scholarly journals Spotting the path that leads nowhere: Modulation of human theta and alpha oscillations induced by trajectory changes during navigation

2018 ◽  
Author(s):  
Amir-Homayoun Javadi ◽  
Eva Zita Patai ◽  
Aaron Margois ◽  
Heng-Ru M. Tan ◽  
Darshan Kumaran ◽  
...  
Keyword(s):  
Temporal Dynamics ◽  
Brain Activity ◽  
Cognitive Map ◽  
Lava Flows ◽  
Neural Dynamics ◽  
Alpha Power ◽  
Neural Basis ◽  
Alpha Oscillations ◽  
Fine Grained ◽  
Desert Island

AbstractThe capacity to take efficient detours and exploit novel shortcuts during navigation is thought to be supported by a cognitive map of the environment. Despite advances in understanding the neural basis of the cognitive map, little is known about the neural dynamics associated with detours and shortcuts. Here, we recorded magnetoencephalography from humans as they navigated a virtual desert island riven by shifting lava flows. The task probed their ability to take efficient detours and shortcuts to remembered goals. We report modulation in event-related fields and theta power as participants identified real shortcuts and differentiated these from false shortcuts that led along suboptimal paths. Additionally, we found that a decrease in alpha power preceded ‘back-tracking’ where participants spontaneously turned back along a previous path. These findings help advance our understanding of the fine-grained temporal dynamics of human brain activity during navigation and support the development of models of brain networks that support navigation.

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 Age-dependent electroencephalogram (EEG) patterns during sevoflurane general anesthesia in infants

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Laura Cornelissen ◽  
Seong-Eun Kim ◽  
Patrick L Purdon ◽  
Emery N Brown ◽  
Charles B Berde
Keyword(s):  
General Anesthesia ◽  
Temporal Dynamics ◽  
Brain Activity ◽  
Body Movement ◽  
Video Recording ◽  
Brain State ◽  
Alpha Power ◽  
State Monitoring ◽  
Spatio Temporal ◽  
Electroencephalogram Eeg

Electroencephalogram (EEG) approaches may provide important information about developmental changes in brain-state dynamics during general anesthesia. We used multi-electrode EEG, analyzed with multitaper spectral methods and video recording of body movement to characterize the spatio-temporal dynamics of brain activity in 36 infants 0–6 months old when awake, and during maintenance of and emergence from sevoflurane general anesthesia. During maintenance: (1) slow-delta oscillations were present in all ages; (2) theta and alpha oscillations emerged around 4 months; (3) unlike adults, all infants lacked frontal alpha predominance and coherence. Alpha power was greatest during maintenance, compared to awake and emergence in infants at 4–6 months. During emergence, theta and alpha power decreased with decreasing sevoflurane concentration in infants at 4–6 months. These EEG dynamic differences are likely due to developmental factors including regional differences in synaptogenesis, glucose metabolism, and myelination across the cortex. We demonstrate the need to apply age-adjusted analytic approaches to develop neurophysiologic-based strategies for pediatric anesthetic state monitoring.

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.

Prestimulus Neural Oscillations Inhibit Visual Perception via Modulation of Response Gain

2014 ◽  
Vol 26 (11) ◽  
pp. 2514-2529 ◽  
Author(s):  
Maximilien Chaumon ◽  
Niko A. Busch
Keyword(s):  
Brain Activity ◽  
Sensory Information ◽  
Inhibitory Effect ◽  
Qualitative Description ◽  
Alpha Power ◽  
Alpha Oscillations ◽  
External Stimuli ◽  
Functional Mechanisms ◽  
The Brain ◽  
Output Transformation

The ongoing state of the brain radically affects how it processes sensory information. How does this ongoing brain activity interact with the processing of external stimuli? Spontaneous oscillations in the alpha range are thought to inhibit sensory processing, but little is known about the psychophysical mechanisms of this inhibition. We recorded ongoing brain activity with EEG while human observers performed a visual detection task with stimuli of different contrast intensities. To move beyond qualitative description, we formally compared psychometric functions obtained under different levels of ongoing alpha power and evaluated the inhibitory effect of ongoing alpha oscillations in terms of contrast or response gain models. This procedure opens the way to understanding the actual functional mechanisms by which ongoing brain activity affects visual performance. We found that strong prestimulus occipital alpha oscillations—but not more anterior mu oscillations—reduce performance most strongly for stimuli of the highest intensities tested. This inhibitory effect is best explained by a divisive reduction of response gain. Ongoing occipital alpha oscillations thus reflect changes in the visual system's input/output transformation that are independent of the sensory input to the system. They selectively scale the system's response, rather than change its sensitivity to sensory information.

The phase of prestimulus alpha oscillations affects tactile perception

2014 ◽  
Vol 111 (6) ◽  
pp. 1300-1307 ◽  
Author(s):  
Lei Ai ◽  
Tony Ro
Keyword(s):  
Brain Activity ◽  
Brain Regions ◽  
Stimulus Onset ◽  
Tactile Perception ◽  
Alpha Power ◽  
Perceptual Awareness ◽  
Alpha Oscillations ◽  
Left Hand ◽  
Tactile Stimuli ◽  
Significant Difference

Previous studies have shown that neural oscillations in the 8- to 12-Hz range influence sensory perception. In the current study, we examined whether both the power and phase of these mu/alpha oscillations predict successful conscious tactile perception. Near-threshold tactile stimuli were applied to the left hand while electroencephalographic (EEG) activity was recorded over the contralateral right somatosensory cortex. We found a significant inverted U-shaped relationship between prestimulus mu/alpha power and detection rate, suggesting that there is an intermediate level of alpha power that is optimal for tactile perception. We also found a significant difference in phase angle concentration at stimulus onset that predicted whether the upcoming tactile stimulus was perceived or missed. As has been shown in the visual system, these findings suggest that these mu/alpha oscillations measured over somatosensory areas exert a strong inhibitory control on tactile perception and that pulsed inhibition by these oscillations shapes the state of brain activity necessary for conscious perception. They further suggest that these common phasic processing mechanisms across different sensory modalities and brain regions may reflect a common underlying encoding principle in perceptual processing that leads to momentary windows of perceptual awareness.

Tracking the Spatiotemporal Neural Dynamics of Real-world Object Size and Animacy in the Human Brain

2018 ◽  
Vol 30 (11) ◽  
pp. 1559-1576 ◽  
Author(s):  
Seyed-Mahdi Khaligh-Razavi ◽  
Radoslaw Martin Cichy ◽  
Dimitrios Pantazis ◽  
Aude Oliva
Keyword(s):  
Human Brain ◽  
Real World ◽  
Temporal Dynamics ◽  
Brain Activity ◽  
Temporal Cortex ◽  
Neural Dynamics ◽  
Control Analysis ◽  
Object Size ◽  
Parahippocampal Cortex ◽  
Early Visual Cortex

Animacy and real-world size are properties that describe any object and thus bring basic order into our perception of the visual world. Here, we investigated how the human brain processes real-world size and animacy. For this, we applied representational similarity to fMRI and MEG data to yield a view of brain activity with high spatial and temporal resolutions, respectively. Analysis of fMRI data revealed that a distributed and partly overlapping set of cortical regions extending from occipital to ventral and medial temporal cortex represented animacy and real-world size. Within this set, parahippocampal cortex stood out as the region representing animacy and size stronger than most other regions. Further analysis of the detailed representational format revealed differences among regions involved in processing animacy. Analysis of MEG data revealed overlapping temporal dynamics of animacy and real-world size processing starting at around 150 msec and provided the first neuromagnetic signature of real-world object size processing. Finally, to investigate the neural dynamics of size and animacy processing simultaneously in space and time, we combined MEG and fMRI with a novel extension of MEG–fMRI fusion by representational similarity. This analysis revealed partly overlapping and distributed spatiotemporal dynamics, with parahippocampal cortex singled out as a region that represented size and animacy persistently when other regions did not. Furthermore, the analysis highlighted the role of early visual cortex in representing real-world size. A control analysis revealed that the neural dynamics of processing animacy and size were distinct from the neural dynamics of processing low-level visual features. Together, our results provide a detailed spatiotemporal view of animacy and size processing in the human brain.

scholarly journals Alpha Oscillations during Incidental Encoding Predict Subsequent Memory for New “Foil” Information

2018 ◽  
Vol 30 (5) ◽  
pp. 667-679 ◽  
Author(s):  
David A. Vogelsang ◽  
Matthias Gruber ◽  
Zara M. Bergström ◽  
Charan Ranganath ◽  
Jon S. Simons
Keyword(s):  
Semantic Processing ◽  
Temporal Dynamics ◽  
Stimulus Onset ◽  
Memory Test ◽  
Oscillatory Activity ◽  
Study Phase ◽  
Alpha Power ◽  
Alpha Oscillations ◽  
Time Frequency ◽  
Frontal Electrode

People can employ adaptive strategies to increase the likelihood that previously encoded information will be successfully retrieved. One such strategy is to constrain retrieval toward relevant information by reimplementing the neurocognitive processes that were engaged during encoding. Using EEG, we examined the temporal dynamics with which constraining retrieval toward semantic versus nonsemantic information affects the processing of new “foil” information encountered during a memory test. Time–frequency analysis of EEG data acquired during an initial study phase revealed that semantic compared with nonsemantic processing was associated with alpha decreases in a left frontal electrode cluster from around 600 msec after stimulus onset. Successful encoding of semantic versus nonsemantic foils during a subsequent memory test was related to decreases in alpha oscillatory activity in the same left frontal electrode cluster, which emerged relatively late in the trial at around 1000–1600 msec after stimulus onset. Across participants, left frontal alpha power elicited by semantic processing during the study phase correlated significantly with left frontal alpha power associated with semantic foil encoding during the memory test. Furthermore, larger left frontal alpha power decreases elicited by semantic foil encoding during the memory test predicted better subsequent semantic foil recognition in an additional surprise foil memory test, although this effect did not reach significance. These findings indicate that constraining retrieval toward semantic information involves reimplementing semantic encoding operations that are mediated by alpha oscillations and that such reimplementation occurs at a late stage of memory retrieval, perhaps reflecting additional monitoring processes.

scholarly journals Alpha oscillations do not implement gain control in early visual cortex but rather gating in parieto-occipital regions

2020 ◽  
Author(s):  
Alexander Zhigalov ◽  
Ole Jensen
Keyword(s):  
Visual Cortex ◽  
Spatial Attention ◽  
Neuronal Excitability ◽  
Brain Activity ◽  
Gain Control ◽  
Alpha Power ◽  
Alpha Band ◽  
Alpha Oscillations ◽  
Early Visual Cortex ◽  
Broadband Frequency

AbstractSpatial attention provides a mechanism for respectively enhancing relevant and suppressing irrelevant information. While it is well-established that attention modulates oscillations in the alpha band, it remains unclear if alpha oscillations are involved in directly modulating the neuronal excitability associated with the allocation of spatial attention. In this study in humans, we utilized a novel broadband frequency (60 – 70 Hz) tagging paradigm to quantify neuronal excitability in relation to alpha oscillations in a spatial attention paradigm. We used magnetoencephalography to characterize ongoing brain activity as it allows for localizing the sources of both the alpha and frequency tagging responses. We found that attentional modulation of alpha power and the frequency tagging response are uncorrelated over trials. Importantly, the neuronal sources of the tagging response were localized in early visual cortex (V1) whereas the sources of the alpha activity were identified around parieto-occipital sulcus. Moreover, we found that attention did not modulate the latency of the frequency tagged responses. Our findings point to alpha band oscillations serving a downstream gating role rather than implementing gain control of excitability in early visual regions.Significance StatementBy combining magnetoencephalography and a novel broadband frequency tagging approach, we show that spatial attention differently modulates alpha oscillations and neuronal excitability. Importantly, the sources of the alpha oscillations and tagging responses were spatially distinct and the alpha power and tagging response were not related over trials. These results are inconsistent with previous ideas suggesting that alpha oscillations are involved in gain control of early sensory regions; rather alpha oscillations are involved in the allocation of neuronal resources in downstream regions.

Neurogenetics of Resilience

2020 ◽  
Author(s):  
Adam Anderson ◽  
Hans Melo
Keyword(s):  
Functional Neuroimaging ◽  
Brain Activity ◽  
Activity Patterns ◽  
Poor Mental Health ◽  
Imaging Genetics ◽  
Synthetic Approach ◽  
Neural Basis ◽  
Fine Grained ◽  
Optimal Functioning ◽  
Methodological Considerations

Our ability to recover from a negative experiences has profound implications not only for mental disorder but also for healthy living; while some individuals are deeply affected by life stressors and develop poor mental health, others seem to overcome even major traumatic events quickly and effortlessly. Critically, individual differences in resilience reflect underlying differences in the neural and genetic mechanisms implemented by different individuals to cope with hardship. Recent advances in functional neuroimaging and molecular genetics have given rise to a synthetic approach referred to as Imaging Genetics with great potential to develop a more fine-grained neurobiological characterization of optimal human functioning. The goal of imaging genetics is to identify mid-level phenotypes, or endophenotypes, in the form of brain activity patterns that reveal genetic influences on specific cognitive and emotional neural processes in the path from genes to behavior, and disorder. Recent years have seen increasing interest in understanding the genetic and neural basis of resilience. In this context, optimal functioning is not defined as the absence of disease but rather as the characteristics and conditions that allow a person to live well, thrive, and flourish. In this chapter we introduce the imaging genetics approach by providing methodological considerations, and discussing relevant studies and future directions as they may relate to resilience and the field of positive psychology in general.

Development of the numerical brain

2014 ◽  
Author(s):  
Liane Kaufmann ◽  
Karin Kucian ◽  
Michael von Aster
Keyword(s):  
Numerical Cognition ◽  
Temporal Dynamics ◽  
Brain Activity ◽  
Brain Regions ◽  
Future Research ◽  
Fine Grained ◽  
Numerical Development ◽  
Technological Advances ◽  
The One ◽  
Neural Signatures

This article focuses on typical trajectories of numerical cognition from infancy all the way through to adulthood (please note that atypical pathways of numerical cognition will be dealt in‘Brain Correlates of Numerical Disabilities’). Despite the fact that developmental imaging studies are still scarce to date there is converging evidence that (1) neural signatures of non-verbal number processing may be observed already in infants; and (2) developmental changes in neural responsivity are characterized by increasing functional specialization of number-relevant frontoparietal brain regions. It has been suggested that age and competence-related modulations of brain activity manifest as an anterior-posterior shift. On the one hand, the recruitment of supporting frontal brain regions decreases, while on the other hand, reliance on number-relevant (fronto-)parietal neural networks increases. Overall, our understanding of the neurocognitive underpinnings of numerical development grew considerably during the last decade. Future research is expected to benefit substantially from the fast technological advances enabling researchers to gain more fine-grained insights into the spatial and temporal dynamics of the neural signatures underlying numerical development.

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