Topology: Building Nets
  - We're treating biological networks as a graph. 
 
  - The nodes are the neurons, and the arcs are the synapses. 
 
  - We have already created a lot of neurons (nodes) of predefined
    types.  We have also already created a lot of synapses (arcs)
    of predefined types.
 
  - There are a lot of ways to use predefined mechanisms for
    connecting neurons, like all-to-all and one-to-all.
    However, they can all be built with list connectors, which we
    have been using.
 
  - If you want to do this right, you're going to have to write a bit
      of python; loops are particularly useful.
 
  - Make 100 nodes of "input neurons and 5 spike generators.
    (You can pick the neuron type including _IF_cond_exp.)
    Make the spike generators for (respectively) at 10,20,30,40 and 50 ms.
 
  - Hook it up (using list connectors) so that the every 5th neuron is
      associated with every 5th generator, and make them all spike.
 
  - Just modify your spike generator to add 1 more.  Hook it up so every
      third neuron gets input from that and makes an extra spike.
 
  - Now, hook up the first 5 neurons so they all stimulate each
      other. 
 
  - Can you get them to fire persistently.
 
  - Take the second five and connect them to the third five and see if
      you can have the first five fire the second (an extra time).
 
  - Can you get the neurons to fire (from just one spike source input)
      for between 500 and 1000 ms?