Dissociative semantic breakdown in Alzheimer's disease: Evidence from multiple category fluency test

Background

Category-specific semantic dissociation particularly in terms of biological and non-biological dichotomy has been described in Alzheimer's disease (AD). We re-examine above finding by performing multiple superordinate category verbal fluency test in AD patients.

Method

We analyze the baseline neuropsychological assessment performance of food and animal fluency test of AD patients from a tertiary hospital that collected prospectively over 5 years period and correlation was calculated by Kappa test. The analysis is stratified according to literacy level (primary: 0–6 years education and secondary: >6 years education) and disease severity (MMSE score: mild 19-24, moderate 13-18 and severe <13).

Result

A total of 296 AD patients were analyzed and only fair to moderate agreement between food and animal category fluency test was found especially in the mild AD cases (primary: kappa 0.42; secondary: kappa 0.40). Kappa agreement level increases when disease progress especially in the secondary education group. Food category, which is a more relevant semantic knowledge to Singapore population, is generally more affected. Higher educated subjects appeared to have less semantic dissociation effect when disease progress.

Conclusion

Despite less primed in daily life, biological category of semantic knowledge appears to be affected less during AD process in highly urbanized Singapore society. Brain appears to have special protective mechanism towards living things. However, education level seems have a modulation effect towards the biological protective mechanism.     

Abstracts of oral presentations,presented at the British Neuropsychological Society (BNS) spring meeting,April 2002, National Hospital,Queen Square,London, UK

Abstract

Visuo-spatial neglect can be conceptualized as a failure of right hemisphere global attentional systems to direct the visual processor of the left hemisphere uniformly across an array. Two patients have recently been reported who show a dissociation of preserved global visual form perception in the context of left neglect for constituent elements. We present the first longitudinal study of the phenomenon which confirms that this pattern of neglect is associated with extensive right hemisphere damage, is fairly stable over time and may persist up to one year post insult. The use of modified Navon figures suggests that task demands may be significant in the manifestation of neglect. Correlation with conventional diagnostic tests for neglect is poor, but results suggest a subgroup of Navon stimuli that may be particularly sensitive to clinical change.     

New classification of tauopathies

Tauopathies are a group of neurodegenerative diseases characterized by pathological intracellular deposits of the protein tau. Isoform composition, morphology and anatomical distribution of cellular tau-immunoreactivities are defining distinct tauopathies as molecular pathological disease entities. The clinical spectrum of tauopathies includes syndromes with primary motor symptoms and with primary cognitive dysfunction. The traditional syndrome-based classification is currently being complemented by a molecular-pathological classification. While the syndrome-based classification is helpful to select symptomatic therapies, and to generate clinical working hypotheses about underlying etiologies, the molecular-pathological classification is most important for the development and application of molecularly tailored disease-modifying therapies.