A new study counters some long-held beliefs on sleep, dreaming, and other consciousness states—such as being under general anesthesia, in a coma, or experiencing an epileptic seizure. The NCCIH co-supported study was led at the University of Wisconsin-Madison and appears in the journal Nature Neuroscience.
It has long been believed that the stage of sleep called rapid-eye movement (REM) owns our dreaming process. However, recent evidence suggests that dreams also occur during non-REM (NREM) sleep and at every stage of NREM, though not as often as in REM. The researchers who conducted this study wanted to gain more clarity on several questions relating to what happens in the brain when we dream (or don’t dream) in REM or NREM sleep states; as read by high, versus low, EEG (electroencephalogram) -frequencies; and with respect to certain types of remembered dream content such as faces, speech, thoughts, or settings. A key question was whether conscious experiences in sleep have a neural correlate, which is an activity, event, or mechanism in the brain that is associated with a particular experience and makes it possible.