If an epoch contains low voltage mixed frequency in the 4-7 Hz range, and no eye movements, which stage of sleep is most likely to be indicated?

The presence of low voltage mixed frequency activity in the 4-7 Hz range, combined with the absence of eye movements, is indicative of Stage N1 sleep.

Stage N1 is characterized by a transition from wakefulness to sleep and is often marked by theta waves, which can be found in the 4-7 Hz frequency range. During this stage, individuals may still exhibit some awareness of their surroundings, and the brain shows a mixture of theta activity without prominent eye movements, which aligns with the scenario described in the question.

Stage N2 would typically show the presence of sleep spindles and K-complexes, which are not mentioned in the scenario. Stage N3, on the other hand, is characterized by delta waves (0.5-4 Hz) and a lack of mixed frequency activity. Finally, during REM sleep, there is usually a predominance of low-voltage mixed-frequency activity, but it is accompanied by rapid eye movements, which are absent in this situation. Thus, the conditions given strongly suggest that the epoch reflects Stage N1 sleep.