Semantic knowledge was investigated in patients diagnosed with Dementia of the Alzheimer's Type (DAT) by means of an off-line probe question battery and an on-line measurement of semantic priming in a lexical decision task (LDT) that varied the stimulus onset asynchrony (SOA). The patients' performance on the detailed probe questions showed that their semantic deficit was confined primarily to animate concepts, characterized by visual descriptive features. In the primed LDT, demented patients demonstrated increased semantic priming compared to age-matched controls. A trend was also found indicating that for both normal controls and DAT subjects the priming magnitude decreased as the SOA increased. These results are interpreted in terms of a distributed representation of semantic knowledge that is impaired in demented patients.

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Alzheimer's disease, the most common form of dementia, is estimated to occur in up to sixteen percent of people between the ages of 75 and 84. Deficits in linguistic skills that effect communication are a hallmark of the disease and have been the primary focus of past Alzheimer's research. Among other deficits, researchers have found that people with Alzheimer's often use indexical expressions without clear referents and convey less information that is relevant to the task they have been asked to perform than healthy subjects. Relatively little research has examined how Alzheimer's subjects use their linguistic knowledge to communicate with others in natural, open-ended interaction. The purpose of the present study was to identify what communication skills remain intact that enable an Alzheimer's subject to maintain conversational fluency despite lexical and pragmatic deficits. The study focused specifically on language skills that play a functional role in facilitating conversation. The data used in this study consisted of eight naturally occurring conversations between the subject and three interlocutors who had a close relationship with the subject. The interactions were recorded in the Alzheimer's wing of the subject's nursing home. The transcribed conversations were analyzed according to three types of functional language drawn from Nattinger and DeCarrico's (1992) work on lexical phrases: (1) conversational maintenance; (2) conversational purpose; and (3) familiar topics. The role played by lexical phrases in facilitating each of these functional categories was also examined. This study found that the subject had an intact knowledge of functional language skills that allowed her to successfully participate in conversation despite serious language deficits. Within the category of conversational maintenance, the subject retained skills necessary to share control in opening and closing conversations as well as nominating and shifting topics and requesting and offering clarification. In the category of conversational purpose, the subject used functional language to signal utterances intended to convey general politeness, gratitude and compliments as well as informing the interlocutor of her attitude in relation to the content of utterances. The study also found that lexical phrases played a central role in facilitating the subject's use of functional language.

Use of time-compressed speech stimuli has been found to be clinically effective in differential diagnosis of lesions of the temporal lobe. However, notably absent from the literature is information concerning performance of adults on time-compressed closed-set speech discrimination tasks. The goal of this study mas to compare performance of 12 males and 12 females between age 50 and age 70 on a time-compressed closed-set speech discrimination test against the performance of 12 males and 12 females between age 10 and age 28 on the same task. The Word Intelligibility by Picture Identification test (WPI) was presented in both non-compressed and time-compressed conditions to all subjects. Previous research suggests that a difference in performance between age groups and between males and females in the older age group should be expected. Average results indicated negligible differences between age or gender groups under any of the conditions tested. Additionally, the test yielded perfect or near perfect scores for all subjects in the non-compressed condition. Lack of differentiation of results suggests that the Word Intelligibility by Picture Identification CUIPI) may be insensitive to the discrimination disorders expected in older adults, that the subjects included in the study were atypical of older adults in general and therefore such discrimination disorders did not exist in the sample, or that the subjects in the study uiere able to apply some type of compensatory strategies which resulted in the unexpected performance.