During which stage of sleep would you most likely see increased delta wave activity?

Increased delta wave activity is most prominently observed during deep sleep, also known as slow-wave sleep or stage N3 of non-REM sleep. Delta waves are characterized by their high amplitude and low frequency, which are indicators of the brain's restorative processes during this stage. During deep sleep, the body's systems undergo essential functions such as tissue growth and repair, regulation of metabolism, and bolstering of the immune system.

In contrast, other stages of sleep have different brain wave patterns. REM sleep features a predominance of theta waves and sawtooth waves, which are associated with dreaming and heightened brain activity. Light sleep is marked by a combination of sleep spindles and theta activity, indicating the transition towards deeper sleep stages. In the awake state, the brain exhibits beta waves, characterized by a fast frequency related to active, alert mental engagement.

Thus, delta wave activity is distinctly associated with deep sleep, making it the correct choice in this context.