Verb deficits in Alzheimer’s disease and agrammatism: Implications for lexical organization

Abstract

This study examined the nature of verb deficits in 14 individuals with probable Alzheimer's Disease (PrAD) and nine with agrammatic aphasia. Production was tested, controlling both semantic and syntactic features of verbs, using noun and verb naming, sentence completion, and narrative tasks. Noun and verb comprehension and a grammaticality judgment task also were administered. Results showed that while both PrAD and agrammatic subjects showed impaired verb naming, the syntactic features of verbs (i.e., argument structure) influenced agrammatic, but not Alzheimer's disease patients' verb production ability. That is, agrammatic patients showed progressively greater difficulty with verbs associated with more arguments, as has been shown in previous studies (e.g., Kim & Thompson, 2000; Thompson, 2003; Thompson, Lange, Schneider, & Shapiro, 1997), and suggest a syntactic basis for verb production deficits in agrammatism. Conversely, the semantic complexity of verbs affected PrAD, but not agrammatic, patients' performance, suggesting "bottom-up" breakdown in their verb lexicon, paralleling that of nouns, resulting from the degradation or loss of semantic features of verbs.

Verb Production in Aphasia: Testing the Division of Labor between Syntax and Semantics

“…One currently known factor affecting the retrieval of verbs specifically is syntactic complexity (i.e., the number of the arguments that the verb takes), which has been shown to influence the success of verb production in agrammatic aphasic individuals. More syntactically-complex verbs have been shown to be more difficult across a variety of tasks for agrammatic aphasic individuals, including picture naming, categorization, and narrative speech production, with difficulty increasing with each additional argument (Thompson et al, 1999;Kim & Thompson, 2000;Kim & Thompson, 2004). Moreover, verbs that take more arguments have been shown to be more difficult even for neurologically healthy individuals to process (Shapiro, Gordon, Hack, & Killackey, 1993;Shapiro & Levine, 1990).…”

“…Similar to syntactic complexity, a few studies have examined the effects of the semantic complexity on the retrieval of verbs by English-speaking individuals with aphasia, comparing the use of verbs with different semantic "weights" Breedin, Saffran, & Schwartz, 1998;Kim & Thompson, 2004;Barde, Schwartz, & Boronat, 2006). Some individuals with aphasia have been shown to use more semantically general "light" verbs (e.g., have, make, do, go) in narrative language production, whereas others have demonstrated a preference for semantically specific "heavy" verbs.…”

Análise de itens lexicais do discurso oral do paciente com doença de Alzheimer

“…Além disso, a dificuldade de nomeação é associada a deficiências na recuperação lexical e dificuldade da representação semântica. Julga-se que isto decorre da desconexão dos circuitos envolvidos na memória semântica (Almor et al, 1999;Almor et al, 2003;Astell & Harley, 2002;Balthazar, 2008;Grossman, 2008;Kim & Thompson, 2004;Mansur, 1996).…”

“…Os pacientes produzem verbos e substantivos de forma inadequada e têm sido bastante relatada (Almor et al, 1999;Apostolova et al, 2008;Astell & Harley, 2002;Chiarelli et al, 2005;Gonnerman et al, 2003;Joubert at al., 2010;Kim et al, 2004;Masterson et al, 2005;Mätzig et al, 2009;Rico Duarte et al, 2009 (Mätzig et al, 2009). …”

“…Em todas as categorias de verbos e substantivos os pacientes moderados tiveram menor número de expressão desses itens. Além disso, em relação aos verbos, foi argumentado que a complexidade dessas classes gramaticais é afetada na doença e está associada à ruptura do léxico dos substantivos (Kim & Thompson, 2004), provavelmente isso indicaria o prejuízo nos verbos derivados dos substantivos. Ademais, há evidências de que os verbos são mais difíceis de serem acessados do que os substantivos pelas ações que expressam e suas localizações frontais no encéfalo (Grossmann, 2008).…”