17 research outputs found
Integrated Information in the Spiking-Bursting Stochastic Model
This study presents a comprehensive analytic description in terms of the
empirical "whole minus sum" version of Integrated Information in comparison to
the "decoder based" version for the "spiking-bursting" discrete-time,
discrete-state stochastic model, which was recently introduced to describe a
specific type of dynamics in a neuron-astrocyte network. The "whole minus sum"
information may change sign, and an interpretation of this transition in terms
of "net synergy" is available in the literature. This motivates our particular
interest to the sign of the "whole minus sum" information in our analytical
consideration. The behavior of the "whole minus sum" and "decoder based"
information measures are found to bear a lot of similarity, showing their
mutual asymptotic convergence as time-uncorrelated activity is increased, with
the sign transition of the "whole minus sum" information associated to a rapid
growth in the "decoder based" information. The study aims at creating a
theoretical base for using the spiking-bursting model as a well understood
reference point for applying Integrated Information concepts to systems
exhibiting similar bursting behavior (in particular, to neuron-astrocyte
networks). The model can also be of interest as a new discrete-state test bench
for different formulations of Integrated Information
Impact of Astrocytic Coverage of Synapses on the Short-Term Memory of a Computational Neuron-Astrocyte Network
Working memory refers to the capability of the nervous system to selectively retain short-term memories in an active state. The long-standing viewpoint is that neurons play an indispensable role and working memory is encoded by synaptic plasticity. Furthermore, some recent studies have shown that calcium signaling assists the memory processes and the working memory might be affected by the astrocyte density. Over the last few decades, growing evidence has also revealed that astrocytes exhibit diverse coverage of synapses which are considered to participate in neuronal activities. However, very little effort has yet been made to attempt to shed light on the potential correlations between these observations. Hence, in this article, we leverage a computational neuron–astrocyte model to study the short-term memory performance subject to various astrocytic coverage and we demonstrate that the short-term memory is susceptible to this factor. Our model may also provide plausible hypotheses for the various sizes of calcium events as they are reckoned to be correlated with the astrocytic coverage
Mammalian Brain As a Network of Networks
Acknowledgements AZ, SG and AL acknowledge support from the Russian Science Foundation (16-12-00077). Authors thank T. Kuznetsova for Fig. 6.Peer reviewedPublisher PD
Brain aging and garbage cleaning : Modelling the role of sleep, glymphatic system, and microglia senescence in the propagation of inflammaging
Brain aging is a complex process involving many functions of our body and described by the interplay of a sleep pattern and changes in the metabolic waste concentration regulated by the microglial function and the glymphatic system. We review the existing modelling approaches to this topic and derive a novel mathematical model to describe the crosstalk between these components within the conceptual framework of inflammaging. Analysis of the model gives insight into the dynamics of garbage concentration and linked microglial senescence process resulting from a normal or disrupted sleep pattern, hence, explaining an underlying mechanism behind healthy or unhealthy brain aging. The model incorporates accumulation and elimination of garbage, induction of glial activation by garbage, and glial senescence by over-activation, as well as the production of pro-inflammatory molecules by their senescence-associated secretory phenotype (SASP). Assuming that insufficient sleep leads to the increase of garbage concentration and promotes senescence, the model predicts that if the accumulation of senescent glia overcomes an inflammaging threshold, further progression of senescence becomes unstoppable even if a normal sleep pattern is restored. Inverting this process by "rejuvenating the brain" is only possible via a reset of concentration of senescent glia below this threshold. Our model approach enables analysis of space-time dynamics of senescence, and in this way, we show that heterogeneous patterns of inflammation will accelerate the propagation of senescence profile through a network, confirming a negative effect of heterogeneity
Noise-induced artificial intelligence
ACKNOWLEDGMENTS The study was supported by Medical Research Council Grant No. MR/R02524X/1. A.E., S.G., and A.Z. thank the Russian Science Foundation under Grant No. 22-12-00216. The work of A.E. was supported by RFBR according to Research Project No. 20-32-90151.Peer reviewedPublisher PD
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Noise-induced artificial intelligence
We show that unavoidable stochastic fluctuations are not only affecting information processing in a destructive or constructive way, but may even induce conditions necessary for the artificial intelligence itself. In this proof-of-principle paper we consider a model of a neuron-astrocyte network under the influence of multiplicative noise and show that information encoding (loading, storage, and retrieval of information patterns), one of the paradigmatic signatures of intelligent systems, can be induced by stochastic influence and astrocytes. Hence, astrocytes, recently proved to play an important role in memory and cognitive processing in mammalian brains, may play also an important role in the generation of a system's features providing artificial intelligence functions. Hence, one could conclude that intrinsic stochasticity is probably positively utilized by brains, not only to optimize the signal response but also to induce intelligence itself, and one of the key roles, played by astrocytes in information processing, could be dealing with noises
Astrocytes mediate analogous memory in a multi-layer neuron-astrocyte network
Modeling the neuronal processes underlying short-term working memory remains the focus of many theoretical studies in neuroscience. In this paper, we propose a mathematical model of a spiking neural network (SNN) which simulates the way a fragment of information is maintained as a robust activity pattern for several seconds and the way it completely disappears if no other stimuli are fed to the system. Such short-term memory traces are preserved due to the activation of astrocytes accompanying the SNN. The astrocytes exhibit calcium transients at a time scale of seconds. These transients further modulate the efficiency of synaptic transmission and, hence, the firing rate of neighboring neurons at diverse timescales through gliotransmitter release. We demonstrate how such transients continuously encode frequencies of neuronal discharges and provide robust short-term storage of analogous information. This kind of short-term memory can store relevant information for seconds and then completely forget it to avoid overlapping with forthcoming patterns. The SNN is inter-connected with the astrocytic layer by local inter-cellular diffusive connections. The astrocytes are activated only when the neighboring neurons fire synchronously, e.g., when an information pattern is loaded. For illustration, we took grayscale photographs of people’s faces where the shades of gray correspond to the level of applied current which stimulates the neurons. The astrocyte feedback modulates (facilitates) synaptic transmission by varying the frequency of neuronal firing. We show how arbitrary patterns can be loaded, then stored for a certain interval of time, and retrieved if the appropriate clue pattern is applied to the input
TREC and KREC Levels as a Predictors of Lymphocyte Subpopulations Measured by Flow Cytometry
Primary immunodeficiency diseases (PID) is a heterogeneous group of disorders caused
by genetic defects of the immune system, which manifests clinically as recurrent
infections, autoimmune diseases, or malignancies. Early detection of other PID remains
a challenge, particularly in older children due to milder and less specific symptoms,
a low level of clinician PID awareness and poor provision of hospital laboratories
with appropriate devices. T-cell recombination excision circles (TREC) and kappadeleting element recombination circle (KREC) in a dried blood spot and in peripheral
blood using real-time polymerase chain reaction (PCR) are used as a tool for severe
combined immune deficiency but not in PID. They represent an attractive and cheap
target for a more extensive use in clinical practice. This study aimed to assess
TREC/KREC correspondence with lymphocyte subpopulations, measured by flow
cytometry and evaluate correlations between TREC/KREC, lymphocyte subpopulations
and immunoglobulins. We carried out analysis of data from children assessed by clinical
immunologists at Speransky Children’s Hospital, Moscow, Russia with suspected
immunodeficiencies between May 2013 and August 2016. Peripheral blood samples
were sent for TREC/KREC, flow cytometry (CD3, CD4, CD8, and CD19), IgA, IgM, and
IgG analysis. A total of 839 samples were analyzed for using TREC assay and flow cytometry and 931 KREC/flow cytometry. TREC demonstrated an AUC of 0.73 (95% CI
0.70–0.76) for CD3, 0.74 (95% CI 0.71–0.77) for CD4 and 0.67 (95% CI 0.63–0.70) for
CD8, respectively, while KREC demonstrated an AUC of 0.72 (95% CI 0.69–0.76) for
CD19. Moderate correlation was found between the levels of TREC and CD4 (r = 0.55,
p < 0.01) and KREC with CD19 (r = 0.56, p < 0.01). In this study, promising prediction
models were tested. We found that TREC and KREC are able to moderately detect
abnormal levels of individual lymphocyte subpopulations. Future research should assess
associations between TREC/KREC and other lymphocyte subpopulations and approach
TREC/KREC use in PID diagnosis