scholarly journals Multiscale dynamics underlying neocortical slow oscillations

2021 ◽  
Author(s):  
Maurizio Mattia ◽  
Maria Perez-Zabalza ◽  
Núria Tort-Colet ◽  
Miguel Dasilva ◽  
Alberto Muñoz ◽  
...  

Slow oscillations in the sleeping and anesthetized brain invariantly emerge as an alternation between Up (high firing) and Down (almost quiescent) states. In cortex, they occur simultaneously in cell assemblies in different layers and propagate as traveling waves, a concerted activity at multiple scales whose interplay and role is still under debate. Slow oscillations have been reported to start in deep layers, more specifically in layer 5. Here, we studied the laminar organization of slow oscillations in the anesthetized rat cortex and we found that the activity leading to Up states actually initiates in layer 6, then spreads towards upper layers. Layer 5 cell assemblies have a threshold-like activation that can persist after layer 6 inactivation, giving rise to hysteresis loops like in "flip-flop" computational units. We found that such hysteresis is finely tuned by the columnar circuitry depending on the recent history of the local ongoing activity. Furthermore, thalamic inactivation reduced infragranular excitability without affecting the columnar activation pattern. We propose a role for layer 6 acting as a hub unraveling a hierarchy of cortical loops.

Soft Matter ◽  
2021 ◽  
Author(s):  
Roberto Cerbino ◽  
Stefano Villa ◽  
Andrea Palamidessi ◽  
Emanuela Frittoli ◽  
Giorgio Scita ◽  
...  

We propose a new tracking-free method for the quantification of multiscale dynamics in 2D and 3D cell collectives.


2014 ◽  
Vol 617 ◽  
pp. 187-192 ◽  
Author(s):  
Boris Melnikov ◽  
Artem Semenov

Fatigue analysis of steel parts of structures, which are subjected to complex irregular loading programs caused by wind, thermal, wave loads, earthquakes and combined imposed actions, requires in some cases using special methods of stress-strain evaluation. The model of the low cycle fatigue nonlinear damage accumulation is developed with taking into account the history of the deformation process. The damage is defined on the base of considering the quasi-static accumulation of maximal strain (stress) and hysteresis loops. The identification of material constants of the model is discussed. Application of the damage model for fatigue analysis of the antennas, pipelines, basements and fasteners units is considered and a comparison with experiments is given.


2021 ◽  
Vol 13 (3-2) ◽  
pp. 337-347
Author(s):  
Larisa Zakhidova ◽  

The best works of modern literature often have mythological overtones that allow us to raise the deep layers of human experience. Mythologism of the XX - XXI centuries is a wide, complex and contradictory phenomenon, requiring also serious penetration into the linguistics of the text of the studied work. The analysis of the literary process, from the 19th century to the 21st century, clearly shows that it is traditional to have vocabulary referring the reader to various cultural subtexts, which we call mythopoetic paradigms that have an associative connection with mythological images and are a means of creating mythological subtext, as well as a means of enriching a literary text with additional meanings. Mythopoetic paradigms help in creating the subtext of a work by their ability to evoke certain models, images, whole cultural traditions in the reader’s mind. A.A. Potebnya believes that the doctrine of ‘mythological devices’ of thought should be given a place in the history of literature: if the previous content of our thought is not a subjective means of cognition, but its source, and the image (being recognized as ‘objective’) is completely transferred into meaning, then in this the case the researcher comes across myth-making. Many myths are generated by the external and especially the internal form of the word. The research of Yu. M. Polyakov’s texts convincingly shows a mythopoetic type of thinking of this writer, since mythopoetic paradigms are cross-cutting and cover almost all of the author’s texts. In this regard a novel “The Mushroom Tsar” by Yu. M. Polyakov is especially specific. Yu. M. Polyakov’s works are rich in mythologemes of various types that allows us to talk about his texts within the framework of the neo-mythological tradition, which provides a deep understanding of the writer’s texts and the system of his idiostyle as a whole.


Author(s):  
J. Kasmire

AbstractThe word “sustainable” débuted in 1987 but has since become a hot topic issue, both for scientific research and wider society. Although sustainability may appear to be a thoroughly twenty-first century goal, sustainability science concepts and goals such as balance, endurance, order and change, reach back at least as far as the proto-scientific investigations of alchemy. Both alchemy and sustainability science can be understood as systems or strategies which individuals and societies can use to organise and manage themselves in a complex world filled with dynamic problems. Alchemy never created a panacea or transmuted base metals into gold because those goals proved to be based on fundamentally flawed theories and premises. Nevertheless, alchemy did succeed in helping adherents manage themselves and their societies in advantageous ways. Alchemy also positively and significantly influenced subsequent scientific development. Likewise, science helps humanity manage itself on multiple scales, from the individual to the international, and will certainly contribute to further scientific research and development. However, it is not yet known whether carbon neutrality, entirely renewable energy and other sustainability goals will be achieved or whether these goals will also come to be seen as based on flawed understandings and theories. For this reason, this article explores key features of alchemy, traces how they persisted through Enlightenment-era science and how they continue to be present and influential within scientific efforts today. The article goes on to reflect on how the history, development and continued use of concepts such as balance, endurance, order and change may be useful portents of how humans and human society will manage themselves in the future. Such reflections may also temper the zeal with which individuals that accept or reject sustainability goals treat each other, thereby offering a way for divergent groups to manage their interactions. Flawed theories prevented alchemy from achieving many of its primary stated goals. However, alchemy was very beneficial, both during its period of use and subsequently through its influence on subsequent development. This article identifies ideas from alchemy that were originally beneficial and that have persisted through Enlightenment-era science and into contemporary science. The article also explores how those ideas continue to influence scientific and sustainability goals today. Understanding and reflecting on alchemy’s successes and failures facilitates reflection on the potential successes and failures of sustainability and the human consequences of trying to manage a sustainable future.


2010 ◽  
Vol 104 (6) ◽  
pp. 3433-3438 ◽  
Author(s):  
Francois Windels ◽  
James W. Crane ◽  
Pankaj Sah

Slow oscillations (<1 Hz) in neural activity occur during sleep and quiet wakefulness in both animals and humans. Single-cell recordings in cortical neurons have shown that these oscillations are driven by a combination of excitatory and inhibitory synaptic inputs. During up-states, although the ratio between them varies between cells, excitation and inhibition follow similar time courses. Neurons in the basolateral amygdala (BLA) also show slow oscillations between the resting membrane potential (down-state) and depolarized potentials (up-states). Delivery of footshock during the down-state fully reproduces up-states in these cells. Here we report that up-states in BLA principal neurons up-states begin with an excitatory drive that is rapidly (within ∼50 ms) overwhelmed by inhibitory input. This excess of inhibitory drive is short lasting (300–400 ms), after which up-states are maintained by a tight balance between excitation and inhibition. This initial large inhibitory input restricts action potential generation and reduces the firing frequency of these cells. These results indicate that, in contrast to cortical neurons, up-states in BLA neurons show an initial period of strong cortically driven feed-forward inhibition. For the remainder of the up-state, feedback inhibition then acts to balance excitatory input.


SLEEP ◽  
2020 ◽  
Vol 43 (12) ◽  
Author(s):  
Jules Schneider ◽  
Penelope A Lewis ◽  
Dominik Koester ◽  
Jan Born ◽  
Hong-Viet V Ngo

Abstract Study Objectives Cortical slow oscillations (SOs) and thalamocortical sleep spindles hallmark slow wave sleep and facilitate memory consolidation, both of which are reduced with age. Experiments utilizing auditory closed-loop stimulation to enhance these oscillations showed great potential in young and older subjects. However, the magnitude of responses has yet to be compared between these age groups. We examined the possibility of enhancing SOs and performance on different memory tasks in a healthy middle-aged population using this stimulation and contrast effects to younger adults. Methods In a within-subject design, 17 subjects (55.7 ± 1.0 years) received auditory stimulation in synchrony with SO up-states, which was compared to a no-stimulation sham condition. Overnight memory consolidation was assessed for declarative word-pairs and procedural finger-tapping skill. Post-sleep encoding capabilities were tested with a picture recognition task. Electrophysiological effects of stimulation were compared to a previous younger cohort (n = 11, 24.2 ± 0.9 years). Results Overnight retention and post-sleep encoding performance of the older cohort revealed no beneficial effect of stimulation, which contrasts with the enhancing effect the same stimulation protocol had in our younger cohort. Auditory stimulation prolonged endogenous SO trains and induced sleep spindles phase-locked to SO up-states in the older population. However, responses were markedly reduced compared to younger subjects. Additionally, the temporal dynamics of stimulation effects on SOs and spindles differed between age groups. Conclusions Our findings suggest that the susceptibility to auditory stimulation during sleep drastically changes with age and reveal the difficulties of translating a functional protocol from younger to older populations.


2018 ◽  
Author(s):  
Laurent Bruxelles ◽  
Dominic J. Stratford ◽  
Richard Maire ◽  
Travis R. Pickering ◽  
Jason L. Heaton ◽  
...  

AbstractThe Sterkfontein Caves has an 80 year history of yielding remarkable evidence of hominin evolution and is currently the world’s richest Australopithecus-beafing site. Included in Sterkfontein’s hominin assemblage is StW 573 (‘Little Foot’). Discovered in the Member 2 deposit in the Silberberg Grotto, StW 573 represents the most complete Australopithecus skeleton yet found. Because of its importance to the fossil hominin record, the geological age of Little Foot has been the subject of significant debate. Two main hypotheses have been proposed regarding the formation and age of Member 2 and by association StW 573. The first, proposes that Member 2 formed relatively rapidly, starting to accumulate at around 2.8 million years ago and that the unit is isolated to the Silberberg Grotto - the underlying chambers and passages forming later. The second proposes that Member 2 formed slowly, its accumulation starting before 3.67 million years ago and that the deposit extends into the Milner Hall and close to the base of the cave system. Both assume a primary association between StW 573 and Member 2, although which sediments in the Silberberg Grotto are associated with Member 2 has also been questioned. Recently a third alternative hypothesis questioning the association of StW 573 to Member 2 sediments proposed a ‘two-stage burial scenario’ in which sediments associated with StW 573 represent a secondary and mixed-age deposit reworked from a higher cave. The stratigraphic and sedimentological implications of these hypotheses are tested here through the application of a multiscale investigation of Member 2, with reference to the taphonomy of the Little Foot skeleton. The complete infilling sequence of Member 2 is described and depositional units are tracked across all exposures of the deposit in the Silberberg Grotto and into the Milner Hall. Facies development follows patterns characteristic of colluvially accumulated taluses with 30-40° angles of repose developing coarser distal facies. Sediments are generally stratified and conformably deposited in a sequence of silty sands eroded from well-developed lateritic soils on the landscape surface. Voids, clasts and bioclasts are organized consistently across and through Member 2 according to the underlying deposit geometry, indicating a gradual deposit accretion with no distinct collapse facies evident, no successive debris flow accumulation, and only localized intra-unit post- depositional modification. The stratigraphy and sedimentology of Member 2 supports a simple single-stage accumulation process through which Member 2 partially fills the Silberberg Grotto and extends into the deeper chambers and passages of the Sterkfontein Caves. Through this work we demonstrate at multiple scales the primary association between the sediments of Member 2 and the StW 573 ‘Little Foot’ skeleton.


Author(s):  
Jules Schneider ◽  
Penelope A. Lewis ◽  
Dominik Koester ◽  
Jan Born ◽  
Hong-Viet V. Ngo

AbstractBackgroundCortical slow oscillations (SOs) and thalamo-cortical sleep spindles hallmark slow wave sleep and facilitate sleep-dependent memory consolidation. Experiments utilising auditory closed-loop stimulation to enhance these oscillations have shown great potential in young and older subjects. However, the magnitude of responses has yet to be compared between these age groups.ObjectiveWe examined the possibility of enhancing SOs and performance on different memory tasks in a healthy older population using auditory closed-loop stimulation and contrast effects to a young adult cohort.MethodsIn a within-subject design, subjects (n = 17, 55.7 ± 1.0 years, 9 female) received auditory click stimulation in synchrony with SO up-states, which was compared to a no-stimulation sham condition. Overnight memory consolidation was assessed for declarative word-pairs and procedural finger-tapping skill. Post-sleep encoding capabilities were tested with a picture recognition task. Electrophysiological effects of stimulation were compared to those reported previously in a younger cohort (n = 11, 24.2 ± 0.9 years, 8 female).ResultsOvernight retention and post-sleep encoding performance of the older cohort revealed no beneficial effect of stimulation, which contrasts with the enhancing effect the same stimulation protocol had in our younger cohort. Auditory stimulation prolonged endogenous SO trains and induced sleep spindles phase-locked to SO up-states in the older population. However, responses were markedly reduced compared to younger subjects. Additionally, the temporal dynamics of stimulation effects on SOs and spindles differed between age groups.ConclusionsOur findings suggest that the susceptibility to auditory stimulation during sleep drastically changes with age and reveal the difficulties of translating a functional protocol from younger to older populations.HighlightsAuditory closed-loop stimulation induced SOs and sleep spindles in older subjectsStimulation effects were reduced and overall susceptibility diminished with ageSlow oscillation and sleep spindle dynamics deviated from those in younger subjectsStimulation shows no evidence for memory effect in older subjects


Author(s):  
Jithender J. Timothy ◽  
Vijaya Holla ◽  
Günther Meschke

We analyse the dynamics of COVID-19 using computational modelling at multiple scales. For large scale analysis, we propose a 2-scale lattice extension of the classical SIR-type compartmental model with spatial interactions called the Lattice-SIRQL model. Computational simulations show that global quantifiers are not completely representative of the actual dynamics of the disease especially when mitigation measures such as quarantine and lockdown are applied. Furthermore, using real data of confirmed COVID-19 cases, we calibrate the Lattice-SIRQL model for 105 countries. The calibrated model is used to make country specific recommendations for lockdown relaxation and lockdown continuation. Finally, using an agent-based model we analyse the influence of cluster level relaxation rate and lockdown duration on disease spreading.


Author(s):  
Wolfgang Mathis

Purpose This work is intended to historically commemorate the one hundredth anniversary of the invention of a new type of electronic circuit, referred to in 1919 by Abraham and Bloch as a multivibrator and by Eccles and Jordan as a trigger relay (later known as a flip-flop). Design/methodology/approach The author also considers the circuit-technical side of this new type of circuit, considering the technological change as well as the mathematical concepts developed in the context of the analysis of the circuit. Findings The multivibrator resulted in a “circuit shape” which became one of the most applied nonlinear circuits in electronics. It is shown that at the beginning the multivibrator as well as the flip-flop circuits were used because their interesting properties in the frequency domain. Originality/value Therefore, it is a very interesting subject to consider the history of the multivibrator as electronic circuits in different technologies including tube, transistors and integrated circuits as well as the mathematical theory based on the concept from electrical circuit theory.


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