One Declarative Memory System or Two? The Relationship Between Episodic and Semantic Memory in Children With Temporal Lobe Epilepsy

Objective: This study explored verbal semantic and episodic memory in children with unilateral temporal lobe epilepsy to determine whether they had impairments in both or only I aspect of memory. and to examine relations between performance in the 2 domains. Method: Sixty-six children and adolescents (37 with seizures of left temporal lobe onset. 29 with right-sided onset) were given 4 tasks assessing different aspect; of semantic memory (picture naming. fluency. knowledge of facts. knowledge of word meanings) and 2 episodic memory tasks (story recall, word list recall). Results: High rates of impairments were observed across tasks, and no differences were found related to the laterality of the seizures. Individual patient analyses showed that there was a double dissociation between the 2 aspects of memory in that some children were impaired on episodic hut not semantic memory, whereas others showed intact episodic hut impaired semantic memory. Conclusions: This double dissociation suggests that these 2 memory systems may develop independently in the context of temporal lobe pathology, perhaps related to differential effects of dysfunction in the lateral and mesial temporal lobe structures.