Abstracts

RATIONALE: Object naming impairment is common among temporal lobe epilepsy (TLE) patients. The consensus opinion in the TLE literature states that this dysnomia represents a word retrieval problem, a deficit of access to an intact semantic system. However, some existing evidence suggests that TLE is associated with abnormal semantic storage (Milberg et al., 1980; Troster et al., 1995). In semantic dementia and Alzheimer's disease patients, the finding of a relation between object naming ability and depth of knowledge for naming test items contributed to the conclusion that these disorders cause a degradation of semantic storage (Hodges et al., 1996; Lambon Ralph et al., 1999). We sought to determine whether there exists a similar relation between "naming and knowing" in TLE patients. Such a finding would support the view that semantic knowledge is deficient at the group level in TLE. METHODS: After administration of the 60-item Boston Naming Test (BNT), controls (n = 23) and early and late onset TLE patients (n = 35) were asked to provide detailed definitions of six of the BNT object names. The definitions were scored quantitatively for intrusions, superordinate labels, and general and specific physical and associative information. RESULTS: The early onset TLE patients demonstrated significant impairment relative to the control and late onset TLE groups in BNT performance and in the ability to produce specific physical and associative defining information for the six selected BNT names. Moreover, the amount of specific information provided by the participants correlated significantly with their ability to name the six objects and with BNT total scores. CONCLUSIONS: Dysnomia in TLE is associated with limited semantic storage and is not merely a word form retrieval problem. Dysnomia in early onset TLE represents a developmental learning deficit, a failure of semantic learning early in life, rather than a degradation of knowledge over time. The results may have educational implications, and they extend our previous finding that object naming failures in this population frequently occur for words that are typically acquired later in childhood.