Final answer:
Spontaneous electrical rhythms recorded from the scalp include alpha, beta, theta, and delta waves, which are associated with different sleep stages and levels of brain activity.
Step-by-step explanation:
Spontaneous electrical rhythms that can be recorded from the surface of the scalp during different stages of sleep include alpha waves, beta waves, theta waves, and delta waves. These various brain waves differ in frequency and amplitude and are associated with different levels of brain activity and states of sleep.
Alpha waves are characteristic of the early part of NREM stage 1 sleep, with low amplitude and a frequency of 8-12 Hz, reflecting a relaxed state. As stage 1 sleep progresses, there is an increase in theta wave activity, which has a lower frequency (4-7 Hz) and higher amplitude, indicating the end of stage 1 and transition into deeper sleep stages. Beta waves denote wakefulness, with the highest frequency (13-30 Hz) and lowest amplitude. Lastly, delta waves signify the deepest level of sleep (stage 3 NREM), with the lowest frequency (less than 3 Hz) and highest amplitude.