scholarly journals Questions and controversies in the study of time-varying functional connectivity in resting fMRI

2020 ◽  
Vol 4 (1) ◽  
pp. 30-69 ◽  
Author(s):  
Daniel J. Lurie ◽  
Daniel Kessler ◽  
Danielle S. Bassett ◽  
Richard F. Betzel ◽  
Michael Breakspear ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Careful Analysis ◽  
Research Area ◽  
Time Varying ◽  
Time Resolved ◽  
Open Questions ◽  
Wide Range ◽  
Neuroimaging Data ◽  
Core Concepts ◽  
New Research

The brain is a complex, multiscale dynamical system composed of many interacting regions. Knowledge of the spatiotemporal organization of these interactions is critical for establishing a solid understanding of the brain’s functional architecture and the relationship between neural dynamics and cognition in health and disease. The possibility of studying these dynamics through careful analysis of neuroimaging data has catalyzed substantial interest in methods that estimate time-resolved fluctuations in functional connectivity (often referred to as “dynamic” or time-varying functional connectivity; TVFC). At the same time, debates have emerged regarding the application of TVFC analyses to resting fMRI data, and about the statistical validity, physiological origins, and cognitive and behavioral relevance of resting TVFC. These and other unresolved issues complicate interpretation of resting TVFC findings and limit the insights that can be gained from this promising new research area. This article brings together scientists with a variety of perspectives on resting TVFC to review the current literature in light of these issues. We introduce core concepts, define key terms, summarize controversies and open questions, and present a forward-looking perspective on how resting TVFC analyses can be rigorously and productively applied to investigate a wide range of questions in cognitive and systems neuroscience.

scholarly journals On the nature of time-varying functional connectivity in resting fMRI

2018 ◽  
Author(s):  
Daniel J Lurie ◽  
Daniel Kessler ◽  
Danielle S Bassett ◽  
Richard F. Betzel ◽  
Michael Breakspear ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Research Area ◽  
Time Varying ◽  
Neural Basis ◽  
Open Questions ◽  
Wide Range ◽  
Neuroimaging Data ◽  
Core Concepts ◽  
And Behavior ◽  
Key Terms

The brain is a complex dynamical system composed of many interacting sub-regions. Knowledge of how these interactions reconfigure over time is critical to a full understanding of the brain’s functional architecture, the neural basis of flexible cognition and behavior, and how neural systems are disrupted in psychiatric and neurological illness. The idea that we might be able to study neural and cognitive dynamics through analysis of neuroimaging data has catalyzed substantial interest in methods which seek to estimate moment-to-moment fluctuations in functional connectivity (often referred to as “dynamic” or time-varying connectivity; TVC). At the same time, debates have emerged regarding the application of TVC analyses to resting fMRI data, and about the statistical validity, physiological origins, and cognitive relevance of resting TVC. These and other unresolved issues complicate the interpretation of resting TVC findings and limit the insights which can be gained from this otherwise promising research area. This article reviews the current resting TVC literature in light of these issues. We introduce core concepts, define key terms, summarize current controversies and open questions, and present a forward-looking perspective on how resting TVC analyses can be rigorously applied to investigate a wide range of questions in cognitive and systems neuroscience.

Biomineralization and biotransformations of actinide materials

MRS Bulletin ◽  
2010 ◽  
Vol 35 (11) ◽  
pp. 849-857 ◽  
Author(s):  
Mary P. Neu ◽  
Hakim Boukhalfa ◽  
Mohamed L. Merroun
Keyword(s):  
Nuclear Waste ◽  
Material Science ◽  
Molecular Complexes ◽  
Research Area ◽  
Science Methods ◽  
Wide Range ◽  
Modern Chemical ◽  
Environmental Bacteria ◽  
Chemical Conditions ◽  
New Research

Microorganisms moderate local chemical conditions and alter forms of metals indirectly or directly to meet their cellular, species, and consortia needs. The diversity of microorganisms and the complexity of biogeochemical systems ensures that bacterially mediated processes yield a wide range of products, which await discovery by material scientists. Few types of materials produced by environmental bacteria have been analyzed by modern chemical and material science methods. Research on actinide biomaterials has focused on the biomineralization of a few chemical forms of uranium, neptunium, and plutonium. The materials produced are molecular complexes, microcrystalline minerals (most commonly oxides and phosphates) within cells and biofilms, and mineral adsorbates. The actinide biomaterials that emerge from this new research area will impact nuclear waste isolation and increase our understanding of environmental and geological metal cycles and may yield new bioremediation methods and industrially useful materials.

scholarly journals Purinergic Signaling and Related Biomarkers in Depression

2020 ◽  
Vol 10 (3) ◽  
pp. 160 ◽  
Author(s):  
Francesco Bartoli ◽  
Geoffrey Burnstock ◽  
Cristina Crocamo ◽  
Giuseppe Carrà
Keyword(s):  
Purinergic Signaling ◽  
Research Area ◽  
Mood Stabilizers ◽  
P2x7 Receptors ◽  
Purinergic System ◽  
Open Questions ◽  
Antidepressant Effects ◽  
Wide Range ◽  
Adenosine Antagonist

It is established that purinergic signaling can shape a wide range of physiological functions, including neurotransmission and neuromodulation. The purinergic system may play a role in the pathophysiology of mood disorders, influencing neurotransmitter systems and hormonal pathways of the hypothalamic-pituitary-adrenal axis. Treatment with mood stabilizers and antidepressants can lead to changes in purinergic signaling. In this overview, we describe the biological background on the possible link between the purinergic system and depression, possibly involving changes in adenosine- and ATP-mediated signaling at P1 and P2 receptors, respectively. Furthermore, evidence on the possible antidepressive effects of non-selective adenosine antagonist caffeine and other purinergic modulators is reviewed. In particular, A2A and P2X7 receptors have been identified as potential targets for depression treatment. Preclinical studies highlight that both selective A2A and P2X7 antagonists may have antidepressant effects and potentiate responses to antidepressant treatments. Consistently, recent studies feature the possible role of the purinergic system peripheral metabolites as possible biomarkers of depression. In particular, variations of serum uric acid, as the end product of purinergic metabolism, have been found in depression. Although several open questions remain, the purinergic system represents a promising research area for insights into the molecular basis of depression.

scholarly journals Progress in Thin Film Solar Cells Based onCu2ZnSnS4

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Hongxia Wang
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Solar Cells ◽  
Research Area ◽  
Thin Film Solar Cells ◽  
Environment Impact ◽  
Wide Range ◽  
Czts Thin Films ◽  
New Research ◽  
Light Absorbers

The research in thin film solar cells has been dominated by light absorber materials based on CdTe and Cu(In,Ga)Se2(CIGS) in the last several decades. The concerns of environment impact of cadmium and the limited availability of indium in those materials have driven the research towards developing new substitute light absorbers made from earth abundant, environment benign materials. Cu2ZnSnS4(CZTS) semiconductor material has emerged as one of the most promising candidates for this aim and has attracted considerable interest recently. Significant progress in this relatively new research area has been achieved in the last three years. Over 130 papers on CZTS have been published since 2007, and the majority of them are on the preparation of CZTS thin films by different methods. This paper, will review the wide range of techniques that have been used to deposit CZTS semiconductor thin films. The performance of the thin film solar cells using the CZTS material will also be discussed.

scholarly journals On the Assumptions That We Make About the World Around Us: A Conceptual Framework for Feature Transformation Effects

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Jan De Houwer ◽  
Juliette Richetin ◽  
Sean Hughes ◽  
Marco Perugini
Keyword(s):  
Conceptual Framework ◽  
Feature Transformation ◽  
Wide Range ◽  
The World ◽  
Core Concepts ◽  
Spontaneous Trait Inferences ◽  
Trait Inferences ◽  
Research Questions ◽  
New Research ◽  
Object Features

Various phenomena such as halo effects, spontaneous trait inferences, and evaluative conditioning have in common that assumptions about object features (e.g., whether a person is intelligent or likeable) are influenced by other object features (e.g., whether that person is attractive or co-occurs with other liked persons). Surprisingly, these phenomena have rarely been related to each other, most likely because different phenomena are described using different terms. To overcome this barrier, we put forward a conceptual framework that can be used to describe a wide range of these phenomena. After introducing the four core concepts of the framework, we illustrate how it can be applied to various phenomena. Doing so helps to reveal similarities and differences between those phenomena, thus improving communication and promoting interactions between different areas of research. Finally, we illustrate the generative power of the framework by discussing some of the new research questions that it highlights.

Сontribution of Vladimir Markovich Fridland to the development of comparative-geographic approach

2019 ◽  
Vol 96 (4-6) ◽  
pp. 64-70
Author(s):  
Mykola Davydiuk
Keyword(s):  
Soil Cover ◽  
Comparative Method ◽  
Field Research ◽  
Research Area ◽  
Soil Science ◽  
Weathering Processes ◽  
The Earth ◽  
Wide Range ◽  
New Research ◽  
Geography Of Soils

The paper is devoted to the outstanding soviet geographer and soil scientist, Doctor of Geographical Sciences (1964), Professor (1968) Vladimir Fridland (1919–1983). A prominent place in his research works was taken by geospatial comparative-geographic studies. V. Fridland took part in many research projects in various parts of the world, including his motherland. From the actualistic and evaluative positions, the paper considers the important (at present) results from the seminal works of V. Fridland, which he had obtained using a wide range of methodological tools and research techniques, including comparative-geographical approach. V. Fridland also made an important contribution to the formation and development of natural geography. He enriched theoretical, methodological and applied aspects not only of soil science, but of geography in general. In his work of 1956, the scientist convincingly, in a concise comparative form and causal relationship, highlighted the natural conditions of the USSR and outlined their foreign analogues. In his influential work of 1964, V. Fridland had investigated the weathering processes, types of weathering, genesis and geography of soils in Northern Vietnam. In the 1970s, the pioneering scientist created a new research area – the doctrine of the structure of soil cover. Through field research in many regions of the Earth, the scientist has used and improved the approaches and methods of many natural sciences, including comparative one. V. Fridland successfully and productively used in scientific research almost the entire range of comparative-geographical methods. V. Fridland was the first one in the soviet geography to identify comparative method as an approach.

scholarly journals The challenges of theory-software translation

F1000Research ◽  
2020 ◽  
Vol 9 ◽  
pp. 1192
Author(s):  
Caroline Jay ◽  
Robert Haines ◽  
Daniel S. Katz ◽  
Jeffrey C. Carver ◽  
Sandra Gesing ◽  
...  
Keyword(s):  
High Performance ◽  
Scientific Theory ◽  
Scientific Practice ◽  
Research Area ◽  
Research Software ◽  
Wide Range ◽  
Software Engineers ◽  
New Research ◽  
Formal Recognition ◽  
Software Translation

Background: Software is now ubiquitous within research. In addition to the general challenges common to all software development projects, research software must also represent, manipulate, and provide data for complex theoretical constructs. Ensuring this process of theory-software translation is robust is essential to maintaining the integrity of the science resulting from it, and yet there has been little formal recognition or exploration of the challenges associated with it. Methods: We thematically analyse the outputs of the discussion sessions at the Theory-Software Translation Workshop 2019, where academic researchers and research software engineers from a variety of domains, and with particular expertise in high performance computing, explored the process of translating between scientific theory and software. Results: We identify a wide range of challenges to implementing scientific theory in research software and using the resulting data and models for the advancement of knowledge. We categorise these within the emergent themes of design, infrastructure, and culture, and map them to associated research questions. Conclusions: Systematically investigating how software is constructed and its outputs used within science has the potential to improve the robustness of research software and accelerate progress in its development. We propose that this issue be examined within a new research area of theory-software translation, which would aim to significantly advance both knowledge and scientific practice.

scholarly journals State and trait characteristics of anterior insula time-varying functional connectivity

2019 ◽  
Author(s):  
Lorenzo Pasquini ◽  
Gianina Toller ◽  
Adam Staffaroni ◽  
Jesse A. Brown ◽  
Jersey Deng ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Emotional Processing ◽  
Anterior Insula ◽  
Time Varying ◽  
Open Questions ◽  
Novel Approach ◽  
Eye Closure ◽  
Functional Connectivity Mri ◽  
Dispositional Empathy ◽  
Over Time

AbstractThe human anterior insula (aINS) is a topographically organized brain region, in which ventral portions contribute to socio-emotional function through limbic and autonomic connections, whereas the dorsal aINS contributes to cognitive processes through frontal and parietal connections. Open questions remain, however, regarding how aINS connectivity varies over time. We implemented a novel approach combining seed-to-whole-brain sliding-window functional connectivity MRI and k-means clustering to assess time-varying functional connectivity of aINS subregions. We studied three independent large samples of healthy participants and longitudinal datasets to assess inter- and intra-subject stability, and related aINS time-varying functional connectivity profiles to dispositional empathy. We identified four robust aINS time-varying functional connectivity modes that displayed both “state” and “trait” characteristics: while modes featuring connectivity to sensory regions were modulated by eye closure, modes featuring connectivity to higher cognitive and emotional processing regions were stable over time and related to empathy measures.

scholarly journals Decreased Directed Functional Connectivity in the Psychedelic State

2019 ◽  
Author(s):  
Lionel Barnett ◽  
Suresh D. Muthukumaraswamy ◽  
Robin L. Carhart-Harris ◽  
Anil K. Seth
Keyword(s):  
Functional Connectivity ◽  
Information Flow ◽  
Large Scale ◽  
Anticonvulsant Drug ◽  
Neural Dynamics ◽  
General Interest ◽  
Neural Basis ◽  
Time Resolved ◽  
Neuroimaging Data ◽  
The Brain

AbstractNeuroimaging studies of the psychedelic state offer a unique window onto the neural basis of conscious perception and selfhood. Despite well understood pharmacological mechanisms of action, the large-scale changes in neural dynamics induced by psychedelic compounds remain poorly understood. Using source-localised, steady-state MEG recordings, we describe changes in functional connectivity following the controlled administration of LSD, psilocybin and low-dose ketamine, as well as, for comparison, the (non-psychedelic) anticonvulsant drug tiagabine. We compare both undirected and directed measures of functional connectivity between placebo and drug conditions. We observe a general decrease in directed functional connectivity for all three psychedelics, as measured by Granger causality, throughout the brain. These data support the view that the psychedelic state involves a breakdown in patterns of functional organisation or information flow in the brain. In the case of LSD, the decrease in directed functional connectivity is coupled with an increase in undirected functional connectivity, which we measure using correlation and coherence. This surprising opposite movement of directed and undirected measures is of more general interest for functional connectivity analyses, which we interpret using analytical modelling. Overall, our results uncover the neural dynamics of information flow in the psychedelic state, and highlight the importance of comparing multiple measures of functional connectivity when analysing time-resolved neuroimaging data.

scholarly journals Probing the association between resting state brain network dynamics and psychological resilience

2021 ◽  
Author(s):  
Dominik Kraft ◽  
Christian Fiebach
Keyword(s):  
Functional Connectivity ◽  
Resting State ◽  
Brain Network ◽  
Original Study ◽  
Node Degree ◽  
Psychological Resilience ◽  
Time Varying ◽  
Time Resolved ◽  
The Difference ◽  
Window Approach

This study aimed at replicating a previously reported negative correlation between node flexibility and psychological resilience. To this end, we acquired multiband resting-state BOLD fMRI (TR = .675 sec) from 60 participants and assessed resilience with three psychological questionnaires. Time resolved functional connectivity was calculated by performing a sliding window approach on averaged time series from the Schaefer 100 parcellation, resulting in 753 connectivity matrices. Node degree was calculated as a proxy for time-varying connectivity. Multilayer modularity detection was performed to track network reconfigurations over time and to calculate node flexibility (the number of times a node changes community assignment) and node promiscuity (the fraction of communities a node participates in). We found no significant correlations between resilience and any of the measures of dynamic functional connectivity, neither at nodal, functional network, or global levels. Results were also robust against down-sampling the data to resemble a conventional TR of ~2 sec (as in the original study) and against the application of different windowing schemes (overlapping vs. non-overlapping, different window lengths). We discuss several methodological reasons that may account for the difference in results between the present and the original study, to inform future network neuroscience studies of mental health.

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