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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.
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 belongs 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 significant. PPA patients named the probe more slowly after a related compared with an unr elated prime. mild cognit ive impairment patients, and healthy control subjects tended to name the probe faster when it was preceded bya 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.