Final answer:
The alpha wave is characteristic of stage 1 sleep, which occurs as we transition from wakefulness to sleep and is marked by a shift to lower frequency and higher amplitude brain waves.
Step-by-step explanation:
The α-alpha wave is characteristic of stage 1 sleep. As we transition from wakefulness to sleep, the brain's electrical activity changes, moving away from the high frequency and low amplitude β-beta waves associated with an awake state. Initially, during this first stage of non-REM (NREM) sleep, alpha waves, which are lower in frequency (8-12 Hz) and higher in amplitude than beta waves, are present. These waves are indicative of a relaxed state and are most prominent in the early part of stage 1 sleep. As stage 1 progresses, there is an increase in θ-theta wave activity, with theta waves being even lower in frequency (4-7 Hz) and higher in amplitude.