Effects of Alzheimer's Disease on Reach-to-Pinch Performance with Multimodal Sensory Feedbacks

This study examined the effects of Alzheimer's Disease (AD) on reach-to-pinch performance with multimodal sensory feedbacks. The sensory modalities include visual and somatosensory feedbacks. Ten patients were selected in the experiment [5 male and 5 female, age: 65.9±9.41 yr (mean ±SE)]. They were instructed to complete the following two tests: (1) reach-to-pinch with and without a mirror; (2) reach-to-pinch an equipped instrument with and without a mirror. A motion capture system was used to record the kinematic signals of the hand. A pinch apparatus was designed to measure fingertip forces at each digit-object interface using two transducers. Results showed that in the first test, the patients with AD showed maximal wrist speed at (3.099 ± 0.923 mm/s) without visual feedback, which were significantly lower than those with visual feedback (3.902±0.844 mm/s). The trajectories of the patients were far less stable and the accuracy reduced. Results showed that in the second test that there was a 12% increase in the load forces occurrence time (tLF) when lifting an object without visual feedback. In the presence of visual feedback, the pinch forces changed more rapidly, etc. These results showed that grasping movements are typically performed toward visually sensed objects. The patients appeared progressive aggravating activities and slow movements in the grasping process. We uses a noninvasive quantitative kinematic method to observe the changes of hand function in patients with Alzheimer's Disease, which is of great significance for early diagnosis of Alzheimer's disease and evaluation of rehabilitation efficacy.