Final answer:
The rhythmic bursts of brain activity during stage 2 sleep are known as sleep spindles, which are associated with higher frequency brain waves and may play a role in learning and memory.
Step-by-step explanation:
The rhythmic bursts of brain activity that occur during stage 2 sleep are called sleep spindles. During stage 2 sleep, the body enters a state of deep relaxation, and the appearance of sleep spindles along with K-complexes is typical of this sleep stage. Sleep spindles are rapid bursts of higher frequency brain waves and are suggested to be important for learning and memory. K-complexes are very high amplitude patterns of brain activity that may respond to environmental stimuli and potentially serve as a bridge to higher levels of arousal.