نوع مقاله: مقاله کامل پژوهشی

نویسندگان

1 دانشجوی دکتری مهندسی پزشکی، گروه بیومکانیک، دانشکده‌ی مهندسی پزشکی، دانشگاه صنعتی امیرکبیر، تهران، ایران

2 استاد، گروه بیوالکتریک، دانشکده‌ی مهندسی پزشکی، دانشگاه صنعتی امیرکبیر، تهران، ایران

3 دانشیار، گروه بیومکانیک، دانشکده‌ی مهندسی پزشکی، دانشگاه صنعتی امیرکبیر، تهران، ایران

چکیده

در سال‌های اخیر، تحلیل سیستم پایداری وضعی انسان، اهمیت زیادی پیدا کرده است. شناخت این سیستم به دلیل فرایند پیچیده‌ی خودسازماندهی آن که متناسب با هر الگوی حرکتی فعال می‌شود، ضروری است. استخراج شاخص‌هایی موثر از این سیستم می تواند در تشخیص ناهنجاری‌های وضعی به پزشکان کمک کرده و در فرایند توان‌بخشی بیماران موثر باشد. سیگنال‌ مرکز فشار، به عنوان یک متغیر تجمعی، حاوی اطلاعاتی از سیستم تعادلی انسان است. نحوه‌ی شکل‌‌گیری ترژکتوری این سیگنال در بازه‌های زمانی مختلف، بیان‌گر فعال شدن فرایندهای کنترلی متنوع است که با ظهور بستر جاذب‌های متفاوت در فضای فاز آن بروز می‌یابد. الگوی هماهنگی دینامیک پایداری سیستم، تعیین کننده‌ی چگونگی سوییچ بین این جاذب‌ها می‌باشد. در بخش اول این مقاله، به منظور کمی‌سازی اطلاعات محلی سیگنال مرکز فشار، دو شاخص "بعد همبستگی محلی" و "دینامیک هماهنگی فاز" تعریف می‌شوند. سپس در یک آزمایش طراحی شده، الگوی تغییر رفتار محلی این سیگنال بر مبنای شاخص‌های پیشنهادی محاسبه می‌شود. در ادامه، با طراحی مدلی که توانایی تولید دینامیک‌های غنی با جاذب‌های چندگانه را دارد، سعی می‌شود که تغییر رفتارها در دادگان دنبال شود. این مدل پیشنهادی بر مبنای نگاشت بوده و پارامترهای آن به کمک شاخص هماهنگی دینامیک فاز، به گونه‌ای هدایت می‌شوند که الگوی تغییر  جاذب‌ها در این مدل با الگوی تغییر بعد همبستگی محلی سیستم هماهنگ شود. دنبال نمودن الگوهای رفتاری سیستم پایداری وضعی از نتایج برجسته‌ی این پژوهش است. مدل پیشنهادی نه تنها قابلیت دنبال کردن رفتار متنوع محلی سیستم را دارد، بلکه دینامیک سراسری آن را نیز دنبال می‌کند. طبق نتایج به دست آمده، تشابه روند کاهشی-افزایشی مقدار بعد همبستگی خروجی مدل و دادگان در تکرارهای آزمایش، یک بازنمایی از الگوی تغییرات درجه‌های آزادی دینامیک این سیستم است.  این مدل پیشنهادی، نخستین مدل رفتاری برای سیستم پایداری وضعی به شمار آمده که می‌توان از روش‌های پیشنهادی در آن برای کمی‌سازی روند تغییر اطلاعات در سایر سیستم‌های زیستی نیز بهره گرفت.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

A New Multi-Attractor Model of Human Posture Stability to Follow Self-Organized Dynamics

نویسندگان [English]

  • Mehdi Yousefi Azar Khanian 1
  • Seyed Mohammad Reza Hashemi Golpayegani 2
  • Mostafa Rostami 3

1 Ph.D. Student, Biomechanic Department, Biomedical Engineering Faculty, Amirkabir University of Technology, Tehran, Iran

2 Professor, Bioelectric Department, Biomedical Engineering Faculty, Amirkabir University of Technology, Tehran, Iran

3 Associate Professor, Biomechanic Department, Biomedical Engineering Faculty, Amirkabir University of Technology, Tehran, Iran

چکیده [English]

Recently, analysis of the human postural stability has gained increasing interest. This is mainly due to the necessity of understanding the self-organization mechanisms in this system activated in response to any motion pattern. The extraction of effective indicators from this system could help clinicians to diagnose patients’ postural disorders and guide the rehabilitation processes. The center of pressure (CoP) signal, as a collective variable, contains information from the human equilibrium system. Through the CoP trajectory production, various control mechanisms are activated at different time intervals, which is equivalent with emerging different basin of attractors in the phase space. The dynamical coordination of this system patterns determines how system switches between these attractors. In this paper, first to quantify the local information of CoP, two indicators are defined; "local correlation dimension (LCD)" and "phase dynamic coordination (PDC)". Then, for a designed experiment, the local behavior pattern of CoP time series is calculated based on the suggested indicators. Next, by designing a model that can generate rich dynamics with multiple attractors, we attempt to follow data behavioral changes. The proposed model is map based. The model parameters are tuned by PCD to follow the pattern of sub-attractors changes with the system LCD. Tracking the behavioral patterns of the posture system is one of the prominent results of this research. The proposed model not only can follow the local behavior of system, but also follows the global dynamics. Accordingly, the similarity of the decreasing-increasing trend of the correlation dimension variations for the model output and data demonstrates the variations of system’s degrees of freedom in the test trials. The proposed model is the first behavioral model for the posture system, which can be used to quantify the variation of information in other biological systems based on the proposed methods.

کلیدواژه‌ها [English]

  • postural stability system
  • multistability
  • Correlation Dimension
  • basin of attractor
  • self-organization

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