  Recently it has been demonstrated by Albo that partial coherence analysis is
sensitive to signal to noise ratio (SNR) and that it will always identify the
signal with the highest SNR among the three signals as the main (driving)
influence. We propose to use time delay analysis in parallel to partial
coherence analysis to identify the connectivities between the multivariate time
series. Both are applied to a theoretical model (used by Albo) to analyse the
connections introduced in the model. Time delay analysis identifies the
connections correctly. We also apply these analyses to the electroencephalogram
(EEG) and electromyogram (EMG) of essential tremor patients and EEG of normal
subjects while bimanually tapping their index fingers. Biologically plausible
cortico-muscular and cortico-cortical connections are identified by these
methods.
