cqvip:Impaired word retrieval is a main symptom of primary progressive aphasia (PPA) . The cognitive features of this impairment in PPA are poorly understood. We stu died 12 patients with PPA(6 English-speaking and 6 Dutch-speak- ing), 7 patients with early-stage clinically probable Alzheimer’s disease (P RAD), 5 patients with mild cognitive impairment (MCI), and 15 age matched,cognit ively intact, control subjects. Subjects had to name a picture (the probe), whic h was preceded by a written word (the prime) that could be the correct name of t he picture,a noun belonging to the same semantic subcategory (related prime), a semantically unrelated noun (unrelated prime), or a pseudoword (neutral control) . Naming latencies were longer in PPA and PRAD patients than in control subjects . Critically, the interaction between group and prime type was highly significan t. PPA patients named the probe more slowly after a related compared with an unr elated prime. In contrast, PRAD patients,mild cognitive impairment patients, and healthy control subjects tended to name the probe faster when it was preceded b y a related prime. The semantic interference effect in PPA generalized across la nguages and PPA subtypes. Selection among competing word forms sharing a same se mantic field is abnormal in PPA. The semantic interference effect constitutes ap ositive distinguishing feature between PPA and PRAD.
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