Effect of Physiologic Insulin Administration on Cognition

After passing the screening, participation in the research study will be approximately three weeks. The participant will have seven study visits all at the Pennington Center. On five occasions, the participant will have a five-hour visit in the inpatient unit. At the study visit blood will be drawn. The total amount of blood drawn during the study is approximately 12 fluid ounces.

This procedure measures how the body responds to insulin. Insulin is normally produced by the body during meals and helps the body use sugar. There will be two IV lines, one in the participant's arm and one in the participant's hand on the opposite side. Small amounts of glucose and insulin will be infused into the participant's arm. The participant's blood sugar level will be checked every 5-10 minutes from the IV in the hand to determine how much glucose the participant should have to keep blood sugar at a normal level. The participant's hand will be placed inside a warming box to increase skin temperature to about 105 degrees Fahrenheit. The temperature will be warm, but not uncomfortable. During the IV procedure, a small amount of the participant's own blood (less than 1 teaspoon) will immediately be returned into the vein through the IV after each specimen is collected.

After the participant rests for 30 minutes, a clear plastic hood will be placed over the participant's head and chest area. The hood is ventilated with fresh air. The participant's oxygen intake and carbon dioxide output will be measured for 30 minutes to determine how many calories the participant burns during the time they are being tested.