This research study will look at how medications affect the pattern of blood flow in the brain. This study will use a special type of MRI (magnetic resonance imaging) scan called perfusion MRI to make measurements of cerebral (brain) blood flow. The medications we will use in this study are scopolamine (commonly used to treat motion sickness), mecamylamine (used to treat high blood pressure), and donepezil (used to treat memory loss). Cognitive testing will also be obtained, and correlated with the blood flow patterns in the brain.

Project Summary: This research project will investigate the value of combined pharmacologic manipulation and arterial spin-labeled perfusion MRI (pharmacologic ASL-pMRI) as an in vivo probe of cholinergic function. Methods to investigate cholinergic function in vivo are needed to better understand the role of acetylcholine in the physiology of the cerebral cortex, and in cognitive processes in health and in disease states. In this study, pharmacologic ASL-pMRI will be used to characterize the normal cerebral perfusion response to cholinergic manipulation in young healthy subjects. Cognitive measures will also be obtained and correlated with cerebral perfusion changes. Pharmacologic ASL-pMRI and cognitive testing will then be used to study how the cholinergic response is altered with normal aging and in delirium

Inclusion Criteria:

• healthy volunteers

Exclusion Criteria:

• Any neurological condition, such as brain tumor, history of stroke, seizure disorder, attention deficit disorder, normal pressure hydrocephalus, dementia, traumatic brain injury
• Any major medical conditions, such a cancer, diabetes, glaucoma, prostate disease, uncontrolled hypertension
• antihistamine use
• tricyclic antidepressant use
• presence of metal in body, including pacemaker, defibrillator, neurostimulator, metal implants, or foreign metal objects such as bullets or shrapnel.
• anxiety or panic disorder
• history of claustrophobia
• pregnancy