The cross-frequency mediation mechanism of intracortical information transactions

TL;DR

This paper develops a quantitative model using statistical mediation analysis to test the hypothesis that slower oscillations mediate the synchronization of faster oscillations across cortical regions, elucidating intracortical information transfer.

Contribution

It introduces a novel multivariate complex-valued mediation model and a new way to quantify mediation effects using dual frequency RV-coupling coefficients.

Findings

Provides a statistical framework for testing cross-frequency mediation in neural signals.

Quantifies mediation effect as the product of dual frequency RV-coupling coefficients.

Enables testing of the von Stein & Sarnthein hypothesis on cortical oscillation interactions.

Abstract

In a seminal paper by von Stein and Sarnthein (2000), it was hypothesized that "bottom-up" information processing of "content" elicits local, high frequency (beta-gamma) oscillations, whereas "top-down" processing is "contextual", characterized by large scale integration spanning distant cortical regions, and implemented by slower frequency (theta-alpha) oscillations. This corresponds to a mechanism of cortical information transactions, where synchronization of beta-gamma oscillations between distant cortical regions is mediated by widespread theta-alpha oscillations. It is the aim of this paper to express this hypothesis quantitatively, in terms of a model that will allow testing this type of information transaction mechanism. The basic methodology used here corresponds to statistical mediation analysis, originally developed by (Baron and Kenny 1986). We generalize the classical mediator model to the case of multivariate complex-valued data, consisting of the discrete Fourier transform coefficients of signals of electric neuronal activity, at different frequencies, and at different cortical locations. The "mediation effect" is quantified here in a novel way, as the product of "dual frequency RV-coupling coefficients", that were introduced in (Pascual-Marqui et al 2016, http://arxiv.org/abs/1603.05343). Relevant statistical procedures are presented for testing the cross-frequency mediation mechanism in general, and in particular for testing the von Stein & Sarnthein hypothesis.