Analysis of abnormal posture in patients with Parkinson's disease using a computational model considering muscle tones

Yuichiro Omura; Hiroki Togo; Kohei Kaminishi; Tetsuya Hasegawa; Ryosuke Chiba; Arito Yozu; Kaoru Takakusaki; Mitsunari Abe; Yuji Takahashi; Takashi Hanakawa; Jun Ota

doi:10.3389/fncom.2023.1218707

Analysis of abnormal posture in patients with Parkinson's disease using a computational model considering muscle tones

Front Comput Neurosci. 2023 Oct 5:17:1218707. doi: 10.3389/fncom.2023.1218707. eCollection 2023.

Authors

Yuichiro Omura¹, Hiroki Togo^{2

3}, Kohei Kaminishi⁴, Tetsuya Hasegawa¹, Ryosuke Chiba⁵, Arito Yozu¹, Kaoru Takakusaki⁵, Mitsunari Abe³, Yuji Takahashi⁶, Takashi Hanakawa^{2

3}, Jun Ota⁴

Affiliations

¹ Department of Precision Engineering, School of Engineering, The University of Tokyo, Tokyo, Japan.
² Department of Integrated Neuroanatomy and Neuroimaging, Kyoto University Graduate School of Medicine and Faculty of Medicine, Kyoto, Japan.
³ Department of Advanced Neuroimaging, Integrative Brain Imaging Center, National Center of Neurology and Psychiatry, Tokyo, Japan.
⁴ Research into Artifacts, Center for Engineering, School of Engineering, The University of Tokyo, Tokyo, Japan.
⁵ Division on Neuroscience, Department of Physiology, Asahikawa Medical University, Asahikawa, Japan.
⁶ Department of Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan.

Abstract

Patients with Parkinson's disease (PD) exhibit distinct abnormal postures, including neck-down, stooped postures, and Pisa syndrome, collectively termed "abnormal posture" henceforth. In the previous study, when assuming an upright stance, patients with PD exhibit heightened instability in contrast to healthy individuals with disturbance, implying that abnormal postures serve as compensatory mechanisms to mitigate sway during static standing. However, limited studies have explored the relationship between abnormal posture and sway in the context of static standing. Increased muscle tone (i.e., constant muscle activity against the gravity) has been proposed as an underlying reason for abnormal postures. Therefore, this study aimed to investigate the following hypothesis: abnormal posture with increased muscle tone leads to a smaller sway compared with that in other postures, including normal upright standing, under the sway minimization criterion. To investigate the hypothesis, we assessed the sway in multiple postures, which is determined by joint angles, including cases with bended hip joints. Our approach involved conducting forward dynamics simulations using a computational model comprising a musculoskeletal model and a neural controller model. The neural controller model proposed integrates two types of control mechanisms: feedforward control (representing muscle tone as a vector) and feedback control using proprioceptive and vestibular sensory information. An optimization was performed to determine the posture of the musculoskeletal model and the accompanied parameters of the neural controller model for each of the given muscle tone vector to minimize sway. The optimized postures to minimize sway for the optimal muscle tone vector of patients with PD were compared to the actual postures observed in these patients. The results revealed that on average, the joint-angle differences between these postures was <4°, which was less than one-tenth of the typical joint range of motion. These results suggest that patients with PD exhibit less sway in the abnormal posture than in other postures. Thus, adopting an abnormal posture with increased muscle tone can potentially serve as a valid strategy for minimizing sway in patients with PD.

Keywords: Parkinson's disease; abnormal posture; computational model; musculoskeletal model; neural controller model.

Grants and funding

This work was partially supported by JSPS KAKENHI, Grant-in-Aid for Scientific Research on Innovative Areas Hyper-adaptability for overcoming body-brain dysfunction: Integrated empirical and system theoretical approaches (Grant Numbers 19H05722 and 19H05730), Grant-in-Aid for JSPS Fellows (Grant Number 23KJ0522), and the Mohammed bin Salman Center for Future Science and Technology for Saudi–Japan Vision 2030 at The University of Tokyo (MbSC2030).