Semantic interference during object naming in agrammatic and logopenic primary progressive aphasia (PPA)

► A semantic interference paradigm examined the time course of naming in PPA. ► Semantic interference at SOA = 0, −100, and −500 ms was seen in PPAs and controls. ► Only PPA participants evinced abnormal SI at −1000 ms. ► A greater magnitude of SI was found for PPAs compared to controls across all SOAs. ► Atrophy in left perisylvian cortex was found for PPAs with abnormal SI effects.