Coupled oscillations induced by synaptic depression

[Walter Senn]

New paper available (to appear in Neural Computation):

 
PATTERN GENERATION BY TWO COUPLED TIME-DISCRETE NEURAL NETWORKS
                  WITH SYNAPTIC DEPRESSION

       W. Senn, Th. Wannier, J. Kleinle, H.-R. Luescher, 
               L. Mueller, J. Streit, K. Wyler


Spinal pattern generators are networks which produce rhythmic contractions
alternating between different groups of muscles involved e.g. in locomotion. 
These networks are generally thought to rely on pacemaker cells or well 
designed circuits consisting of inhibitory and excitatory neurons. Recent 
experiments in organotypic cultures of embryonic rat spinal cord, however, 
have shown that neuronal networks with random and purely excitatory 
connections may oscillate as well, even without pacemaker cells. The reason 
of these oscillations was identified to be a fast depression of the activated 
synapses. In this theoretical study, we explore the dynamical behavior emerging
by weakly coupling two random excitatory networks with synaptic depression. 
We discuss a time-discrete mean field model describing the average activity and 
the average synaptic depression of the two networks. As a mathematical tool we 
adapt the Average Phase Difference (APD) theory, originally developed for flows, 
to the present case of maps. Depending on the parameter values of the 
depression, one may predict whether the oscillations will be in-phase, 
anti-phase, quasiperiodic or phase-trapped. We put forward the hypothesis that 
pattern generators may rely on activity dependent tuning of the synaptic 
depression.


The manuscript (262 KB) can be downloaded from: 
http://iamwww.unibe.ch:80/~brainwww/publications/pub_walter.html