ucresearch:  Scientists find neural switch that turns dreams on and off At the flip of a switch, UC Berkeley neuroscientists can send a sleeping mouse into dreamland. The researchers inserted an optogenetic switch into a group of nerve  cells located in the ancient part of the brain called the medulla,  allowing them to activate or inactivate the neurons with laser light. When the neurons were activated, sleeping mice entered REM sleep within  seconds. REM sleep, characterized by rapid eye movements, is the dream  state in mammals accompanied by activation of the cortex and total  paralysis of the skeletal muscles, presumably so that we don’t act out  the dreams flashing through our mind. The discovery will not only help scientists better understand the complex role of sleep and dreaming in the brain, but may help us learn why we dream in the first place. “Many psychiatric disorders, especially mood disorders, are  correlated with changes in REM sleep, and some widely used drugs affect  REM sleep, so it seems to be a sensitive indicator of mental and  emotional health,” said first author Franz Weber, a UC Berkeley  postdoctoral fellow. “We are hoping that studying the sleep circuit  might lead us to new insights into these disorders as well as  neurological diseases that affect sleep, like Parkinson’s and  Alzheimer’s diseases.” Read more about this neural switch and its impact on sleeping and eating