SCALING ANALYSIS OF PARKINSONIAN TREMOR

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。帕金森氏病患者表现出特征性的震颤，表现为傅立叶频谱，在谐波频率处有宽峰。这种频域内的谐波结构可能是由两类机制引起的：一种是非线性振荡过程，另一种是多个独立振荡模式的叠加。宽峰频谱通常表示信号是具有可变周期的半周期信号。这些“嘈杂的”波动可能具有内在的顺序，可以用标度分析来量化。我们开发了一种方法来提取多峰振荡周期动力学中的相关(标度)性质，以区分非线性振荡和单个振荡模式的叠加。该方法是基于我们的发现，即单个振子起伏周期中的时间相关性的信息量包含在功率谱的有限频带内，允许通过带通滤波来分解模式。我们对非线性振动的模拟表明，每个“谐”模都具有相同的标度性质。相比之下，当该方法应用于帕金森氏病患者的震颤记录时，前两种振荡模式产生不同的比例模式，这表明这些模式可能不是最初假设的简单谐波。在后续工作中，我们正在开发另一种方法，通过分析不同模式之间的同步性，来研究颤振频谱中多个峰值的来源。这些方法和结果对帕金森震颤的生理学建模和鉴别诊断以及对其他生理学时间序列的研究具有重要意义。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Patients with Parkinson's disease exhibit characteristic tremor, showing a Fourier spectrum with broad peaks at harmonic frequencies. This type of harmonic structure in the frequency domain may be due to two classes of mechanisms: a nonlinear oscillatory process or the superposition of multiple independent modes of oscillation. A broad peak spectrum generally indicates that the signal is semi-periodic with a variable period. These "noisy" fluctuations may possess intrinsic order that can be quantified using scaling analysis. We developed a method to extract the correlation (scaling) properties in the periodic dynamics of multi-modal oscillations, in order to distinguish between a nonlinear oscillation and a superposition of individual modes of oscillations. The method is based on our finding that the information content of the temporal correlations in the fluctuating period of a single oscillator is contained in a finite frequency band in the power spectrum, allowing for decomposition of modes by bandpass filtering. Our simulations for a nonlinear oscillation show that each of the "harmonic" modes possesses the same scaling properties. In contrast, when the method is applied to tremor records from patients with Parkinson's disease, the first two modes of oscillations yield different scaling patterns, suggesting that these modes may not be simple harmonics, as might be initially assumed. In follow-up work, we are developing another method to study the origin of the multiple peaks in the frequency spectrum of tremor, by analyzing the synchronization between different modes. These methods and findings have implications for physiologic modeling of Parkinsonian tremor and its differential diagnosis, as well as for the study of other physiologic time series.