Gresty M, Buckwell D
Medical Research Council Human Movement and Balance Unit, National Hospital, London, United Kingdom.
J Neurol Neurosurg Psychiatry. 1990 Nov;53(11):976-81. doi: 10.1136/jnnp.53.11.976.
Spectral analysis of a tremor record can sometimes produce a spectrum with multiple components of significant amplitude. The problem is to determine whether the presence of several peaks represents the coexistence of separate tremor mechanisms or be a consequence of fluctuations in the frequency or amplitude of a single tremor. The spectrum of a tremor whose frequency or amplitude vary and are independent has the recognisable pattern of a central carrier frequency with sidebands of equal amplitudes distributed symmetrically around the carrier. However, if tremor amplitude and frequency fluctuate and are not independent, (frequency proportional to amplitude or frequency inversely proportional to amplitude), the spectrum has a pattern of sidebands which are asymmetrical in amplitudes and may resemble the spectrum of the combined signal from different independent oscillators. The investigation of sidebands in spectra has been neglected in tremor studies and multiple irregular peaks on a tremor spectrum have sometimes been used wrongly as evidence for the coexistence of multiple tremor mechanisms or frequency components assumed to be concurrent.
震颤记录的频谱分析有时会产生一个具有多个显著幅度成分的频谱。问题在于确定多个峰值的出现是代表不同震颤机制的共存，还是单个震颤频率或幅度波动的结果。频率或幅度变化且相互独立的震颤频谱具有可识别的模式，即有一个中心载波频率，其边带幅度相等且围绕载波对称分布。然而，如果震颤幅度和频率波动且不独立（频率与幅度成正比或频率与幅度成反比），频谱的边带模式在幅度上是不对称的，可能类似于来自不同独立振荡器的组合信号的频谱。在震颤研究中，对频谱中边带的研究被忽视了，震颤频谱上的多个不规则峰值有时被错误地用作多种震颤机制共存或假定同时存在的频率成分的证据。
