Ventriculo–arterial interaction may be assessed by Oscillatory Power Fraction

2019 ◽  
Vol 39 (5) ◽  
pp. 308-314 ◽  
Author(s):  
Tomas Dybos Tannvik ◽  
Audun Eskeland Rimehaug ◽  
Morten Smedsrud Wigen ◽  
Lasse Løvstakken ◽  
Idar Kirkeby‐Garstad
Keyword(s):  
Oscillatory Power ◽  
Power Fraction

scholarly journals Dynamic arterial elastance during experimental endotoxic septic shock

2020 ◽  
Author(s):  
Manuel Ignacio Monge García ◽  
Pedro Guijo González ◽  
Paula Saludes Orduña ◽  
Manuel Gracia Romero ◽  
Anselmo Gil Cano ◽  
...  
Keyword(s):  
Septic Shock ◽  
Cardiac Output ◽  
Arterial Pressure ◽  
Left Ventricular ◽  
Aortic Blood Flow ◽  
Total Work ◽  
Arterial Elastance ◽  
Flow Measurements ◽  
Oscillatory Power ◽  
Power Fraction

Abstract Background: Dynamic arterial elastance (Ea dyn ), the ratio between pulse pressure variation (PPV) and stroke volume variation (SVV), has been suggested as a functional parameter that is a surrogate of arterial load. We aimed to determine the effects of endotoxic septic shock and hemodynamic resuscitation on Ea dyn . Results: Experimental randomized study in a university animal research laboratory with 18 New Zealand rabbits. Animals received placebo (SHAM, n=6) or intravenous lipopolysaccharide (LPS, Escherichia coli serotype 055:B5, 1 mg·kg -1 ) with or without (EDX-R, n=6; EDX-NR, n=6) hemodynamic resuscitation (fluid bolus of 20 ml·kg -1 and norepinephrine for restoring mean arterial pressure). Continuous arterial pressure and aortic blood flow measurements were obtained simultaneously. Cardiovascular efficiency was evaluated by the oscillatory power fraction (%Osc: oscillatory work / left ventricular (LV) total work) and the energy efficiency ratio (EER = LV total work/cardiac output). The LPS-induced endotoxic shock produced a hyperdynamic shock with high cardiac output and arterial hypotension. Ea dyn increased in septic animals (from 0.73 to 1.70; p=0.012) and dropped after hemodynamic resuscitation. Ea dyn was related with the %Osc and EER [estimates: -0.101 (-0.137 – -0.064) and -9.494 (-11.964 – -7.024); p<0.001, respectively]. So, the higher the Ea dyn, the better the cardiovascular efficiency (lower %Osc and EER). Conclusions: In this experimental model, Ea dyn increased during endotoxic septic shock and decreased with hemodynamic resuscitation. Sepsis resulted in a reduced oscillatory power fraction and lowered EER, reflecting a better cardiovascular efficiency that was tracked by Ea dyn . Ea dyn could be a potential index of cardiovascular efficiency during septic shock.

Cognitive architectures as a tool for investigating the role of oscillatory power and coherence in cognition

NeuroImage ◽  
2014 ◽  
Vol 85 ◽  
pp. 685-693 ◽  
Author(s):  
Marieke K. van Vugt
Keyword(s):  
Cognitive Architectures ◽  
Oscillatory Power

Review and present status of the TEXTOR radiative improved (RI) mode

1998 ◽  
Vol 59 (4) ◽  
pp. 587-610 ◽  
Author(s):  
P. E. VANDENPLAS ◽  
A. M. MESSIAEN ◽  
J. P. H. E. ONGENA ◽  
U. SAMM ◽  
B. UNTERBERG
Keyword(s):  
Density Profile ◽  
High Power ◽  
Present Status ◽  
Particle Transport ◽  
Density Limit ◽  
Radiated Power ◽  
Edge Radiation ◽  
Intermediate Size ◽  
Power Fraction ◽  
Better Than

From 1990, the boronized TEXTOR tokamak was characterized by an improved confinement (coined the ‘I mode’) at high power that was substantially better than the L mode, but densities had to be limited to n[bar]e0/nGR[lsim ]0.5–0.6, where nGR is the Greenwald density limit. With the injection of Ne, Si or Ar in order to increase the edge radiation and provided that γ=Prad/Ptot[greater, similar]0.5, PNBI-co/Ptot[greater, similar]0.25 and n[bar]e0/nGR[greater, similar]0.75, a further improved confinement called the radiative improved mode (RI mode) was discovered in 1993 on TEXTOR, a tokamak of intermediate size, and confirmed on TEXTOR-94. The radiated power fraction γ can reach 0.9, and the radiation is nearly isotropically distributed over the torus wall. The RI mode is characterized by its ability to obtain simultaneously and stationarily high densities and high confinement. It is linked to a substantial lowering of edge ne, Te and Ti, a reduction in particle transport and a peaking of the density profile. The RI-mode confinement scales on TEXTOR as τE= (n[bar]e0/nGR)τITERH93-P and values up to n[bar]e0/nGR≈1.2 are obtained. There is no detrimental concentration of the seeded impurity at the centre of the plasma. Results of three different interpretative and modelling approaches are in agreement with the improved confinement features; the preliminary indications are that ITG turbulence is strongly reduced. The Z mode observed on ISX-B has a clear resemblance to the RI mode. The very favourable features of the RI mode justify efforts in trying to establish it on larger machines to verify if the present scaling then holds.

scholarly journals Analysis of Functional Connectivity and Oscillatory Power Using DICS: From Raw MEG Data to Group-Level Statistics in Python

2018 ◽  
Vol 12 ◽  
Author(s):  
Marijn van Vliet ◽  
Mia Liljeström ◽  
Susanna Aro ◽  
Riitta Salmelin ◽  
Jan Kujala
Keyword(s):  
Functional Connectivity ◽  
Group Level ◽  
Level Statistics ◽  
Oscillatory Power

scholarly journals Fronto-medial theta coordinates posterior maintenance of working memory content

2021 ◽  
Author(s):  
Oliver Ratcliffe ◽  
Kimron Shapiro ◽  
Bernhard P. Staresina
Keyword(s):  
Working Memory ◽  
Computational Models ◽  
Medial Cortex ◽  
Duty Cycles ◽  
Machine Learning Approach ◽  
Theta Frequency ◽  
Oscillatory Power ◽  
Posterior Parietal ◽  
Memory Content ◽  
Memory Contents

AbstractHow does the human brain manage multiple bits of information to guide goal-directed behaviour? Successful working memory (WM) functioning has consistently been linked to oscillatory power in the theta frequency band (4-8 Hz) over fronto-medial cortex (fronto-medial theta, FMT). Specifically, FMT is thought to reflect the mechanism of an executive sub-system that coordinates maintenance of memory contents in posterior regions. However, direct evidence for the role of FMT in controlling specific WM content is lacking. Here we collected high-density Electroencephalography (EEG) data whilst participants engaged in load-varying WM tasks and then used multivariate decoding methods to examine WM content during the maintenance period. Higher WM load elicited a focal increase in FMT. Importantly, decoding of WM content was driven by posterior/parietal sites, which in turn showed load-induced functional theta coupling with fronto-medial cortex. Finally, we observed a significant slowing of FMT frequency with increasing WM load, consistent with the hypothesised broadening of a theta ‘duty cycle’ to accommodate additional WM items. Together these findings demonstrate that frontal theta orchestrates posterior maintenance of WM content. Moreover, the observed frequency slowing elucidates the function of FMT oscillations by specifically supporting phase-coding accounts of WM.Significance StatementHow does the brain juggle the maintenance of multiple items in working memory (WM)? Here we show that increased WM demands increase theta power (4-8 Hz) in fronto-medial cortex. Interestingly, using a machine learning approach, we found that the content held in WM could be read out not from frontal, but from posterior areas. These areas were in turn functionally coupled with fronto-medial cortex, consistent with the idea that frontal cortex orchestrates WM representations in posterior regions. Finally, we observed that holding an additional item in WM leads to significant slowing of the frontal theta rhythm, supporting computational models that postulate longer ‘duty cycles’ to accommodate additional WM demands.

scholarly journals Depressive rumination is correlated with brain responses during self-related processing

2021 ◽  
Author(s):  
Tzu-Yu Hsu ◽  
Tzu-Ling Liu ◽  
Paul Z. Cheng ◽  
Hsin-Chien Lee ◽  
Timothy J. Lane ◽  
...  
Keyword(s):  
Depressive Symptoms ◽  
Low Frequency ◽  
Event Related Potentials ◽  
Unipolar Depression ◽  
Brain Responses ◽  
Late Event ◽  
Oscillatory Power ◽  
Related Aspect ◽  
Related Potentials ◽  
Central Symptom

AbstractBackgroundRumination, a tendency to focus on negative self-related thoughts, is a central symptom of depression. Studying the self-related aspect of such symptoms is challenging due to the need to distinguish self effects per se from the emotional content of task stimuli. This study employs an emotionally neutral self-related paradigm to investigate possible altered self processing in depression and its link to rumination.MethodsPeople with unipolar depression (MDD; n = 25) and controls (n = 25) underwent task-based EEG recording. Late event-related potentials were studied along with low frequency oscillatory power. EEG metrics were compared between groups and correlated with depressive symptoms and reported rumination.ResultsThe MDD group displayed a difference in late potentials across fronto-central electrodes between self-related and non-self-related conditions. No such difference was seen in controls. The magnitude of this difference was positively related with depressive symptoms and reported rumination. MDD also had elevated theta oscillation power at central electrodes in self-related conditions, which was not seen in controls.ConclusionsRumination appears linked to altered self-related processing in depression, independently of stimuli-related emotional confounds. This connection between self-related processing and depression may point to self-disorder being a core component of the condition.

scholarly journals Imaging of neural oscillations with embedded inferential and group prevalence statistics

2017 ◽  
Author(s):  
Peter W. Donhauser ◽  
Esther Florin ◽  
Sylvain Baillet
Keyword(s):  
Brain Activity ◽  
Signal Strength ◽  
Brain Regions ◽  
Oscillatory Activity ◽  
Neural Oscillations ◽  
Source Reconstruction ◽  
Signal To Noise ◽  
Source Imaging ◽  
Methodological Challenges ◽  
Oscillatory Power

AbstractMagnetoencephalography and electroencephalography (MEG, EEG) are essential techniques for studying distributed signal dynamics in the human brain. In particular, the functional role of neural oscillations remains to be clarified. Imaging methods need to identify distinct brain regions that concurrently generate oscillatory activity, with adequate separation in space and time. Yet, spatial smearing and inhomogeneous signal-to-noise are challenging factors to source reconstruction from external sensor data. The detection of weak sources in the presence of stronger regional activity nearby is a typical complication of MEG/EEG source imaging. We propose a novel, hypothesis-driven source reconstruction approach to address these methodological challenges1. The imaging with embedded statistics (iES) method is a subspace scanning technique that constrains the mapping problem to the actual experimental design. A major benefit is that, regardless of signal strength, the contributions from all oscillatory sources, which activity is consistent with the tested hypothesis, are equalized in the statistical maps produced. We present extensive evaluations of iES on group MEG data, for mapping 1) induced oscillations using experimental contrasts, 2) ongoing narrow-band oscillations in the resting-state, 3) co-modulation of brain-wide oscillatory power with a seed region, and 4) co-modulation of oscillatory power with peripheral signals (pupil dilation). Along the way, we demonstrate several advantages of iES over standard source imaging approaches. These include the detection of oscillatory coupling without rejection of zero-phase coupling, and detection of ongoing oscillations in deeper brain regions, where signal-to-noise conditions are unfavorable. We also show that iES provides a separate evaluation of oscillatory synchronization and desynchronization in experimental contrasts, which has important statistical advantages. The flexibility of iES allows it to be adjusted to many experimental questions in systems neuroscience.Author summaryThe oscillatory activity of the brain produces a repertoire of signal dynamics that is rich and complex. Noninvasive recording techniques such as scalp magnetoencephalography and electroencephalography (MEG, EEG) are key methods to advance our comprehension of the role played by neural oscillations in brain functions and dysfunctions. Yet, there are methodological challenges in mapping these elusive components of brain activity that have remained unresolved. We introduce a new mapping technique, called imaging with embedded statistics (iES), which alleviates these difficulties. With iES, signal detection is constrained explicitly to the operational hypotheses of the study design. We show, in a variety of experimental contexts, how iES emphasizes the oscillatory components of brain activity, if any, that match the experimental hypotheses, even in deeper brain regions where signal strength is expected to be weak in MEG. Overall, the proposed method is a new imaging tool to respond to a wide range of neuroscience questions concerning the scaffolding of brain dynamics via anatomically-distributed neural oscillations.

scholarly journals Solar feature tracking in both spatial and temporal domains

2007 ◽  
Vol 3 (S247) ◽  
pp. 288-295
Author(s):  
D. B. Jess ◽  
M. Mathioudakis ◽  
R. Erdélyi ◽  
G. Verth ◽  
R. T. J. McAteer ◽  
...  
Keyword(s):  
Coronal Loop ◽  
Feature Tracking ◽  
New Method ◽  
Kink Mode ◽  
Spatial Periodicity ◽  
Mode Oscillation ◽  
Oscillatory Power ◽  
Solar Feature

AbstractA new method for automated coronal loop tracking, in both spatial and temporal domains, is presented. The reliability of this technique was tested with TRACE 171 Å observations. The application of this technique to a flare-induced kink-mode oscillation, revealed a 3500 km spatial periodicity which occur along the loop edge. We establish a reduction in oscillatory power, for these spatial periodicities, of 45% over a 322 s interval. We relate the reduction in oscillatory power to the physical damping of these loop-top oscillations.

Modulation of brain states on fractal and oscillatory power of EEG in brain-computer interfaces

2021 ◽  
Author(s):  
Shangen Zhang ◽  
Xinyi Yan ◽  
Yijun Wang ◽  
Baolin Liu ◽  
Xiaorong Gao
Keyword(s):  
Brain Computer Interfaces ◽  
Computer Interfaces ◽  
Oscillatory Power ◽  
Brain States

Functional Wounds of an Invisible Injury

2020 ◽  
pp. 347-358
Author(s):  
Benjamin T. Dunkley ◽  
Margot J. Taylor
Keyword(s):  
Resting State ◽  
Psychological Injury ◽  
Threat Perception ◽  
Post Traumatic Stress ◽  
Ventral Medial Prefrontal Cortex ◽  
Behavioral Dysfunction ◽  
Oscillatory Power ◽  
Post Traumatic ◽  
Analytical Approaches ◽  
The Brain

In this chapter we review magnetoencephalography (MEG) studies of post-traumatic stress disorder (PTSD). The work reviewed spans multiple analytical approaches, including task-evoked and induced studies, primarily examining cognitive and behavioral dysfunction in the disorder, as well as resting-state studies of regional oscillatory power and synchrony. Disordered memory, elevated threat perception, and dysfunctional emotional control are primary symptoms of PTSD, but there are also secondary “knock-on” effects to cognition and executive functioning that can be debilitating. MEG approaches have proved to be a powerful way to examine maladaptive neural circuits underlying these deficits in PTSD, particularly the brain networks involving the hippocampi, amygdalae, and ventral medial prefrontal cortex. Finally, the authors briefly discuss these findings in relation to mild traumatic brain injury, a physical as opposed to psychological injury that can nevertheless leave mental wounds that exhibit a similar presentation to PTSD, and how MEG can be used to tease apart these different types of trauma.

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