Preservation of Person-Specific Semantic Knowledge in Semantic Dementia: Does Direct Personal Experience Have a Specific Role?

Julie A. Péron,Francis Eustache,Serge Belliard,Emmanuelle Leray,Pascale Piolino,Laetitia Bon,Isabelle Biseul,Béatrice Desgranges,Sandrine Le Moal-Boursiquot

doi:10.3389/fnhum.2015.00625

Abstract

Semantic dementia patients seem to have better knowledge of information linked to the self. More specifically, despite having severe semantic impairment, these patients show that they have more general information about the people they know personally by direct experience than they do about other individuals they know indirectly. However, the role of direct personal experience remains debated because of confounding factors such as frequency, recency of exposure, and affective relevance. We performed an exploratory study comparing the performance of five semantic dementia patients with that of 10 matched healthy controls on the recognition (familiarity judgment) and identification (biographic information recall) of personally familiar names vs. famous names. As expected, intergroup comparisons indicated a semantic breakdown in semantic dementia patients as compared with healthy controls. Moreover, unlike healthy controls, the semantic dementia patients recognized and identified personally familiar names better than they did famous names. This pattern of results suggests that direct personal experience indeed plays a specific role in the relative preservation of person-specific semantic meaning in semantic dementia. We discuss the role of direct personal experience on the preservation of semantic knowledge and the potential neurophysiological mechanisms underlying these processes.

Highlights

Semantic dementia, known as the temporal variant of frontotemporal dementia (Goulding et al, 1989; Snowden et al, 1989; Hodges et al, 1992; Hodges and Graham, 2001), is characterized by a progressive and selective disorder of semantic knowledge (Hodges et al, 1992)
Material Sixty names, divided into three categories, were used for each participant: (i) 20 personally familiar names, consisting of people the participant knew personally; (ii) 20 names involving no direct personal experience, consisting of famous people the participant had known before the onset of the illness; and (iii) 20 unknown names that were especially constructed for the experiment that served as distracters
Intra-Group Comparisons Analyses revealed a significant effect of experimental condition in the semantic dementia group: the personally familiar names were far better recognized as being familiar than the famous names were (Z = −1.75, p < 0.05)

Summary

Introduction

Known as the temporal variant of frontotemporal dementia (Goulding et al, 1989; Snowden et al, 1989; Hodges et al, 1992; Hodges and Graham, 2001), is characterized by a progressive and selective disorder of semantic knowledge (Hodges et al, 1992). Autobiographical relevance influences the arithmetic performance of semantic dementia patients (Julien et al, 2010); they are able to categorize images or words that are relevant to their own experience but are unable to perform formal categorization tasks as well (Snowden et al, 1995) They seem to recognize and identify their relatives more than they do other famous individuals who are not relevant to their autobiography (Snowden et al, 1994; Graham et al, 1997; Westmacott et al, 2001, 2004; Joubert et al, 2004). This phenomenon has been called ‘‘cognitive egocentrism’’ (Belliard et al, 2001) in reference to the behavioral egocentrism that characterizes behavioral changes in semantic dementia (Bozeat et al, 2000; Rankin et al, 2005; Lough et al, 2006)

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