scholarly journals Motor primitives in space and time via targeted gain modulation in cortical networks

2018 ◽  
Author(s):  
Jake P. Stroud ◽  
Mason A. Porter ◽  
Guillaume Hennequin ◽  
Tim P. Vogels
Keyword(s):  
Neuronal Network ◽  
Learning Rule ◽  
Network Models ◽  
Network Activity ◽  
Movement Speed ◽  
Control Units ◽  
Dimensional Network ◽  
Wide Range ◽  
New Perspective

AbstractMotor cortex (M1) exhibits a rich repertoire of activities to support the generation of complex movements. Although recent neuronal-network models capture many qualitative aspects of M1 dynamics, they can generate only a few distinct movements. Additionally, it is unclear how M1 efficiently controls movements over a wide range of shapes and speeds. We demonstrate that simple modulation of neuronal input–output gains in recurrent neuronal-network models with fixed architecture can dramatically reorganize neuronal activity and thus downstream muscle outputs. Consistent with the observation of diffuse neuromodulatory projections to M1, we show that a relatively small number of modulatory control units provide sufficient flexibility to adjust high-dimensional network activity using a simple reward-based learning rule. Furthermore, it is possible to assemble novel movements from previously learned primitives, and one can separately change movement speed while preserving movement shape. Our results provide a new perspective on the role of modulatory systems in controlling recurrent cortical activity.

scholarly journals Host-microbiome coevolution promotes cooperation in a rock-paper-scissor dynamic

2019 ◽  
Author(s):  
Ohad Lewin-Epstein ◽  
Lilach Hadany
Keyword(s):  
Computational Modeling ◽  
Potential Role ◽  
Evolution Of Cooperation ◽  
Host Behavior ◽  
Wide Range ◽  
Forms Of Life ◽  
New Perspective ◽  
Almost All ◽  
And Behavior

AbstractCooperation is a fundamental behavior observed in all forms of life. The evolution of cooperation has been widely studied, but almost all theories focused on the cooperating individual and its genes. We suggest a different approach, taking into account the microbes carried by the interacting individuals. Accumulating evidence reveal that microbes can affect their host wellbeing and behavior, yet hosts can evolve mechanisms to resist the manipulations of their microbes. We thus propose that coevolution of microbes with their hosts may favor microbes that induce their host to cooperate. Using computational modeling, we show that microbe-induced cooperation can evolve and be maintained in a wide range of conditions, including when facing hosts’ resistance to the microbial effect. We find that host-microbe coevolution leads the population to a rock-paper-scissors dynamic, that enables maintenance of cooperation in a polymorphic state. This theory may help explain occurrences of cooperation in a wide variety of organisms, including in cases that are difficult to explain by current theories. In addition, this study provides a new perspective on the coevolution of hosts and their microbiome, emphasizing the potential role of microbes in shaping their host behavior.

The Role of Prior Assumptions for Leak Localisation in Water Networks with Uncertainties

2021 ◽  
Author(s):  
Caroline Blocher ◽  
Filippo Pecci ◽  
Ivan Stoianov
Keyword(s):  
Network Models ◽  
Water Networks ◽  
Water Network ◽  
Sensitivity Matrix ◽  
Search Area ◽  
Leak Location ◽  
Wide Range ◽  
Coefficient Vector ◽  
Resistance Coefficients

Abstract Hydraulic model-based leak (burst) localisation in water networks is a challenging problem due to uncertainties, the limited number of hydraulic measurements, and the wide range of leak properties. In this study, we investigate the use of prior assumptions to improve the leak localisation in the presence of model uncertainties. For example, 𝓁2-regularisation relies on the assumption that the Euclidean norm of the leak coefficient vector should be minimised. This approach is compared with a method based on the sensitivity matrix, which assumes the existence of only a single leak. We show that while applying the sensitivity matrix often yields a better estimate of the leak location in single leak scenarios, the 𝓁2-regularisation successfully identifies a leak search area for pinpointing the accurate leak location. Furthermore, we demonstrate that the additional error introduced by a quadratic approximation of the Hazen-Williams formula for the solution of the localisation problem is negligible given the uncertainties in Hazen-Williams resistance coefficients in operational water network models.

scholarly journals Shark skin-inspired designs that improve aerodynamic performance

2018 ◽  
Vol 15 (139) ◽  
pp. 20170828 ◽  
Author(s):  
August G. Domel ◽  
Mehdi Saadat ◽  
James C. Weaver ◽  
Hossein Haj-Hariri ◽  
Katia Bertoldi ◽  
...  
Keyword(s):  
Separation Bubble ◽  
Suction Side ◽  
Aerodynamic Performance ◽  
Parametric Modelling ◽  
Low Profile ◽  
Wide Range ◽  
Simulation Based ◽  
New Perspective ◽  
Drag Ratio

There have been significant efforts recently aimed at improving the aerodynamic performance of aerofoils through the modification of their surfaces. Inspired by the drag-reducing properties of the tooth-like denticles that cover the skin of sharks, we describe here experimental and simulation-based investigations into the aerodynamic effects of novel denticle-inspired designs placed along the suction side of an aerofoil. Through parametric modelling to query a wide range of different designs, we discovered a set of denticle-inspired surface structures that achieve simultaneous drag reduction and lift generation on an aerofoil, resulting in lift-to-drag ratio improvements comparable to the best-reported for traditional low-profile vortex generators and even outperforming these existing designs at low angles of attack with improvements of up to 323%. Such behaviour is enabled by two concurrent mechanisms: (i) a separation bubble in the denticle's wake altering the flow pressure distribution of the aerofoil to enhance suction and (ii) streamwise vortices that replenish momentum loss in the boundary layer due to skin friction. Our findings not only open new avenues for improved aerodynamic design, but also provide new perspective on the role of the complex and potentially multifunctional morphology of shark denticles for increased swimming efficiency.

scholarly journals Stable modulation of neuronal oscillations produced through brain-machine equilibrium

2021 ◽  
Author(s):  
Colin G McNamara ◽  
Max Rothwell ◽  
Andrew Sharott
Keyword(s):  
Neural Circuit ◽  
Network Activity ◽  
Movement Speed ◽  
External Stimulation ◽  
Cycle Basis ◽  
Brain Functions ◽  
Closed Loop Systems ◽  
Modify Activity ◽  
Machine Interaction

Brain stimulation is predominantly delivered independent of ongoing activity, whereas closed-loop systems can modify activity through interaction. They have the unrealised potential to continuously bind external stimulation to specific dynamics of a neural circuit. Such manipulations are particularly suited to rhythmic activities, where neuronal activity is organised in oscillatory cycles. Here, we developed a fast algorithm that responds on a cycle-by-cycle basis to stimulate basal ganglia nuclei at predetermined phases of successive cortical beta cycles in parkinsonian rats. Using this approach, we demonstrate a stable brain-machine interaction. An equilibrium emerged between the modified brain signal and feedback-dependent stimulation pattern, which led to sustained amplification or suppression of the oscillation. Sustained beta amplification slowed movement speed by altering the mode of locomotion. Integrating an external stimulus with network activity in this way could be used to correct maladaptive activities and to define the role of oscillations in fundamental brain functions.

scholarly journals Role of Interleukin-6 in Depressive Disorder

2020 ◽  
Vol 21 (6) ◽  
pp. 2194 ◽  
Author(s):  
Emily Yi-Chih Ting ◽  
Albert C. Yang ◽  
Shih-Jen Tsai
Keyword(s):  
Depressive Disorder ◽  
Interleukin 6 ◽  
Depressive Symptomatology ◽  
Antidepressive Agents ◽  
Great Promise ◽  
Study Results ◽  
Wide Range ◽  
Physical Disorders ◽  
New Perspective

Major depressive disorder (MDD), which is a leading psychiatric illness across the world, severely affects quality of life and causes an increased incidence of suicide. Evidence from animal as well as clinical studies have indicated that increased peripheral or central cytokine interleukin-6 (IL-6) levels play an important role in stress reaction and depressive disorder, especially physical disorders comorbid with depression. Increased release of IL-6 in MDD has been found to be a factor associated with MDD prognosis and therapeutic response, and may affect a wide range of depressive symptomatology. However, study results of the IL6 genetic effects in MDD are controversial. Increased IL-6 activity may cause depression through activation of hypothalamic-pituitary-adrenal axis or influence of the neurotransmitter metabolism. The important role of neuroinflammation in MDD pathogenesis has created a new perspective that the combining of blood IL-6 and other depression-related cytokine levels may help to classify MDD biological subtypes, which may allow physicians to identify the optimal treatment for MDD patients. To modulate the IL-6 activity by IL-6-related agents, current antidepressive agents, herb medication, pre-/probiotics or non-pharmacological interventions may hold great promise for the MDD patients with inflammatory features.

scholarly journals Emergence of oscillations via spike timing dependent plasticity

2018 ◽  
Author(s):  
Sarit Soloduchin ◽  
Maoz Shamir
Keyword(s):  
Phase Diagram ◽  
Neuronal Network ◽  
Learning Process ◽  
Learning Rule ◽  
Spike Timing ◽  
Oscillatory Activity ◽  
Spike Timing Dependent Plasticity ◽  
Dependent Plasticity ◽  
Wide Range ◽  
Stdp Rule

AbstractNeuronal oscillatory activity has been reported in relation to a wide range of cognitive processes. In certain cases changes in oscillatory activity has been associated with pathological states. Although the specific role of these oscillations has yet to be determined, it is clear that neuronal oscillations are abundant in the central nervous system. These observations raise the question of the origin of these oscillations; and specifically whether the mechanisms responsible for the generation and stabilization of these oscillations are genetically hard-wired or whether they can be acquired via a learning process.Here we focus on spike timing dependent plasticity (STDP) to investigate whether oscillatory activity can emerge in a neuronal network via an unsupervised learning process of STDP dynamics, and if so, what features of the STDP learning rule govern and stabilize the resultant oscillatory activity?Here, the STDP dynamics of the effective coupling between two competing neuronal populations with reciprocal inhibitory connections was analyzed using the phase-diagram of the system that depicts the possible dynamical states of the network as a function of the effective inhibitory couplings. This phase diagram yields a rich repertoire of possible dynamical behaviors including regions of different fixed point solutions, bi-stability and a region in which the system exhibits oscillatory activity. STDP introduces dynamics for the inhibitory couplings themselves and hence induces a flow in the phase diagram. We investigate the conditions for the flow to converge to an oscillatory state of the neuronal network and then characterize how the features of the STDP rule govern and stabilize these oscillations.

scholarly journals Training a spiking neuronal network model of visual-motor cortex to play a virtual racket-ball game using reinforcement learning

2021 ◽  
Author(s):  
Haroon Anwar ◽  
Simon Caby ◽  
Salvador Dura-Bernal ◽  
David D'Onofrio ◽  
Daniel Hasegan ◽  
...  
Keyword(s):  
Reinforcement Learning ◽  
Neuronal Network ◽  
Learning Rule ◽  
Network Models ◽  
Learning Mechanisms ◽  
Motion Direction ◽  
Information Encoding ◽  
Ball Game ◽  
Learning Rules ◽  
Visual Motor

Recent models of spiking neuronal networks have been trained to perform behaviors in static environments using a variety of learning rules, with varying degrees of biological realism. Most of these models have not been tested in dynamic visual environments where models must make predictions on future states and adjust their behavior accordingly. The models using these learning rules are often treated as black boxes, with little analysis on circuit architectures and learning mechanisms supporting optimal performance. Here we developed visual/motor spiking neuronal network models and trained them to play a virtual racket-ball game using several reinforcement learning algorithms inspired by the dopaminergic reward system. We systematically investigated how different architectures and circuit-motifs (feed-forward, recurrent, feedback) contributed to learning and performance. We also developed a new biologically-inspired learning rule that significantly enhanced performance, while reducing training time. Our models included visual areas encoding game inputs and relaying the information to motor areas, which used this information to learn to move the racket to hit the ball. Neurons in the early visual area relayed information encoding object location and motion direction across the network. Neuronal association areas encoded spatial relationships between objects in the visual scene. Motor populations received inputs from visual and association areas representing the dorsal pathway. Two populations of motor neurons generated commands to move the racket up or down. Model-generated actions updated the environment and triggered reward or punishment signals that adjusted synaptic weights so that the models could learn which actions led to reward. Here we demonstrate that our biologically-plausible learning rules were effective in training spiking neuronal network models to solve problems in dynamic environments. We used our models to dissect the circuit architectures and learning rules most effective for learning. Our models offer novel predictions on the biological mechanisms supporting learning behaviors.

Buddhism in Australia

2021 ◽  
Keyword(s):  
Immigrant Identity ◽  
Buddhist Practice ◽  
Wide Range ◽  
Australian Education ◽  
Engaged Buddhism ◽  
Academic Publications ◽  
Significant Addition ◽  
New Perspective ◽  
The Buddha

Buddhism comprised 2.4 percent of the Australian population at the most recent census in 2016. While reflection on Buddhism’s growth in Australia is recorded as early as 1961, the first major body of work in the field was documentation of the early history in Buddhism in Australia, 1848–1988 (Croucher 1989 [cited under History]). The study of Buddhism in Australia has grown since the 1990s, with a small number of books and academic theses now available. An edited volume, Buddhism in Australia: Traditions in Change (Rocha and Barker 2011) [cited under Overviews]) provides a significant addition in showcasing a broad range of work from researchers and leading teachers. “Bibliography: Buddhism in Australia” (Fitzpatrick, et al. 2012 [cited under History]) provides a bibliography of all the works in the field that records more than ninety academic publications and forty other resources. A total of forty of these were completed between 2003 and 2012, and it would be reasonable to assume that approximately forty more have been added from 2012 to 2021, suggesting that there are now more than 175 studies relevant to this field. This review of key works in the field focuses on five areas: Overviews, History, Major Schools, Buddhist Identity, and Expressions of Buddhism. The history section ranges from historical overviews to community profiles, culminating in the exploration in “The Buddhist Council of Victoria and the Challenges of Recognizing Buddhism as a Religion in Australia” (Cousens 2011 [cited under History]) on the efforts to encourage government recognition of Buddhism as a designated religion in Australia. As for many countries in Europe and North America, a wide range of Buddhist schools took root through various means, and examination of these has increased to enable the section on major schools to encompass at least one work on most major traditions, often by researchers who are also practitioners. Consideration of the diversity of Buddhist traditions represented in Australia leads into the section Buddhist Identity, which includes studies on both immigrant identity and conversion in relation to Buddhist practice. The final section contains references dealing with how aspects of Buddhist teachings have been expressed in practice, including feminism, engaged Buddhism, and incorporation into Australian education systems. “Women and Ultramodern Buddhism in Australia” (Halafoff, et al. 2018 [cited under Expressions of Buddhism]) provides a valuable update and new perspective on the role of women in Australian Buddhist history, and The Buddha Is in the Street: Engaged Buddhism in Australia (Sherwood 2003 [cited under Expressions of Buddhism]) illustrates expressions of engaged Buddhism in the Australian context.

scholarly journals Integrated Brain Circuits: Neuron-Astrocyte Interaction in Sleep-Related Rhythmogenesis

2010 ◽  
Vol 10 ◽  
pp. 1634-1645 ◽  
Author(s):  
Michael M. Halassa ◽  
Marco Dal Maschio ◽  
Riccardo Beltramo ◽  
Philip G. Haydon ◽  
Fabio Benfenati ◽  
...  
Keyword(s):  
Glial Cells ◽  
Neuronal Network ◽  
Information Transfer ◽  
Neuronal Excitability ◽  
Network Activity ◽  
Slow Oscillations ◽  
Neuronal Network Activity ◽  
Brain Circuits ◽  
Circuit Function

Although astrocytes are increasingly recognized as important modulators of neuronal excitability and information transfer at the synapse, whether these cells regulate neuronal network activity has only recently started to be investigated. In this article, we highlight the role of astrocytes in the modulation of circuit function with particular focus on sleep-related rhythmogenesis. We discuss recent data showing that these glial cells regulate slow oscillations, a specific thalamocortical activity that characterizes non-REM sleep, and sleep-associated behaviors. Based on these findings, we predict that our understanding of the genesis and tuning of thalamocortical rhythms will necessarily go through an integrated view of brain circuits in which non-neuronal cells can play important neuromodulatory roles.

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