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Roles played by depressing synapses in neural circuits


Joanna Jędrzejewska-Szmek (University of Warsaw Faculty of Physics), Jarosław Żygierewicz (University of Warsaw Faculty of Physics)

Synapses exhibiting short-term synaptic depression can be found in different locations in neural circuits [1], e.g. pyramid-pyramid and interneuron-pyramid connections. Based on these findings, two Wilson-Cowan type models with depressing synapses were constructed, following formalism presented in [2]. First one comprised a depressing positive feedback, the second one comprised a depressing negative feedback (synapse is between the inhibitory and excitatory population). The models' parameters were provided
 by [1,3]. Both models generated oscillatory signals as predicted by [2,3].

In case of both models a regime exists with high frequency oscillations (higher than 80 Hz) and high amplitude of oscillations corresponding to 'high-gamma' characteristics [4]. The model with depressing positive feedback showed three regimes: 1) oscillations in the theta band almost independent of external input of the excitatory population, 2) high-frequency oscillations with an envelope frequency in the theta band. In the third regime we observed oscillations in theta and 'high-gamma band'. An increase of the external input can abruptly change the oscillation frequency from the theta band to 'high-gamma'. Excitatory population firing rate is shown in the Figure below. One can see, that generated activity is similar to the theta/gamma oscillations [5] linked to short-term memory [5,6].

Short-term synaptic depression plays important role in generation of not only slow
oscillations activity [3] and theta waves, but also higher frequency phenomena such as 'high-gamma'. It
might also serve as a basis for coupling between the high- and low-frequency bands of
ongoing electrical activity in the human brain [5,6,7].

[1] Bannister AP, Thomson AM. Cerebral Cortex 2007
[2] Tsodyks MV, Pawelzik K, Markram H. Neural Computation 1998
[3] Melamed O, Barak O, Silberberg G, Markram H, Tsodyks M. Journal of Computational Neuroscience 2008
[4] Ray S, Maunsell JHR. PloS Biology 2011
[5] Lisman J. Hippocampus 2005
[6] Lisman J, Idiart MA. Science 1995
[7] Canolty RT, Edwards E, Dalal SS, Soltani M, Nagarajan SS, Kirsch HE, Berger MS, Barbaro NM, Knight RT. Science 2006
Roles played by depressing synapses in neural circuits
Oscillations in the gamma band with modulation frequency in the theta band generated by the Wilson-Cowan type model with depressing synapse in the negative feedback loop (connections from inhibitory to excitatory population).
Preferred presentation format: Poster
Topic: Computational neuroscience