Coherence: The Measurement and Application of Brain Connectivity

While much knowledge has been gained by the endeavor to link specific brain sites with specific cognitive functions, modern conceptualizations of brain activity focus much more on the function of networks of brain regions.  A key construct in defining these networks has been the study of connectivity across regions.  In this review, we discuss several methods of measuring connectivity and focus primarily on the utility of electroencephalographic (EEG) coherence.  While over- and under-connectivity have been related to numerous clinical phenomena, we focus our discussion on the role of connectivity in reading and language disorders, and present a Neurocognitive Connectivity (NCC) framework for understanding these disorders.  We argue that EEG coherence presents a unique target for treatment of these and other populations, in that the ability to modulate connectivity via EEG neurofeedback has been shown to be of significant clinical utility.