Principal component analysis of language performances in Alzheimer's disease

Phonological processing in Chinese word repetition: Dementia effect and age effect

This paper examined phonological processing as reflected in Mandarin word and non-word repetition. Issues related to dementia effects, age effects, and linguistic variables are discussed. Forty-five speakers of Mandarin Chinese in Taiwan took part in this study. Fourteen seniors with Alzheimer's disease (AD), 14 healthy adults, and 17 healthy seniors individually completed a task of word repetition. Scores of accurate repetition were calculated, and error types as well as error frequency were analysed. Linguistic variables, including lexicality, frequency, non-word, and syllable length, were discussed. Major findings were indicative of a significant dementia effect, in which participants with AD were significantly impaired in repeating words with more syllables, specifically 5-syllable non-words of low frequency. Numerous significant age effects were noted. Theoretical implications and directions for future study are discussed.

An Overview of ICA/BSS-Based Application to Alzheimer's Brain Signal Processing

Alzheimer's disease (AD) is by far the most common cause of dementia associated with aging. Early and accurate diagnosis of AD and ability to track progression of the disease is increasingly important as potential disease-modifying therapies move through clinical trials. With the advent of biomedical techniques, such as computerized tomography (CT), electroencephalography (EEG), magnetoencephalography (MEG), positron emission tomography (PET), magnetic resonance imaging (MRI), and functional magnetic resonance imaging (fMRI), large amounts of data from Alzheimer's patients have been acquired and processed from which AD-related information or "signals" can be assessed for AD diagnosis. It remains unknown how best to mine complex information from these brain signals to aid in early diagnosis of AD. An increasingly popular technique for processing brain signals is independent component analysis or blind source separation (ICA/BSS) that separates blindly observed signals into original signals that are as independent as possible. This overview focuses on ICA/BSS-based applications to AD brain signal processing.

Reading ability mediates the relationship between education and executive function tasks

Neuropsychological test results are affected by multiple factors, but usually age and education are the only variables by which norms are stratified. Some authors have questioned whether these variables alone are sufficient (e.g., Marcopulos et al., 1997; Manly et al., 2002), since such norms have lead to problems, such as poor specificity for African Americans on dementia screening devices (Fillenbaum et al., 1990). Recent research has shown that reading ability, a measure of educational quality, attenuated racial differences in test performance (Manly et al., 2002). We specifically examined whether reading ability would account for a greater amount of variance than education in executive function tests in a population traditionally subject to poor educational quality. Results determined that reading ability accounted for a significantly greater amount of variance than years of education for Letter-Number Sequencing, Similarities, COWA, Trail Making Test, and Coloured Progressive Matrices. Reading ability was found to significantly mediate the relationship between each of these tests and education. Animal naming appears to be least affected by educational quality or quantity. These findings hold implications for the interpretation of neuropsychological test results, especially in those exposed to substandard educational quality, and for the way that test norms are constructed.

Sentence repetition and processing resources in Alzheimer's disease

Sentence processing in Alzheimer's disease (AD) has been found to be influenced by several grammatical and extragrammatical factors, including phrase structure and verb-argument relations, number of propositions/verbs, and processing resource capacity. This study examines the effects of these variables on sentence production in AD. Normal control and AD subjects were asked to repeat six types of sentences varying along the above dimensions of complexity. Subjects' processing resource capacity was measured using several verbal working memory tests. AD subjects' sentence-repetition performance was impaired compared to the normal control group. Significant effects were observed for branching direction of phrase structure, canonicity of verb-argument relations, and serial position of errors. Sentence-repetition performance significantly correlated with working memory scores. The findings are interpreted within a resource capacity theory of sentence processing.