as a function of distance are related to PR duration. Higher sample rates should be used to further test the temporal synchrony limits as reported in this study. Another limitation are analyses only of the delta frequency band. Because of the large volume of data and limitations of publication space it was necessary to limit the analyses to a single frequency band, i.e., the delta frequency band (1–4 Hz). Different relations are present at different frequency bands as well as cross-frequency band coupling and these relations have been measured and will be the subject of future publications. Another limitation is the use of a center frequency of a narrow band that is necessary with the Hilbert transform. The Gabor transform is independent of a center frequency and provides optimal time frequency resolution (Witte and Schack, 2003) and higher temporal-spatial resolution and can yield more detailed time-frequency information than Complex Demodulation. While cross-frequency phase shift and phase lock measurements is important, however, because of page limitations this topic will be also presented in future studies.
