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 relationship between motor activity (MA) and sleep states, forty clinically and neurologically normal infants were recorded polygraphically and grouped according to their gestational (GA, prematures: < 36 weeks, full-term: 37-41 weeks) and conceptional (CA, 37-38 and 39-41 weeks) ages. Sleep states (active: AS, and quiet: QS) were defined by the concordance of EEG and rapid eye movement criteria. Movements of both upper (UL) and lower (LL) limbs were independently recorded. In all groups the amount of MA in both UL and LL clearly predominated in AS compared with QS (p < 0.02). Contrariwise, both the longest period without movement and the no-movement 20-sec epochs were significantly higher in QS than in AS (p < 0.005). In AS, age-related modifications and modulation of MA amount throughout the state were similar for PRT and FT groups: a) in both groups a significant decrease of MA with advancing CA was observed (p < 0.05); b) MA throughout the state was randomly distributed regardless of CA. In QS, however, PRT were distinguishable from FT by the absence of: a) a significant decrease of MA amount with advancing CA, together with a reduced increase of both the longest period without movements and the no-movement 20-sec epochs; b) prevalence of MA in LL compared with UL; c) modulation of the distribution of MA throughout the state.