On the Nature of Functional Differentiation: The Role of Self-Organization with Constraints

Ichiro Tsuda, Hiroshi Watanabe, Hiromichi Tsukada, and Yutaka Yamaguti

Entropy 2022, 24(2), 240

The focus of this article is the self-organization of neural systems under constraints. In 2016, we proposed a theory for self-organization with constraints to clarify the neural mechanism of functional differentiation. As a typical application of the theory, we developed evolutionary reservoir computers that exhibit functional differentiation of neurons. Regarding the self-organized structure of neural systems, Warren McCulloch described the neural networks of the brain as being “heterarchical”, rather than hierarchical, in structure. Unlike the fixed boundary conditions in conventional self-organization theory, where stationary phenomena are the target for study, the neural networks of the brain change their functional structure via synaptic learning and neural differentiation to exhibit specific functions, thereby adapting to nonstationary environmental changes. Thus, the neural network structure is altered dynamically among possible network structures. We refer to such changes as a dynamic heterarchy. Through the dynamic changes of the network structure under constraints, such as physical, chemical, and informational factors, which act on the whole system, neural systems realize functional differentiation or functional parcellation. Based on the computation results of our model for functional differentiation, we propose hypotheses on the neuronal mechanism of functional differentiation. Finally, using the Kolmogorov–Arnold–Sprecher superposition theorem, which can be realized by a layered deep neural network, we propose a possible scenario of functional (including cell) differentiation.

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Stress-ridden Finance and Growth Losses: Does Financial Development Break the Link?

Serafín Martínez-Jaramillo Ricardo Montañez-Enríquez Matias Ossandon Busch Manuel Ramos-Francia Anahí Rodríguez-Martínez José Manuel Sánchez-Martínez

Does financial development shield countries from the pass-through of financial shocks to real outcomes? We evaluate this question by characterising the probability density of expected GDP growth conditional on financial stability indicators in a panel of 28 countries. Our robust results unveil a non-linear nexus between financial stability and expected GDP growth, depending on countries’ degree of financial development. While both domestic and global financial factors affect expected growth, the effect of global factors is moderated by financial development. This result highlights a previously unexplored channel trough which financial development can break the link between financial (in)stability and GDP growth.

Read the full article at: www.iwh-halle.de

The shape of memory in temporal networks

Oliver E. Williams, Lucas Lacasa, Ana P. Millán & Vito Latora 

Nature Communications volume 13, Article number: 499 (2022)

How to best define, detect and characterize network memory, i.e. the dependence of a network’s structure on its past, is currently a matter of debate. Here we show that the memory of a temporal network is inherently multidimensional, and we introduce a mathematical framework for defining and efficiently estimating the microscopic shape of memory, which characterises how the activity of each link intertwines with the activities of all other links. We validate our methodology on a range of synthetic models, and we then study the memory shape of real-world temporal networks spanning social, technological and biological systems, finding that these networks display heterogeneous memory shapes. In particular, online and offline social networks are markedly different, with the latter showing richer memory and memory scales. Our theory also elucidates the phenomenon of emergent virtual loops and provides a novel methodology for exploring the dynamically rich structure of complex systems.

Read the full article at: www.nature.com