Skip to main content
. 2011 Jul 26;5:11. doi: 10.3389/fninf.2011.00011

Figure 3.

Figure 3

General Network enables rapid parameter switching for simulating diverse network types. (A) A sample feed-forward network is implemented in GenNet to illustrate the capability of the software to quickly and easily change fundamental properties. The sample network contains two cells with noisy drive coupled either by feed-forward excitation (left) or feed-forward inhibition (right). Cell 1 is made to fire tonically triggering post-synaptic currents in Cell 2. (B) When excitatory coupling is used, the spikes of Cell 2 (middle panel) closely track those of Cell 1 (top panel). The excitatory synaptic currents (bottom panel) are sufficient to elicit a spike in Cell 2 each time a Cell 1 spikes. The synaptic current also illustrates the voltage dependence of synaptic transmission. When a post-synaptic spike raises the voltage of Cell 2 past the reversal potential of the synapse, the sign of the synaptic current changes. Vertical gray dashed lines indicate the timing of spikes in Cell 1. Horizontal gray dashed line indicates −50 mV. (C) The same network can be run with the synapse switched to be inhibitory. In this case, post-synaptic spiking in Cell 2 is irregular and does not track pre-synaptic spiking (middle panel). The effect of pre-synaptic spikes (top panel) on the post-synaptic voltage can be observed as small, hyperpolarizing deflections in the voltage. Spiking in Cell 2 occurs when the natural evolution of the voltage overcomes the periodic inhibition from Cell 1. As a result, firing in Cell 2 is slower than when inputs were excitatory. (D) Spike time histograms (plotted as Cell 2 spike times relative to the phase of Cell 1) show the distribution of spikes in Cell 2 depending on the coupling type used. Excitation causes Cell 2 to become entrained to Cell 1 (top panel) and Cell 2 spike occur in a small time window only. Inhibition causes spiking in Cell 2 to be biased to occur in the second half of the Cell 1 period when inhibition has had sufficient time to wear off (bottom panel) but overall spikes are spread over a wider time window than when excitation was used.