SS WERE STUDIED WHILE SLEEPING IN THE LABORATORY DURING THE AFTERNOON HOURS. THE SLEEP OF THESE SS NEITHER RESEMBLED THAT FOUND DURING THE LAST 2 HR. OF NOCTURNAL SLEEP NOR THAT FOUND IN THE 1ST 2 HR. THE DATA INDICATED THAT THE AMOUNT OF STAGE 4 AND 1 REM FOUND DURING AN INTERJECTED SLEEP EVENT IS A FUNCTION OF ITS PROXIMITY TO THE ONSET OR THE TERMINATION OF THE REGULAR SLEEP PERIOD. (PsycINFO Database Record (c) 2006 APA, all rights reserved)