Master Thesis: Synchronization between populations of neurons

In order to execute cognitive functions the brain must bind features and information which occurs at different cortical areas. The most accepted hypothesis to underlie such integration of information is the binding by synchrony. Accordingly to it: two brain regions interact with each other whenever they have coherent activity. The mechanism of this phenomenon has been subject of controversial debate for many years: how can two distant dynamical elements synchronize at zero lag even in the presence of non-negligible delays in the transfer of information between them? So far, complex mechanisms and neural architectures have been proposed to answer this question. However, a simple and robust mechanism has been proposed recently. Zero-lag synchronization between two elements is achieved by relaying the dynamics via a third mediating element. The synchronization thus obtained is robust over a considerable parameter range. In this work we study the dynamical relay phenomenon in complex networks of chemically coupled neurons, specifically the capacity to provide the basis for the binding by synchrony process. We show that three identical neuronal populations satisfy the minimum conditions to produce lag-free synchrony among delayed populations reciprocally connected to a central relay population. We also investigate the dynamical behavior of the thalamocortical circuit whose relay station role is played by the thalamus. We found that the thalamocortical circuit supports the dynamical relay mechanism. More importantly, we report the identification of a variable that might be responsible to control the on-off synchronization of the cortical populations depending only on the ratio of dorsal over ventral thalamus external activity. The simplicity of the key controlling element in the model also suggests that both bottom-up and top-down incoming stimulus to thalamic region share responsibilities in the cortical synchronization phenomenon, in contrast to previous hypothesis. This work supports the binding by synchrony theory and helps to establish solid bases for this phenomenon.