Determining the impact of autobiographical experience on "meaning": New insights from investigating sports-related vocabulary and knowledge in two cases with semantic dementia

Snowden, Griffiths, and Neary (1994, 1995) have proposed that autobiographical experience helps to maintain the integrity of semantic memory in patients with semantic dementia. We investigated this hypothesis by testing knowledge related to golf and bowls in two case studies. If Snowden and colleagues' hypothesis is correct, our two patients should have better semantic knowledge for the sport that they regularly experience, compared with knowledge of other sports. In keeping with Snowden et al's hypothesis, we found that autobiographical experience influenced the ability of the patients to match up a surname with a first name: The names of personally and currently relevant golf/bowls partners were more likely to be matched correctly than such personally relevant names from the past, or the names of famous sports celebrities. Unlike Snowden et al., however, we found that knowledge of people, in all categories, was severely impoverished and that any semantic information was produced as part of an autobiographical memory. Likewise, detailed study of each patient's understanding of their favourite sport revealed no significant effect of autobiographical experience on true semantic knowledge. We propose that the ability of semantic dementia patients to encode, albeit temporarily, recent autobiographical memories via a spared hippocampal complex supports the production of highly autobiographically constrained semantic-like facts and, to a lesser extent, frequently encountered names. There is, however, no direct effect of autobiographical experience on previously established semantic memory, i.e. knowledge of golf, bowls, and people, presumably stored within the temporal neocortex. These results are discussed with respect to current anatomically based computational models of long-term memory.