Matching synaptic type with postsynaptic firing class shapes the encoding of either stimulus rate or rate change
© Mohan et al; licensee BioMed Central Ltd. 2011
Published: 18 July 2011
The synergy between synaptic and postsynaptic firing dynamics in shaping neuronal encoding has not been explored. We show that by matching short-term synaptic dynamics with postsynaptic firing class, either stimulus rate or a rate change are encoded. The result may be relevant to understand the function of cortical microcircuits.
Short-term synaptic dynamics and firing dynamics of neurons can each be classified into two types. In short-term plasticity, type 1 synapses show release-dependent depression and constant rate of recovery. They appear to encode a stimulus rate change. Type 2 synapses show release-independent depression and faster recovery at higher stimulus frequencies. They can follow the stimulus rate . Postsynaptic firing characteristics conform either to class 1 or 2 on the basis of phase-reset curves (PRCs) . Class 1 neurons can fire at arbitrarily low frequencies and do not exhibit spike frequency adaptation. Class 2 neurons exhibit subthreshold oscillations and spike frequency adaption.
We investigate if different combinations of synaptic and postsynaptic dynamics can shape neuronal encoding.
Spiny stellate cells in the layer IV microcircuit preferentially receive inputs from type 1 synapses while star pyramidal neurons receive type 2 inputs . Even though the PRC for these cell types have not been characterized yet, our results pinpoint the possibility that in layer IV rate changes are encoded in the network of spiny stellate and stimulus rate in that of star pyramidal cells.
Mark D. McDonnell is supported by the Australian Research Council (grant DP1093425).
- Fuhrmann G, Cowan A, Segev I, Tsodyks M, Stricker C: Multiple mechanisms govern the dynamics of depression at neocortical synapses of young rats. J Physiol. 2004, 557: 415-438. 10.1113/jphysiol.2003.058107.PubMed CentralView ArticlePubMedGoogle Scholar
- Ermentrout B: Type I membranes, phase resetting curves, and synchrony. Neural Comput. 1996, 8: 979-1001. 10.1162/neco.1918.104.22.1689.View ArticlePubMedGoogle Scholar
- Stiefel KM, Gutkin BS, Sejnowski TJ: The effects of cholinergic neuromodulation on neuronal phase-response curves of modeled cortical neurons. J Comput Neurosci. 2009, 26: 289-301. 10.1007/s10827-008-0111-9.PubMed CentralView ArticlePubMedGoogle Scholar
- Cowan AI, Stricker C: Functional connectivity in layer IV local excitatory circuits of rat somatosensory cortex. J Neurophysiol. 2004, 557: 415-438.Google Scholar
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