Association of an individual's ability to overcome desire to fall asleep with a higher anterior-posterior gradient in electroencephalographic indexes of sleep pressure.

Individual differences in ability to overcome desire to fall asleep cannot be accurately predicted from subjective and objective measurements of sleepiness level. Previously, we showed that an exponential buildup of sleep pressure during prolonged wakefulness can be accurately traced with electroencephalographic (EEG) indexes, such as Spectral Sleep Pressure Component (SSPC) score and score on the 2nd principal component (2PC) of the EEG spectrum. The anterior-posterior gradients in SSPC and 2PC scores were calculated as the differences between frontal and occipital scores and examined as possible correlates of individual's ability to overcome desire of falling asleep. Fifteen young and 15 older adults participated in two identically designed sleep deprivation experiments. After, at least, 12hours of wakefulness, resting EEG recordings were obtained from frontal and occipital derivations with 2-h intervals during 26-50hours. Due to irresistible desire to sleep, 11 young and 5 older adults completed <25 required EEG recordings. SSPC and 2PC scores were computed and, by subtracting occipital scores from frontal scores, the anterior-posterior gradients in SSPC and 2PC scores were calculated on one-min intervals of 5-min eyes closed EEG records. The analysis of these anterior-posterior gradients revealed their age-related difference and association with the number of completed EEG recording sessions (13-25). This association remained significant after accounting for age, alertness-sleepiness level, minute of eyes closed recording, and day of experiment. It seems that the anterior-posterior gradients in the EEG indexes of sleep pressure are the objective correlates of individual's ability to overcome desire to fall asleep.