A Comprehensive Evaluation of the Process of Copying a Complex Figure in Early- and Late-Onset Alzheimer Disease: A Quantitative Analysis of Digital Pen Data (Preprint)

Abstract

BACKGROUND The Rey-Osterrieth Complex Figure Test (RCFT) is a neuropsychological test that is widely used to assess visual memory and visuoconstructional deficits in patients with cognitive impairment, including Alzheimer disease (AD). Patients with AD have an increased tendency for exhibiting extraordinary behaviors in the RCFT for selecting the drawing area, organizing the figure, and deciding the order of images, among other activities. However, the conventional scoring system based on pen and paper has a limited ability to reflect these detailed behaviors. OBJECTIVE This study aims to establish a scoring system that addresses not only the spatial arrangement of the finished drawing but also the drawing process of patients with AD by using digital pen data. METHODS A digital pen and tablet were used to copy complex figures. The stroke patterns and kinetics of normal controls (NCs) and patients with early-onset AD (EOAD) and late-onset AD (LOAD) were analyzed by comparing the pen tip trajectory, spatial arrangement, and similarity of the finished drawings. RESULTS Patients with AD copied the figure in a more fragmented way with a longer pause than NCs (EOAD: <i>P</i>=.045; LOAD: <i>P</i>=.01). Patients with AD showed an increased tendency to draw the figures closer toward the target image in comparison with the NCs (EOAD: <i>P</i>=.005; LOAD: <i>P</i>=.01) Patients with AD showed the lower accuracy than NCs (EOAD: <i>P</i>=.004; LOAD: <i>P</i>=.002). Patients with EOAD and LOAD showed similar but slightly different drawing behaviors, especially in space use and in the initial stage of drawing. CONCLUSIONS The digitalized complex figure test evaluated copying performance quantitatively and further elucidated the patients’ ongoing process during copying. We believe that this novel approach can be used as a digital biomarker of AD. In addition, the repeatability of the test will delineate the process of executive functions and constructional organization abilities with disease progression.

Eye-Tracking Metrics for Figure-Copying Processes in Early- vs. Late-Onset Alzheimer's Disease

“…In this study, we used eye-tracking glasses to assess eye-tracking metrics in patients with EOAD, patients with LOAD, and NC participants while they copied the simplified RCFT, which was created and validated in our previous study ( 39 ). We constructed perceptual and working AOIs to investigate the different stages of copying, and then, we compared the number and duration of fixations and saccades, and number of switches across the two AOIs, between the two patient groups with AD and the NC participants.…”

“…In previous research, we modified the original RCFT into a simpler version and validated our simplified RCFT against the original RCFT ( 39 ). Our simplified RCFT comprises 4 global (large rectangle and diagonal, horizontal, and vertical crosses) and 4 local (a square, double circles, three triangles, and four arrows) components ( Figure 1A ).…”

“… Drawing from the simplified RCFT and an illustration of eye-tracking metrics. (A) Modified figure from previous publication ( 39 ). The simplified RCFT was shown on a tablet computer (size = 12 in, resolution = 2,160 x 1,440, Samsung Galaxy Book 12, Samsung Electronics, Suwon, Korea) with a screen width of 162 mm and a screen height of 258 mm.…”

“…The pen the participants used was a digital pen for pen trajectory data acquisition. The digital pen data from a subset of the individuals who participated in this study were previously published elsewhere ( 39 ).…”