View source for Silicon neurons

== Implementing dendrites and synapses ==
Interconnecting silicon neurons is necessary for building network models. Where there are multiple neurons on a single chip, it may be desirable to place the interconnecting circuitry on the same chip. However, where there are multiple chips, some way of transmitting the spiking outputs between chips is necessary. One standard for this is the address-event representation (AER) (Boahen, 2000). 

Two questions arise: where on the neuron's dendrites should the synapse be placed (and what should the effect of the dendritic morphology on the synapse be), and how should the synapse be modelled?

Synapse location affects synaptic effect, both in terms of overall effect (Williams and Stuart, 2002), and interaction between post-synaptic potentials. Northmore et al. (1996) modeled this, resulting in near-linear summation for mode distant synapses, plus the possibility of local saturation for nearby synapses. 

How should the effect of a synapse be modelled? Chemical synapses change the depolarisation level post-synaptically because the  neurotransmitter released  at the presynaptic terminal binds to sites postsynaptically, resulting in the opening of some ion channels (and hence changes in conductance): ions then cross the membrane.  Westerman et al. (1997) used the selection of one of an array of conductances. Vogelstein et al. (2007) used an off-chip look-up table whose values determine a conductance which is determined from a number of release sites, a probability of release and a quantum size: this emulates a more detailed model of a synapse.