Final answer:
Deep sleep, which occurs in stages 3 and 4 of NREM, is more prevalent during the first half of the night and is essential for restorative processes. Alpha brain wave activity during deep sleep can make one feel less refreshed, and the sleep cycle typically varies throughout the night with deep sleep decreasing and REM sleep increasing towards morning.
Step-by-step explanation:
We are more likely to experience deep sleep, also known as stages 3 and 4 of Non-Rapid Eye Movement (NREM) sleep, during the first half of the night. This deep sleep is characterized by low frequency, high amplitude delta waves which represent the deepest levels of sleep. During deep sleep, our heart rate and respiration slow significantly, and it is much harder to awaken someone. These stages are crucial for restorative processes, and an increase in alpha brain wave activity during this time may result in feeling less refreshed upon waking.
Our sleep stages cycle throughout the night, generally following a pattern from stage 1 to REM sleep, through multiple cycles. As the night progresses, the duration of each stage varies, with a greater amount of deep sleep happening in earlier cycles and longer periods of REM sleep occurring towards the morning. This pattern is influenced by our circadian rhythms, which can be disrupted by factors such as travel or shift work. To maintain adequate deep sleep, it is important to keep a regular sleep schedule and to manage potential disruptions to our body's biological clock.