Word Processing Is Faster than Picture Processing in Alzheimer’s Disease

Figure 5

Hypothesis of cognitive route of visual spellings and pictures in AD. AD = Alzheimer’s disease. We showed our hypothesis of the information processing for visual spelling and photos in AD patients. The dashed lines indicate the decreased processing function. In this figure, routes (1) to (3) show the dual-route cascaded model of visual word recognition and reading aloud. Word processing may be faster than nonsense syllables and pictures, because the excitatory connection in word processing from “orthographic input lexicon” may work normally. Nonsense syllables’ processing, in the case of 300 ms, may be slower than word processing, because “Grapheme-Phoneme Rule (GRS) System” may not have an excitatory connection from “Phoneme System.” When AD patients saw the multiple components of characters, they might process them as “meaningful” words (for example, in the case of “Ha-Mi-Sa (nonsense syllable)” as a correct answer, the participant misread it as “Ha-Sa-Mi (shears)”). In our hypothesis, since pictures contain the amount of visual information rather than words, AD patients need to take more time than healthy controls in the process of forming the morphological image by integrating them. During the short presentation time, the connection of the particular visual information and the semantic system in an incomplete processing may lead to the selection of the wrong answer in the naming task (for example, in the case of “shears” as a correct answer, the subject named it “knife” incorrectly).