title: New levels of language processing complexity and organization revealed by granger causation.
abstract: Granger causation analysis of high spatiotemporal resolution reconstructions of brain activation offers a new window on the dynamic interactions between brain areas that support language processing. Premised on the observation that causes both precede and uniquely predict their effects, this approach provides an intuitive, model-free means of identifying directed causal interactions in the brain. It requires the analysis of all non-redundant potentially interacting signals, and has shown that even "early" processes such as speech perception involve interactions of many areas in a strikingly large network that extends well beyond traditional left hemisphere perisylvian cortex that play out over hundreds of milliseconds. In this paper we describe this technique and review several general findings that reframe the way we think about language processing and brain function in general. These include the extent and complexity of language processing networks, the central role of interactive processing dynamics, the role of processing hubs where the input from many distinct brain regions are integrated, and the degree to which task requirements and stimulus properties influence processing dynamics and inform our understanding of "language-specific" localized processes.
authors.affiliation: Neuropsychology Laboratory, Massachusetts General Hospital Boston, MA, USA ; Department of Psychology, Salem State University Salem, MA, USA ; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital Charlestown, MA, USA ; Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology Cambridge, MA, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Gow
authors.forename: David N
authors.initials: DN
authors.lastname: Caplan
keywords: EEG; Granger causation analysis; MEG; effective connectivity; rich-club connectivity; small world connectivity; speech perception; superior temporal gyrus