  P. polycephalum may be considered as a spatially represented parallel
unconventional computing substrate, but how can this `computer' be programmed?
In this paper we examine and catalogue individual low-level mechanisms which
may be used to induce network formation and adaptation in a multi-agent model
of P. polycephalum. These mechanisms include those intrinsic to the model
(particle sensor angle, rotation angle, and scaling parameters) and those
mediated by the environment (stimulus loca- tion, distance, angle,
concentration, engulfment and consumption of nutrients, and the presence of
simulated light irradiation, repellents and obstacles). The mechanisms in- duce
a concurrent integration of chemoattractant and chemorepellent gradients
diffusing within the 2D lattice upon which the agent population resides,
stimulating growth, move- ment, morphological adaptation and network
minimisation. Chemoattractant gradients, and their modulation by the engulfment
and consumption of nutrients by the model population, represent an efficient
outsourcing of spatial computation. The mechanisms may prove useful in
understanding the search strategies and adaptation of distributed organisms
within their environment, in understanding the minimal requirements for com-
plex adaptive behaviours, and in developing methods of spatially programming
parallel unconventional computers and robotic devices.
