Comprehension of Syntactically Complex Sentences in Broca's Aphasia: Evidence From the Northwestern Assessment of Verbs and Sentences in Italian

Broca’s aphasia entails difficulty in understanding syntactically complex sentences, e.g., passive (P), object-cleft (OC), object-relative (OR) sentences as compared to their counterparts, i.e., active (A), subject-cleft (SC), and subject-relative (SR) sentences. One of the theories proposed to account for this deficit, the Trace-Deletion Hypothesis (TDH, Grodzinski, 2000), assumes an underlying difficulty in computing syntactic dependencies and the concomitant use of a “guessing strategy” that randomly assigns the role of Agent to the participants in the sentence. Seven patients with Broca’s aphasia were tested on the sentence comprehension test (SCT) of the Italian version of the Northwestern Assessment of Verbs and Sentences (NAVS, Cho-Reyes & Thompson, 2012). Syntactically complex sentences were significantly more impaired than their counterparts (P>A: p = .046; OC>SC: p < .001; OR>SR: p = .0015) at a group level. However, the analysis of single profiles reveals significant dissociation in accuracy patterns among P versus OC and OR sentences in two participants (PMA and LB), suggesting different underlying computational processes. In both participants, accuracy on P sentences in one case (PMA: 0%) and on OC and OR sentences in the other case (LB: 10%) is in contrast with the TDH-based predictions of “at chance” performance on sentences entailing syntactic movement.