Volume 12 Supplement 1
The influence of stationary synaptic activity on the PRC
© Garcia et al; licensee BioMed Central Ltd. 2011
Published: 18 July 2011
A useful measurable property of a neural oscillator is its Phase Response Curve (PRC). PRCs measure the phase-shift resulting from perturbing the oscillator with a brief stimulus at different times of the cycle. They have been extensively used to understand the synchronous activity patterns emerging from a network of weakly coupled oscillators.
PRCs have been classified into two types: type I (PRC is always positive) and type II (PRC has positive and negative regions) . Theoretical results  have shown that the type of PRC combined with the temporal dynamics of the synapses yield different synchronization properties when two neurons are coupled together (neurons can synchronize in-phase, out of phase or in anti-phase).
PRCs are typically measured in vitro, considering only the intrinsic properties of the neuron. However, in vivo neurons constantly receive background synaptic inputs that play an important role sculpting the dynamics of neurons. Indeed experimental data showed that membrane excitability  can change in response to variations in background synaptic activity .
In this work we study the effects of the background synaptic activity on the shape of the Phase Response Curve, and its synchronization properties. To perform this study, we consider two neuron models: the Wang-Buzsáki model  and the Morris-Lecar model . We explore the effect of a constant excitatory and inhibitory synaptic conductance input (that can be seen as an average of the background input) on the type of membrane excitability and PRC shape in the spiking regime.
We found that changes in the mean background conductances in a biologically plausible range  lead to changes in the type of PRC. As we increased the inhibitory conductance, for a constant value of the excitatory one, we observed a switch from type I to type II PRC. We correlated the shape of the PRC with the synchronization properties. We studied the effect of the temporal dynamics of synaptic activation on the synchronization properties of a coupled pair of neurons, as we switched them from type I to type II PRC. We characterized how solutions change with these parameters in a network motif of two reciprocally coupled neurons.
- Ermentrout GB: Type I membranes, Phase Resetting Curves, and Synchrony. Neural Computation. 1996, 8 (5): 979-1001. 10.1162/neco.19126.96.36.1999.View ArticlePubMedGoogle Scholar
- Vreeswijk C, Abbott LF, Ermentrout GB: When inhibition not excitation synchronizes neural firing. Journal of Computational Neuroscience. 1994, 1 (4): 313-321. 10.1007/BF00961879.View ArticlePubMedGoogle Scholar
- Rinzel J, Ermentrout GB: Analysis of Neural Excitability and Oscillations. Methods in neuronal modeling: from ions to networks. Edited by: Koch C and Segev I. 1998, Cambridge: MIT Press, 2Google Scholar
- Prescott SA, Ratte S, De Koninck Y, Sejnowski TJ: Pyramidal Neurons Switch from Integrators In Vivo to Resonators Under in Vivo-Like Conditions. J. Neurophysiology. 2008, 100 (6): 3030-3042. 10.1152/jn.90634.2008.View ArticlePubMedGoogle Scholar
- Wang XJ, Buzsáki G: Gamma Oscillation by Synaptic Inhibition in Hippocampal Interneuronal Network Model. The journal of Neuroscience. 1996, 16 (20): 6402-6413.PubMedGoogle Scholar
- Morris C, Lecar H: Voltage Oscillations in the Barnacle Giant Muscle Fiber. Biophysical Journal. 1981, 35 (1): 193-213. 10.1016/S0006-3495(81)84782-0.PubMed CentralView ArticlePubMedGoogle Scholar
- Destexhe A, Rudolph M, Fellous JM, Sejnowski TJ: Fluctuating synaptic conductances recreate in vivo-like activity in neocortical neurons. Neuroscience. 2001, 107 (1): 13-24. 10.1016/S0306-4522(01)00344-X.PubMed CentralView ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.