SEMANTIC-EPISODIC MEMORY INTERACTIONS IN SEMANTIC DEMENTIA - IMPLICATIONS FOR RETROGRADE MEMORY FUNCTION

Semantic dementia refers to a multi-modal loss of semantic knowledge, resulting from degeneration of the anterior temporal neocortex. Loss o f information is not absolute. We have previously demonstrated (Snowde n, Griffiths, & Neary, 1994, 1995) that autobiographical experience ha s an important role in influencing information preservation, and have argued that patients' preserved experiential memory helps to invest wo rds and objects with meaning that would otherwise be lost. Those studi es suggested a particularly critical role of current autobiographical experience. The present study aimed to explore the generality of the o bserved current information superiority in an investigation of patient s' knowledge of celebrities, understanding of a contemporary and obsol ete monetary system, and autobiographical memory. Performance was supe rior for contemporary (recent) than for past (remote) information, bot h factual and autobiographic, suggesting an inverse of the temporally graded pattern of retrograde memory found in classical amnesia. It is argued that the findings are consistent with explanations of the ''tem poral gradient'' effect of retrograde amnesia in terms of qualitative differences in recent and remote memories. The findings indicate a bid irectional interaction between autobiographic and semantic memorising, and emphasise a continuous, dynamic interrelationship rather than a t ime-limited role. An important distinction is highlighted between auto biographical and impersonal episodic memory. The findings have signifi cant theoretical implications both for the understanding of retrograde memory function and the interrelationship between episodic and semant ic memory.