Objectives: Contingent negative variation (CNV) is an event-related potential proportional to vigilance degree. A CNV graph shows an inverted U-shape, and this bioreaction disappears after falling below a threshold of vigilance degree. Previous studies have shown that the event-related potential gained with time decreases with sleep deprivation, and a decrease in the vigilance degree has been confirmed using Flicker values (FV) and the Stanford Sleepiness Scale (SSS) score. The minimum integrated value was recorded 24 h after the onset of sleep deprivation. In a present study, we used 36-h sleep deprivation. The FVs, SSS scores, and stabilograms were obtained every 90 min for 52 h, except for the 12 h of sleep. We herein examine whether the biocontrol system is changed by sleep deprivation.

Results: The time sequences in FV and SSS score showed that the degree of vigilance markedly decreased 22.5 h after the onset of this experiment, which supported CNV disappearance with sleep deprivation. The sway value with subjects’ eyes closed was greatest 22.5 h after the onset of this experiment. Furthermore, there were no significant differences between the sway value during the above-mentioned sleep deprivation and that after 12 h of sleep. We considered that the equilibrium function and vigilance after 36-h sleep deprivation did not recover markedly well with sleep of sufficient duration. That is, the biocontrol process in the subconscious still proceeds after awakening.

Conclusions: In this study, we focused on bioprocessing, especially the equilibrium function, during sleep deprivation and investigated the relationship between the equilibrium function and sleep deprivation. We obtained evidence supporting CNV disappearance after sleep deprivation for 36 h. The equilibrium control system without CNV was compared with that with CNV.