p061fig02.08 The existence of forward and backward associations, such as from A to B and from B to A is naturally explained by a network of neurons with their own activities or STM traces, and bidirectional connections between them with their own adaptive weights or LTM traces.<BR>||  How these results led to neural networks (Grossberg 1957). Networks can learn forward and backward associations!  Practice A->B also learn B<-A.  Because learning AB is not the same as learning BA, you need STM traces, or activations, xp at the nodes, or cells, and LTM traces, or adaptive weights, zg, for learning at the synapses.