The main objective of biological-type neural nets is to develope a synthetic element for verifying hypotheses concerning biological systems.
Neurons and the interconnections synapses constitute the key elements for neural information processing. See this figure.
Most neurons possess tree-like structures called dendrites wich receive income signals from other neurons across junction called synapses. Some neurons communicate with only a few nerby ones, whereas others make contact with thousands.
There are three parts in a neuron:
A neuron collects signals at its synapses by summing all the excitatory and inhibitory influences acting on it. If the excitatory influences are dominant, then the neuron fires and sends this message to other neurons via the outgoing synapses. In this sense, the neuron function can be modeled as a simple threshold function f(.). As shown in the following figure the neuron fires if the combined signal strength exceeds a certain threshold, in the general case the neuron value is given by an activation function f(.).
Artificial Neural Networks