Which of the following sleep transients is predominantly observed in infants aged 2 to 3 months?

The presence of sleep spindles is predominantly observed in infants aged 2 to 3 months as they begin transitioning through different sleep cycles. Sleep spindles are burst patterns of brain activity that occur during light sleep, specifically in non-REM sleep stages. In infants, these spindles help in consolidating memory and are markers of brain maturation. Their emergence typically coincides with developmental changes in the brain during the early stages of life, particularly after the initial few months after birth.

In contrast, the other transients mentioned have distinct associations with different ages or sleep stages. For example, POSTs, which are positive temporally synchronized events, are often more prominent in older infants and children. V waves are also seen in sleep but are not as characteristic of the infant stage as sleep spindles are. K complexes are more prevalent in adults during sleep, representing responses to external stimuli, rather than being a main feature of infant sleep. Understanding these distinctions highlights the significance of sleep spindles in early brain development and their role as indicators of the evolving sleep architecture during infancy.