Preserved meaning in the context of impaired naming in temporal lobe epilepsy.

Abstract

Word-finding difficulties are a common complaint among individuals with left (domain) temporal lobe epilepsy (TLE). We tested the hypothesis that these difficulties stem from a deficit in semantic processing. We tested and compared semantic processing in left and right TLE patients and healthy controls. To avoid the confound of word retrieval, we used two semantic tasks (semantic priming and picture-matching) that did not require spoken word production. In addition to accuracy, we recorded response time in an effort to achieve a sensitive assessment of semantic processing. Semantic priming was in all respects comparable between left TLE patients with documented word-finding difficulty and right TLE patients without word-finding difficulty. Likewise, performances were comparable between groups on picture matching, which demanded knowledge of detailed semantic features for decisions regarding subtle differences in semantic relatedness. Overall, these results, which demonstrate a relative preservation of semantic processing in left TLE, suggest that the probable cause of word-finding difficulty in this group relates to processes that follow semantic retrieval in word production, involving the retrieval of lexical/phonological information. In addition to clinical implications for remediation, these results refine our understanding of the neurocognitive organization of temporal mechanisms supporting spoken word production.