Optimising coherence estimation to assess the functional correlation of tremor-related activity between the subthalamic nucleus and the forearm muscles.

Application of coherence estimation needs not only to correctly estimate coherence values but also to efficiently test the statistical significance of the estimates. In the present report, we have explained the approach of optimising a coherence estimator by restricting its normalised bias error and random error. In addition to the commonly used independence threshold, two more tests based on the probability of detection and the exact confidence interval have been proposed for detecting the significance of the coherence estimates. All three methods have been used to evaluate the significant functional correlation between oscillatory field potentials (FPs) in the subthalamic nucleus (STN) and the surface electromyogram (EMG) of the forearm muscles during tremor in Parkinson's disease. Copyright 2004 Elsevier B.V.