לוח שנה משולב

Local brain circuits are believed to exhibit diverse connectivity patterns. It is not yet clear to what extent these patterns are hard-wired genetically, or whether they arise during development under the influence of local plasticity mechanisms. In this talk I will address how spike-timing dependent plasticity (STDP) may affect the global structure of a neural circuit. We recently developed a theoretical framework that allows to address the consequences of STDP in recurrent neural circuits of arbitrary connectivity. I will show that in addition to the local influence of STDP on the synapses that connect pairs of neurons reciprocally, STDP induces non-local interactions between synapses of different neurons. These "high-order" interactions, which were neglected in previous studies, can have a pivotal influence on the global structure of a neural network in steady state. As an example, I will consider in the talk the spontaneous formation of two simple structures: wide synfire chains, in which groups of neurons project to each other sequentially, and self connected assemblies - both of which are important models for generation of structured neural dynamics. I will show that with appropriate choice of the biophysical parameters, these ordered structures can emerge autonomously under the influence of STDP and heterosynaptic competition, without exposing the neural network to any structured external inputs during learning. If time permits, I will also present briefly another recent work, concerned with the coding of an animal's position by grid cells in the entorhinal cortex.