Advanced Phase Sleep Type Disorder (ASPD) - A Circadian Rhythm Disorder characterized by characterized by habitually early sleep-onset and wake times, compared with societal or preferred norms.
Alpha waves - Occur during wakefulness and periods of relaxation (i.e., during meditation). These waves are slower, and have less amplitude and variability than beta waves.
Apnea - Cessation of airflow for a minimum of 10 seconds in adults, or 2 respiratory cycle lengths in children.
Apnea-Hypopnea Index (AHI) - The average number of apneas and hypopneas obtained per hour of sleep. The index is used to diagnose sleep disorders, and is similar to the Respiratory Disturbance Index (RDI), but does not count Respiratory Effort Related Arousals (RERA).
Ascending Reticular Activating System (ARAS) - Wakefulness is promoted by the activation of the ARAS the by monoaminergic and cholinergic projections from the brainstem, thalamus, hypothalamus, basal forebrain, and cortex.
Attention-deficit hyperactivity disorder (ADHD) - A brain disorder characterized by a pattern of inattention and/or hyperactivity-impulsivity, which interferes with an individual’s ability to function, quality of life, and/or development.
Augmentation (as in restless legs syndrome) - Shifting of symptoms to an earlier time in the evening than was previously typical, the intensification of symptoms, and/or the presence of symptoms in additional body parts as a consequence dopaminergic drug therapy.