[Features of the sleep/wakefulness cycle in long-term isolation]

The sleep/wakefulness cycle was the subject of polysomonographic and actographic studies in two experiments with isolation and confinement of six volunteer operators for 135 and 90 days. The dynamics of sleep structure was the target parameter before, during, and after the experiments. The sleep structure dynamics and changes in the motor activity differed in their directionality. At all the stages of experiments the operators' sleep structure had some unique peculiarities. Discussion is centered around the cases of shortened duration of delta-sleep and altered latent periods of specific stages. During the off-nominal situation (ONS) with 45 hour sleep deprivation polysomnographs recorded episodes of latent sleep which became more multiple during the second ONS and were combined with signs of "slow" sleep, and increases in the index of motor activity during night sleep post ONS. Hence, adaptation to changed physical and social environments is manifested by a specific functional restructurization of the sleep/wakefulness cycle.