Short term synaptic depression with stochastic vesicle dynamics imposes a frequency-dependent filter on information transfer
Sunday, Oct 14, 2012, 9:00 AM -10:00 AM
, J. RUBIN, *B. D. DOIRON;
Mathematcis, Univ. of Pittsburgh, Pittsburgh, PA
Synaptic responses are modulated by a form of short term depression arising from the depletion of neurotransmitter vesicles. A widely used model of synaptic depression accurately captures the trial-averaged synaptic response to a presynaptic spike train (1). However, the release and recovery of these vesicles is stochastic in nature, and this model fails to capture the variability of synaptic response introduced by stochasticity (2). We examine the impact of this variability on the filtering and information processing properties of synapses.
We derive compact mathematical expressions for the synaptic filter induced by short term depression when stochastic vesicle dynamics are taken into account and when they are not. We find that stochastic vesicle dynamics fundamentally alter the way in which a synapse filters rate-coded information. In particular, a model that ignores synaptic variability transmits slowly varying signals with the same fidelity as rapidly varying signals (3), but a model that takes this variability into account transmits rapidly varying signals with higher fidelity than more slowly varying signals (4). Differences between the models persist even when a presynaptic cell makes many contacts onto the postsynaptic cell. At the population level, we show that a slowly varying signal must be encoded by a large presynaptic population if it is to be reliably transmitted through depressing synapses, but more rapidly varying signals can be reliably encoded by smaller populations. Our results provide useful analytical tools for understanding the filtering properties of depressing synapses and have important consequences for neural coding.
1. Tsodyks MV, Markram H: The neural code between neocortical pyramidal neurons depends on neurotransmitter release probability. Proc Natl Acad Sci USA 1997, 94: 719-723.
2. de la Rocha J, Parga N: Short-term synaptic depression causes a non-monotonic response to correlated stimuli. J Neurosci 2005, 25: 8416-8431.
3. Lindner B, Gangloff D, Longtin A, Lewis JE: Broadband Coding with Dynamic Synapses. J Neurosci 2009, 29: 2076-2087.
4. Rosenbaum R, Rubin J, Doiron B: Short term synaptic depression imposes a frequency dependent filter on synaptic information transfer, PLoS Comput Biol, In Press, 2012.
[Authors]. [Abstract Title]. Program No. XXX.XX. 2012 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2012. Online.
2012 Copyright by the Society for Neuroscience all rights reserved. Permission to republish any abstract or part of any abstract in any form must be obtained in writing by SfN office prior to publication.
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