The organization and neural basis of long-term memory and knowledge: Background

This broad programme of research aims to eludicate the cognitive and neural organisation of human long-term memory, in particular episodic and semantic memory. Episodic memory refers to memory for personally experienced and temporally specific events or episodes. Semantic memory, by contrast, refers to our permanent store of representational knowledge including facts, concepts, as well as words and their meaning (see Figures 2 & 3).

Figure 2

Figure 3

The organisation of these two components of long-term memory, and the relationship between them is a topic of considerable debate. For example, initially, episodic and semantic memory were thought to represent cognitively and neurally separate systems (Tulving, 1972), but findings from amnesic patients, such as the famous HM (Scoville and Milner, 1957), challenged this assumption. First, the impairment in episodic memory seen in amnesia was not complete: some patients were found to be able to retrieve memories from the remote past (e.g., childhood or early adulthood) despite their inability to recall recent events (see Figure 4). Second, amnesic patients were found to be unable to acquire both episodic and semantic memories after damage to medial temporal lobe regions (see Figure 5).

Figure 4

Figure 5

These findings imply that a simple fractionation between episodic and semantic memory is oversimplistic, and our research is aimed at obtaining a more complete understanding of how episodic and semantic memory are organised in the brain, and the nature of the interactions between these memory systems and other cognitive processes (e.g., language and vision).

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