Final answer:
Theta waves are the brain waves that have an even lower frequency (4-7 Hz) and higher amplitude than alpha waves and that continue through stage 1 sleep. These waves signify a transition to deeper stages of sleep, particularly as one moves into stage 2 and ultimately to stage 3 sleep, which is characterized by delta waves.
Step-by-step explanation:
Brain Waves during Stage 1 Sleep
The brain waves that are of even lower frequency and higher amplitude than alpha waves and continue through stage 1 sleep are known as theta waves. During the early part of stage 1 sleep, the brain produces alpha waves, which have a frequency of 8-12 Hz and are indicative of a relaxed state. As an individual moves deeper into stage 1 sleep, there is an increase in theta wave activity. These theta waves have a lower frequency (4-7 Hz) and higher amplitude when compared to alpha waves and signify deeper relaxation and the transition toward stage 2 sleep.
In the subsequent stage 2 sleep, theta waves continue to dominate while being interspersed with sleep spindles and K-complexes, both of which are associated with learning and memory processes. Finally, stage 3 sleep, also known as deep sleep or slow-wave sleep, is characterized by delta waves. These have the lowest frequency (less than 3 Hz) and highest amplitude among the sleep-related brain waves and represent the deepest level of sleep.