Professor Hiroki R. Ueda (RIKEN Center for Functional Biology, concurrently team lead), Dr. Kazuhiro Kon (at the time of the research, currently a postdoctoral fellow at Johns Hopkins University) and their colleagues at Graduate School of Medicine, The University of Tokyo, have elucidated the importance of proper regulation of the activity of parvalbumin (PV)-expressing neurons, the major inhibitory neurons in the cerebral cortex, in the long, deep sleep (rebound sleep) that occurs after prolonged wakefulness.