It has been a long time since I scored EEG records for sleeping participants, but my recollection is that the shift was gradual.
A stage of sleep is classified by certain criteria (e.g., the percentage of time in a one-minute epoch in which alpha activity is present, the occurrence of a specific number of sleep spindles or K-complex formations in the EEG trace, etc.). On an epoch-by-epoch basis, you could observe epochs when a person was awake, then Stage 1, then awake or similar alternations between Stage 1 and 2, etc. So, although each stage is distinctive in its EEG signature, the EEG records from the transitional periods, as a person moves from one stage to another, can show a mix of the two signatures. The change in appearance of the sleep record from awake to Stage 1 can be subtle. Basically, you see more and more alpha activity until finally an epoch has more than 50% time spent in alpha activity. The appearance of sleep spindles and k-complexes are more distinct (plus they appear against an EEG with diminishing alpha and more slow-wave activity). Claudia At 04:58 PM 2/21/2005 -0500, you wrote: >TIPSters, >I know what Intro Psych texts say about stages of sleep and what kinds >of brain waves there are in each, et. But when the EEG from a sleeping >person is examined, is it obvious when the person passed from one stage >into another? Or is it gradual? Could a line be drawn across the paper >marking where Stage 2 stops and Stage 3 starts? > ________________________________________________________ Claudia J. Stanny, Ph.D. Associate Professor Web Site: http://uwf.edu/cstanny/ General Track Coordinator [EMAIL PROTECTED] Department of Psychology Phone: (850) 474 - 3163 University of West Florida FAX: (850) 857 - 6060 Pensacola, FL 32514 - 5751 --- You are currently subscribed to tips as: [email protected] To unsubscribe send a blank email to [EMAIL PROTECTED]
