The visual pathway is composed of 0(109) neurons each interacting with 0(104) other neurons, involving time scales ranging from sub milliseconds to many seconds. Direct simulation of enumerated neurons is neither practical nor desirable. Instead the development of probabilistic mathematical models for this system will be presented. This results in a class of 'populational models' which will be analyzed under a variety of mathematical frameworks. Analytical and computational results will be presented, and compared with experiments.