Alzheimer's disease (AD) is a progressive disorder marked by widespread cortical degeneration, accompanied by a corresponding degeneration of cognitive abilities. It is therefore quite interesting, on both neurological and psycholinguistic grounds, that the dissolution of language is neither global nor diffuse (e.g. semantic processing appears to erode before grammar). We propose an investigation of grammatical abilities in AD, focussed on the difference between those aspects of grammar that do show signs of softening early in the disease (i.e. comprehension, metalinguistic judgments, use of he grammar in large discourse frames) compared with aspects that are relatively resistant to cortical degeneration (i.e. production across short discourse units, receptive tasks that reflect the automatic and unconscious effects of grammatical and semantic structure). This distinction between """"""""automatic"""""""" and """"""""controlled"""""""" processing has implications for theories of neurological organization, in both aphasia and dementia. We will also focus on the bilateral nature of AD, using language tasks that discriminate between patients with left- and right-hemisphere lesions (including measures of discourse and formulaic speech that are characteristic indicators of RH damage). AD patients should show the predicted progression from controlled to automatic processing within both hemispheres, displaying features of both left and right focal syndromes. Results for AD patients will be compared with a large existing base of data with other populations, using the same measures: fluent and non-fluent aphasics, RH patients, age-matched controls, as well as developmental data from normal and brain-damaged children.
