scholarly journals Alpha rhythms reveal when, where and how memories are retrieved

2019 ◽  
Author(s):  
María Carmen Martín-Buro ◽  
Maria Wimber ◽  
Richard N. Henson ◽  
Bernhard P. Staresina
Keyword(s):  
Episodic Memory ◽  
Temporal Dynamics ◽  
Item Recognition ◽  
Alpha Power ◽  
List Type ◽  
The Core ◽  
Left Posterior ◽  
Posterior Parietal ◽  
Associative Recall ◽  
Recall Effect

SummaryOur memories for past experiences can range from vague recognition to full-blown recall of associated details. Neuroimaging research has tried to understand the brain mechanisms underlying qualitatively different memories for decades (Yonelinas, 2002). On the one hand, Electroencephalography (EEG) has shown that recall signals unfold a few hundred milliseconds after simple recognition and are hallmarked by sustained voltage deflections over left posterior sensors (Herron, 2007; Johansson & Mecklinger, 2003; Mecklinger, Rosburg, & Johansson, 2016; Rugg & Curran, 2007). However, sensor-based analyses only provide limited insights into the supporting brain networks. On the other hand, functional magnetic resonance imaging (fMRI) has revealed a ‘core recollection network’ centred on posterior parietal and medial temporal lobe (MTL) regions (Hayama, Vilberg, & Rugg, 2012; Johnson, Suzuki, & Rugg, 2013; King, de Chastelaine, Elward, Wang, & Rugg, 2015; Rugg, Johnson, & Uncapher, 2015; Rugg & Vilberg, 2013; Thakral, Benoit, & Schacter, 2017). However, due to the relatively poor time resolution of fMRI, the temporal dynamics of these regions during retrieval remain largely unknown. In order to overcome these modality-specific limitations, we here used Magnetoencephalography (MEG) in a verbal episodic memory paradigm assessing correct rejection (CR) of lures, item recognition (IR) of old words and associative recall (AR) of paired target words. We found that power decreases in the alpha frequency band (10-12 Hz) systematically track different mnemonic outcomes in both time and space: Over left posterior sensors, alpha power decreased in a stepwise fashion from 500 ms onward, first from CR to IR and then from IR to AR. When projecting alpha power into source space, the ‘core recollection network’ known from fMRI studies emerged, including posterior parietal cortex (PPC) and hippocampus. While PPC showed a linear change across conditions, hippocampal effects were specific to recall. Critically, the hippocampal recall effect emerged ∼200 ms before the PPC recall effect, suggesting a bottom-up recall signal from hippocampus to PPC. Our data thus link engagement of the core recollection network to the temporal dynamics of episodic memory and suggest that alpha rhythms constitute a fundamental oscillatory mechanism revealing when, where and how our memories are retrieved.HighlightsAlpha rhythms distinguish between different retrieval outcomesAlpha power time courses track item recognition and associative recallSource alpha power decreases track the fMRI core recollection networkHippocampal recall signal precedes parietal signal

scholarly journals Can evolutionary thinking shed light on gender diversity?

2019 ◽  
Vol 25 (6) ◽  
pp. 351-362 ◽  
Author(s):  
Bernadette Wren ◽  
John Launer ◽  
Michael J. Reiss ◽  
Annie Swanepoel ◽  
Graham Music
Keyword(s):  
Gender Identity ◽  
Gender Diversity ◽  
Medical Intervention ◽  
List Type ◽  
Sex And Gender ◽  
Medical Interventions ◽  
The Core ◽  
Causal Pathways ◽  
And Gender ◽  
Shed Light

SUMMARYIssues of sexual reproduction lie at the core of evolutionary thinking, which often places an emphasis on how individuals attempt to maximise the number of successful offspring that they can produce. At first sight, it may therefore appear that individuals who opt for gender-affirming medical interventions are acting in ways that are evolutionarily disadvantageous. However, there are persuasive hypotheses that might make sense of such choices in evolutionary terms and we explore these here. It is premature to claim knowledge of the extent to which evolutionary arguments can usefully be applied to issues of gender identity, although worth reflecting on the extent to which nature tends towards diversity in matters of sex and gender. The importance of acknowledging and respecting different views in this domain, as well as recognising both the uncertainty and likely multiplicity of causal pathways, has implications for clinicians. We make some suggestions about how clinicians might best respond when faced with requests from patients in this area.LEARNING OBJECTIVESAfter reading this article you will be able to:•understand evolutionary arguments about diversity in human gender identity•identify strengths and weaknesses in evolutionary arguments applied to transgender issues•appreciate the range and diversity of gender experience and gender expression among people who present to specialist gender services, as well as the likely complexities of their reasons for requesting medical intervention.

scholarly journals THE DUAL-TASK COST IS DUE TO NEURAL INTERFERENCES DISRUPTING THE OPTIMAL SPATIO-TEMPORAL DYNAMICS OF THE COMPETING TASKS

2020 ◽  
Author(s):  
Diego Mac-Auliffe ◽  
Benoit Chatard ◽  
Mathilde Petton ◽  
Anne-Claire Croizé ◽  
Florian Sipp ◽  
...  
Keyword(s):  
Dual Task ◽  
Temporal Dynamics ◽  
Anterior Cingulate ◽  
List Type ◽  
Intracranial Eeg ◽  
Ample Evidence ◽  
Dual Tasking ◽  
Dual Task Cost ◽  
Neural Origin ◽  
Spatio Temporal

ABSTRACTDual-tasking is extremely prominent nowadays, despite ample evidence that it comes with a performance cost: the Dual-Task (DT) cost. Neuroimaging studies have established that tasks are more likely to interfere if they rely on common brain regions, but the precise neural origin of the DT cost has proven elusive so far, mostly because fMRI does not record neural activity directly and cannot reveal the key effect of timing, and how the spatio-temporal neural dynamics of the tasks coincide.Recently, DT electrophysiological studies in monkeys have recorded neural populations shared by the two tasks with millisecond precision to provide a much finer understanding of the origin of the DT cost. We used a similar approach in humans, with intracranial EEG, to assess the neural origin of the DT cost in a particularly challenging naturalistic paradigm which required accurate motor responses to frequent visual stimuli (task T1) and the retrieval of information from long-term memory (task T2), as when answering passengers’ questions while driving.We found that T2 elicited neuroelectric interferences in the gamma-band (>40 Hz), in key regions of the T1 network including the Multiple Demand Network. They reproduced the effect of disruptive electrocortical stimulations to create a situation of dynamical incompatibility, which might explain the DT cost. Yet, participants were able to flexibly adapt their strategy to minimize interference, and most surprisingly, reduce the reliance of T1 on key regions of the executive control network – the anterior insula and the dorsal anterior cingulate cortex – with no performance decrement.HIGHLIGHTS- First direct evidence in humans of neural interferences between two tasks.- First explanation of the Dual-Task cost at the neural level in humans.- First Dual-Tasking study with intracranial EEG in naturalistic conditions.

scholarly journals A simplified analysis of the Chernobyl accident

2021 ◽  
Vol 7 ◽  
pp. 1
Author(s):  
Bertrand Mercier ◽  
Di Yang ◽  
Ziyue Zhuang ◽  
Jiajie Liang
Keyword(s):  
Numerical Models ◽  
List Type ◽  
Flash Evaporation ◽  
The Core ◽  
Large Size ◽  
Reaction Coefficient ◽  
Pressure Tubes ◽  
Void Effect ◽  
Reactivity Coefficient ◽  
Reactivity Increase

We show with simplified numerical models, that for the kind of RBMK operated in Chernobyl: The core was unstable due to its large size and to its weak power counter-reaction coefficient, so that the power of the reactor was not easy to control even with an automatic system. Xenon oscillations could easily be activated. When there was xenon poisoning in the upper half of the core, the safety rods were designed in such a way that, at least initially, they were increasing (and not decreasing) the core reactivity. This reactivity increase has been sufficient to lead to a very high pressure increase in a significant amount of liquid water in the fuel channels thus inducing a strong propagating shock wave leading to a failure of half the pressure tubes at their junction with the drum separators. The depressurization phase (flash evaporation) following this failure has produced, after one second, a significant decrease of the water density in half the pressure tubes and then a strong reactivity accident due to the positive void effect reactivity coefficient. We evaluate the fission energy released by the accident

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 CORE-Kids: a protocol for the development of a core outcome set for childhood fractures

BMJ Open ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. e036224 ◽  
Author(s):  
Ben Arthur Marson ◽  
Joseph C Manning ◽  
Marilyn James ◽  
Simon Craxford ◽  
Sandeep R Deshmukh ◽  
...  
Keyword(s):  
Core Outcome Set ◽  
Significant Heterogeneity ◽  
List Type ◽  
Core Outcome ◽  
The Core ◽  
Outcome Set ◽  
Study Results ◽  
Orthopaedic Literature ◽  
Registration Number ◽  
Limb Fractures

IntroductionLimb fractures in children are common yet there are few trials that compare treatments for these injuries. There is significant heterogeneity in the outcomes reported in the paediatric orthopaedic literature, which limits the ability to compare study results and draw firm conclusions. The aim of the CORE-Kids Study is to develop a core outcome set for use in research studies of childhood limb fractures. A core outcome set will provide a minimum set of outcomes to be measured in all trials to minimise the heterogeneity of outcomes reported and minimise reporting bias. A core outcome set ensures that outcomes are reported that are relevant to families as well as clinicians. The core outcome set will include additional upper and lower limb modules.MethodsThe development of the core outcome set will require four phases to evaluate:What are the outcomes that are relevant to professionals?What are the outcomes that are relevant to families?What are the most important of these outcomes?Which outcomes should be included in the core outcome set?This will be completed through a systematic review of trials to identify the outcomes domains that are relevant to trialists. A series of semi-structured interviews will be completed with families to identify the outcome domains that are relevant to families. These outcome domains will be used in a three-round Delphi Study to analyse the importance of these outcome domains to a range of stakeholders including parents, clinicians and researchers. Following this, the core outcome set will be decided at a consensus meeting.Ethics and disseminationEthical approval has been awarded HRA/REC IRAS number 262503. Date of approval 06/08/2019. Dissemination will be through scientific literature and international societies.Trial registrationCore Outcome Measures in Effectiveness Trials Initiative, registration number: 1274. Date of registration 13/12/2018.PROSPERO registration numberCRD42018106605.

scholarly journals On the existence of Kobayashi and Bergman metrics for Model domains

2020 ◽  
Author(s):  
Nikolay Shcherbina
Keyword(s):  
Entire Function ◽  
Continuous Function ◽  
Pseudoconvex Domain ◽  
Plurisubharmonic Function ◽  
Holomorphic Curves ◽  
List Type ◽  
Bergman Metric ◽  
The Core ◽  
Bounded Smooth ◽  
Bergman Metrics

Abstract We prove that for a pseudoconvex domain of the form $${\mathfrak {A}} = \{(z, w) \in {\mathbb {C}}^2 : v > F(z, u)\}$$ A = { ( z , w ) ∈ C 2 : v > F ( z , u ) } , where $$w = u + iv$$ w = u + i v and F is a continuous function on $${\mathbb {C}}_z \times {\mathbb {R}}_u$$ C z × R u , the following conditions are equivalent: The domain $$\mathfrak {A}$$ A is Kobayashi hyperbolic. The domain $$\mathfrak {A}$$ A is Brody hyperbolic. The domain $$\mathfrak {A}$$ A possesses a Bergman metric. The domain $$\mathfrak {A}$$ A possesses a bounded smooth strictly plurisubharmonic function, i.e. the core $$\mathfrak {c}(\mathfrak {A})$$ c ( A ) of $$\mathfrak {A}$$ A is empty. The graph $$\Gamma (F)$$ Γ ( F ) of F can not be represented as a foliation by holomorphic curves of a very special form, namely, as a foliation by translations of the graph $$\Gamma ({\mathcal H})$$ Γ ( H ) of just one entire function $${\mathcal {H}} : {\mathbb {C}}_z \rightarrow {\mathbb {C}}_w$$ H : C z → C w .

scholarly journals TMS-Adaptation Reveals Abstract Letter Selectivity in the Left Posterior Parietal Cortex

2009 ◽  
Vol 19 (10) ◽  
pp. 2321-2325 ◽  
Author(s):  
Z. Cattaneo ◽  
F. Rota ◽  
V. Walsh ◽  
T. Vecchi ◽  
J. Silvanto
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Left Posterior ◽  
Posterior Parietal

scholarly journals White Dwarfs

1994 ◽  
Vol 146 ◽  
pp. 71-78
Author(s):  
Peter Thejll
Keyword(s):  
Mass Loss ◽  
White Dwarfs ◽  
Main Sequence ◽  
Asymptotic Giant Branch ◽  
List Type ◽  
Stellar Core ◽  
The Core ◽  
Long Time ◽  
Red Giant ◽  
Carbon Burning

It is the intention of this review to explain what white dwarfs are and why it is interesting to study them, and why the H+2molecule is of special interest.The evolution, from start to finish, of a star of mass less than about 2 solar masses (M⊙), can roughly be summarized as follows:–A cloud of gas contracts from the interstellar medium until hydrogen ignites at the center and amain sequence(MS) star forms. H is transformed to He and the MS phase continues until H is exhausted in the stellar core.–H continues burning in a shell outside the He core while the core contracts. He “ashes” are added to the core, and ared giantstar is formed as the envelope expands. The star evolves up the Red Giant Branch (RGB) (i.e. it becomes more and more luminous and the surface cools).–Towards the end of the RGB phase, mass-loss from the upper layers increases until helium to carbon burning in the core ignites suddenly under degenerate conditions – this is called theHelium Flash(HF). The HF terminates the RGB evolution, and therefore also the mass-loss and the growth of the stellar core.–The star readjusts its structure and the He-core burns steadily on thehorizontal branch(HB) (a phase of nearly-constant luminosity) until fuel is exhausted in the He-core.–Then the C/O core contracts anew and the expansion of the envelope, and the growth of the core, during He-shell burning, mimics RGB evolution but relatively little mass is added to the core this time.–The second ascent of the giant branch (the so-called Asymptotic Giant Branch, or AGB) continues with increased mass loss towards the end–Rapid detachment of a considerable fraction of the remaining envelope and the hot core takes place, sometimes observable as thePlanetary Nebulae(PN) phase.–The PN is dispersed as the core contracts to a white dwarf (WD).–The WD cools for a long time, as internal kinetic energy and latent heat is released.

Sign in / Sign up

Export Citation Format

Share Document