Verb production and comprehension in primary progressive aphasia

Studies of word class processing have found verb retrieval impairments in individuals with primary progressive aphasia (Bak et al., 2001; Cappa et al., 1998; Cotelli et al., 2006; Hillis, Heidler-Gary, et al., 2006; Hillis, Oh, & Ken, 2004; Marcotte et al., 2014; Rhee, Antiquena, & Grossman, 2001; Silveri & Ciccarelli, 2007; Thompson, Lukic, et al., 2012) associated primarily with the agrammatic variant. However, fewer studies have focused on verb comprehension, with inconsistent results. Because verbs are critical to both production and comprehension of clauses and sentences, we investigated verb processing across domains in agrammatic, logopenic, and semantic PPA and a group of age-matched healthy controls. Participants completed a confrontation naming task for verb production and an eye-tracking word-picture matching task for online verb comprehension. All PPA groups showed impaired verb production and comprehension relative to healthy controls. Most notably, the PPA-S group performed more poorly than the other two PPA variants in both domains. Overall, the results indicate that semantic deficits in the PPA-S extend beyond object knowledge to verbs as well, adding to our knowledge concerning the nature of the language deficits in the three variants of primary progressive aphasia.