“Dynamic” connectivity in neural systems

The study of functional interdependences between brain regions is a rapidly growing focus of neuroscience research. This endeavor has been greatly facilitated by the appearance of a number of innovative methodologies for the examination of neurophysiological and neuroimaging data. The aim of this article is to present an overview of dynamical measures of interdependence and contrast these with statistical measures that have been more widely employed. We first review the motivation, conceptual basis, and experimental approach of dynamical measures of interdependence and their application to the study of neural systems. A consideration of boot-strap “surrogate data” techniques, which facilitate hypothesis testing of dynamical measures, is then used to clarify the difference between dynamical and statistical measures of interdependence. An overview of some of the most active research areas—such as the study of the “synchronization manifold,” dynamical interdependence in neurophysiology data and the putative role of nonlinear desynchronization—is then given. We conclude by suggesting that techniques based on dynamical interdependence—or “dynamical connectivity”—show significant potential for extracting meaningful information from functional neuroimaging data.