HEART-RATE AND SLEEP STATES IN INFANTS

Heart Rate (HR) was analyzed during the first six Quiet Sleep (QS)- Pa radoxical Sleep (PS) cycles of the polygraphically-recorded nocturnal sleep in three groups of six infants each, aged respectively 1 to 2 we eks, 15 to 19 weeks, and 25 to 47 weeks. HR decreased with age, and wa s higher during PS than during QS, without difference between odd QS p hases(lst, 3rd and 5th, which contain always, but only in oldest infan t's group, Slow wave sleep (SWS) stage 3 and 4 episodes), and even QS phases (2nd, 4th and 6th, never containing SWS episodes). In the oldes t infant's group, in odd QS phase only, HR was higher in the first hal f with respect to the second half. The HR modulation according to the QS-PS alternance was obvious in all infant groups. In the oldest infan t's group the QS phases without SWS episodes were characterized by a d issociaton between EEC activity level (close to that of PS) and HR (si milar to that of QS phases with SWS); in QS phases with SWS, howewer, the HR was modulated according to the type of EEG activity (stage 2 vs SWS).