  
Yuan Ouyang ◽  
Hsiao-Lung Chan ◽  
Ya-Ju Chang ◽  
...  
Keyword(s):  
Resistance Exercise ◽  
High Resistance ◽  
Exercise Intensity ◽  
Spectral Power ◽  
Brain Activity ◽  
Phase Locking ◽  
Cycle Ergometer ◽  
Cortical Activation ◽  
Alpha Band ◽  
Beta Band

Abstract Background EEGs are frequently employed to measure cerebral activations during physical exercise or in response to specific physical tasks. However, few studies have attempted to understand how exercise-state brain activity is modulated by exercise intensity. Methods Ten healthy subjects were recruited for sustained cycle ergometer exercises at low and high resistance, performed on two separate days a week apart. Exercise-state EEG spectral power and phase-locking values (PLV) are analyzed to assess brain activity modulated by exercise intensity. Results The high-resistance exercise produced significant changes in beta-band PLV from early to late pedal stages for electrode pairs F3-Cz, P3-Pz, and P3-P4, and in alpha-band PLV for P3-P4, as well as the significant change rate in alpha-band power for electrodes C3 and P3. On the contrary, the evidence for changes in brain activity during the low-resistance exercise was not found. Conclusion These results show that the cortical activation and cortico-cortical coupling are enhanced to take on more workload, maintaining high-resistance pedaling at the required speed, during the late stage of the exercise period.

scholarly journals Individual alpha frequency increases during a task but is unchanged by alpha-band flicker

2019 ◽  
Author(s):  
Michael J. Gray ◽  
Tatiana A. Emmanouil
Keyword(s):  
Visual Stimulation ◽  
Behavioral Measure ◽  
Neural Oscillations ◽  
Alpha Band ◽  
Frequency Bands ◽  
Alpha Frequency ◽  
Separate Source ◽  
Individual Alpha Frequency ◽  
Short Time ◽  
The Relationship

AbstractVisual perception fluctuates in-synch with ongoing neural oscillations in the delta, theta, and alpha frequency bands of the human EEG. Supporting the relationship between alpha and perceptual sampling, recent work has demonstrated that variations in individual alpha frequency (IAF) correlate with the ability to discriminate one from two stimuli presented briefly in the same location. Other studies have found that after being presented with a flickering stimulus at alpha frequencies, perception of near-threshold stimuli fluctuates for a short time at the same frequency. Motivated by previous work, we were interested in whether this alpha entrainment involves shifts in IAF. While recording EEG, we tested whether two-flash discrimination (a behavioral correlate of IAF) can be influenced by ∼1s of rhythmic visual stimulation at two different alpha frequencies (8.3hz and 12.5hz). Speaking against the bottom-up malleability of IAF, we found no change in IAF during stimulation and no change in two-flash discrimination immediately afterwards. We also found synchronous activity that persisted after 12.5hz stimulation, which suggests that a separate source of alpha was entrained. Importantly, we replicated the correlation between IAF and two-flash discrimination in a no-stimulation condition, demonstrating the sensitivity of our behavioral measure. We additionally found that IAF increased during the task compared to rest, which demonstrates that IAF is influenced by top-down factors but is not involved in entrainment. In the framework of existing findings, we suggest that visual entrainment may involve ongoing perceptually-relevant oscillations from the delta to alpha frequency bands, serving to maintain rhythmic temporal expectations.

Compensation through Increased Functional Connectivity: Neural Correlates of Inhibition in Old and Young

2012 ◽  
Vol 24 (10) ◽  
pp. 2057-2069 ◽  
Author(s):  
Linda Geerligs ◽  
Emi Saliasi ◽  
Natasha M. Maurits ◽  
Monicque M. Lorist
Keyword(s):  
Functional Connectivity ◽  
Phase Locking ◽  
Age Groups ◽  
Stimulus Presentation ◽  
Neural Correlates ◽  
Irrelevant Information ◽  
General Mechanism ◽  
Alpha Band ◽  
Beta Band ◽  
Attention Task

With increasing age, people experience more difficulties with suppressing irrelevant information, which may have a major impact on cognitive functioning. The extent of decline of inhibitory functions with age is highly variable between individuals. In this study, we used ERPs and phase locking analyses to investigate neural correlates of this variability in inhibition between individuals. Older and younger participants performed a selective attention task in which relevant and irrelevant information was presented simultaneously. The participants were split into high and low performers based on their level of inhibition inefficiency, that is, the slowing of RTs induced by information that participants were instructed to ignore. P1 peak amplitudes were larger in low performers than in high performers, indicating that low performers were less able to suppress the processing of irrelevant stimuli. Phase locking analyses were used as a measure of functional connectivity. Efficient inhibition in both age groups was related to the increased functional connectivity in the alpha band between frontal and occipito-parietal ROIs in the prestimulus interval. In addition, increased power in the alpha band in occipito-parietal ROIs was related to better inhibition both before and after stimulus onset. Phase locking in the upper beta band before and during stimulus presentation between frontal and occipito-parietal ROIs was related to a better performance in older participants only, suggesting that this is an active compensation mechanism employed to maintain adequate performance. In addition, increased top–down modulation and increased power in the alpha band appears to be a general mechanism facilitating inhibition in both age groups.

scholarly journals Modifications in the Topological Structure of EEG Functional Connectivity Networks during Listening Tonal and Atonal Concert Music in Musicians and Non-Musicians

2021 ◽  
Vol 11 (2) ◽  
pp. 159
Author(s):  
Almudena González ◽  
Manuel Santapau ◽  
Antoni Gamundí ◽  
Ernesto Pereda ◽  
Julián J. González
Keyword(s):  
Topological Structure ◽  
Phase Synchronization ◽  
Random Network ◽  
Small World ◽  
Surrogate Data ◽  
Musical Structure ◽  
Beta Band ◽  
Tonal Music ◽  
Frequency Bands ◽  
Concert Music

The present work aims to demonstrate the hypothesis that atonal music modifies the topological structure of electroencephalographic (EEG) connectivity networks in relation to tonal music. To this, EEG monopolar records were taken in musicians and non-musicians while listening to tonal, atonal, and pink noise sound excerpts. EEG functional connectivities (FC) among channels assessed by a phase synchronization index previously thresholded using surrogate data test were computed. Sound effects, on the topological structure of graph-based networks assembled with the EEG-FCs at different frequency-bands, were analyzed throughout graph metric and network-based statistic (NBS). Local and global efficiency normalized (vs. random-network) measurements (NLE|NGE) assessing network information exchanges were able to discriminate both music styles irrespective of groups and frequency-bands. During tonal audition, NLE and NGE values in the beta-band network get close to that of a small-world network, while during atonal and even more during noise its structure moved away from small-world. These effects were attributed to the different timbre characteristics (sounds spectral centroid and entropy) and different musical structure. Results from networks topographic maps for strength and NLE of the nodes, and for FC subnets obtained from the NBS, allowed discriminating the musical styles and verifying the different strength, NLE, and FC of musicians compared to non-musicians.

EEG Responses to Low-Level Chemicals in Normals and Cacosmics

1994 ◽  
Vol 10 (4-5) ◽  
pp. 633-643
Author(s):  
Gary E. Schwartz ◽  
Iris R. Bell ◽  
Ziya V. Dikman ◽  
Mercedes Fernandez ◽  
John P. Kline ◽  
...  
Keyword(s):  
College Students ◽  
Low Frequency ◽  
Normal Subjects ◽  
The Elderly ◽  
Isoamyl Acetate ◽  
Alpha Activity ◽  
Low Intensity ◽  
Liquid Silicone ◽  
Increased Sensitivity ◽  
The University

Recent studies from the University of Arizona indicate that normal subjects, both college students and the elderly, can register the presence of low-intensity odors in the electroencephalogram (EEG) in the absence of conscious awareness of the odors. The experimental paradigm involves subjects sniffing pairs of bottles, one containing an odorant (e.g. isoamyl acetate) dissolved in an odorless solvent (water or liquid silicone), the other containing just the solvent, while 19 channels of EEG are continuously recorded. For the low-intensity odor conditions, concentrations are adjusted downward (decreased) until subjects correctly identify the odor bottle at chance (50). The order of odorants, concentrations, and hand holding the control bottle, are counterbalanced within and across subjects. Three previous experiments found that alpha activity (8-12 hz) decreased in midline and posterior regions when subjects sniffed the low-intensity odors. The most recent study suggests that decreased theta activity (4-8 hz) may reflect sensory registration and decreased alpha activity may reflect perceptual registration. In a just completed experiment involving college students who were selected based on combinations of high and low scores on a scale measuring cacosmia (chemical odor intolerance) and high and low scores on a scale measuring depression, cacosmic subjects (independent of depression) showed greater decreases in low-frequency alpha (8-10 hz) and greater increases in low-frequency beta (12-16 hz) to the solvent propylene glycol compared to an empty bottle. Topographic EEG mapping to low-intensity odorants may provide a useful tool for investigating possible increased sensitivity to specific chemicals in chemically sensitive individuals.

scholarly journals Stimulus-driven brain rhythms within the alpha band: The attentional-modulation conundrum

2018 ◽  
Author(s):  
Christian Keitel ◽  
Anne Keitel ◽  
Christopher SY Benwell ◽  
Christoph Daube ◽  
Gregor Thut ◽  
...  
Keyword(s):  
Spatial Attention ◽  
Visual Processing ◽  
Visual Stimulation ◽  
Brain Activity ◽  
Gain Control ◽  
Sensory Stimulation ◽  
Alpha Band ◽  
Visual Evoked Response ◽  
Brain Rhythms ◽  
Inhibitory Function

Two largely independent research lines use rhythmic sensory stimulation to study visual processing. Despite the use of strikingly similar experimental paradigms, they differ crucially in their notion of the stimulus-driven periodic brain responses: One regards them mostly as synchronised (entrained) intrinsic brain rhythms; the other assumes they are predominantly evoked responses (classically termed steady-state responses, or SSRs) that add to the ongoing brain activity. This conceptual difference can produce contradictory predictions about, and interpretations of, experimental outcomes. The effect of spatial attention on brain rhythms in the alpha-band (8-13 Hz) is one such instance: alpha-range SSRs have typically been found to increase in power when participants focus their spatial attention on laterally presented stimuli, in line with a gain control of the visual evoked response. In nearly identical experiments, retinotopic decreases in entrained alpha-band power have been reported, in line with the inhibitory function of intrinsic alpha. Here we reconcile these contradictory findings by showing that they result from a small but far-reaching difference between two common approaches to EEG spectral decomposition. In a new analysis of previously published EEG data, recorded during bilateral rhythmic visual stimulation, we find the typical SSR gain effect when emphasising stimulus-locked neural activity and the typical retinotopic alpha suppression when focusing on ongoing rhythms. These opposite but parallel effects suggest that spatial attention may bias the neural processing of dynamic visual stimulation via two complementary neural mechanisms.

scholarly journals Envelope analysis of the human alpha rhythm

2021 ◽  
Author(s):  
Víctor Manuel Hidalgo ◽  
Javier Díaz ◽  
Jorge Mpodozis ◽  
Juan-Carlos Letelier
Keyword(s):  
Gaussian Noise ◽  
Alpha Rhythm ◽  
Phase Locking ◽  
Gaussian White Noise ◽  
Occipital Cortex ◽  
Neural Population ◽  
Envelope Analysis ◽  
Weakly Coupled ◽  
Neural Signal Analysis ◽  
New Interpretation

The origin of the human alpha rhythm has been a matter of debate since Lord Adrian attributed it to synchronous neural populations in the occipital cortex. While some authors have pointed out the Gaussian characteristics of the alpha rhythm, their results have been repeatedly disregarded in favor of Adrian′s interpretation; even though the first EEG Gaussianity reports can be traced back to the origins of EEG. Here we revisit this problem using the envelope analysis — a method that relies on the fact that the coefficient of variation of the envelope (CVE) for continuous-time zero-mean Gaussian white noise (as well as for any filteredsub-band) is equal to √(4−π)/π≈0.523, thus making the CVE a fingerprint for Gaussianity. As a consequence, any significant deviation from Gaussianity is linked to synchronous neural dynamics. Low-CVE signals come from phase-locking dynamics, while mid-CVE signals constitute Gaussian noise. High-CVE signals have been linked to unsteady dynamics in populations of nonlinear oscillators. We analyzed occipital EEG and iEEG data from massive public databases and the order parameter of a population of weakly coupled oscillators using the envelope analysis. Our results showed that the human alpha rhythm can be characterized as a rhythmic, Gaussian, or pulsating signal due to intra- and inter-subject variability. Furthermore, Fourier analysis showed that the canonical spectral peak at≈10[Hz] is present in all three CVE classes, thus demonstrating that this same peak can be produced by rhythms, Gaussian noise, and pulsating ripples. Alpha-like signals obtained from a population of non-linear oscillators showed a different CVE depending only on the coupling constant, suggesting that the same neural population can produce the amplitude modulation patterns observed in experimental data. iEEG data, however, was found to be mostly Gaussian, specially the signals recorded from the calcarine cortex. These results suggest that a new interpretation for EEG event-related synchronization/desynchronization (ERS/ERD) may be needed. Envelope analysis constitutes a novel complement to traditional Fourier-based methods for neural signal analysis relating amplitude modulations (CVE) to signal energy.

scholarly journals Perceptual Weighting of Binaural Lateralization Cues across Frequency Bands

2020 ◽  
Vol 21 (6) ◽  
pp. 485-496
Author(s):  
Axel Ahrens ◽  
Suyash Narendra Joshi ◽  
Bastian Epp
Keyword(s):  
Auditory System ◽  
Phase Locking ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Low Frequencies ◽  
Frequency Bands ◽  
Relative Contribution ◽  
Highest Weight ◽  
Auditory Enhancement ◽  
Spectral Weighting

Abstract The auditory system uses interaural time and level differences (ITD and ILD) as cues to localize and lateralize sounds. The availability of ITDs and ILDs in the auditory system is limited by neural phase-locking and by the head size, respectively. Although the frequency-specific limitations are well known, the relative contribution of ITDs and ILDs in individual frequency bands in broadband stimuli is unknown. To determine these relative contributions, or spectral weights, listeners were asked to lateralize stimuli consisting of eleven simultaneously presented 1-ERB-wide noise bands centered between 442 and 5544 Hz and separated by 1-ERB-wide gaps. Either ITDs or ILDs were varied independently across each noise band, while fixing the other interaural disparity to either 0 dB or 0 μs. The weights were obtained using a multiple linear regression analysis. In a second experiment, the effect of auditory enhancement on the spectral weights was investigated. The enhancement of single noise bands was realized by presenting ten of the noise bands as preceding and following sounds (pre- and post-cursors, respectively). Listeners were asked to lateralize the stimuli as in the first experiment. Results show that in the absence of pre- and post-cursors, only the lowest or highest frequency band received highest weight for ITD and ILD, respectively. Auditory enhancement led to significantly enhanced weights given to the band without the pre- and post-cursor. The weight enhancement could only be observed at low frequencies, when determined with ITD cues and for low and high frequencies for ILDs. Hence, the auditory system seems to be able to change the spectral weighting of binaural information depending on the information content.

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