Static Synapses

• In PyNN and Nest neural models include behaviour from the neurons.
• There are synapse models, but these are about plasticity, changing weights.
• One of the key issues is how the weight is transmitted.
• There are two main mechanisms, and exponential synapse and an alpha synapse.
• An exponential synapses starts out sending a large amount, which is reduced (exponentially) each subsequent step.
• An alpha synapse rapidly increases the amount it sends each step, but then it decays.
• These both model chemical synapses, and of course the actual time varies from synapse to synapse.
• Another major type of synapse is an electrical synapse, a gap junction.
• It typically takes 10s of ms for a chemical synapse to transfer all its weight. Electrical synapses are much faster.