Poster Abstract

Introduction/Objectives: Sleep and wakefulness do not reflect \nmutually-exclusive states, but instead represent local phenomena. \nDespite the massive age-related modifications occurring during lifespan, \nthe electrophysiological (EEG) Sleep Onset (SO) features in preadolescence \nand healthy aging have not been exhaustively \ninvestigated. Thus, we aimed to describe spatiotemporal EEG dynamics \nof SO in preadolescents and older adults. \nMethods: The pre- vs- post-SO changes in the topography of EEG \npower (1-Hz-frequency-resolution) and the time course of the EEG \nfrequency bands during SO were assessed in a group of 23 preadolescents \n(9–14 years, Experiment 1) and in a group of 36 older participants \n(59–81 years, Experiment 2). Additionally, we compared delta/ \nbeta ratio and delta activity during SO between these groups \n(Experiment 1: preadolescents, Experiment 2: elderly) and a group of \n40 young adults (18–29 years). \nResults: Experiment 1. Preadolescents showed a postSO increase \n(A) of power spectra in the low frequencies (0.5–6 Hz), with a \ncentral predominance (0.5–2 Hz), (B) at 12–13 and 14–15 Hz \nlocalized over frontal and central areas, respectively, and (C) of \nthe lowest beta over central areas. Preadolescents showed higher \ndelta/beta ratio in posterior areas (pre and postSO), higher delta \npower over posterior (preSO) and centro-posterior areas (postSO) \nand reduced delta/beta ratio and delta power in frontal areas \n(postSO). \nExperiment 2. Elderly exhibited a power increase postSO of lower frequencies; \nthe alpha band showed a particular pattern of postSO modifications; \nsigma power slightly increased postSO and its highest bins \nshowed a decrease in frontotemporal areas. Compared to young \nadults, elderly displayed a reduced delta power and delta/beta ratio \nboth before and after SO. \nConclusions: Preadolescents showed not entirely mature spindles and \na more posterior delta activity, expression of strong homeostatic need \nfrom the “developing” areas; the decreased delta activity in elderly \nmight reflect a reduced homeostatic regulation during SO. Taken \ntogether, these findings depict the scenario known for adults but with \npeculiarities pointing to different homeostatic regulation likely \naccountable for the observed age-related SO dynamics.