AN EXTENDED DIFFERENCE OF COHERENCE TEST FOR COMPARING AND COMBINING SEVERAL INDEPENDENT COHERENCE ESTIMATES - THEORY AND APPLICATION TO THE STUDY OF MOTOR UNITS AND PHYSIOLOGICAL TREMOR

Recently there has been an increase in the use of spectral methods for the analysis of experimental data. These analytical methods allow the study of interactions between simultaneously recorded signals and are particularly suited to the study of systems displaying rhythmic behav iour. A useful parameter in this context is the coherence function whi ch provides a bounded measure of linear association between two signal s. In this report we introduce two new techniques for dealing with an arbitrary number of independent coherence estimates. The first techniq ue provides a test to compare the coherence estimates for statisticall y significant differences. The second allows the original coherence es timates to be combined, or 'pooled' into a single representative estim ate. These two measures, taken together, provide a powerful tool for c haracterising and summarising the correlations within data sets. Appli cations of the techniques are illustrated by analysing the interaction s between single motor unit discharges and finger tremor, and between pairs of motor unit discharges in human subjects. (C) 1997 Elsevier Sc ience B.V.