| L. L. Gollo1, J. Iglesias2, A. Villa2 and C. Mirasso1 1- Instituto de Física Interdisciplinar y Sistemas Complejos (IFISC, CSIC-UIB), Campus Universitat des Illes Balears, E-07122 Palma de Mallorca, Spain 2- Grenoble Institut des Neurosciences-GIN, Centre de Recherche Inserm U 836-UJF-CEA-CHU, NeuroHeuristic Research Group, University Joseph Fourier, Grenoble, France In order to execute cognitive functions the brain must bind features and information which occurs at different cortical areas. One of the most accepted hypotheses to underlie such integration of information is the binding by synchrony. However it is still unclear the brain structures that are involved in the process and how does the synchrony control takes place despite the non-negligible delays between the cortical areas. Recently, a simple motif composed by two populations of neurons bidirectionally coupled through a third one acting as a relay (in a chain configuration), has been shown to yield a robust zero, or almost zero, phase synchronization between the dynamics of the outer populations*. It was also suggested in that paper that the thalamus could act as the relay population. In this work we study the dynamics and synchronization properties of a thalamocortical circuit. Inhibitory neurons of the reticular (RT) and perigeniculate (PGN) nuclei are assumed to make strong inhibitory connections with excitatory thalamocortical neurons. Thalamocortical cells, which are important for the relay of sensory information from the periphery to the cerebral cortex, are assumed to send excitatory projection to the cortical areas. The different areas are connected with a certain delay, which is longer than the internal time scale of the neurons. We find that in the biologically plausible regime cortical lag-free oscillations can be obtained throw thalamic relay despite of the transmission delays among distant regions. More importantly, we show a control mechanism to turn on and off the synchrony mechanism depending only on the external input activity innervated into dorsal and ventral thalamus neuronal populations. Correspondingly, it 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 report contributes to the establishment of solid bases for the binding by synchrony theory. *Dynamical relaying can yield zero time lag neuronal synchrony despite long conduction delays, R. Vicente, L. L. Gollo, C. R. Mirasso, I. Fischer and G. Pipa, Proceedings of the National Academy of Sciences USA 105, 17157 (2008). |
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