(Medical Xpress) — The link between dreaming and rapid eye movement (REM) sleep are well understood – but the fact that consciousness is reduced during nonrapid eye movement (NREM) sleep is not. Recently, scientists in the Cyclotron Research Centre at the University of Liège, in Liège, Belgium, and the Institut National de la Santé et de la Recherche Médicale at the Université Pierre et Marie Curie in Paris, and the Functional Neuroimaging Unit at the Montreal Geriatrics Institute, investigated NREM sleep with the hypothesis that this phenomenon is associated with increased modularity of the brain’s functional activity during these periods. Using functional clustering – which estimates how integration is hierarchically organized within and across the constituent parts of a system they found that while in NREM sleep, hierarchically-organized large-scale neural networks were disaggregated into smaller independent modules. The researchers concluded that this difference could reduce the ability of the brain to integrate information, thereby accounting for the decreased consciousness experienced during NREM sleep.