High capacity associative memories and connection constraints

High capacity associative neural networks can be built from networks of perceptrons, trained using simple perceptron training. Such networks perform much better than those trained using the standard Hopfield one shot Hebbian learning. An experimental investigation into how such networks perform when the connection weights are not free to take any value is reported. The three restrictions investigated are: a symmetry constraint, a sign constraint and a dilution constraint. The selection of these constraints is motivated by both engineering and biological considerations.