Microstructural electroencephalographic changes during the wakefulness^sleep transition have been investigated by comparing two de¢nitions of sleep onset: the ¢rst occurrence of stage 1 and of stage 2. Power values were calculated across a 1^28-Hz frequency range in a 1-Hz bin resolution in the sleep recordings of 26 normal subjects. Quantitative changes were assessed after averaging individual time series, aligned with respect to the ¢rst occurrence of stage 1 or of stage 2. The time course of the single-Hz activity revealed a linear increase of power in the 1^6-Hz range and a linear decrease in the 9^12- and 16^28-Hz ranges during the stage 1 transition. During the stage 2 transition, electroencephalogram power linearly increased in the 1^7- and 14^15-Hz ranges and decreased in the 18^28-Hz range, while the 8^12-Hz range ¢tted a second-order polynomial curve. The two `switch' points were also compared in their ability to di¡erentiate Hz by Hz wakefulness from sleep: a lower mean power was found after stage 1 onset in the 9^11-Hz and 20^28-Hz bins and a higher one in the 1^5-Hz bins, while a higher power was found in the 1^8-Hz and 12^16-Hz bins and a lower one in 18^ 28-Hz bins after stage 2 onset. The time course of three electroencephalographic frequency ranges [delta/theta/sigma (1^7 and 12^16 Hz); beta (17^28 Hz); alpha (8^11 Hz)], grouped on the basis of a principal component analysis, ¢tted a ¢rstorder polynomial curve for the ¢rst two ranges, and a second-order polynomial curve for the last, with a progressive decrease during wakefulness, a minimum point during stage 1, and a subsequent increase during stage 2. The uniformly increasing electroencephalographic power across the 1^16-Hz frequency range during stage 2 and the shift of functional meaning for the alpha power during stage 1 point to the start of stage 2 as a more reliable boundary between wakefulness and sleep. ß 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.
The boundary between wakefulness and sleep: quantitative electroencephalographic changes during the sleep onset period / DE GENNARO, Luigi; Ferrara, M; Bertini, Mario. - In: NEUROSCIENCE. - ISSN 0306-4522. - 107 (1):(2001), pp. 1-11. [10.1016/S0306-4522(01)00309-8]
The boundary between wakefulness and sleep: quantitative electroencephalographic changes during the sleep onset period
DE GENNARO, Luigi;BERTINI, Mario
2001
Abstract
Microstructural electroencephalographic changes during the wakefulness^sleep transition have been investigated by comparing two de¢nitions of sleep onset: the ¢rst occurrence of stage 1 and of stage 2. Power values were calculated across a 1^28-Hz frequency range in a 1-Hz bin resolution in the sleep recordings of 26 normal subjects. Quantitative changes were assessed after averaging individual time series, aligned with respect to the ¢rst occurrence of stage 1 or of stage 2. The time course of the single-Hz activity revealed a linear increase of power in the 1^6-Hz range and a linear decrease in the 9^12- and 16^28-Hz ranges during the stage 1 transition. During the stage 2 transition, electroencephalogram power linearly increased in the 1^7- and 14^15-Hz ranges and decreased in the 18^28-Hz range, while the 8^12-Hz range ¢tted a second-order polynomial curve. The two `switch' points were also compared in their ability to di¡erentiate Hz by Hz wakefulness from sleep: a lower mean power was found after stage 1 onset in the 9^11-Hz and 20^28-Hz bins and a higher one in the 1^5-Hz bins, while a higher power was found in the 1^8-Hz and 12^16-Hz bins and a lower one in 18^ 28-Hz bins after stage 2 onset. The time course of three electroencephalographic frequency ranges [delta/theta/sigma (1^7 and 12^16 Hz); beta (17^28 Hz); alpha (8^11 Hz)], grouped on the basis of a principal component analysis, ¢tted a ¢rstorder polynomial curve for the ¢rst two ranges, and a second-order polynomial curve for the last, with a progressive decrease during wakefulness, a minimum point during stage 1, and a subsequent increase during stage 2. The uniformly increasing electroencephalographic power across the 1^16-Hz frequency range during stage 2 and the shift of functional meaning for the alpha power during stage 1 point to the start of stage 2 as a more reliable boundary between wakefulness and sleep. ß 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
