Which sleep stage contains "Berger" waves of 8 - 13 hertz?

The stage containing "Berger" waves, which are also known as alpha waves, is the stage characterized by brain activity in the frequency range of 8 to 13 hertz. Alpha waves are typically observed during relaxed wakefulness and can also appear when a person transitions into light sleep (N1). This stage is where individuals are still somewhat aware of their surroundings but are beginning to disengage from external stimuli.

In this context, N1 is the initial stage of non-REM sleep, marked by a certain level of cortical activity that is indicative of relaxation and the onset of sleep. The presence of Berger waves in this stage is a significant indicator of its unique characteristics. Other sleep stages have distinct brainwave patterns; for instance, N2 is known for sleep spindles and K-complexes, N3 is identified by delta waves (high-amplitude, low-frequency), and REM sleep is characterized by low-amplitude, mixed-frequency waves somewhat similar to wakefulness but is distinct in its function and features, including rapid eye movements and increased brain activity.

Therefore, recognizing that N1 is the stage where alpha waves (Berger waves) are predominant leads to the conclusion that this option is the correct answer.