Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.06.19.162065v1?rss=1 Authors: O'Reilly, C., Elsabbagh, M. Abstract: Whether neuronal populations exhibit zero-lag (in-phase or in-antiphase) functional connectivity is a fundamental question when conceptualizing communication between cell assemblies. It also has profound implications on how we assess such interactions. Given that the brain is a delayed network due to the finite conduction velocity of the electrical impulses traveling across its fibers, the existence of zero-lag functional connectivity may be considered improbable. However, in this study, using intracranial recordings we demonstrate that most inter-hemispheric connectivity between homologous cerebral regions is zero-lagged and that this type of connectivity is ubiquitous. Volume conduction can be safely discarded as a confounding factor since it is known to drop almost completely within short inter-electrode distances (< 20 mm) in intracranial recordings. This finding should guide future electrophysiological connectivity studies and highlight the importance of considering the role of zero-lag connectivity in our understanding of communication between cell assemblies. Copy rights belong to original authors. Visit the link for more info