LEXICAL-SEMANTIC DEFICITS IN 2 PATIENTS WITH DOMINANT THALAMIC INFARCTION

Two patients with dominant thalamic infarction, one in the tuberothala mic artery territory, the other in the paramedian artery territory, de monstrated language impairment limited to word retrieval difficulties in spontaneous language and structured naming tasks. Using a cognitive neuropsychological model of lexical processing developed in the study of patients with cortical lesions, we carried out a detailed investig ation of their lexical abilities. Both patients demonstrated impairmen t restricted to oral and written picture naming and oral naming to def inition, and spared performance on tasks of lexical comprehension, ora l word reading, and writing to dictation, as well as syntactic compreh ension and production. Naming impairment disproportionately affected l ower frequency words, and word substitutions often corresponded to obj ects that were semantically-related to target words. We propose that o ur patients' word retrieval impairments reflect a failure of thalamic input to effectively engage the cortical networks subserving lexical-s emantic processing, leading to degraded levels of activation as the se mantic system interfaces with subsequent stages of lexical processing. Copyright (C) 1996 Elsevier Science Ltd.