Description

The goal of the workshop is to bring together leading scientists to discuss recent theoretical and experimental progress in studies of search processes, and to advance the synergies between the communities working in condensed matter and statistical physics, quantitative biology, and mathematics.

Organizers
Carlos Mejia-Monasterio Raul Toral Horacio Wio

Speaker
M.V. Sánchez-Vives

Description Understanding complex systems like brain networks is a challenge. Cortical networks can perform computations of remarkable complexity, accounting for a large variety of behaviours and cognitive states. At the same time, the same networks can engage in stereotypical patterns of spatio-temporal activation, such as the ones that can be observed during sleep, anaesthesia and in cortical slices [1]. Collective phenomena emerging from activity reverberation in cortical circuits at different spatio-temporal scales results in a rich variety of dynamical states. Slow (around or below 1 Hz) and fast (15-100 Hz) rhythms are spontaneously generated by the cortical network and propagate or synchonize populations across the cortex [2]. This is the case even in isolated pieces of the cortical network, or in vitro maintained cortical slices, where both slow [3] and fast oscillations [4] are also spontaneously generated. Interestingly, cortical slices lack any inputs from other brain areas, thus representing what the recurrency within the isolated cortical network can autonomously generate. The similarity between some of these patterns both in vivo and in vitro suggests that they are somehow a default activity from the cortical network. We understand that these emergent patterns provide information on the structure, dynamics and function of the underlying cortical network. In this talk I will discuss what we do know and what some of the challenges that we are facing in order to understand cortical dynamics. 1. Steriade, M., The corticothalamic system in sleep. Front Biosci, 2003. 8: p. d878-99. 2. Massimini, M., et al., The sleep slow oscillation as a traveling wave. J Neurosci., 2004. 24(31): p. 6862-6870. 3. Sanchez-Vives, M.V. and D.A. McCormick, Cellular and network mechanisms of rhythmic recurrent activity in neocortex. Nat Neurosci, 2000. 3(10): p. 1027-34. 4. Compte, A., et al., Spontaneous high-frequency (10-80 Hz) oscillations during up states in the cerebral cortex in vitro. J Neurosci, 2008. 28(51): p. 13828-44.

Speaker
F.J. Pérez-Reche

Description Statistical physics has traditionally dealt with complex physical systems and it is increasingly being recognised as a powerful framework to deal with biological systems. In this seminar, I will present examples in which an interdisciplinary research at the interfaces physics/epidemiology and physics/environment proves useful. One of the main questions in epidemiology regards the outbreak of epidemics, i.e. whether an infectious disease can spread throughout a given ensemble of hosts or not. Similar questions are addressed in ecology and sociology which deal with the spread of agents such as behaviour or opinion in populations of animals. The challenge lies in dealing with factors such as heterogeneity, stochasticity, and behavioural trends associated with both the spreading agent and the population of hosts [1-5]. I will start with a survey of experimental results illustrating each of these factors at the host level and for small populations. I will then propose mathematical models inspired from statistical physics whose main aims are to (i) link the factors at the host level to the probability of invasion at the population level, (ii) devise control strategies for invasion, and (iii) predict invasion from the early stage of an epidemic. As an illustration of the interplay physics/environment, I will consider the environmental role played by the biological processes in soil. Understanding the factors that influence the soil microbial activity is important but highly challenging due to the opacity of soil and the difficulty of interfering with soil microorganisms in a controlled manner. We have recently proposed a framework that shows that the structural heterogeneity of the soil habitatmay have a very significant influence on the size of microbial invasions of the soil pore space [6]. Our approach uses a network representation of real soil samples (see figure) to build mathematical models for microbial spread.

Speaker
Marisela Vélez

Speaker
Anatoly B. Kolomeisky

Description Concentration profiles of signaling molecules, also known as morphogen gradients, play a critical role in the development of multi-cellular organisms by determining polarity and spatial patterning that leads to further tissue differentiation. Large advances in studying morphogen gradients have been achieved recently when the formation of signaling molecules profiles has been visualized with high temporal and spatial resolution. A widely used approach to explain the establishment of concentration gradients assumes that signaling molecules are produced locally, then spread via a free diffusion and degraded uniformly. However, recent experiments have produced controversial observations concerning the feasibility of this theoretical description. In addition, latest theoretical analysis of times to establish the morphogen gradient yield surprising linear scaling as a function of length, not expected for the systems with unbiased diffusion process. We propose here a theoretical approach that provides a possible microscopic explanation of these observations. It is argued that relaxation times are mostly determined by first-passage times and the degradation effectively accelerates diffusion of signaling particles by removing slow moving molecules. Our theoretical analysis indicates that spatial and temporal features of degradation efficiently control the establishment of signaling molecules profiles.