Neural Nets and Theories of Memory
A number of models developed in work often called "neural-net" research may be of interest to physiologists working on the problem of memory. From this work comes a variety of ideas on how networks of neuron-like elements can be made to act as learning machines. Some of these may suggest ways in which memory may be stored in nervous systems. It is important, perhaps, to recognize that these models were not founded at all on physiological ideas; they really stem from psychological and introspective notions. They all involve some form of alteration of synaptic transmission properties contingent on the pre- and post-synaptic activity during and after the relevant behavior. This notion is suggested not so much by actual observation of synapses as by the introspective simile of wearing down a path -- the "ingraining" of a frequently-traveled route. Below we shall argue that this idea is useful and suggestive, but not sufficient. These models can be made to account for learning connections between stimuli and responses on a low level, but do not seem to account for higher, symbolic behavior. We will argue that the latter suggests a return to the search for localization of memory, a topic that has been unpopular for many years.