To elucidate the earliest changes of language function in patients with dementia of Alzheimer's type (DAT), performance on the various semantic language tasks were compared between patients with amnestic mild cognitive impairment (aMCI) (n=20), mild DAT (n=20) and normal cognition elderly individuals (NC, n=20).

Language tasks included levels of word, sentence and discourse. In the word level, confrontation naming test (Korean version-Boston Naming Test, K-BNT) and the verbal fluency (semantic and phonemic fluency) tasks were used. In the sentence level, the verbal definition tasks including 24 nouns four categories were used. In the discourse level, the Boston Cookie-Theft picture description task was used. The picture description task was analyzed for both productive aspect (total number of sentences, total number of phrases and phrases per sentence) and semantic aspect (ratio of CIU: Correct Information Unit).

The results from this study are as follow: 1) In the confrontation naming test, mild DAT group showing worse performances than the NC and aMCI group. However, no differences were observed between the NC and aMCI group. 2) The performances of verbal fluency task showed significantly differences between the all groups. 3) In the verbal definition task, performances of NC group showing better performances than aMCI and mild DAT group. However, no differences were observed between the aMCI and mild DAT group. 4) In the picture description task, performances of the aMCI and mild DAT group were non-informative and inefficient in semantic aspect compared to the NC group. However, no differences were observed between the three groups on productive aspect.

These results demonstrated that the deficit of semantic language is readily identified in the aMCI stage, and it can be revealed by tasks of sentence and discourse level.