Simple stimulus patterns, in this case visual, are represented by spatiotemporal Boolean functions that can be summarized in a 4 $\times $ 4 look-up table of 16 templates behind each sensory neuron. These groups of templates correspond to groups of neurons in columns behind each receptor. They abstract specific combinations of input in simple combinations and include two successive states in time. A template is like a neuron field at threshold, and responds as the field is convolved with the stimulus pattern. The same structure can be repeated in successive layers to make progressive categorization and to reject inappropriate combinations. At any level, the templates act in groups, so providing a very large number of combinations that can represent more complex stimulus patterns at deeper levels.