Final answer:
Ventilation response to CO2 is generally depressed during NREM sleep, indicating less sensitivity to CO2 levels compared to wakefulness and REM sleep.
Step-by-step explanation:
The student's question is regarding the response to carbon dioxide (CO₂) during the Non-Rapid Eye Movement (NREM) stage of sleep. During the stages of NREM sleep, specifically stage 1, which is the transitional phase between wakefulness and sleep, there is a noted slowdown in respiration. This indicates that ventilation response to CO₂ is generally depressed during NREM sleep compared to wakefulness. In other stages of NREM, respiration rates continue to be more regular and less responsive to CO₂ than during wakefulness, suggesting that CO₂ response is not as sensitive during NREM sleep as it is when we are awake or during REM sleep.