Description Biological neural networks exhibit ongoing, spatiotemporal patterns of spiking activity. Evidence shows that spike dynamics shift from one transient attractor to another, i.e. they appear to be metastable. Metastability is theorized to be adaptive for neural and cognitive function, but learning must somehow remain stable in the context of highly variable spike dynamics. Stable learning is challenging in part because it appears that functions of homeostatic regulation and learning are both expressed through potentiation and de-potentiation of synapses. In this talk, Prof. Kello will present a spiking neural network model that integrates homeostatic regulation with learning via a local, biological plausible process of synaptic modulation. Homeostatic regulation towards the critical branching point results in power law spike dynamics, while learning shapes those dynamics to maximize reward and minimize punishment. The model is shown to simulate intrinsic fluctuations in neural and behavioral activity, and the efficacy of learning is demonstrated using time-delayed XOR classification as a simple test function, and real-time phoneme recognition in naturalistic speech as a more challenging test.

Description In recent years, the possibility to access large digital databases, as well as the development and deployment of large scale monitoring frameworks, has allowed to peer for the first time into the statistical properties of human behavior. To our surprise, the patterns of human activity have been shown to be extremely bursty, characterized by long tailed distributions, in opposition to the Poissonian behavior expected from traditional mathematical approaches. Apart from the insights that these discoveries have in the description and hypothetical predictability of human behavior, they are most relevant due to the direct connection between the patterns of human activity and the topological description of the representative social networks. Here we will discuss recent modeling efforts designed to understand and reproduce the empirical properties of social networks, as well as their effects on simple dynamical processes.

Description The Kolmogorov-Smirnov (KS) distribution appears in statistics when testing for the maximum distance between a one-dimensional empirical distribution and some proposed reference distribution. A well-known Brownian bridge construction leads to its calculation, and further identifications with e.g. Brownian excursions or Bessel processes show that this same distribution describes a surprisingly wide variety of random observables. Intriguingly, the KS distribution is also encountered in the observables of a number of models in statistical physics, such as the height of an Edwards-Wilkinson interface, or the order parameter in mean-field critical percolation. Meanwhile, the two-dimensional analogue of the KS distribution describes e.g. the steady-state height of an Edwards-Wilkinson membrane, and the order parameter of the XY model at low tempetaures. My talk will survey such examples of the KS distribution in statistical physics.

Description

- Acte de presentació del llibre Complèxica. Cervell, societat i llengua des de la transdisciplinarietat, coordinat per Àngels Massip i Bonet i Albert Bastardas i Boada (Publicacions i Edicions de la UB). - Taula rodona: «Cognició, comunicació i comportament social en els humans: quins camins per a avançar complèxicament?», a càrrec de Frederic Munné (Psicologia social, UB); Sebastià Serrano (Lingüística General i Comunicació, UB); Òscar Vilarroya (Neurociència cognitiva, UAB). Resum de l'acte: Els fenòmens produïts a l’entorn del triangle ‘llengua-comunicació-societat’ presenten trets singulars que desafien les aproximacions científiques tradicionals i també les més formalitzadores dels sistemes complexos. ¿Com seria possible concebre i definir una classe diferent d’esdeveniments, propis dels organismes i les societats humans, que no poden ser fàcilment codificats o encapsulats per un formalisme matemàtic? Per on i com cal continuar avançant per aprofundir la seva comprensió transdisciplinària?

Organizers
Grup de Complexitat, Comunicació i Sociolingüística i el Projecte Scripta, amb el suport del Centre Universitari de Sociolingüística i Comunicació (CUSC-UB)

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