In the following paragraphs, the different connectivity methods will be classified as frequency-specific or cross-frequency phase-coupling methods, depending on whether they allow investigating the phase coupling at the same or different frequencies, respectively. Moreover, they will be divided into univariate and multivariate methods; the formers are designed to assess connectivity from two univariate (or scalar) time series, while the latter take as input multivariate (or vector) time series (see also Table 2).
