Patients with mild Alzheimer's disease produced shorter outgoing saccades when reading sentences

Abstract

In the present work we analyzed forward saccades of thirty five elderly subjects (Controls) and of thirty five mild Alzheimer's disease (AD) during reading regular and high-predictable sentences. While they read, their eye movements were recorded. The pattern of forward saccade amplitudes as a function of word predictability was clearly longer in Controls. Our results suggest that Controls might use stored information of words for enhancing their reading performance. Further, cloze predictability increased outgoing saccades amplitudes, as this increase stronger in high-predictable sentences. Quite the contrary, patients with mild AD evidenced reduced forward saccades even at early stages of the disease. This reduction might reveal impairments in brain areas such as those corresponding to working memory, memory retrieval, and semantic memory functions that are already present at early stages of AD. Our findings might be relevant for expanding the options for the early detection and monitoring of in the early stages of AD. Furthermore, eye movements during reading could provide a new tool for measuring a drug's impact on patient's behavior.

Keywords: Alzheimer’s disease; Cloze predictability; Eye movements; Outgoing saccade amplitude; Reading.