  Using picture description speech for dementia detection has been studied for
30 years. Despite the long history, previous models focus on identifying the
differences in speech patterns between healthy subjects and patients with
dementia but do not utilize the picture information directly. In this paper, we
propose the first dementia detection models that take both the picture and the
description texts as inputs and incorporate knowledge from large pre-trained
image-text alignment models. We observe the difference between dementia and
healthy samples in terms of the text's relevance to the picture and the focused
area of the picture. We thus consider such a difference could be used to
enhance dementia detection accuracy. Specifically, we use the text's relevance
to the picture to rank and filter the sentences of the samples. We also
identified focused areas of the picture as topics and categorized the sentences
according to the focused areas. We propose three advanced models that
pre-processed the samples based on their relevance to the picture, sub-image,
and focused areas. The evaluation results show that our advanced models, with
knowledge of the picture and large image-text alignment models, achieve
state-of-the-art performance with the best detection accuracy at 83.44%, which
is higher than the text-only baseline model at 79.91%. Lastly, we visualize the
sample and picture results to explain the advantages of our models.
