Ordered Retinotectal Projections and Brain Organization

The analogy of brain to computer has been sporadically popular. This chapter pursues instead the analogy between brain function and cooperative effects. As an example, the cooperative theory for the establishment of topologically ordered fiber projections is discussed, according to which fibers growing from the retina to the optic tectum retain or recover the geometric relations that they had in the retina by sensing signals transmitted via the optic axons to the tectal cells. By comparison between a retinal cell’s signal and that which it senses in tectal cells it contacts, its synapses are either reinforced (eventually to become permanent) or extinguished (in which case the retinal cell’s projection withdraws from that tectal cell). This proposal has been tested by extensive computer simulations, which correctly describe normal and experimentally perturbed development in many different situations by means of a single algorithm and one set of parameter values.