A REVERSAL OF THE TEMPORAL GRADIENT FOR FAMOUS PERSON KNOWLEDGE IN SEMANTIC DEMENTIA - IMPLICATIONS FOR THE NEURAL ORGANIZATION OF LONG-TERM-MEMORY

On tests of autobiographical memory, patients with semantic dementia d emonstrate significantly better retrieval of episodic events from the recent past compared with the distant past. This reversal of the Ribot effect has been attributed to the relative sparing of the hippocampal complex in the disorder. Current computational models of long-term me mory predict a similar time-dependent pattern of impairment on tests o f remote semantic memory. Five patients with semantic dementia were te sted on recognition (familiarity) and identification (knowledge) of fa mous names selected from four different time-periods: 1950's, 1980's, 1990-1993 (early 1990's) and 1994-1996 (current). As expected, it was found that one patient DM (who had focal left temporal lobe atrophy) s howed no significant impairment on recognition of famous names, but wa s significantly better at producing information about people who were currently famous compared to people famous in the other three time-per iods. The other four patients (who had bilateral temporal lobe damage) showed better recognition of famous names from the current time-perio d (and to a lesser extent the 1950's), yet were profoundly impaired on the identification component, producing very little information acros s all four time-periods. The results are discussed with respect to cur rent views of the neural organisation of person-specific and general s emantic memory. (C) 1998 Elsevier Science Ltd. All rights reserved.