The autonomic nervous system plays an underappreciated role in age-related change in the brain and cognition. But the sympathetic hub region in the brain (the locus coeruleus) is one of the first brain regions affected by Alzheimer’s disease pathology and deep sleep, a period of high parasympathetic activity, is critical for clearing out the potentially toxic proteins generated by the brain’s activity during the day (it is the aggregation of such proteins that leads to the hallmark plaques and tangles seen in Alzheimer’s disease). Our research is investigating how both sympathetic and parasympathetic function affect brain function and cognition in aging and how interventions that increase parasympathetic activity may enhance brain function in older adults.