Abstract
The paper reports findings derived from three experiments examining syntactic and morphosyntactic processing in individuals with agrammatic and logopenic variants of primary progressive aphasia (PPA-G and PPA-L, respectively) and stroke-induced agrammatic and anomic aphasia (StrAg and StrAn, respectively). We examined comprehension and production of canonical and noncanonical sentence structures and production of tensed and nontensed verb forms using constrained tasks in experiments 1 and 2, using the Northwestern Assessment of Verbs and Sentences (NAVS [57]) and the Northwestern Assessment of Verb Inflection (NAVI, Thompson and Lee, experimental version) test batteries, respectively. Experiment 3 examined free narrative samples, focusing on syntactic and morphosyntactic measures, i.e. production of grammatical sentences, noun to verb ratio, open-class to closed-class word production ratio, and the production of correctly inflected verbs. Results indicate that the two agrammatic groups (i.e., PPA-G and StrAg) pattern alike on syntactic and morphosyntactic measures, showing more impaired noncanonical compared to canonical sentence comprehension and production and greater difficulties producing tensed compared to nontensed verb forms. Their spontaneous speech also contained significantly fewer grammatical sentences and correctly inflected verbs, and they produced a greater proportion of nouns compared to verbs, than healthy speakers. In contrast, PPA-L and StrAn individuals did not display these deficits, and performed significantly better than the agrammatic groups on these measures. The findings suggest that agrammatism, whether induced by degenerative disease or stroke, is associated with characteristic deficits in syntactic and morphosyntactic processing. We therefore recommend that linguistically sophisticated tests and narrative analysis procedures be used to systematically evaluate the linguistic ability of individuals with PPA, contributing to our understanding of the language impairments of different PPA variants.
Highlights
A large body of literature exists, which describes the linguistic deficits associated with different types of aphasia caused by stroke (StrAph)
Post-hoc analysis using the Mann-Whitney test revealed that the progressive aphasia (PPA)-L group performed significantly better than the PPA-G group in production of noncanonical sentences (Z = −2.19, p = 0.028)
As in Experiment 1, no differences were found between the two agrammatic groups
Summary
A large body of literature exists, which describes the linguistic deficits associated with different types of aphasia caused by stroke (StrAph). Many individuals with stroke-induced agrammatic aphasia (StrAg) of Broca’s type present a characteristic pattern of nonfluent speech, as well as grammatical, or (morpho)syntactic, deficits. The latter are exhibited by impaired comprehension and production of sentences with complex syntactic structures, in particular semantically reversible noncanonical sentences involving syntactic movement Individuals with the PPA-G variant present with nonfluent speech, verb production deficits, and difficulties with comprehension and production of syntactically complex sentences [13,32,34, 48,55,64,67]. The term progressive nonfluent aphasia (PNFA) used in the earlier literature has inconsistently included what is known as PPA-G and PPA-L patients without making a distinction between the two groups
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