DYNAMICS OF EEG BACKGROUND ACTIVITY LEVEL WITHIN QUIET SLEEP IN SUCCESSIVE CYCLES IN INFANTS

We investigated in infants the emergence of the trends of the EEG sync hronization throughout quiet sleep (QS) as a function of the QS rank. The night sleep of 3 groups with 6 subjects each (aged respectively 9- 18 weeks, 21-37 weeks, and 16-45 years) was recorded. A parameter valu e reflecting the degree of synchronization of the EEG background activ ity for successive epochs was computed by automatic analysis. For each QS phase 3 indicators of the dynamics of the time course of the EEG p arameter activity were determined: the range (difference between the E EG parameter value at the beginning of the QS episode and that at the trough), the trough latency (after QS onset), and the rare of synchron ization (range/trough latency). The range and the trough latency incre ased with age, whereas the rate of synchronization decreased. The rang e and the rate of synchronization decreased in the successive cycles, whereas the trough latency increased. These results provide further su pport for the hypothesis of the early emergence of the process S mecha nisms and suggest that the framework of the 2-process model could acco unt also for the development of both the EEG background activity dynam ics and the sleep-wake organization.