Thin arrows represent a connection from one unit to another.
Fat arrows which go from a layer to a unit indicate that each unit of the layer is connected to the target unit. Similarly a fat arrow from a unit to a layer means that the source unit is connected to each of the units in the target layer. The two big arrows in the middle represent the full connection between comparison and recognition layer and the one between delay and comparison layer, respectively. The topology of ART1 networks in SNNS has been chosen to to perform most of the ART1 algorithm within the network itself. This means that the mathematics is realized in the activation and output functions of the units.