scholarly journals An Analysis of the External Validity of EEG Spectral Power in an Uncontrolled Outdoor Environment during Default and Complex Neurocognitive States

2021 ◽  
Vol 11 (3) ◽  
pp. 330
Author(s):  
Dalton J. Edwards ◽  
Logan T. Trujillo
Keyword(s):  
External Validity ◽  
Spectral Power ◽  
Brain Activity ◽  
Outdoor Environment ◽  
Oscillatory Activity ◽  
Brain State ◽  
Beta Band ◽  
Eeg Spectral Power ◽  
Eeg Power ◽  
Human Participants

Traditionally, quantitative electroencephalography (QEEG) studies collect data within controlled laboratory environments that limit the external validity of scientific conclusions. To probe these validity limits, we used a mobile EEG system to record electrophysiological signals from human participants while they were located within a controlled laboratory environment and an uncontrolled outdoor environment exhibiting several moderate background influences. Participants performed two tasks during these recordings, one engaging brain activity related to several complex cognitive functions (number sense, attention, memory, executive function) and the other engaging two default brain states. We computed EEG spectral power over three frequency bands (theta: 4–7 Hz, alpha: 8–13 Hz, low beta: 14–20 Hz) where EEG oscillatory activity is known to correlate with the neurocognitive states engaged by these tasks. Null hypothesis significance testing yielded significant EEG power effects typical of the neurocognitive states engaged by each task, but only a beta-band power difference between the two background recording environments during the default brain state. Bayesian analysis showed that the remaining environment null effects were unlikely to reflect measurement insensitivities. This overall pattern of results supports the external validity of laboratory EEG power findings for complex and default neurocognitive states engaged within moderately uncontrolled environments.

scholarly journals Brain–Heart Interaction During Transcutaneous Auricular Vagus Nerve Stimulation

2021 ◽  
Vol 15 ◽  
Author(s):  
Kathrin Machetanz ◽  
Levan Berelidze ◽  
Robert Guggenberger ◽  
Alireza Gharabaghi
Keyword(s):  
Vagus Nerve ◽  
Nerve Stimulation ◽  
Vagus Nerve Stimulation ◽  
Heart Function ◽  
Brain Activity ◽  
Gamma Band ◽  
Cortical Activation ◽  
Oscillatory Activity ◽  
Beta Band ◽  
Rr Intervals

ObjectivesTranscutaneous auricular vagus nerve stimulation (taVNS) modulates brain activity and heart function. The induced parasympathetic predominance leads to an increase of heart rate variability (HRV). Knowledge on the corresponding cortical activation pattern is, however, scarce. We hypothesized taVNS-induced HRV increases to be related to modulation of cortical activity that regulates the autonomic outflow to the heart.Materials and MethodsIn thirteen healthy subjects, we simultaneously recorded 64-channel electroencephalography and electrocardiography during taVNS. Two taVNS stimulation targets were investigated, i.e., the cymba conchae and inner tragus, and compared to active control stimulation in the anatomical vicinity, i.e., at the crus helicis and outer tragus. We used intermitted stimulation bursts of 25 Hz applied at a periodicity of 1 Hz. HRV was estimated with different time-domain methodologies: standard deviation of RR (SDNN), the root mean squares of successive differences (RMSSD), the percentage of RR-intervals with at least 50 ms deviation from the preceding RR-interval (pNN50), and the difference of consecutive RR intervals weighted by their mean (rrHRV).ResultsThe stimulation-induced HRV increases corresponded to frequency-specific oscillatory modulation of different cortical areas. All stimulation targets induced power modulations that were proportional to the HRV elevation. The most prominent changes that corresponded to HRV increases across all parameters and stimulation locations were frontal elevations in the theta-band. In the delta-band, there were frontal increases (RMSSD, pNN50, rrHRV, SDNN) and decreases (SDNN) across stimulation sites. In higher frequencies, there was a more divers activity pattern: Outer tragus/crus helicis stimulation increased oscillatory activity with the most prominent changes for the SDNN in frontal (alpha-band, beta-band) and fronto-parietal (gamma-band) areas. During inner tragus/cymba conchae stimulation the predominant pattern was a distributed power decrease, particularly in the fronto-parietal gamma-band.ConclusionNeuro–cardiac interactions can be modulated by electrical stimulation at different auricular locations. Increased HRV during stimulation is correlated with frequency-specific increases and decreases of oscillatory activity in different brain areas. When applying specific HRV measures, cortical patterns related to parasympathetic (RMSSD, pNN50, rrHRV) and sympathetic (SDNN) modulation can be identified. Thus, cortical oscillations may be used to define stimulation locations and parameters for research and therapeutic purposes.

scholarly journals Monitoring Brain State and Behavioral Performance during Repetitive Visual Stimulation

2021 ◽  
Vol 11 (23) ◽  
pp. 11544
Author(s):  
Alexander K. Kuc ◽  
Semen A. Kurkin ◽  
Vladimir A. Maksimenko ◽  
Alexander N. Pisarchik ◽  
Alexander E. Hramov
Keyword(s):  
Visual Stimulation ◽  
Brain Activity ◽  
Decision Time ◽  
Task Demands ◽  
Brain State ◽  
Time On Task ◽  
Behavioral Performance ◽  
Task Effects ◽  
Perceptual Performance ◽  
Eeg Power

We tested whether changes in prestimulus neural activity predict behavioral performance (decision time and errors) during a prolonged visual task. The task was to classify ambiguous stimuli—Necker cubes; manipulating the degree of ambiguity from low ambiguity (LA) to high ambiguity (HA) changed the task difficulty. First, we assumed that the observer’s state changes over time, which leads to a change in the prestimulus brain activity. Second, we supposed that the prestimulus state produces a different effect on behavioral performance depending on the task demands. Monitoring behavioral responses, we revealed that the observer’s decision time decreased for both LA and HA stimuli during the task performance. The number of perceptual errors lowered for HA, but not for LA stimuli. EEG analysis revealed an increase in the prestimulus 9–11 Hz EEG power with task time. Finally, we found associations between the behavioral and neural estimates. The prestimulus EEG power negatively correlated with the decision time for LA stimuli and the erroneous responses rate for HA stimuli. The obtained results confirm that monitoring prestimulus EEG power enables predicting perceptual performance on the behavioral level. The observed different time-on-task effects on the LA and HA stimuli processing may shed light on the features of ambiguous perception.

scholarly journals Interictal epileptiform discharges in focal epilepsy are preceded by a gradual increase in low-frequency oscillations

2020 ◽  
Author(s):  
Karin Westin ◽  
Gerald Cooray ◽  
Daniel Lundqvist
Keyword(s):  
Gradual Increase ◽  
Focal Epilepsy ◽  
Brain Activity ◽  
Low Frequency ◽  
Negative Influence ◽  
Oscillatory Activity ◽  
Brain State ◽  
Negative Effects ◽  
Epileptiform Discharges ◽  
Interictal Epileptiform Discharges

AbstractEpilepsy is characterized by recurrent seizures and may also have negative influence on cognitive function. In addition to ictal activity, the epileptic brain also gives rise to interictal epileptiform discharges (IEDs). These IEDs constitute the diagnostic hallmark of epilepsy, and have been linked to impaired memory formation and negative effects on neurodevelopment. The neurophysiological dynamics underlying IED generation seem to resemble those underlying seizure development. Understanding the neurophysiological characteristics surrounding and preceding IED development would hence provide valuable insights into the pathophysiology of the epileptic brain. In order to improve this understanding, we aimed to characterize the dynamical activity changes that occurs immediately prior to an IED onset. We used magnetoencephalography (MEG) recordings from nine focal epilepsy patients to characterize the oscillatory activity preceding IED onsets. Our results showed a systematic and gradual increase in oscillatory delta and theta band activity (1-4 Hz and 4-8 Hz, respectively) during this pre-IED interval, reaching a maximum power at IED onset. These results indicate that the pre-IED brain state is characterized by a gradual synchronization that culminates in the neuronal hypersynchronization underlying IEDs. We discuss how IED generation might resemble seizure development, where physiological brain activity similarly undergoes a gradual synchronization that terminates in seizure onset.

scholarly journals The Dream Catcher experiment: blinded analyses failed to detect markers of dreaming consciousness in EEG spectral power

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
William Wong ◽  
Valdas Noreika ◽  
Levente Móró ◽  
Antti Revonsuo ◽  
Jennifer Windt ◽  
...  
Keyword(s):  
Spectral Power ◽  
Brain Activity ◽  
Phenomenal Consciousness ◽  
Learning Classifier ◽  
Data Team ◽  
Eeg Spectral Power ◽  
Core Idea ◽  
Brain Measurements ◽  
First Time ◽  
The Explanatory Gap

Abstract The Dream Catcher test defines the criteria for a genuine discovery of the neural constituents of phenomenal consciousness. Passing the test implies that some patterns of purely brain-based data directly correspond to the subjective features of phenomenal experience, which would help to bridge the explanatory gap between consciousness and brain. Here, we conducted the Dream Catcher test for the first time in a step-wise and simplified form, capturing its core idea. The Dream Catcher experiment involved a Data Team, which measured participants’ brain activity during sleep and collected dream reports, and a blinded Analysis Team, which was challenged to predict, based solely on brain measurements, whether or not a participant had a dream experience. Using a serial-awakening paradigm, the Data Team prepared 54 1-min polysomnograms of non-rapid eye movement sleep—27 of dreamful sleep and 27 of dreamless sleep (three of each condition from each of the nine participants)—redacting from them all associated participant and dream information. The Analysis Team attempted to classify each recording as either dreamless or dreamful using an unsupervised machine learning classifier, based on hypothesis-driven, extracted features of electroencephalography (EEG) spectral power and electrode location. The procedure was repeated over five iterations with a gradual removal of blindness. At no level of blindness did the Analysis Team perform significantly better than chance, suggesting that EEG spectral power could not be utilized to detect signatures specific to phenomenal consciousness in these data. This study marks the first step towards realizing the Dream Catcher test in practice.

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 The Dream Catcher experiment: Blinded analyses disconfirm markers of dreaming consciousness in EEG spectral power

2019 ◽  
Author(s):  
William Wong ◽  
Valdas Noreika ◽  
Levente Móró ◽  
Antti Revonsuo ◽  
Jennifer Windt ◽  
...  
Keyword(s):  
Spectral Power ◽  
Brain Activity ◽  
Conscious Experience ◽  
Phenomenal Consciousness ◽  
Nrem Sleep ◽  
List Type ◽  
Data Team ◽  
Eeg Spectral Power ◽  
Core Idea ◽  
Better Than

AbstractThe Dream Catcher test defines the criteria for a genuine discovery of the neural constituents of phenomenal consciousness. Passing the test implies that some patterns of purely brain-based data directly correspond to the subjective features of phenomenal experience, which would help to bridge the explanatory gap between consciousness and brain. Here, we conducted the Dream Catcher test for the first time in a graded and simplified form, capturing its core idea. The experiment involved a Data Team, who measured participants’ brain activity during sleep and collected dream reports, and a blinded Analysis Team, who was challenged to predict better than chance, based solely on brain measurements, whether or not a participant had a dream experience. Using a serial-awakening paradigm, the Data Team prepared 54 one-minute polysomnograms of NREM sleep—27 of dreamful sleep (3 from each of the 9 participants) and 27 of dreamless sleep—redacting from them all associated participant and dream information. The Analysis Team attempted to classify each recording as either dreamless or dreamful using an unsupervised machine learning classifier, based on hypothesis-driven, extracted features of EEG spectral power and electrode location. The procedure was repeated over five iterations with a gradual removal of blindness. At no level of blindness did the Analysis Team perform significantly better than chance, suggesting that EEG spectral power does not carry any signatures of phenomenal consciousness. Furthermore, we demonstrate an outright failure to replicate key findings of recently reported correlates of dreaming consciousness.HighlightsThe first reported attempt of the Dream Catcher test.The correlates of conscious experience may not lie in EEG spectral power.Reported markers of NREM dreaming consciousness misperformed in a blinded setting.Those markers also could not be confirmed in an unblinded setting.

Inducing Neuroplasticity through Intracranial Theta Burst Stimulation in the Human Sensorimotor Cortex

2021 ◽  
Author(s):  
Jose L Herrero ◽  
Alexander Smith ◽  
Akash Mishra ◽  
Noah Markowitz ◽  
Ashesh D Mehta ◽  
...  
Keyword(s):  
Sensorimotor Cortex ◽  
Brain Activity ◽  
Activity Patterns ◽  
Oscillatory Activity ◽  
Theta Burst Stimulation ◽  
Burst Stimulation ◽  
Beta Band ◽  
Sensorimotor Network ◽  
Intracranial Electrodes ◽  
Theta Burst

The progress of therapeutic neuromodulation greatly depends on improving stimulation parameters to most efficiently induce neuroplasticity effects. Intermittent Theta Burst stimulation (iTBS), a form of electrical stimulation that mimics natural brain activity patterns, has proved to efficiently induce such effects in animal studies and rhythmic Transcranial Magnetic Stimulation studies in humans. However, little is known about the potential neuroplasticity effects of iTBS applied through intracranial electrodes in humans. This study characterizes the physiological effects of intracranial iTBS in humans and compare them with alpha frequency stimulation, another frequently used neuromodulatory pattern. We applied these two stimulation patterns to well-defined regions in the sensorimotor cortex, which elicited contralateral hand muscle contractions during clinical mapping, in epilepsy patients implanted with intracranial electrodes. Treatment effects were evaluated using oscillatory coherence across areas connected to the treatment site, as defined with cortico-cortical evoked potentials. Our results show that iTBS increases coherence in the beta frequency band within the sensorimotor network indicating a potential neuroplasticity effect. The effect is specific to the sensorimotor system, the beta-band and the stimulation pattern, and outlasted the stimulation period by ~3 minutes. The effect occurred in 4/7 subjects depending on the build-up of the effect during iTBS treatment and other patterns of oscillatory activity related to ceiling effects within the beta-band and to pre-existent coherence within the alpha-band. By characterizing the neurophysiological effects of iTBS within well-defined cortical networks, we hope to provide an electrophysiological framework that allows clinicians/researchers to optimize brain stimulation protocols which may have translational value.

scholarly journals Separable neural signatures of confidence during perceptual decisions

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Tarryn Balsdon ◽  
Pascal Mamassian ◽  
Valentin Wyart
Keyword(s):  
Decision Making ◽  
Neural Circuit ◽  
Spectral Power ◽  
Brain Activity ◽  
Neural Representation ◽  
Perceptual Decision Making ◽  
Perceptual Decision ◽  
Decision Confidence ◽  
Electrical Brain Activity ◽  
Human Participants

Perceptual confidence is an evaluation of the validity of perceptual decisions. While there is behavioural evidence that confidence evaluation differs from perceptual decision-making, disentangling these two processes remains a challenge at the neural level. Here, we examined the electrical brain activity of human participants in a protracted perceptual decision-making task where observers tend to commit to perceptual decisions early whilst continuing to monitor sensory evidence for evaluating confidence. Premature decision commitments were revealed by patterns of spectral power overlying motor cortex, followed by an attenuation of the neural representation of perceptual decision evidence. A distinct neural representation was associated with the computation of confidence, with sources localised in the superior parietal and orbitofrontal cortices. In agreement with a dissociation between perception and confidence, these neural resources were recruited even after observers committed to their perceptual decisions, and thus delineate an integral neural circuit for evaluating perceptual decision confidence.

scholarly journals Separable neural signatures of confidence during perceptual decisions

2021 ◽  
Author(s):  
T. Balsdon ◽  
P. Mamassian ◽  
V. Wyart
Keyword(s):  
Decision Making ◽  
Neural Circuit ◽  
Spectral Power ◽  
Brain Activity ◽  
Neural Representation ◽  
Perceptual Decision Making ◽  
Perceptual Decision ◽  
Electrical Brain Activity ◽  
Sensory Evidence ◽  
Human Participants

AbstractPerceptual confidence is an evaluation of the validity of perceptual decisions. While there is behavioural evidence that confidence evaluation differs from perceptual decision-making, disentangling these two processes remains a challenge at the neural level. Here we examined the electrical brain activity of human participants in a protracted perceptual decision-making task where observers tend to commit to perceptual decisions early whilst continuing to monitor sensory evidence for evaluating confidence. Premature decision commitments were revealed by patterns of spectral power overlying motor cortex, followed by an attenuation of the neural representation of perceptual decision evidence. A distinct neural representation was associated with suboptimalities affecting confidence reports, with sources localised in the superior parietal and orbitofrontal cortices. In agreement with a dissociation between perception and confidence, these neural resources were recruited even after observers committed to their perceptual decisions, and thus delineate an integral neural circuit for the computation of confidence.

Disruption of the Prefrontal Cortex Improves Implicit Contextual Memory-Guided Attention: Combined Behavioral and Electrophysiological Evidence

2019 ◽  
Vol 30 (1) ◽  
pp. 20-30 ◽  
Author(s):  
Mario Rosero Pahi ◽  
Juliana Cavalli ◽  
Frauke Nees ◽  
Herta Flor ◽  
Jamila Andoh
Keyword(s):  
Prefrontal Cortex ◽  
Brain Activity ◽  
Learning Task ◽  
Contextual Learning ◽  
Learning Performance ◽  
Oscillatory Activity ◽  
Beta Band ◽  
Top Down ◽  
Contextual Memory ◽  
Electrical Brain Activity

Abstract Many studies have shown that the dorsolateral prefrontal cortex (DLPFC) plays an important role in top-down cognitive control over intentional and deliberate behavior. However, recent studies have reported that DLPFC-mediated top-down control interferes with implicit forms of learning. Here we used continuous theta-burst stimulation (cTBS) combined with electroencephalography to investigate the causal role of DLPFC in implicit contextual memory-guided attention. We aimed to test whether transient disruption of the DLPFC would interfere with implicit learning performance and related electrical brain activity. We applied neuronavigation-guided cTBS to the DLPFC or to the vertex as a control region prior to the performance of an implicit contextual learning task. We found that cTBS applied over the DLPFC significantly improved performance during implicit contextual learning. We also noted that beta-band (13–19 Hz) oscillatory power was reduced at fronto-central channels about 140 to 370 ms after visual stimulus onset in cTBS DLPFC compared with cTBS vertex. Taken together, our results provide evidence that DLPFC-mediated top-down control interferes with contextual memory-guided attention and beta-band oscillatory activity.

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