Brain and Mind Institute Seminar

19.03.09 Thursday, 14h15, AAB032

Moritz Helias
Bernstein Center for Computational Neuroscience (BCCN), Albert-Ludwig University Freiburg, Germany
http://www.bccn.uni-freiburg.de/People/members/helias

Structural plasticity controlled by calcium based correlation detection

Abstract:

The connectivity structure of cortical networks was recently found to exhibit plastic changes even in adult animals [1]: There is a constant considerable synapse turnover. It is still unclear, how networks can maintain their functionality despite this plasticity and what are the mechanisms to ensure network stability. Prior to addressing these questions, a model of synapse creation and synapse death has to be developed. The theory of Hebbian learning assumes the correlation of pre- and postsynaptic spiking activity to play a crucial role and synapse turnover was indeed found to be activity dependent [2]. Here we follow the idea of 'correlation based sorting' and present a postsynaptic selection rule for synapse elimination. Our model utilizes biologically realistic pathways and constitutes a robust mechanism of a correlation dependent pruning process. In recurrent networks it acts as a homeostasis mechanism that guarantees network stability in certain ranges of activity. In addition, cooperation and competition between synapses emerges directly from the microscopic model. This enables neurons to learn patterns of coactive inputs. In parallel to direct numerical simulations, we derive analytic results that allow to address the problem of structural plasticity in recurrent networks on a more abstract level.

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