MODULATION OF MOTOR-ACTIVITY PATTERNS AND SLEEP STATES IN LOW-RISK PREMATURELY BORN INFANTS REACHING NORMAL TERM - A COMPARISON WITH FULL-TERM NEWBORNS

To evaluate the influence of prematurity and postnatal age on the rela tionship between motor activity (MA) and sleep states, forty clinicall y and neurologically normal infants were recorded polygraphically and grouped according to their gestational (GA, prematures: < 36 weeks, fu ll-term: 37-41 weeks) and conceptional (CA, 37-38 and 39-41 weeks) age s. Sleep states (active: AS, and quiet: QS) were defined by the concor dance of EEG and rapid eye movement criteria. Movements of both upper (UL) and lower (LL) limbs were independently recorded. In all groups t he amount of MA in both UL and LL clearly predominated in AS compared with QS (p < 0.02). Contrariwise, both the longest period without move ment and the no-movement 20-sec epochs were significantly higher in QS than in AS (p < 0.005). In AS, age-related modifications and modulati on of MA amount throughout the state were similar for PRT and FT group s: a) in both groups a significant decrease of MA with advancing CA wa s observed (p < 0.05); b) MA throughout the state was randomly distrib uted regardless of CA. In QS, however, PRT were distinguishable from F T by the absence of: a) a significant decrease of MA amount with advan cing CA, together with a reduced increase of both the longest period w ithout movements and the no-movement 20-sec epochs; b) prevalence of M A in LL compared with UL; c) modulation of the distribution of MA thro ughout the state.