scholarly journals Attention and Temporal Expectations Modulate Power, Not Phase, of Ongoing Alpha Oscillations

2015 ◽  
Vol 27 (8) ◽  
pp. 1573-1586 ◽  
Author(s):  
Rosanne M. van Diepen ◽  
Michael X Cohen ◽  
Damiaan Denys ◽  
Ali Mazaheri
Keyword(s):  
Phase Angle ◽  
Phase Locking ◽  
Auditory Target ◽  
Alpha Power ◽  
Visual Condition ◽  
Top Down ◽  
Alpha Oscillations ◽  
Alpha Oscillation ◽  
Sensory Cortices ◽  
Phase Angles

The perception of near-threshold visual stimuli has been shown to depend in part on the phase (i.e., time in the cycle) of ongoing alpha (8–13 Hz) oscillations in the visual cortex relative to the onset of that stimulus. However, it is currently unknown whether the phase of the ongoing alpha activity can be manipulated by top–down factors such as attention or expectancy. Using three variants of a cross-modal attention paradigm with constant predictable stimulus onsets, we examined if cues signaling to attend to either the visual or the auditory domain influenced the phase of alpha oscillations in the associated sensory cortices. Importantly, intermixed in all three experiments, we included trials without a target to estimate the phase at target presentation without contamination from the early evoked responses. For these blank trials, at the time of expected target and distractor onset, we examined (1) the degree of the uniformity in phase angles across trials, (2) differences in phase angle uniformity compared with a pretarget baseline, and (3) phase angle differences between visual and auditory target conditions. Across all three experiments, we found that, although the cues induced a modulation in alpha power in occipital electrodes, neither the visual condition nor the auditory cue condition induced any significant phase-locking across trials during expected target or distractor presentation. These results suggest that, although alpha power can be modulated by top–down factors such as attention and expectation, the phase of the ongoing alpha oscillation is not under such control.

scholarly journals Prefrontal cortex modulates posterior alpha oscillations during top-down guided visual perception

2017 ◽  
Vol 114 (35) ◽  
pp. 9457-9462 ◽  
Author(s):  
Randolph F. Helfrich ◽  
Melody Huang ◽  
Guy Wilson ◽  
Robert T. Knight
Keyword(s):  
Visual Perception ◽  
Alpha Activity ◽  
Alpha Power ◽  
Top Down ◽  
Visual Stream ◽  
Alpha Oscillations ◽  
Fine Grained ◽  
Oscillatory Dynamics ◽  
Delta Activity ◽  
And Behavior

Conscious visual perception is proposed to arise from the selective synchronization of functionally specialized but widely distributed cortical areas. It has been suggested that different frequency bands index distinct canonical computations. Here, we probed visual perception on a fine-grained temporal scale to study the oscillatory dynamics supporting prefrontal-dependent sensory processing. We tested whether a predictive context that was embedded in a rapid visual stream modulated the perception of a subsequent near-threshold target. The rapid stream was presented either rhythmically at 10 Hz, to entrain parietooccipital alpha oscillations, or arrhythmically. We identified a 2- to 4-Hz delta signature that modulated posterior alpha activity and behavior during predictive trials. Importantly, delta-mediated top-down control diminished the behavioral effects of bottom-up alpha entrainment. Simultaneous source-reconstructed EEG and cross-frequency directionality analyses revealed that this delta activity originated from prefrontal areas and modulated posterior alpha power. Taken together, this study presents converging behavioral and electrophysiological evidence for frontal delta-mediated top-down control of posterior alpha activity, selectively facilitating visual perception.

Working Memory Processes Are Mediated by Local and Long-range Synchronization of Alpha Oscillations

2013 ◽  
Vol 25 (8) ◽  
pp. 1343-1357 ◽  
Author(s):  
Maite Crespo-Garcia ◽  
Diego Pinal ◽  
Jose L. Cantero ◽  
Fernando Díaz ◽  
Montserrat Zurrón ◽  
...  
Keyword(s):  
Working Memory ◽  
Long Range ◽  
Alpha Phase ◽  
Alpha Power ◽  
Phase Synchrony ◽  
Top Down ◽  
Alpha Oscillations ◽  
Memory Processes ◽  
Time Frequency ◽  
Cortical Regions

Different cortical dynamics of alpha oscillations (8–13 Hz) have been associated with increased working memory load, which have been mostly interpreted as a neural correlate of functional inhibition. This study aims at determining whether different manifestations of load-dependent amplitude and phase dynamics in the alpha band can coexist over different cortical regions. To address this question, we increased information load by manipulating the number and spatial configuration of domino spots. Time–frequency analysis of EEG source activity revealed (i) load-independent increases of both alpha power and interregional alpha-phase synchrony within task-irrelevant, posterior cortical regions and (ii) load-dependent decreases of alpha power over areas of the left pFC and bilateral posterior parietal cortex (PPC) preceded in time by load-dependent decreases of alpha-phase synchrony between the left pFC and the left PPC. The former results support the role of alpha oscillations in inhibiting irrelevant sensorimotor processing, whereas the latter likely reflect release of parietal task-relevant areas from top–down inhibition with load increase. This interpretation found further support in a significant latency shift of 15 msec from pFC to the PPC. Together, these results suggest that amplitude and phase alpha dynamics in both local and long-range cortical networks reflect different neural mechanisms of top–down control that might be crucial in mediating the different working memory processes.

scholarly journals Top-down inhibition of irrelevant information indexed by alpha rhythms is disrupted in migraine

2021 ◽  
Author(s):  
Rémy Masson ◽  
Hesham A ElShafei ◽  
Geneviève Demarquay ◽  
Lesly Fornoni ◽  
Yohana Lévêque ◽  
...  
Keyword(s):  
Cognitive Processing ◽  
Gamma Activity ◽  
Auditory Target ◽  
Alpha Power ◽  
Top Down ◽  
Significant Group ◽  
Bottom Up ◽  
Power Increase ◽  
Visual Areas ◽  
Healthy Participants

There is growing evidence that migraine is associated with attentional abnormalities, both during and outside migraine attacks, which would impact the cognitive processing of sensory stimulation. However, these attention alterations are poorly characterized and their neurophysiological basis is still unclear. Nineteen migraineurs without aura and nineteen healthy participants were recruited to perform a task which used visually-cued auditory targets and distracting sounds to evaluate conjointly top-down and bottom-up attention mechanisms. Magnetoencephalography (MEG) signals were recorded. We investigated anticipatory alpha activity (power increase and decrease) and distractor-induced gamma activity as markers for top-down (inhibition and facilitation) and bottom-up attention, respectively. Compared to healthy participants, migraineurs presented a significantly less prominent alpha power increase in visual areas in anticipation of the auditory target, indexing a reduced inhibition of task-irrelevant visual areas. However, there was no significant group difference regarding the alpha power decrease in the relevant auditory cortices in anticipation of the target, nor regarding the distractor-induced gamma power increase in the ventral attention network. These results in the alpha band suggest that top-down inhibitory processes in the visual cortices are deficient in migraine but there is no clear evidence supporting a disruption of top-down facilitatory attentional processes. This relative inability to suppress irrelevant sensory information may be underlying the self-reported increased distractibility and contribute to sensory disturbances in migraine.

scholarly journals Reduction in left frontal alpha oscillations by transcranial alternating current stimulation in major depressive disorder is context-dependent in a randomized-clinical trial

2021 ◽  
Author(s):  
Justin Riddle ◽  
Morgan L. Alexander ◽  
Crystal Edler Schiller ◽  
David R. Rubinow ◽  
Flavio Frohlich
Keyword(s):  
Clinical Trial ◽  
Major Depressive Disorder ◽  
Depressive Disorder ◽  
Alpha Power ◽  
Single Session ◽  
Major Depressive ◽  
Alpha Oscillations ◽  
Alpha Frequency ◽  
Alpha Oscillation ◽  
Transcranial Alternating Current Stimulation

Background: Left frontal alpha oscillations are associated with decreased approach motivation and have been proposed as a target for non-invasive brain stimulation for the treatment of depression and anhedonia. Indeed, transcranial alternating current stimulation (tACS) at the alpha frequency reduced left frontal alpha power and was associated with a higher response rate than placebo stimulation in patients with major depressive disorder (MDD) in a recent double-blind placebo controlled clinical trial. Methods: In this current study, we aimed to replicate such successful target engagement by delineating the effects of a single session of bifrontal tACS at the individualized alpha frequency (IAF-tACS) on alpha oscillations in patients with MDD. Electrical brain activity was recorded during rest and while viewing emotionally-salient images before and after stimulation to investigate if the modulation of alpha oscillation by tACS exhibited specificity with regards to valence. Results: In agreement with the previous study of tACS in MDD, we found that a single session of bifrontal IAF-tACS reduced left frontal alpha power during the resting state when compared to placebo. Furthermore, the reduction of left frontal alpha oscillation by tACS was specific for stimuli with positive valence. In contrast, these effects on left frontal alpha power were not found in healthy control participants. Conclusion: Together these results support an important role of tACS in reducing left frontal alpha oscillations as a future treatment for MDD. National Clinical Trial: NCT03449979, Single Session of tACS in a Depressive Episode (SSDE) https://www.clinicaltrials.gov/ct2/show/NCT03449979 .

Prestimulus Oscillations in the Alpha Band of the EEG Are Modulated by the Difficulty of Feature Discrimination and Predict Activation of a Sensory Discrimination Process

2014 ◽  
Vol 26 (8) ◽  
pp. 1615-1628 ◽  
Author(s):  
Daniel M. Roberts ◽  
John R. Fedota ◽  
George A. Buzzell ◽  
Raja Parasuraman ◽  
Craig G. McDonald
Keyword(s):  
Spatial Attention ◽  
Cortical Excitability ◽  
Control Process ◽  
Discrimination Performance ◽  
Stimulus Onset ◽  
Time On Task ◽  
Alpha Power ◽  
Top Down ◽  
Alpha Oscillation ◽  
Selection Tasks

Recent work has demonstrated that the occipital–temporal N1 component of the ERP is sensitive to the difficulty of visual discrimination, in a manner that cannot be explained by simple differences in low-level visual features, arousal, or time on task. These observations provide evidence that the occipital–temporal N1 component is modulated by the application of top–down control. However, the timing of this control process remains unclear. Previous work has demonstrated proactive, top–down modulation of cortical excitability for cued spatial attention or feature selection tasks. Here, the possibility that a similar top–down process facilitates performance of a difficult stimulus discrimination task is explored. Participants performed an oddball task at two levels of discrimination difficulty, with difficulty manipulated by modulating the similarity between target and nontarget stimuli. Discrimination processes and cortical excitability were assessed via the amplitude of the occipital–temporal N1 component and prestimulus alpha oscillation of the EEG, respectively. For correct discriminations, prestimulus alpha power was reduced, and the occipital–temporal N1 was enhanced in the hard relative to the easy condition. Furthermore, within the hard condition, prestimulus alpha power was reduced, and the occipital–temporal N1 was enhanced for correct relative to incorrect discriminations. The generation of ERPs contingent on relative prestimulus alpha power additionally suggests that diminished alpha power preceding stimulus onset is related to enhancement of the occipital–temporal N1. As in spatial attention, proactive control appears to enhance cortical excitability and facilitate discrimination performance in tasks requiring nonspatial, feature-based attention, even in the absence of competing stimulus features.

scholarly journals Frontal and parietal alpha oscillations reflect attentional modulation of cross-modal matching

2018 ◽  
Author(s):  
Jonas Misselhorn ◽  
Uwe Friese ◽  
Andreas K. Engel
Keyword(s):  
Gamma Activity ◽  
Multisensory Perception ◽  
Top Down ◽  
Bottom Up ◽  
Alpha Oscillations ◽  
Sensory Inputs ◽  
Gamma Power ◽  
Sensory Cortices ◽  
Underlying Mechanisms ◽  
Selection Of

Multisensory perception is shaped by both attentional selection of relevant sensory inputs and exploitation of stimulus-driven factors that promote cross-modal binding. Underlying mechanisms of both top-down and bottom-up modulations have been linked to changes in alpha/gamma dynamics in primary sensory cortices and temporoparietal cortex. Accordingly, it has been proposed that alpha oscillations provide pulsed inhibition for gamma activity and thereby dynamically route cortical information flow. In this study, we employed a recently introduced multisensory paradigm incorporating both bottom-up and top-down aspects of cross-modal attention in an EEG study. The same trimodal stimuli were presented in two distinct attentional conditions, focused on visual-tactile or audio-visual components, for which cross-modal congruence of amplitude changes had to be evaluated. Neither top-down nor bottom-up cross-modal attention modulated alpha or gamma power in primary sensory cortices. Instead, we found alpha band effects in bilateral frontal and right parietal cortex. We propose that frontal alpha oscillations reflect the origin of top-down control regulating perceptual gains and that modulations of parietal alpha oscillations relates to intersensory re-orienting. Taken together, we suggest that the idea of selective cortical routing via alpha oscillations can be extended from sensory cortices to the frontoparietal attention network.

scholarly journals Dynamics of Alpha Control: Preparatory Suppression of Posterior Alpha Oscillations by Frontal Modulators Revealed with Combined EEG and Event-related Optical Signal

2014 ◽  
Vol 26 (10) ◽  
pp. 2400-2415 ◽  
Author(s):  
Kyle E. Mathewson ◽  
Diane M. Beck ◽  
Tony Ro ◽  
Edward L. Maclin ◽  
Kathy A. Low ◽  
...  
Keyword(s):  
Temporal Dynamics ◽  
Brain Activity ◽  
Conscious Experience ◽  
Optical Signal ◽  
Alpha Power ◽  
Top Down ◽  
Spatiotemporal Resolution ◽  
Attention Networks ◽  
Alpha Oscillations ◽  
Eeg Alpha

We investigated the dynamics of brain processes facilitating conscious experience of external stimuli. Previously, we proposed that alpha (8–12 Hz) oscillations, which fluctuate with both sustained and directed attention, represent a pulsed inhibition of ongoing sensory brain activity. Here we tested the prediction that inhibitory alpha oscillations in visual cortex are modulated by top–down signals from frontoparietal attention networks. We measured modulations in phase-coherent alpha oscillations from superficial frontal, parietal, and occipital cortices using the event-related optical signal (EROS), a measure of neuronal activity affording high spatiotemporal resolution, along with concurrently recorded EEG, while participants performed a visual target detection task. The pretarget alpha oscillations measured with EEG and EROS from posterior areas were larger for subsequently undetected targets, supporting alpha's inhibitory role. Using EROS, we localized brain correlates of these awareness-related alpha oscillations measured at the scalp to the cuneus and precuneus. Crucially, EROS alpha suppression correlated with posterior EEG alpha power across participants. Sorting the EROS data based on EEG alpha power quartiles to investigate alpha modulators revealed that suppression of posterior alpha was preceded by increased activity in regions of the dorsal attention network and decreased activity in regions of the cingulo-opercular network. Cross-correlations revealed the temporal dynamics of activity within these preparatory networks before posterior alpha modulation. The novel combination of EEG and EROS afforded localization of the sources and correlates of alpha oscillations and their temporal relationships, supporting our proposal that top–down control from attention networks modulates both posterior alpha and awareness of visual stimuli.

scholarly journals Top–Down Control of Alpha Phase Adjustment in Anticipation of Temporally Predictable Visual Stimuli

2018 ◽  
Vol 30 (8) ◽  
pp. 1157-1169 ◽  
Author(s):  
Rodolfo Solís-Vivanco ◽  
Ole Jensen ◽  
Mathilde Bonnefond
Keyword(s):  
Visual Processing ◽  
Visual Information ◽  
Alpha Phase ◽  
Stimulus Onset ◽  
Gamma Activity ◽  
Alpha Power ◽  
Top Down ◽  
Alpha Oscillations ◽  
Phase Adjustment ◽  
Visual Areas

Alpha oscillations (8–14 Hz) are proposed to represent an active mechanism of functional inhibition of neuronal processing. Specifically, alpha oscillations are associated with pulses of inhibition repeating every ∼100 msec. Whether alpha phase, similar to alpha power, is under top–down control remains unclear. Moreover, the sources of such putative top–down phase control are unknown. We designed a cross-modal (visual/auditory) attention study in which we used magnetoencephalography to record the brain activity from 34 healthy participants. In each trial, a somatosensory cue indicated whether to attend to either the visual or auditory domain. The timing of the stimulus onset was predictable across trials. We found that, when visual information was attended, anticipatory alpha power was reduced in visual areas, whereas the phase adjusted just before the stimulus onset. Performance in each modality was predicted by the phase of the alpha oscillations previous to stimulus onset. Alpha oscillations in the left pFC appeared to lead the adjustment of alpha phase in visual areas. Finally, alpha phase modulated stimulus-induced gamma activity. Our results confirm that alpha phase can be top–down adjusted in anticipation of predictable stimuli and improve performance. Phase adjustment of the alpha rhythm might serve as a neurophysiological resource for optimizing visual processing when temporal predictions are possible and there is considerable competition between target and distracting stimuli.

Rhythmic Activity and Individual Variability in Recognition Memory: Theta Oscillations Correlate with Performance whereas Alpha Oscillations Correlate with ERPs

2017 ◽  
Vol 29 (1) ◽  
pp. 183-202 ◽  
Author(s):  
Yvonne Y. Chen ◽  
Jeremy B. Caplan
Keyword(s):  
Individual Differences ◽  
Recognition Memory ◽  
Memory Task ◽  
Rhythmic Activity ◽  
Individual Variability ◽  
Theta Oscillations ◽  
Alpha Oscillations ◽  
Alpha Oscillation ◽  
Familiarity And Recollection ◽  
Visual Inattention

During study trials of a recognition memory task, alpha (∼10 Hz) oscillations decrease, and concurrently, theta (4–8 Hz) oscillations increase when later memory is successful versus unsuccessful (subsequent memory effect). Likewise, at test, reduced alpha and increased theta activity are associated with successful memory (retrieval success effect). Here we take an individual-differences approach to test three hypotheses about theta and alpha oscillations in verbal, old/new recognition, measuring the difference in oscillations between hit trials and miss trials. First, we test the hypothesis that theta and alpha oscillations have a moderately mutually exclusive relationship; but no support for this hypothesis was found. Second, we test the hypothesis that theta oscillations explain not only memory effects within participants, but also individual differences. Supporting this prediction, durations of theta (but not alpha) oscillations at study and at test correlated significantly with d′ across participants. Third, we test the hypothesis that theta and alpha oscillations reflect familiarity and recollection processes by comparing oscillation measures to ERPs that are implicated in familiarity and recollection. The alpha-oscillation effects correlated with some ERP measures, but inversely, suggesting that the actions of alpha oscillations on memory processes are distinct from the roles of familiarity- and recollection-linked ERP signals. The theta-oscillation measures, despite differentiating hits from misses, did not correlate with any ERP measure; thus, theta oscillations may reflect elaborative processes not tapped by recollection-related ERPs. Our findings are consistent with alpha oscillations reflecting visual inattention, which can modulate memory, and with theta oscillations supporting recognition memory in ways that complement the most commonly studied ERPs.

scholarly journals Three times NO: no relationship between frontal alpha asymmetry and depressive disorders in a multiverse analysis of three studies

2020 ◽  
Author(s):  
Aleksandra Kołodziej ◽  
Mikołaj Magnuski ◽  
Anastasia Ruban ◽  
Aneta Brzezicka
Keyword(s):  
Data Analysis ◽  
Analytical Approach ◽  
Depressive Disorders ◽  
Alpha Power ◽  
Alpha Oscillations ◽  
Alpha Asymmetry ◽  
Eeg Data ◽  
Theoretical Assumptions ◽  
Frontal Alpha Asymmetry ◽  
Eeg Alpha

AbstractFor decades, the frontal alpha asymmetry (FAA) - a disproportion in EEG alpha oscillations power between right and left frontal channels - has been one of the most popular measures of depressive disorders (DD) in electrophysiology studies. Patients with DD often manifest a left-sided FAA: relatively higher alpha power in the left versus right frontal lobe. Recently, however, multiple studies failed to confirm this effect, questioning its reproducibility. Our purpose is to thoroughly test the validity of FAA in depression by conducting a multiverse analysis - running many related analyses and testing the sensitivity of the effect to changes in the analytical approach - on data from three independent studies. Only two of the 81 analyses revealed significant results. We conclude the paper by discussing theoretical assumptions underlying the FAA and suggest a list of guidelines for improving and expanding the EEG data analysis in future FAA studies.

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