Abstract
Human memory is considered to consist of several separate but interacting systems. The multiple-system views of memory have attempted to organize various dichotomous classifications, such as episodic/semantic, declarative/procedural, and implicit/explicit, into more comprehensive classificatory schemes. Yet the structure of long-term memory remains a matter of controversy. In this paper three issues are discussed. First, it is still open to debate whether episodic and semantic memory represent two separate systems or the same system operating under different circumstances. Second, recent research has revealed the hierarchical structure of autobiographical knowledge base, and at least three layers of knowledge have been identified. Finally, amnesic patients have been found to be capable of learning new semantic information, suggesting that semantic knowledge can be acquired without functioning episodic memory system.
