The organization of memory. A parallel distributed processing perspective.

Parallel distributed processing (PDP) provides a contemporary framework for thinking about the nature and organization of perception, memory, language, and thought. In this talk I describe the overall framework briefly and discuss its implications of procedural, semantic, and episodic memory. According to the PDP approach, the processing of information takes place through the interaction of a large number of simple processing units organized into modules. Storage occurs through the modification of connection weights based on the system's response to its input, that provides an opportunity for incremental storage. I will describe how connection modification may give rise through the course of experience to procedural learning and to the formation of semantic memories, structured by their semantic content. I will argue that the discovery of semantic structure requires gradual learning, with repeated exposure to representative samples of the structure to be learned. I will then describe two neuropsychological implications of the PDP approach. First, I will consider the possible modular organization of semantic information in the brain. Then, I will examine the role of the hippocampus in learning and memory. In the first case, we will see how the PDP approach leads us to see how brain damage might produce apparent dissociations between categories, when in fact the underlying organization is not by category but by modality. In the second case, we will see that the PDP approach gives us a new way to understand why it is important that unique, arbitrary associations not be stored all at once in the same memory's systems used for semantic information.(ABSTRACT TRUNCATED AT 250 WORDS)