https://www.selleckchem.com/products/GDC-0941.html In eyes closed condition, an increase of sleepiness level is associated with a decrease of the spectral electroencephalographic (EEG) power in the fast frequency rage (i.e., alpha activity) and with an increase of the power in the slow frequency range (i.e., theta activity). It was suggested that the changes in the fast and slow frequency ranges might determine two - the earlier and later - drowsiness stages preceding sleep onset, respectively. We tested whether such spectral EEG signatures of sleepiness vary with age or gender. The EEG signal was recorded with two-h intervals in 48 volunteers (15-67 years, 27 females) deprived from sleep between Friday evening to Sunday evening. The EEG signatures of sleepiness were calculated by the expressing each EEG spectrum as a deviation from the initial (Friday evening) EEG spectrum. The age- and gender-specific variation in such signatures was found. Only the pattern of age-associated variation changed with an increase of sleepiness level. Two-stage response to the increase of sleepiness was confirmed, but only in younger study participants. Subjective sleepiness was associated with neither age nor gender. In sleep deprivation research, the accounting for the age- and gender-specific variation in the spectral EEG measures of drowsiness might be recommended. The results did not reveal any disturbance of motivational function of subjective sleepiness in older study participants. In sleep deprivation research, the accounting for the age- and gender-specific variation in the spectral EEG measures of drowsiness might be recommended. The results did not reveal any disturbance of motivational function of subjective sleepiness in older study participants.No Abstract required.The quality of reconstructed dynamic PET images, as well as the statistical reliability of the estimated pharmacokinetic parameters is often compromised by high levels of statistical noise, particularly at the