The study of breathing in sleep is clinically and scientifically important. Sleep apnea has a high incidence that increases with age. This application proposes study of respiration in sleep-wakefulness. We want to understand how breathing is automatically excited in wakefulness, how voluntary control of breathing occurs, and how REM and NREM sleep breathing patterns develop. This research involves study of respiration in chronic animals. We will test these hypotheses: 1) That respiratory neurons vary in the strength and consistency of their respiratory activity and that neurons having weak and inconsistent respiratory signals mediate state effects on the respiratory system. We will quantify the respiratory value of respiratory activity and relate this value to changes across states. 2) That the respiratory system functions differently depending on the sleep posture, and that the respiratory system, as other motor systems, is controlled in REM sleep by state-specific processes. We will study the effect of sleep posture on intercostal muscle activity, and we will determine whether pontine lesions that eliminate the atonia of some muscles in REM sleep also eliminate intercostal and upper airway atonia in that state. 3) That midbrain regions mediating arousal have direct connections with brainstem respiratory areas and that these connections cause an automatic facilitation of breathing in wakefulness. We will inject horseradish peroxidase into brainstem respiratory areas and look for transport into the midbrain. If mesencephalopontine and mesencephalobulbar projections exist, the behavior of the parent midbrain cells will be studied in sleep-wakefulness. 4) That animals can be conditioned to voluntarily control their breathing. This is the first step for studying the voluntary control of breathing.