The union of the state: Myoclonic twitching is coupled with nuchal muscle atonia in infant rats

Abstract

behavioral state in newborn rats. Historically, AS has been considered a developmental precursor of REM sleep, but recently this idea has been questioned. In the present study, the authors assess, in 2-, 5-, and 8-day-old rats, the relationship between MT and nuchal muscle atonia, a widely recognized component of REM sleep. At all ages, muscle atonia preceded MT and persisted until awake behaviors occurred. In addition, muscle tone decreased gradually during transitions from awake behavior to twitching. Thus, MT during infancy occurs against a backdrop of muscle atonia, a result that is consistent with the view that AS is a developmental precursor of REM sleep. Rapid eye movement (REM), or paradoxical, sleep in adult mammals has been classically defined as the appearance of a low-voltage, high-frequency (i.e., desynchronized) electroenceph-alograph (EEG); low muscle tone; and, of course, REMs (Carska-don & Dement, 2000; Rechtschaffen & Kales, 1968). Other com-ponents of REM sleep include respiratory and cardiac irregularity, a hippocampal theta rhythm, pontine–geniculo–occipital (PGO) waves, and myoclonic twitching (MT) of the distal limbs. Al