What is meant by "light sleep" during polysomnography?

"Light sleep" during polysomnography refers specifically to stages 1 and 2 of non-rapid eye movement (NREM) sleep.

In this context, stage 1 is a transitional phase that occurs when a person is first falling asleep, typically lasting only a few minutes, where the individual can be easily awakened and may experience muscle relaxation and slow eye movements. Stage 2 follows and is characterized by the occurrence of sleep spindles and K-complexes on the EEG, indicating a deeper level of sleep than stage 1, yet still considered light sleep. This stage constitutes a significant portion of the sleep cycle and serves essential functions such as memory consolidation and bodily restoration.

The other choices do not accurately define "light sleep" within the framework of polysomnography. While transitions between different sleep states are important, they do not specifically represent the stages identified as light sleep. Rapid eye movement (REM) sleep, characterized by vivid dreams and increased brain activity, is distinct and not classified as light sleep. Lastly, describing light sleep as a state of non-restful sleep does not capture its physiological significance and contribution to overall sleep cycles.