The standard approach to the evaluation of tremor in medical practice is subjective scoring. The objective of this study was to show that signal processing of physiological data, that are known to be altered by tremor in Parkinson's disease (PD), can quantify the postural dynamics and the effects of DBS. We measured postural control and its capacity to adapt to balance perturbations with a force platform and perturbed balance by altering visual feedback and using pseudo-random binary sequence perturbations (PRBS) of different durations. Our signal processing involved converting the postural control data into spectral power with Fast-Fourier Transformation across a wide bandwidth and then subdividing this into three bands (0–4 Hz, 4–7 Hz and 7–25 Hz). We quantified the amount of power in each bandwidth.

From 25 eligible participants, 10 PD participants (9 males, mean age 63.8 years) fulfilled the inclusion criteria; idiopathic PD responsive to l-Dopa; >1 year use of bilateral STN stimulation. Seventeen controls (9 males, mean age 71.2 years) were studied for comparison. Participants with PD were assessed after overnight withdrawal of anti-PD medications. Postural control was measured with a force platform during quiet stance (35 s) and during PRBS calf muscle vibration that perturbed stance (200 s). Tests were performed with eyes open and eyes closed and with DBS ON and DBS OFF. The balance perturbation period was divided into five sequential 35-s periods to assess the subject's ability to address postural imbalance using adaptation.

The signal processing analyses revealed that DBS did not significantly change the dynamics of postural control in the 0–4 Hz spectral power but the device reduced the use of spectral power >4 Hz; a finding that was present in both anteroposterior and lateral directions, during vibration, and more so in eyes open tests. Visual feedback, which usually improves postural stability, was less effective in participants with PD with DBS OFF across all postural sway frequencies during quiet stance and during balance perturbations. The expected adaptation of postural control was found in healthy participants between the first and last balance perturbation period. However, adaptation was almost abolished across all spectral frequencies in both the anteroposterior and lateral directions, with both eyes open and eyes closed and DBS ON and OFF in participants with PD.

To conclude, this study revealed that DBS altered the spectral frequency dynamics of postural control in participants through a reduction of the power used >4 Hz. Moreover, DBS tended to increase the stabilizing effect of vision across all spectral bands. However, the signal processing analyses also revealed that DBS was not able to restore adaptive motor control abilities in PD.

在医学实践中评估震颤的标准方法是主观评分。这项研究的目的是证明生理数据的信号处理（已知会因帕金森氏病（PD）震颤而改变）可以量化姿势动力学和DBS的影响。我们通过改变视觉反馈并使用不同持续时间的伪随机二进制序列扰动（PRBS），测量了姿势控制及其适应力平台和平衡扰动的能力。我们的信号处理包括在宽带宽上通过快速傅立叶变换将姿势控制数据转换为频谱功率，然后将其细分为三个频段（0–4 Hz，4–7 Hz和7–25 Hz）。我们量化了每个带宽中的电量。

在25名合格参与者中，有10名PD参与者（9名男性，平均年龄63.8岁）符合纳入标准；对1- Dopa有反应的特发性PD ；使用双侧STN刺激> 1年。研究了十七名对照（9名男性，平均年龄71.2岁）进行比较。隔夜停用抗PD药物后评估PD参与者。在安静姿势（35 s）以及PRBS小腿肌肉振动姿势（200 s）期间，用力平台测量姿势控制。睁开眼睛，闭上眼睛，DBS打开和DBS关闭，进行测试。将平衡扰动周期分为五个连续的35 s周期，以评估受试者使用适应力解决姿势不平衡的能力。

信号处理分析表明，在0–4 Hz频谱功率下，DBS不会显着改变姿势控制的动力学，但该设备减少了> 4 Hz频谱功率的使用。在振动过程中，前后方向和横向都有此发现，而睁眼测试更是如此。视觉反馈通常可以改善姿势稳定性，在安静姿势和平衡扰动期间，PD参与者在所有姿势摆动频率上都处于DBS OFF状态时，其效果较差。在健康参与者中，在第一个和最后一个平衡扰动周期之间发现了预期的姿势控制适应性。但是，前后方向和侧向方向上所有频谱频率的适应性几乎都消失了，

总而言之，这项研究表明，DBS通过降低> 4 Hz的功率来改变参与者姿势控制的频谱频率动态。此外，DBS趋向于提高所有光谱带上的视觉稳定效果。但是，信号处理分析还显示，DBS无法恢复PD中的自适应电机控制能力。