  Neural networks are dynamical systems that compute with their dynamics. One
example is the Hopfield model, forming an associative memory which stores
patterns as global attractors of the network dynamics. From studies of
dynamical networks it is well known that localized attractors also exist. Yet,
they have not been used in computing paradigms. Here we show that interacting
localized attractors in threshold networks can result in universal computation.
We develop a rewiring algorithm that builds universal Boolean gates in a
biologically inspired two-dimensional threshold network with randomly placed
and connected nodes using collision-based computing. We aim at demonstrating
the computational capabilities and the ability to control local limit cycle
attractors in such networks by creating simple Boolean gates by means of these
local activations. The gates use glider guns, i.e., localized activity that
periodically generates "gliders" of activity that propagate through space.
Several such gliders are made to collide, and the result of their interaction
is used as the output of a Boolean gate. We show that these gates can be used
to build a universal computer.
