Neural Networks B, SS06 1

UA Dr. Robert Legenstein, WiMAus Prashant Joshi, M.S.

Institute for Theoretical Computer Science
Technische Universität Graz
A-8010 Graz, Austria
{legi, joshi}@igi.tugraz.at



NACHNAME Vorname Matrikelnmr Teammitglieder
       
       
       



Synchrony of two I&F Neurons

NOTE: You can download this exercise in pdf or postscript(ps) format here.

The questions 1 to 5 are for 10 points in total. Question 6 is a bonus question for 3 points.

The action potentials of two coupled I&F neurons may synchronize. In this exercise, you will examine the circumstances under which two coupled I&F neurons synchronise.

The Matlab program http://www.igi.tugraz.at/lehre/NNB/SS06/aufgaben/sync.m simulates two I&F neuons which are mutually coupled by two synapses. It plots the temporal evolution of the membrane potential, the spikes and the PSCs. You need to unzip the file http://www.igi.tugraz.at/lehre/NNB/SS05/aufgaben/csim.zip into the same directory as sync.m to make sync.m work. (it contains csim.dll for Windows and csim.mexglx for Linux).

1)
Do a simulation with the standard parameters. Describe / explain the result. At which rates2 do the neurons fire?

2)
Do a simultaion with I1=I2=18. I1 resp. I2 are external currents $ I_1$, $ I_2$ which are injected into the neurons. Describe the results. Why do the neurons not synchronize?

3)
Do a simultaion with I1=I2=18, w = 30 resp. w=10. Describe the results. Describe the mechanism that leads to synchronization.

4)
Do a simultaion with w=30, Tsim=5.0, I1=18 and I2=18.5 respectively I2=22. Tsim defines the duration of the simulation. Describe / explain the results.

5)
Make some diagrams (think about well suited diagrams) which show quantitatively how the quality and speed of synchrony depends on which parameters. Describe / explain your approach and the results.

6*)
Examine how the results change if you add noise to the model (set the parameter Inoise $ > 0$). Describe / explain the results.

Notes

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Neural Networks B, SS06 1

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Footnotes

... SS061
Class Website: http://www.igi.tugraz.at/lehre/NNB/SS06/
... rates2
The vectors st1 and st2 contain all firing times of neuons 1 and 2.
... PSCs3
The PSCs are available in the vectors psc1 and psc2.


Joshi Prashant 2006-05-02