Directed Spectral Methods Definition

Directed spectral measures quantify, in the frequency domain, directed statistical interactions between time-series variables. Most commonly, the various measures are computed based on a (linear) multi-variate autoregressive (MVAR) model of the data. The various methods quantify in different ways the strength of interaction terms in the Fourier transform of the MVAR model. While these methods are sometimes referred to as capturing ‘causal’ or ‘effective’ connectivity, they are most properly described as reflecting ‘directed functional connectivity’ (Friston et al. 2013).