Sensorimotor Control of Reach-to-Pinch Kinematics in Individuals with Alzheimer's Disease

Abstract

Alzheimer's disease (AD) is a chronic neurodegenerative disease that could reduce the sensory and motor function. This study aimed to investigate the effects of AD on sensorimotor control of hand kinematics during a reach-to-pinch a target. Eight patients with AD and eight healthy volunteers participated in the experiment. Retro-reflective markers were attached to the fingertips of the thumb and index finger, hand and wrist. The kinematic data were recorded using a 3D motion capture system during reach to pinch a custom designed instrument with and without visual guidance. The mean error of contact position in the x direction showed that the mean error increased in AD compared with the controls (AD = 52.2 mm; HC = 12.7 mm, p < 0.05). The AD patients also demonstrated increased variability of the distances between the contact points and the target without visual guidance (AD = 25.9 mm; HC = 11.2 mm, p < 0.05). However, for the movement duration, there was no significant difference between the AD and the controls. These results revealed that the AD affects the capacity of sensorimotor control of reach-to-pinch kinematics by decreasing the pinch accuracy but increasing the pinch variability. This finding could be applied in clinical diagnosis and evaluation of AD.