Time reference, morphology and prototypicality: tense production in stroke aphasia and semantic dementia in Greek.

The present study aims at investigating verb inflection in aphasia and semantic dementia. In particular, it addresses the contribution of time reference and morphological complexity. Moreover, it investigates whether the lexical properties of the verb, such as argument structure and lexical aspect interact with the production of tense. Ten individuals with (different types of) stroke aphasia and five individuals with semantic dementia and their respective control groups conducted a sentence completion task. Three tenses were tested: past perfective, past imperfective and present. All tenses had to be produced with three different verb classes, which differed with respect to syntactic and semantic properties: unergative, unaccusative and transitive verbs. The findings imply problems with marking aspect and an interaction between inflection and lexical aspect but no effect of morphological complexity or across the board difficulties with reference to the past in aphasia. Moreover, the results suggest problems with inflection in semantic dementia, an interaction between inflection and lexical aspect and a selective difficulty with imperfective tenses. The study contributes to a better understanding of inflection problems in aphasia and it provides evidence for inflection problems in semantic dementia.