Objective: 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. Method: 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. Results: 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. Conclusions: 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.
