Strategies and Structures in Verbal Fluency Tasks in Patients with Alzheimer’s Disease

J Kessler,M Bley,R Mielke,E Kalbe

doi:10.1155/1997/695154

Abstract

Reduced word production in verbal fluency tasks is a sensitive indicator for brain damage. Patients with Alzheimer’s disease (AD) are supposedly more affected in semantic than in letter fluency, which is probably resulting from partially destroyed structure of semantic knowledge, whereas in letter fluency tasks the patients can use phonemic cues for searching. In this study, 21 patients with probable AD according to NINCDS-ADRDA criteria were examined on a verbal fluency task with F, A, S as initial letters, and a supermarket task. Performances were compared with a control group. Patients with AD showed lower word rate in all tasks than the control group. The difference was most significant in the supermarket task. Both groups produced most of the words in the supermarket task, followed by S, A and F. They both showed a percentuallikely distribution pattern of items into different supermarket categories. The items of the supermarket task were mostly ranged in clusters (patients with AD 70%, control group 83%). Patients with AD, however, on average, used fewer categories which they also filled with fewer items. In the F, A, S test, patients with AD mainly produced nouns, whereas the control group named nearly twice as many adjectives and verbs. In patients with AD word generation was highly correlated with degree of dementia, free recall of a verbal memory task, and the Token test. Low word production and qualitatively changed output in patients with AD might relate to an inefficient searching strategy, attentional deficits and/or degraded semantic knowledge.

Highlights

In verbal fluency tasks subjects have to produce words under a restricted search condition
It has been argued that this finding results from impaired semantic memory, whereas in letter fluency tasks patients rather profit from orientation to phonemic cues
In the supermarket task 180 items were quoted, which corresponds to a mean rate of x= 8.57 (SD = 4.98)

Summary

INTRODUCTION

In verbal fluency tasks subjects have to produce words under a restricted search condition. They can be limited to semantic classes, such as animals, clothes, what can be bought in a supermarket, or to words beginning with F, A, S, for example. In most studies patients with AD have more severe deficits in semantic tasks than in letter fluency tasks. A 'type-taken-ratio' that indicates how many words were named more than once was obtained by dividing the types (number of different words produced) by total output. The total number of correct words was registered and all words were classified according to word class (nouns, verbs, adjectives/adverbs) In this task, phonological clusters (two or more consecutive responses with the same second phoneme) were counted The type-token-ratio was obtained as described above and the frequency of each type was counted, too

RESULTS

DISCUSSION

CONCLUSION